Prelimbic and infralimbic responsivity to amygdala input is modified by gonadal hormones in parallel to low anxiety-like behavior in ovariectomized rats.

Gonadal hormones may influence sexual activity by reducing anxiety. The basolateral amygdala (BLA) and prelimbic (PL) and infralimbic (IL) cortical regions comprise a loop that is related to fear, anxiety, and social behavior. In female ovariectomized rats, actions of estradiol, progesterone, and sequential estradiol and progesterone administration were explored in the open field test (OFT) and plus maze test (PMT) to evaluate signs of anxiety-like behavior. The three hormonal treatments reduced indicators of anxiety in the PMT but did not influence behavior in the OFT. In the same behaviorally tested rats under urethane anesthesia, single-unit extracellular recordings were obtained from the PL and IL during electrical stimulation of the BLA. The analysis of 250 ms peristimulus histograms showed that BLA stimulation produced two kinds of response. A small group of neurons increased their firing rate after BLA stimulation. Most neurons exhibited a reduction of spiking. Neurons that increased their firing rate after BLA stimulation did not show any difference with the hormonal treatments. In neurons that were inhibited by BLA stimulation, estradiol reduced the neuronal firing rate in the PL and IL, and progesterone alone and the sequential administration of estradiol followed by progesterone administration 24 h later (priming) increased the firing rate during the 240 ms before BLA stimulation. Analyses of responsivity of the PL and IL during electrical stimulation of the BLA indicated that estradiol, progesterone, and estradiol followed by progesterone administration 24 h later (priming) reduced inhibitory actions of the BLA on the PL but not IL. In the BLA-IL connection, progesterone exacerbated the inhibitory response. These findings indicate that anxiolytic actions of estradiol, progesterone, and estradiol followed by progesterone administration 24 h later (priming) correspond to lower BLA-PL responsivity. Actions of progesterone on BLA-IL responsivity appear to contribute to sexual activity by interacting with other forebrain structures that are also related to sexual receptivity.

Protocol for indirect and direct co-culture between human cancer cells and endothelial cells.

The cross talk between cancer cells and endothelial cells (ECs) within the tumor microenvironment plays a critical role in tumor progression, recurrence, and cancer stemness. Here, we present a protocol containing two in vitro approaches to study such interactions. We first describe an indirect co-culture system to study the regulation of stemness markers in cancer cells by secreted factors from ECs. We then detail a direct co-culture system to study juxtracrine communications between the cell types. For complete details on the use and execution of this protocol, please refer to Sewell-Loftin et al.1 and Guo et al.2.

Notch Signaling in Vascular Endothelial Cells, Angiogenesis, and Tumor Progression: An Update and Prospective.

The Notch signaling pathway plays an essential role in a wide variety of biological processes including cell fate determination of vascular endothelial cells and the regulation of arterial differentiation and angiogenesis. The Notch pathway is also an essential regulator of tumor growth and survival by functioning as either an oncogene or a tumor suppressor in a context-dependent manner. Crosstalk between the Notch and other signaling pathways is also pivotal in tumor progression by promoting cancer cell growth, migration, invasion, metastasis, tumor angiogenesis, and the expansion of cancer stem cells (CSCs). In this review, we provide an overview and update of Notch signaling in endothelial cell fate determination and functioning, angiogenesis, and tumor progression, particularly in the development of CSCs and therapeutic resistance. We further summarize recent studies on how endothelial signaling crosstalk with the Notch pathway contributes to tumor angiogenesis and the development of CSCs, thereby providing insights into vascular biology within the tumor microenvironment and tumor progression.

¿Los protocolos experimentales son un símil real de la diabetes humana? / Are experimental protocols an authentic simile of human diabetes?

Resumen Para el estudio de la diabetes se dispone de diversas estrategias metodológicas en modelos animales, tales como, técnicas quirúrgicas, modificaciones dietéticas, incluso manipulación genética y la administración de fármacos específicos, por su toxicidad. En animales, la diabetes experimental se logra con el uso de fármacos, como la aloxana o la estreptozotocina, los cuales producen daño irreversible en las células β-pancreáticas, aunque causan una alta mortalidad, debido a la cetosis asociada al daño agudo de estas células pancreáticas. El objetivo de este trabajo fue analizar los protocolos farmacológicos y otras estrategias disponibles, para determinar si la diabetes experimental realmente emula la diabetes humana. La diabetes es un proceso progresivo y crónico, en el que la mayor parte de las alteraciones clínicas son consecuencia, en el largo plazo, de alteraciones micro y macrovasculares. Por ello, es conveniente diferenciar entre los efectos de una hiperglucemia aguda, con aquellos que se observan cuando la hiperglucemia se prolonga a lo largo del tiempo, a fin de establecer analogías, entre el modelo experimental animal, con el síndrome diabético humano, mediante datos de laboratorio y de tipo clínico, de uso habitual en el diagnóstico y manejo de la diabetes humana.

Abstract For the study of diabetes, several methodological strategies use animal models. Such methodologies involve surgical techniques, diet modifications, some genetic manipulations and specific toxic drugs. The experimental production of diabetes in animal models use the administration of alloxan or streptozotocin and these drugs produce irreversible damage to pancreatic β-cells. However, its use is associated to a ketosis high mortality rate due to the acute damage of pancreatic cells. The aim of this review consisted in the analysis of the pharmacological diabetes production protocols as well as other available strategies, in order to elucidate which is potentially the ideal protocol that emulates human diabetes. Diabetes is a progressive and chronic process, in which most of the clinical alterations are a long-term consequence of micro and macrovascular alterations. Therefore, it is convenient to establish a difference between the effects of acute hyperglycemia, with those effects observable when hyperglycemia is present over the long-term in order to reach enough analogies between the animal experimental model with the human diabetes syndrome, through the use of laboratory and clinical indicators commonly employed for the diagnoses and management of human diabetes.

