Peripheral administration of a κ-opioid receptor agonist nalfurafine inactivates gonadotropin-releasing hormone pulse generator activity in goats.

Neurons co-expressing kisspeptin, neurokinin B, and dynorphin A (KNDy neurons), located in the arcuate nucleus (ARC) of the hypothalamus, are indicated to be the gonadotropin-releasing hormone (GnRH) pulse generator. Dynorphin A is reported to suppress GnRH pulse generator activity. Nalfurafine is a selective agonist of the κ-opioid receptor (KOR), a receptor for dynorphin A, clinically used as an anti-pruritic drug. This study aimed to evaluate the effects of nalfurafine on GnRH pulse generator activity and luteinizing hormone (LH) pulses using female goats. Nalfurafine (0, 2, 4, 8, or 16 µg/head) was intravenously injected into ovariectomized Shiba goats. The multiple unit activity (MUA) in the ARC area was recorded, and plasma LH concentrations were measured 2 and 48 h before and after injection, respectively. The MUA volley interval during 0-2 h after injection was significantly increased in the nalfurafine 8 and 16 µg groups compared with the vehicle group. In 0-2 h after injection, the number of LH pulses was significantly decreased in the nalfurafine 8 and 16 µg groups, and the mean and baseline LH were significantly decreased in all nalfurafine-treated groups (2, 4, 8, and 16 µg) compared with the vehicle group. These results suggest that nalfurafine inhibits the activity of the GnRH pulse generator in the ARC, thus suppressing pulsatile LH secretion. Therefore, nalfurafine could be used as a reproductive inhibitor in mammals.

27-Hydroxycholesterol acts on estrogen receptor α expressed by POMC neurons in the arcuate nucleus to modulate feeding behavior.

Oxysterols are metabolites of cholesterol that regulate cholesterol homeostasis. Among these, the most abundant oxysterol is 27-hydroxycholesterol (27HC), which can cross the blood-brain barrier. Because 27HC functions as an endogenous selective estrogen receptor modulator, we hypothesize that 27HC binds to the estrogen receptor α (ERα) in the brain to regulate energy balance. Supporting this view, we found that delivering 27HC to the brain reduced food intake and activated proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (POMCARH) in an ERα-dependent manner. In addition, we observed that inhibiting brain ERα, deleting ERα in POMC neurons, or chemogenetic inhibition of POMCARH neurons blocked the anorexigenic effects of 27HC. Mechanistically, we further revealed that 27HC stimulates POMCARH neurons by inhibiting the small conductance of the calcium-activated potassium (SK) channel. Together, our findings suggest that 27HC, through its interaction with ERα and modulation of the SK channel, inhibits food intake as a negative feedback mechanism against a surge in circulating cholesterol.

GLP-1 increases preingestive satiation via hypothalamic circuits in mice and humans.

Glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1RAs) are effective antiobesity drugs. However, the precise central mechanisms of GLP-1RAs remain elusive. We administered GLP-1RAs to patients with obesity and observed a heightened sense of preingestive satiation. Analysis of human and mouse brain samples pinpointed GLP-1 receptor (GLP-1R) neurons in the dorsomedial hypothalamus (DMH) as candidates for encoding preingestive satiation. Optogenetic manipulation of DMHGLP-1R neurons caused satiation. Calcium imaging demonstrated that these neurons are actively involved in encoding preingestive satiation. GLP-1RA administration increased the activity of DMHGLP-1R neurons selectively during eating behavior. We further identified that an intricate interplay between DMHGLP-1R neurons and neuropeptide Y/agouti-related peptide neurons of the arcuate nucleus (ARCNPY/AgRP neurons) occurs to regulate food intake. Our findings reveal a hypothalamic mechanism through which GLP-1RAs control preingestive satiation, offering previously unexplored neural targets for obesity and metabolic diseases.

Raphe glucose-sensing serotonergic neurons stimulate KNDy neurons to enhance LH pulses via 5HT2CR: rat and goat studies.