Estrogen and progesterone priming induces lordosis in female rats by reversing the inhibitory influence of the infralimbic cortex on neuronal activity of the lateral septal nucleus.

The lateral septal nucleus (LSN) exerts inhibitory control over lordosis in female rats, but the influence of forebrain structures, such as prelimbic (PL) and infralimbic (IL) regions of the medial prefrontal cortex (mPFC), on LSN activity during sexual receptivity is unknown. We hypothesized that the neural responsivity of these connections may differ depending on sexual receptivity. Gonadally intact female Wistar rats received sequential priming injections of estradiol and progesterone (E2-P4). The presence of lordosis was then confirmed by exposing the female rats to a sexually experienced male rat. Intromission was not allowed. Vaginal smear analyses verified that the rats were in proestrus-estrus of the estrous cycle. The results were compared with a diestrus group, which was verified by vaginal smears and the absence of lordosis. Under ethyl-carbamate anesthesia, single-unit extracellular recordings of the LSN were performed during electrical stimulation of the PL and IL to evaluate possible changes in the responsivity of neural connections. Stimulation of the PL or IL produced a short-latency, brief-duration (paucisynaptic) excitatory response in the LSN, followed by a period of afterhyperpolarization. Responsivity of the PL-LSN pathway was unaffected by E2-P4 priming. The paucisynaptic response of the IL-LSN pathway was significantly greater in the E2-P4-primed group than in the diestrus group, and the afterhyperpolarization response decreased to nearly zero. These findings indicate that the IL exerts inhibitory control over the LSN during diestrus in rats, but this inhibitory control decreases under the action of gonadal steroids, seemingly favoring sexual receptivity.

Diisononyl Phthalate Differentially Affects Sirtuin Expression in the HepG2 Cell Line.

Human exposure to phthalates has received special attention due to their possible adverse human health effects. Diisononyl phthalate (DINP) is a plasticizer still widely used in many products, despite being considered an endocrine disruptor. In this study, we evaluated DINP's cytotoxicity, its effect on the levels of reactive oxygen species (ROS), and its effect on sirtuin expression in HepG2 cells. Results showed that 1 µg/mL DINP significantly downregulated Sirt1, Sirt2, Sirt3, and Sirt5 gene expression (p < 0.05), while other sirtuins remained unaffected. Furthermore, protein levels of Sirt1 and Sirt3 were significantly downregulated by 1 µg/mL DINP. On the other hand, 100 µg/mL DINP doubled the levels of lysine acetylation proteins (increased 2-fold) as well as reactive oxygen species (ROS) compared with the controls. In conclusion, our study suggests, for the first time, that DINP regulates the potential epigenetic disruptor sirtuin family and leads to induction of ROS via sirtuins.

Phthalates affect the in vitro expansion of human hematopoietic stem cell.

Phthalates are esters of phthalic acid used industrially as plastic additives, however, these are not covalently bound to the polymer matrix and therefore can be released to the environment. The aim of this study was to evaluate the effect of four phthalates: dibutyl phthalate (DBP), benzyl butyl phthalate (BBP), diethyl phthalate (DEP) and diethylhexyl phthalate (DEHP) on the in vitro expansion of human hematopoietic cells from umbilical cord blood. For this, 0.5 × 106 cells/mL were exposure to concentrations ranging from 0.1 to 100 µg/mL and the total cell expansion was determined after 14 days of culture in IMDM-cytokines medium. The control cultures attained 1.31 ± 0.21 × 106 cell/mL, whereas the cultures exposed to DBP, BBP and DEHP showed a reduction from 23 to 81%, 17 to 69% and 15 to 93.5%, respectively. DEP did not affect the total cell expansion. The most significant decrease on total cell expansion was observed at 0.1 µg/mL DBP, 100 µg/mL BBP and 10 µg/mL DEHP (p < 0.05). Additionally, the effect of these compounds on the expansion of hematopoietic progenitors was analyzed by clonogenic assays as colony forming units (CFU). The CFU decreased considerably compared with respect to the control cultures. The reduction was 74.6 and 99.1% at 10 and 100 µg/mL DBP respectively, whereas 100 µg/mL BBP and 100 µg/mL DEHP reduced the CFU expansion in 97.1% and 81%, respectively. Cultures exposed to DEP did not show significant differences. The results demonstrate the toxicity of DBP, BBP and DEHP on the human hematopoietic stem cells.

Autoeficacia académica y ansiedad, como incidente crítico, en mujeres y hombres universitarios / Academic Self-efficacy and Anxiety, as a Critical Incident in Female and Male University Students

Resumen Con el objetivo de explorar las relaciones entre la autoeficacia académica y la ansiedad, como inciden te crítico, el presente estudio descriptivo-correlacional incluyó una muestra de 310 estudiantes (183 mujeres y 127 hombres), quienes respondieron a la Escala de Autoeficacia en Conductas Académicas (EACA), la Escala de Ansiedad ZUNG y el Inventario de Ansiedad Estado-Rasgo (IDARE). La prueba de Pearson indicó una correlación positiva significativa entre las puntuaciones de autoeficacia percibida, deseable y alcanzable en EACA, pero una correlación negativa con el índice de mejora de la misma prueba; es decir, los puntajes de autoeficacia percibida, deseable y alcanzable se com portan de manera similar; pero, a medida en que los puntajes de estos tres indicadores disminuyen, la puntuación del índice de mejora es mayor. Por lo tanto, la autoeficacia percibida se tomó como el principal indicador de EACA, la cual se correlacionó inversamente con los puntajes de las escalas de ZUNG e IDARE; es decir, cuanto menor es la autoeficacia percibida mayor es el nivel de ansie dad. En un segundo análisis, un criterio arbitrario permitió definir tres rangos de puntuaciones en autoeficacia percibida: baja (puntuación 1-7.4), intermedia (puntuación 7.5-8.9) y alta (puntuación 9.0-10.0). Un ANOVA de dos vías indicó que los estudiantes, con niveles de autoeficacia percibida baja, obtuvieron los niveles de ansiedad más altos con la conocida tendencia del género femenino a desarrollar mayores puntajes de ansiedad. En conclusión, los estudiantes con baja autoeficacia perci bida manifiestan ansiedad en el momento de la prueba. Permanece pendiente la exploración de una relación causa-efecto.

Abstract: With the aim of exploring relationships between academic self-efficacy and anxiety, as critical incidents, this des criptive study included a sample of 310 students (183 women and 127 men). Volunteers responded to the Self-efficacy in Academic Behavior Scale (EACA), ZUNG anxiety scale and State-Trait Anxiety Inventory (STAI). A correlation analysis was performed between the different levels of perceived, desirable, achievable self-efficacy and an improvement index with anxiety indicators. A Pearson analysis indicated a moderate but significant positive correlation among perceived, desirable, and attainable self-efficacy scores in the EACA test, but a negative corre lation among these three indicators and the same test's improvement index. In other words, perceived, desirable, and attainable self-efficacy scores tabulated similarly, but as the scores of these three indicators rose, the score of the improvement index declined. Therefore, the perceived self-efficacy was taken as main indicator of EACA. The perceived self-efficacy correlated inversely with the scores obtained on ZUNG and STAI scales, i.e., as lower the perceived self-efficacy, the higher the level of anxiety. In second analyses, an arbitrary criterion allowed the esta blishment of three ranges of perceived self-efficacy scores into low (score 1-7.4), intermediate (score 7.5-8.9) and high (score 9.0-10.0). A two-way ANOVA indicated that students in the low range of perceived self-efficacy also scored the highest anxiety levels, with the well-known trend of feminine gender to express high levels of anxiety. In conclusion, students with low perceived self-efficacy are also anxious at the moment of the test, leaving for the future an exploration of a cause and effect relationship.

Progesterone modifies the responsivity of the amygdala-mPFC connection in male but not female Wistar rats.

Amygdala-medial prefrontal cortex (mPFC) connections partially regulate fear, anxiety, and the acquisition of conditioned fear. Progesterone exerts some effects on anxiety and fear. Currently unknown, however, are the actions of progesterone on the responsivity of amygdala-mPFC connections and possible sex differences. We performed single-unit extracellular recordings from the prelimbic (PL) and infralimbic (IL) cortices of the mPFC during stimulation of the basal amygdala (BA) in anesthetized male and diestrus female rats. Basal amygdala stimulation produced an initial excitatory paucisynaptic response that was similar between sexes and unaffected by progesterone. A long-lasting inhibitory response followed the initial brief excitatory response, which was more pronounced in the PL region in males. The unit activity ratio analysis indicated that progesterone negated the sex difference in the PL region response to BA stimulation. The results suggest that progesterone decreases the responsivity to amygdala stimulation, particularly in males compared with diestrus females, which may be related to sex differences in the strategies to cope with threatening situations.

An alarm pheromone increases the responsivity of amygdaline-hippocampal neurons / Una feromona de alarma incrementa la responsividad de neuronas amigdalino-hipocampales

The capability to perceive and emit alarm substances, such as 2-heptanone, makes animals aware of the presence of danger, leading to some strategies directed towards survival. Strategies of survival involve emotional memory which is processed by deep temporal lobe structures, such as amygdaloid complex and hippocampus. In the Wistar rat, 2-heptanone produces anxiety-like behavior and an increased firing rate of basal amygdaline neurons. However, it is unknown whether 2-heptanone modifies the responsivity of medial amygdaline-hippocampal connection. Therefore, we placed a group (n=10) of Wistar rats in a plexiglass cage impregnated with 2-heptanone. Rats from control group (n=10) were introduced into a similar clean cage. Twenty four hours later we obtained single-unit extracellular recordings from the hippocampus (CA1-CA3) neurons identified by their connection to medial amygdala. Although the basal neuronal firing rate was similar between groups, first order interval distribution histogram analysis showed that 2-heptanone produced shorter intervals of firing rate. Peristimulus histograms indicated that: i) the amygdaline stimulation produces an increased firing rate in hippocampal neurons; and ii) this response is increased and enlarged on the 2-heptanone group. Since a single exposure to an alarm pheromone seems to facilitate the amygdala-hippocampal connection, results suggest the initial formation of contextual memories related with fear.