Dysfunction of central serotonergic neurons is known to cause depressive disorders in humans, who often show reproductive and/or glucose metabolism disorders. This study examined whether dorsal raphe (DR) serotonergic neurons sense high glucose availability to upregulate reproductive function via activating hypothalamic arcuate (ARC) kisspeptin neurons (= KNDy neurons), a dominant stimulator of gonadotropin-releasing hormone (GnRH)/gonadotropin pulses, using female rats and goats. RNA-seq and histological analysis revealed that stimulatory serotonin-2C receptor (5HT2CR) was mainly expressed in the KNDy neurons in female rats. The serotonergic reuptake inhibitor administration into the mediobasal hypothalamus (MBH), including the ARC, significantly blocked glucoprivic suppression of luteinizing hormone (LH) pulses and hyperglycemia induced by intravenous 2-deoxy-D-glucose (2DG) administration in female rats. A local infusion of glucose into the DR significantly increased in vivo serotonin release in the MBH and partly restored LH pulses and hyperglycemia in the 2DG-treated female rats. Furthermore, central administration of serotonin or a 5HT2CR agonist immediately evoked GnRH pulse generator activity, and central 5HT2CR antagonism blocked the serotonin-induced facilitation of GnRH pulse generator activity in ovariectomized goats. These results suggest that DR serotonergic neurons sense high glucose availability to reduce gluconeogenesis and upregulate reproductive function by activating GnRH/LH pulse generator activity in mammals.

Putative identification of proopiomelanocortin and neuropeptide-Y neurons of the arcuate nucleus by their response to leptin: in vivo electrophysiology study in male and female rats.

The arcuate nucleus (ARN) of the hypothalamus is involved in multiple biological functions, such as feeding, sexual activity, and the regulation of the cardiovascular system. It was reported that leptin increased c-Fos expression in the proopiomelanocortin (POMC)- and decreased it in the neuropeptide-Y (NPY)-positive neurons of the ARN, suggesting that it stimulates the former, and inhibits the later. This study aimed at the direct electrophysiological examination of the effect of leptin on ARN neurons and to investigate potential sex-dimorphic changes. Wistar rats were anesthetized with urethane and the electrodes were inserted into the ARN. After a spontaneous active neuron was recorded for at least one minute, leptin was administered intravenously, and the firing activity of the same neuron was recorded for two additional minutes. It was found that approximately half of the ARN neurons had an excitatory, and another half an inhibitory response to the leptin administration. The excitability of the neurons with excitatory response to leptin was not different between the sexes. The average firing rate of the neurons with inhibitory response to leptin in females was, however, significantly lower comparing to the males. The obtained results demonstrate that the ARN neurons with stimulatory response to leptin are POMC and those with inhibitory response are NPY neurons. NPY Y1 receptor be might responsible, at least in part, for the sex differences in the excitability of the neurons putatively identified as NPY neurons.

Repeated binge-like ethanol administration during adolescence cause decreased C-Fos immunoreactivity in amygdala and arcuate nucleus in adult Sprague-Dawley rats / La administración repetida de etanol, tipo atracón, durante la adolescencia provoca descenso en la expresión de C-Fos en la amígdala y núcleo arqueado de ratas Sprague-Dawley adultas

Binge alcohol drinking during adolescence has been associated with neurotoxicity and increased risk for the development of alcohol use disorders. There is evidence that acute and chronic ethanol administration alters c-fos expression, an indirect index of cellular activity, in different brain regions in adult rats. We evaluate here if a binge-like pattern of ethanol exposure during adolescence has a relevant impact on basal and/or ethanol-stimulated regional c-fos activity during adulthood. For that aim, Sprague-Dawley rats PND 25 were saline pre-treated, (SP group) or binge-ethanol pre-treated (BEP group) for two­consecutive days, at 48-h intervals, over a 14-day period (PND 25 to PND 38). At adult stage (PND 63) and following 25 ethanol-free days, we evaluated c-fos immunoreactivity in response to saline or acute ethanol (1.5 or 3.0 g/kg) in the hypothalamus and amygdala. We found that acute ethanol administration dose-dependently increased c-fos activity in the the Paraventricular nucleus of the hypothalamus (PVN). Interestingly, binge-ethanol exposure during adolescence significantly reduced basal c-fos activity during adulthood in the Central nucleus of the amygdala (CeA) and the Arcuate nucleus of hypothalamus (Arc). We conclude that binge-like ethanol administration during adolescence causes long-term disturbances in basal neural activity in brain areas critically involved with ethanol consumption.