La percepción olfatoria de feromonas de alarma, como la 2-heptanona, promueve ciertas estrategias de supervivencia con la participación de la memoria emocional, integrada en estructuras del lóbulo temporal, como la amígdala y el hipocampo. En la rata Wistar, la olfacción de 2-heptanona genera conductas sugerentes de ansiedad y un incremento de la tasa de disparo neuronal del núcleo basal de la amígdala. Sin embargo, no se conoce si la 2-heptanona modifica la responsividad de la conexión amígdala medial-hipocampo. Un grupo de ratas Wistar (n=10) fue colocado dentro de una caja de acrílico impregnada con 2-heptanona; el grupo control (n=10) fue introducido en una caja limpia. Veinticuatro horas después se obtuvo el registro unitario extracelular de neuronas del hipocampo (CA1-CA3) identificadas por su conexión con la amígdala medial. Aunque la tasa de disparo basal fue similar entre los grupos experimentales, el histograma de distribución de intervalos de primer orden indicó un predominio de intervalos de breve duración en el grupo 2-heptanona. Los histogramas periestímulo indicaron que: i) las neuronas hipocampales responden con un incremento en la tasa de disparo neuronal ante la estimulación amigdalina; ii) la respuesta es de mayor magnitud y duración en el grupo previamente expuesto a 2-heptanona. Dado que una sola exposición a una feromona de alarma facilita la conexión amígdala medial-hipocampo, los resultados sugieren la formación inicial de una memoria contextual relacionada con el miedo.

Anxiolytic-like effects of human amniotic fluid and its fatty acids in Wistar rats.

Odors from amniotic fluid produce signs of calmness in mammals suggesting some anxiolytic-like properties. Experimental models, such as the defensive burying, elevated plus maze, and open field tests offer well-controlled approaches to the study of putative anxiolytic substances using rats. Using gas chromatography-mass spectrometry, we first identified eight fatty acids (lauric, myristic, palmitic, palmitoleic, stearic, oleic, elaidic, and linoleic acids) as consistently present in human amniotic fluid. We then used the defensive burying and elevated plus maze tests to compare the action of diazepam (2 mg/kg), fresh amniotic fluid, and a mixture of its fatty acids with two vehicles (i.e. propylene glycol and centrifuged amniotic fluid with a low fatty acid content). No significant differences in estradiol or progesterone content were found between fresh amniotic fluid and centrifuged amniotic fluid using the microparticle enzyme immunoassay. Compared with the vehicle, diazepam, fresh amniotic fluid, and the fatty acid mixture increased burying latency, reduced cumulative burying, and increased the time spent in the open arms of the elevated plus maze in both sexes without altering general locomotor activity. We conclude that the fatty acids contained in human amniotic fluid exert anxiolytic-like effects, with minimal or no participation of female gonadal steroids.

Timing of progesterone and allopregnanolone effects in a serial forced swim test / Duración del efecto de progesterona y alopregnanolona en la prueba de nado forzado seriada

The forced swim test (FST) is commonly employed to test the potency of drugs to reduce immobility as an indicator of anti-despair. Certainly, antidepressant drugs reduce the total time of immobility and enlarge the latency to the first immobility period. FST is preceded by the open field test (OFT) to discard any influence of changes in general motor activity that could interfere with immobility in the FST. Albeit progesterone and its a-reduced metabolite allopregnanolone produce antidepressant-like effects in the FST, the timing of actions is unknown. We hypothesized that the latency and duration of effects produced by progesterone and allopregnanolone may be characterized by repeated FST sessions; we therefore devised a serial-FST experimental design to evaluate the timing effects of these steroids on immobility, locomotion in the open field test, and grooming in the later as an indicator of response to stress. We included fifty-one ovariectomized adult Wistar rats weighing 200-250 g at the beginning of the experiments. They were ovariectomized by abdominal approach under anesthesia. Rats were housed six per cage, at room temperature (25 ± 1°C) under a 12 h/12 h light/dark cycle (lights ON at 7:00 a.m.) with ad libitum access to purified water and food. All of the experimental procedures followed National Institutes of Health Guidelines. The local Ethics Committee (Biomedical Research Institute, Universidad Nacional Autónoma de México) approved the experimental protocol. A first group received vehicle (2-hidroxypropyl-γ-cyclodextrin dissolved in injectable sterilized water to obtain a 35% solution, control group n=17), the second group progesterone (1.0 mg/kg, n=17), and the third group allopregnanolone (1.0 mg/kg, n=17). All single injections were applied by intraperitoneal route at a volume of 0.8 ml/kg. The effects of treatments were evaluated in the serial-FST at 0.25, 0.5, 1, 2, 4, 6, and 24 h after injection, in a rectangular pool (height, 60 cm; length, 30 cm; width, 50 cm), with 24 cm deep water (25 ± 1°C). We evaluated the total time of immobility, during 5 min, considered as the principal indicator of an anti-despair effect. Before each session of serial-FST, locomotion was evaluated in the OFT during 5 minutes. The apparatus consisted on an acrylic box (height, 20 cm; length, 44 cm; width, 33 cm), with twelve squares delineated on the floor (11x11 cm). In the same OFT sessions, grooming was evaluated as an indicator of response to stress. Statistical analysis consisted in two-way analysis of variance (ANOVA) and Student-Newman-Keuls as post hoc test. Total time in immobility was the highest and remained at similar levels only in the control group throughout the seven sessions of the serial-FST. In the allopregnanolone group a reduction in immobility was observed beginning 0.5 h after injection and lasted approximately 1.5 h. Similarly, progesterone reduced immobility beginning 1.0 h after injection, and the reduction lasted for approximately 5.0 h. In all groups, locomotion in the OFT was reduced after the first serial-FST session and remained at similar low levels during the serial-FST. In the control group, grooming was reduced after the first serial-FST session and lasted 24 h, but grooming did not change in the progesterone-or allopregnanolone-treated rats. From a serial-FST design, we conclude that progesterone and allopregnanolone exert short time-dependent reductions in immobility and anti-stress-like effects no longer than 24 hrs, and seemingly a reduction in the response to stress, which may have some clinical applications.

Introducción La progesterona y su metabolito activo alopregnanolona se han estudiado ampliamente en modelos experimentales de ansiedad y depresión, y por su propiedad de ser sintetizadas en el cerebro se les considera como neuroesteroides. Entre las pruebas que permiten determinar la potencia antidepresiva de ciertos fármacos se encuentra la prueba de nado forzado, la cual se diseñó originalmente para detectar la potencia de sustancias con propiedades antidepresivas. Estas sustancias reducen el tiempo de inmovilidad y alargan la latencia al primer periodo de inmovilidad, lo cual es considerado como un efecto antidepresivo. Usualmente, la prueba de nado forzado se aplica dos veces, una sesión de preprueba que dura 15 minutos, en la cual la rata o ratón desarrolla el estado de desesperanza. La preprueba es seguida de la sesión de prueba que se realiza 24 horas después durante 5 minutos. En ella se evalúa el efecto de las sustancias con propiedades antidepresivas. Además, la prueba de nado forzado es precedida por la prueba de campo abierto con la finalidad de identificar cambios en la actividad motora general (hipoactividad o hiperactividad) que pudiera interferir con la interpretación de las variables evaluadas en la prueba de nado forzado. Algunos esteroides, como la progesterona y alopregnanolona, reducen la inmovilidad y alargan la latencia a la primera inmovilidad en la prueba de nado forzado, lo que indica su efecto tipo-antidepresivo. Sin embargo, la latencia y la duración de los efectos farmacológicos son desconocidas. La hipótesis de este trabajo fue que, si utilizábamos la prueba de nado forzado de forma repetida, podríamos identificar el tiempo de duración de los efectos de estos esteroides. Por lo tanto, diseñamos un experimento con la prueba de nado forzado seriada para evaluar el tiempo de permanencia de los efectos de progesterona y alopregnanolona en esta prueba conductual. Materiales y métodos Sujetos: En este estudio se incluyeron 51 ratas adultas ovariectomizadas de la cepa Wistar, con peso entre 200 y 250 g al inicio de los experimentos. Las ratas fueron anestesiadas y ovariectomizadas por aproximación ventral y fueron alojadas en cajas de acrílico trasparente (n=6), con una temperatura ambiente de 25 ± 1°C y con un ciclo de luz-oscuridad de 12 ×12 h (la luz se encendió a las 7:00 am). Las ratas tuvieron libre acceso al agua purificada y al alimento (Purina). Todos los procedimientos realizados en este estudio fueron de acuerdo con las normas éticas en el uso de animales de experimentación, basándonos en la Guía del National Institute of Health, y el protocolo fue aprobado por el Comité de Ética del Instituto de Investigaciones Biomédicas de la Universidad Nacional Autónoma de México. Grupos y tratamientos: Las ratas del grupo control recibieron el vehículo (solución al 35% de 2-hidroxipropil-g-ciclodextrina), el segundo grupo recibió progesterona (1.0 mg/kg) y el tercero recibió alopregnanolona (1.0 mg/kg) por vía intraperitoneal, en un volumen de 0.8 ml/kg. Pruebas conductuales: El efecto de los tratamientos fue evaluado en la prueba de nado forzado a las 0.25, 0.5, 1, 2, 4, 6 y 24 horas después de la administración. Utilizamos un estanque rectangular (base 50 × 34 cm, altura 60 cm), con agua a 25°C y una altura de 24 cm. Sólo se evaluó el tiempo total de inmovilidad, considerando que es el principal indicador de un efecto antidesesperanza. Antes de cada sesión de nado forzado se evaluó la actividad motora (cuadros deambulados) y el acicalamiento en campo abierto. Esta prueba consistió en colocar a la rata en una caja de acrílico (base 33 × 44 cm, altura 20 cm) con el piso dividido en 12 cuadros de 11 × 11 cm. Los resultados obtenidos de ambas pruebas fueron evaluados por medio de una ANOVA de dos vías y como prueba post hoc se aplicó Student-Newman-Keuls. Resultados La prueba de nado forzado aplicada de forma repetida resultó ser útil para evaluar los efectos temporales producidos por dos esteroides con potencia antidepresiva. Las ratas del grupo control mostraron los valores más altos de inmovilidad en la prueba de nado forzado, los cuales se mantuvieron así durante las sesiones de prueba. En los grupos tratados con progesterona o alopregnanolona hubo una reducción de la inmovilidad, gradual y temporal. Los animales tratados con alopregnanolona redujeron la inmovilidad a partir de las 0.5 horas después de la administración, efecto que se mantuvo por un periodo de 1.5 h. Los animales tratados con progesterona redujeron la inmovilidad a partir de 1.0 hora después de la administración, efecto que se mantuvo por un periodo de 5.0h. En campo abierto, independientemente del tratamiento, hubo una reducción del número de cuadros cruzados después de la primera sesión de nado forzado, efecto que permaneció hasta las 24h. En el acicalamiento, se observó que sólo los animales del grupo control redujeron significativamente el tiempo empleado en esta conducta, mientras que los animales inyectados con progesterona o alopregnanolona no modificaron esta variable. Es decir, mantuvieron niveles semejantes durante todas las sesiones de prueba y estuvieron por arriba de los valores encontrados en los animales control. Conclusión La progesterona y la alopregnanolona ejercen un efecto antidesesperanza de breve latencia, no mayor a 24 horas. Este hallazgo podría tener implicaciones clínicas en pacientes con depresión refractaria al tratamiento convencional.