El consumo en atracón durante la adolescencia está asociado con neurotoxicidad y con el riesgo de desarrollar un trastorno en el uso de alcohol. Diversos estudios muestran que la administración aguda y crónica de alcohol en ratas adultas altera la expresión de c-fos, un marcador indirecto de actividad celular, en diferentes áreas cerebrales. Nosotros evaluamos si el patrón de consumo de alcohol en atracón durante la adolescencia tiene un impacto en la actividad basal de c-fos en esas regiones activadas por el alcohol. Utilizamos ratas Sprague-Dawley en su día post-natal 25 (PND25) tratadas con suero salino (grupo SP) o con etanol tipo atracón (grupo BEP) durante dos días consecutivos, en intervalos de 48 h, durante 14 días (PND25- PND38). En la edad adulta (PND63) y después de 25 días sin etanol, evaluamos la inmunorreactividad para c-fos en respuesta a una administración aguda de suero salino o etanol (1,5 ó 3,0 g/kg) en diferentes regiones cerebrales. La administración de alcohol incrementó de manera dosis-dependiente la actividad de c-fos en el núcleo paraventricular del hipotálamo. Además la exposición a etanol tipo atracón durante la adolescencia disminuyó la actividad basal de c-fos en la adultez en el núcleo central de la amígdala y en el núcleo arqueado del hipotálamo. Concluimos que el consumo de alcohol en atracón durante la adolescencia causa problemas a largo plazo en la actividad basal de regiones cerebrales implicadas en el consumo de alcohol.

A single high dose of chlorpyrifos reduces long-term basal c-fos expression in the rat arcuate hypothalamic nucleus / La administración de una dosis aguda de clorpirifós reduce a largo plazo la expresión basal de c-fos en el núcleo arqueado del hipotálamo

Chlorpyrifos (CPF) is an organophosphate compound used worldwide as a pesticide in agriculture that, after subcutaneous injection, keeps acetylcholinesterase (AChE) activity inhibited within an organism for months. Ample clinical and experimental evidence shows that CPF exposure induces relevant and persistent neurobehavioral deficits in humans and animals, even after one single episode/injection. Additionally, clinical and epidemiological studies evidence that a significant percentage (60%) of Gulf War veterans as well as agricultural workers suffering from acute OP intoxication may have developed intolerance to nicotine and ethanol-containing beverages. Consistent with it, administration of a single high dose of CPF to adult Wistar rats elicited long-lasting reduced voluntary ethanol drinking and increased sedation to ethanol without evidence of altered ethanol metabolism, which indicates that CPF-ethanol neurobiological interactions may exist. In this study, we explore whether CPF exposure induces significant disturbances in basal and/or ethanol-evoked neural activity in a set of cholinoceptive brain regions critically involved with neurobiological responses to ethanol. For this aim, brain regional c-fos expression in response to acute ethanol (1.5 or 3.0 g/kg, i.p.) or saline was assessed in adult male Wistar rats previously injected with either a single high dose of CPF (250 mg/kg, sc) or vehicle. We found that CPF administration reduces long-term basal, but not ethanol-evoked, c-fos expression in the arcuate hypothalamic nucleus. Because independent brain pathways may modulate acute responses to ethanol and voluntary ethanol consumption, we do not rule out the contribution of basal neural disturbances observed in the Arc to CPF-elicited ethanol avoidance.

El clorpirifós (CPF) es un compuesto organofosforado utilizado como plaguicida en todo el mundo. Después de ser inyectado de manera subcutánea, mantiene la actividad de la enzima acetilcolinesterasa (AChE) inhibida durante meses. Estudios clínicos y experimentales muestran que la exposición al CPF induce déficits neuroconductuales persistentes en seres humanos y animales, incluso después de un solo episodio/inyección. Además, estudios epidemiológicos evidencian que un porcentaje significativo (60%) de los veteranos de la Guerra del Golfo, así como los agricultores que sufren una intoxicación aguda por organofosforados, desarrollan intolerancia a la nicotina y las bebidas que contienen etanol. Datos experimentales mostraron que la administración de una sola dosis alta de CPF en ratas Wistar adultas provoca una reducción a largo plazo del consumo voluntario de etanol y un incremento en la sedación provocada por etanol sin evidencias de alteración del metabolismo de esta sustancia, lo que indica que pueden existir interacciones neurobiológicas entre CPF-etanol. En este estudio, se explora si la exposición a CPF induce alteraciones significativas en la actividad neuronal basal o evocada por el etanol en un conjunto de regiones colinoceptivas del cerebro involucradas en las respuestas neurobiológicas al etanol. Para ello, se evaluó la expresión de c-fos en respuesta a una dosis de etanol aguda (1.5 o 3.0 g/kg, ip) o solución salina en ratas Wistar macho adultas previamente inyectados con dosis aguda de CPF (250 mg/kg, sc) o un vehículo. Encontramos que la administración de CPF redujo la expresión basal de c-fos a largo plazo, pero no la evocada por el etanol en el núcleo arqueado del hipotalámo. Debido a que vías cerebrales independientes podrían modular las respuestas agudas al etanol y el consumo voluntario del mismo, no se descarta la contribución de las alteraciones neuronales basales observadas en el Arc en la evitación del consumo de etanol provocado por CPF.