Testosterone reduces cumulative burying in female Wistar rats with minimal participation of estradiol.

Testosterone exerts anxiolytic effects, but the participation of its aromatase metabolic product estradiol is controversial. Therefore, we used the defensive burying paradigm in female Wistar rats to explore testosterone's (1.0 mg/rat, s.c.) interactions with picrotoxin (a noncompetitive gamma-aminobutyric acid-A receptor [GABA(A)] antagonist; 1.0 mg/kg, i.p.), formestane (an aromatase inhibitor; 3.0 mg/rat, s.c.), and tamoxifen (an estrogen receptor-beta antagonist; 1.0 mg/kg, s.c.). Serum levels of testosterone, estradiol, and progesterone were determined in the same rats. Burying latency and locomotion did not significantly change. Systemic testosterone administration enhanced serum testosterone and estradiol levels and reduced defensive burying. This reduction in total burying was blocked by pretreatment with picrotoxin and tamoxifen, but not formestane. We conclude that testosterone produced anxiolytic-like effects in female rats that were mediated by actions at the GABA(A) receptor, with participation of the estradiol receptor-beta, rather than estradiol aromatization.

El suicidio y algunos de sus correlatos neurobiológicos. Primera parte / Suicide and some neurobiologic correlates. First part

Suicidal behavior is a complex and multifactorial phenomenon. At present, growing evidence shows the participation of biological traits in suicidality. Some findings suggest the dysfunction of the serotonin system, since serotonin and some of its receptor subtypes are involved in the modulation of such as affective behavior and cognition, among other behavioral processes. The content of 5-hydroxyindoleacetic acid, the major serotonin metabolite, is reduced in the cerebrospinal fluid of violent suicide attempters, independently of any other previous psychiatric diagnosis. In fact, this reduction may predict future suicide attempts and suicide completion. Post-mortem studies of ventromedial prefrontal cortex from suicide victims show decreased density of the 5-HT1A presynaptic serotonergic receptor subtype, and a compensatory upregulation of the 5-HT2A serotonergic post-synaptic receptor subtype. These observations on suicide strongly suggest a role of the two serotonin receptor subtypes located in this cortical brain region. Dysfunction of this region may support the diathesis concept (vulnerability) associated to suicidal behavior. In fact, some people display impulsive and self-aggressive behavior as part of their suicidality. This dysfunction is associated with alterations in the polymorphisms of tryptophan hydroxylase gene expression, i.e., the rate-limiting enzyme which in turn modifies the biosynthesis of serotonin, contributing to the reduction of serotonergic activity. Since the prefrontal cortex and related structures play a major role in mood regulation, their participation in the pathophysiology of affective disorders and suicide is currently being discussed. A circuit integrated by prefrontal cortex, hippocampus, amygdaloid complex, lateral septal nucleus and other functionally related structures could be involved in the regulation of emotional memory, hedonism and decision-taking. The hippocampus is implicated in cognition and is one of the cerebral structures strongly affected by stress. Structural abnormalities in cortical and hippocampal areas and reduced hippocampal plasticity have been demonstrated in patients suffering from chronic stress and affective disorders. Reduced neurotrophin expression may be associated with structural abnormalities and reduced hippocampal plasticity. A decrease in the content of neurotrophins in the prefrontal cortex and hippocampus could be of relevance in suicidal behavior. Human post-mortem studies supported by living animals studies have demonstrated that antidepressants increase the activity of the brain-derived neurotrophic factor (BDNF) and increase the density of its receptor (BDNF-tyrosine kinase receptor B: trkB), which seems to participate in the therapeutic effects of drugs used in the treatment of depression. On the contrary, the reduction of BNDF trkB-receptor mRNA has been related to suicidal behavior, since a reduction of plasma BNDF levels has been reported in major depression. BNDF levels have also been suggested as a biological marker of suicidal depression. Abnormalities in the ventromedial prefrontal cortex in suicidal individuals largely correlate with the neurochemical deficits reported in this population. In fact, prefrontal hypofunction and impaired serotonergic responsivity are proportional to the lethality of the suicide attempt. Positron emission tomographic studies indicate lower ventromedial prefrontal cortex activity, behaviorally associated with high impulsivity, higher planning of suicidal intent, and higher-lethality suicide attempts. Other studies have also related structural abnormalities in amygdala with suicidality. The function of this region is critical regarding fear, anxiety, aggression and the recognition and response to danger, i.e., some behavioral patterns involved in suicidality. Anxiety commonly follows or precedes depression. Therefore, amygdaline dysfunction may increase the risk of suicidal behavior. For depressive-suicide attempters, the suicide act itself occurs at a moment of extreme anxiety, strongly suggesting amygdaloid complex participation in the process. Lastly, the lateral septal nucleus is related with anhedonia and hopelessness (despair). Since its neuronal firing rate increases after the experimental application of clinically effective antidepressant treatments. The septal nucleus is considered a target of these drugs, a suggestion supported by the observation that anhedonia is one of the main symptoms in depression and lateral septal nucleus activity is involved in hedonic process. Anhedonia, hopelessness and other depressive symptoms are significantly related to suicidal ideation. Taking into account that some patients with major depression are vulnerable to suicide, this vulnerability may result from the interaction of suicidality with environmental precipitants and a lowered threshold for suicidal behavior. Certainly, one of the psychiatric disorders associated with suicide is depression, which suggests a causal relationship and suggests the involvement of these brain structures in suicidality.

El suicidio es un fenómeno complejo y multifactorial. A pesar de que varios de los factores de riesgo ya han sido identificados, las bases neurobiológicas del suicidio no se han esclarecido del todo, aunque se han enfocado particularmente hacia la disfunción del sistema serotonérgico. Los primeros estudios indicaban que, en sujetos con intentos suicidas, se encuentran niveles reducidos del ácido 5-hidroxiindol-acético, principal metabolito de la serotonina, en el líquido cefalorraquídeo, independientemente del diagnóstico psiquiátrico previo. Más adelante, algunos estudios post-mortem han identificado alteraciones en los receptores presinápticos (5-HT1A) y postsinápticos (5-HT2A, 5-HT1A) de la corteza prefrontal ventromedial. Esta disfunción, al parecer, se asocia con alteraciones en los genes que codifican la expresión de enzimas implicadas en la síntesis y metabolismo de la serotonina, aunada a una alteración en la expresión genética de factores neurotróficos derivados del cerebro, los cuales intervienen en la regulación funcional de las neuronas serotonérgicas. En conjunto, estas alteraciones se han relacionado con la vulnerabilidad o la diátesis para el comportamiento suicida en individuos con predisposición a la conducta violenta e impulsiva o autoagresiva. Además, confluye una hiperactividad del eje hipotálamo-hipófisis-adrenal, confirmada por un incremento de la hormona adrenocorticotrófica y una reducción del número de receptores para esta hormona en la corteza prefrontal de suicidas. La corteza prefrontal desempeña un papel fundamental en la regulación del estado de ánimo y se le ha implicado tanto en la fisiopatología de los trastornos afectivos como en el suicidio. Por medio de estudios con tomografía por emisión de positrones, se determinó que en los sujetos con intento de suicidio existe una hipofuncionalidad de la corteza prefrontal ventromedial, lo cual se ha asociado con la impulsividad y la planeación para intentar suicidarse. Asimismo, el hipocampo se ha implicado en la cognición y es una estructura que participa en el estrés, un factor predisponente al suicidio. Algunos sistemas celulares también han sido implicados, por ejemplo, los factores de transcripción CREB (proteína ligada al AMP cíclico), los cuales están disminuidos en la corteza prefrontal, hipocampo y amígdala de suicidas. Algunos otros estudios sugieren incluso anormalidades estructurales en la amígdala. Aunque es especulativo proponer que la amígdala cumpla un papel específico en el suicidio, tal propuesta no carece de bases dado que esta región es crítica en la integración de la ansiedad y en la agresión, además de que guía las respuestas apropiadas que deben emitirse bajo situaciones de peligro. Por otro lado, el núcleo septal lateral se ha implicado en la desesperanza y en las acciones de diversos tratamientos antidepresivos. Entonces, se puede integrar un circuito anatómico y funcional en el cual participan como entrada los sistemas sensoriales, de ahí a estructuras integradoras de la memoria emocional, ubicadas principalmente en el lóbulo temporal, para de ahí pasar a estructuras de la neocorteza, principalmente la corteza prefrontal, mediante las proyecciones de núcleos talámicos. Esta vía integra la percepción del ambiente, información que es contrastada en los circuitos de la memoria emocional, para de ahí pasar a la toma de decisiones. Las alteraciones funcionales de este circuito, aunadas a factores ambientales adversos, parecen promover el acto suicida. En fin, en el suicidio participan estructuras cerebrales integradoras del estado afectivo, la memoria emocional, la impulsividad y la toma de decisiones. Quizá por todo ello, aunque se acepta la eficacia de los antidepresivos, del litio y de los antipsicóticos de segunda generación, se cuestiona aún la eficacia de los antipsicóticos convencionales, por su escasa acción en el estado afectivo. Aunque la depresión es una entidad clínica de riesgo para el suicidio, no es la única, pues también son factores de riesgo el trastorno bipolar y el trastorno esquizoafectivo. Cualquiera de ellos, aunado a agitación e impulsividad, debe llamar la atención para seleccionar el tratamiento farmacológico preventivo pertinente.

El suicidio, conceptos actuales

resumen está disponible en el texto completo

Abstract: One current problem in Public Health relates to suicide and the identification of the risk factors needs to be clarified accurately. The bases of suicide involve complex multiple factors. In a high proportion of nations, mainly in industry-developing countries, suicide is placed among the first three causes of death in groups aged from 15 to 34 years. In Mexico, suicide represents the ninth cause of mortality, within a wide scale of age ranging from 15 to 64 years. Some risk factors have been identified. Epidemiological studies show that males commit suicide more frequently than females, in a proportion of 5:1. Consummate suicide occurs in men about 50 years old, mainly by hanging or fire arms. Females between 20 and 29 years old, on the contrary, carry out more frequent unsuccessful attempts in the same proportion, by using pesticides and medical drugs. However, in recent years an increase in the number of suicides among young people from 15 to 24 years old has been observed, commonly in lowincome sectors, in subjects with a previous history of psychiatric disorders, mainly personality disorders, abuse of substances and prior suicidal attempts. The risk of suicide generally increases after 45, and becomes especially serious in older people. The phenomenon of suicide in the elderly deserves special attention, due to the fact that the population over 65 years old is continuously increasing. This group displays fewer attempts than youths, but they achieve their aim more often through a silent suicide, by refusing to eat or to accept and follow medical prescriptions. Some psychiatric disturbances are intimately related to suicide. It is considered that 50% or more of the consummate suicides are performed by people suffering from an affective disorder, mainly depression. In this sense, it is noteworthy that most of these patients had been misdiagnosed and in many cases had not received any proper treatment. In addition, the abuse of or dependence on alcohol is present in about 20% of consummate suicides, and high rates of suicide are also observed in schizophrenia. Another common disturbance associated with suicide is anxiety. The simultaneous presence of anxiety and depression must be considered as a great risk factor, since the depressed patient has a high risk of committing suicide under phases of increased anxiety. All of these observations imply an alert signal for medical care units concerning the importance of detecting signs of the presence of risk factors and suicidal ideation, and of implementing adequate therapeutic management, namely, a supervised pharmacological treatment of depression and anxiety, including hospitalization, if it were the case. The risk factors in potential suicide include isolation, poor health, depression, alcoholism, lowered selfesteem, despair and feelings of social and family refusal. Frequently, the potential suicide directly or indirectly gives behavioral and verbal cues of his or her suicidal intention. Roughly, 60% of the victims of suicide had attended some medical care unit in the month previous to the suicide and had commented something about their desires and feelings about death at some moment, and 30% had clearly revealed their suicidal ideation. For such reason, the evaluation of risk of the potentially suicidal patient should be a common practice in medical care units. Therefore, the early detection of the presence of risk factors of suicide, including the report of self-harm and of a detectable incapacity for solving problems, mainly of social type may provide an invaluable time to permit its prevention. Another current aspect awaiting conclusive evidence is associated with some controversial data regarding the impact that the use of antidepressants could have upon suicide. The Food and Drug Administration office (USA) pointed out that deficiencies in information do not allow to confirm any existing relation between the use of serotonin selective reuptake inhibitors (SS-RIs) and suicide in youths. The suicidal risk after initiating the treatment is similar in the patient receiving tricyclics, or seroton-in selective reuptake inhibitors. The risk of suicide can increase significantly in the first month of antidepressant treatment, especially during the first nine days. Consequently, the observation that patients receiving antidepressants attempt suicide, is due, at least partly, to the fact that for still unknown reasons, antidepres-sants require from three to four weeks of impregnation to attain clear therapeutic effects. Therefore, it is indispensable to carry out further clinical and experimental studies to determine the variables that could be implied in this time lag in the action of antidepressants. However, fluoxetine represents a useful alternative in the management of depressive disorders; albeit as in the case of other antidepressants, it requires a strict follow-up of the patient receiving such treatments to avoid the risk of a fatal complication. In conclusion, the suicide risk, being a serious problem of public health, requires special attention. Recent research indicates that the prevention of suicide includes a series of activities, such as educational programs for children and youths, teachers and educators, and also primary health care units for the early detection of suicide risk factors. And, of course, medical training for the management of the potential suicide. For all of them, some relevant facts must be taken into account: Depression can be present in children and adolescents. Access to means of committing suicide, such as weapons, must be avoided. People from medical care units should be on the alert when any one shows signs and symptoms of despair and impulsiveness. Suicide, anxiety and depression have a biological basis; there-fore it is not a matter of cowardice or an act of defiance. An inadequate and inopportune diagnosis may increase the suicidal risk. Parents and teachers should be instructed to detect any sign of suicidal ideation and despair. Therefore, this revision intends to bring some recent data to bear upon the factors of the risk of suicide that provide the reader with information for a more effective prevention.

Intraaccumbens dopaminergic lesion suppresses desipramine effects in the forced swim test but not in the neuronal activity of lateral septal nucleus.

The nucleus accumbens (NAcc) function is related to locomotor activity, while the lateral septal nucleus (LSN) is related to the motivational aspects of behavior. Thus, a dopaminergic lesion of the NAcc blocks the antiimmobility effect of desipramine (DMI) and this tricyclic increases the firing rate of the LSN; however, it is unknown whether a relation exists between a dopaminergic lesion of the NAcc and the response of LSN neurons to DMI treatment. Therefore, we conducted a longitudinal study to further explore the participation of NAcc dopaminergic terminals in the immobility reduction exerted by DMI in the forced swim test and its relation to the firing rate of the LSN, at the same time exploring motor and motivational aspects of DMI-dopaminergic relationships in the animals. A dopaminergic lesion was bilaterally produced by 6-hydroxydopamine (6-OHDA) injection into the NAcc of adult ovariectomized Wistar rats pretreated with DMI (25 mg/kg ip, 30 min before lesion to protect NA terminals but to destroy DA endings). Treatments with DMI or saline began 24 h after stereotaxic surgery. The results showed that DMI once a day during 9 days (10 mg/kg) reduced immobility in the forced swim test in the sham-lesion group (P<.02); however, in the dopaminergic lesion group submitted to DMI treatment, immobility remained at control level in agreement with other reports. DMI increased the firing rate of the LSN (P<.001) independently of the 6-OHDA lesion. In conclusion, the dopaminergic terminals of the NAcc seem to be essential for the motor manifestation associated with motivation induced by DMI in the forced swim test, given that the antiimmobility actions of DMI are blocked after a dopaminergic NAcc lesion; however, the effect on the firing rate of LSN neurons is still present.