Effects of a Service-Learning Neuroscience Course on Mood and Intergroup Anxiety.

"Everyday Neuroscience" is an academically based community service (ABCS) course in which college students teach basic neuroscience lab activities to high school students in an under-funded school district, working in small groups on hands-on science activities for 10 weekly sessions. The present study examined the possible psychological and social effects of this experience on the college students, in comparison with peers not enrolled in such a course, by observing and surveying the high school and college students across the 10-week course period. First, the teaching-learning sessions in the course successfully promoted science-focused discussion between the high school and college students for 45 to 60 minutes each week. Second, college students in "Everyday Neuroscience" reported higher positive affect and less intergroup anxiety at the end of the semester compared with the control group of college students who were not in the course. Finally, surveys of the high school students revealed that they found the sessions to be positive social experiences. These findings reveal that a neuroscience-based community engagement course can be both a positive experience for the community partner and a benefit for college students by promoting psychological and social wellness.

Everyday Neuroscience: A Community Engagement Course.

The University of Pennsylvania offers "Academically Based Community Service" courses, which equip college students with real-world problem-solving skills relevant to their discipline of study in the service of the local community. The present report describes such a course called Everyday Neuroscience, in which Penn undergraduates developed ten neuroscience-relevant laboratory activities for high school students attending a nearby under-resourced public high school. For the community service component of the course, students ran these lab activities with small, consistent groups of high school students, based on topics that included traumatic brain injury, vision, reflexes, and attention. The academic component of the course included written reflections, reading scholarly works about education disparities, and making presentations to the class. At the end of the semester, the undergraduates self-reported that the course improved specific professional skills, namely teaching and communication, innovation and creativity, and critical thinking. Results of the before-and-after survey indicated that certain aspects of psychological and social well-being were rated more positively at the end of the semester compared with the beginning. In particular, students experienced a significant increase in confidence to express their own ideas and the feeling that they had something important to contribute to society. Their reflections revealed a theme of increased awareness of social issues, such as educational disparities. In sum, these results suggest that Everyday Neuroscience imparts professional skills related to communication, innovation and critical thinking, as well as improved social awareness.

Differential effects of mineralocorticoid and angiotensin II on incentive and mesolimbic activity.

The controls of thirst and sodium appetite are mediated in part by the hormones aldosterone and angiotensin II (AngII). The present study examined the behavioral and neural mechanisms of altered effort-value in animals treated with systemic mineralocorticoids, intracerebroventricular AngII, or both. First, rats treated with mineralocorticoid and AngII were tested in the progressive ratio operant task. The willingness to work for sodium versus water depended on hormonal treatment. In particular, rats treated with both mineralocorticoid and AngII preferentially worked for access to sodium versus water compared with rats given only one of these hormones. Second, components of the mesolimbic dopamine pathway were examined for modulation by mineralocorticoids and AngII. Based on cFos immunohistochemistry, AngII treatment activated neurons in the ventral tegmental area and nucleus accumbens, with no enhancement by mineralocorticoid pretreatment. In contrast, Western blot analysis revealed that combined hormone treatment increased levels of phospho-tyrosine hydroxylase in the ventral tegmental area. Thus, mineralocorticoid and AngII treatments differentially engaged the mesolimbic pathway based on tyrosine hydroxylase levels versus cFos activation.

The role of the hypothalamic paraventricular nucleus and the organum vasculosum lateral terminalis in the control of sodium appetite in male rats.

Angiotensin II (AngII) and aldosterone cooperate centrally to produce a robust sodium appetite. The intracellular signaling and circuitry that underlie this interaction remain unspecified. Male rats pretreated with both deoxycorticosterone (DOC; a synthetic precursor of aldosterone) and central AngII exhibited a marked sodium intake, as classically described. Disruption of inositol trisphosphate signaling, but not extracellular-regulated receptor kinase 1 and 2 signaling, prevented the cooperativity of DOC and AngII on sodium intake. The pattern of expression of the immediate early gene product cFos was used to identify key brain regions that may underlie this behavior. In the paraventricular nuclei (PVN) of the hypothalamus, DOC pretreatment diminished both AngII-induced cFos induction and neurosecretion of oxytocin, a peptide expressed in the PVN. Conversely, in the organum vasculosum lateral terminalis (OVLT), DOC pretreatment augmented cFos expression. Immunohistochemistry identified a substantial presence of oxytocin fibers in the OVLT. In addition, when action potentials in the PVN were inhibited with intraparenchymal lidocaine, AngII-induced sodium ingestion was exaggerated. Intriguingly, this treatment also increased the number of neurons in the OVLT expressing AngII-induced cFos. Collectively, these results suggest that the behavioral cooperativity between DOC and AngII involves the alleviation of an inhibitory oxytocin signal, possibly relayed directly from the PVN to the OVLT.

Estradiol regulates markers of synaptic plasticity in the hypothalamic ventromedial nucleus and amygdala of female rats.

Ovarian hormones act in multiple brain regions to modulate specific behaviors and emotional states. For example, ovarian hormones promote female sexual receptivity in the hypothalamic ventromedial nucleus (VMH) and modulate anxiety in the amygdala. Hormone-induced changes within the VMH include structural modifications, such as changes in dendritic spines, dendrite length and the number of synapses. In some situations, dendrite remodeling requires actin polymerization, which depends on phospho-deactivation of the enzyme cofilin, or the ionotropic AMPA-type glutamate receptors, especially the GluA1 and GluA2 subunits. The present experiments used immunohistochemistry to test the hypothesis that ovarian hormone-induced neural plasticity in the VMH and amygdala involves the regulation of phospho-cofilin, GluA1 and GluA2. These proteins were assessed acutely after estradiol administration (0.5, 1.0 and 4.0h), as well as three days after hormone treatment. Both brain regions displayed rapid (4.0h or less) and transient estradiol-induced increases in the level of phospho-cofilin. At the behaviorally relevant time point of three days, differential changes in AMPA receptor subunits were observed. Using Golgi impregnation, the effect of estradiol on amygdala dendrites was examined. Three days after estradiol treatment, an increase in the length of dendrites in the central nucleus of the amygdala was observed. Thus, estradiol initiates structural changes in dendrites in both the VMH and amygdala associated with an early phospho-deactivation of cofilin, followed by dynamic, brain region-specific changes in AMPA receptor composition.

Dendritic arbor of neurons in the hypothalamic ventromedial nucleus in female prairie voles (Microtus ochrogaster).

Female mating behavior in rats is associated with hormone-induced changes in the dendritic arbor of neurons in the ventromedial nucleus of the hypothalamus (VMH), particularly the ventrolateral portion. Regulation of mating behavior in female prairie voles differs substantially from that in rats; therefore, we examined the dendritic morphology of VMH neurons in this species. Sexually naïve adult female prairie voles were housed with a male to activate the females' reproductive endocrine system. Following 48 h of cohabitation, females were tested for evidence of reproductive activation by assessing the level of male sexual interest, after which their brains were processed using Golgi impregnation, which allowed ventrolateral VMH neurons to be visualized and analyzed. Dendritic arborization in the female prairie vole VMH neurons was strikingly similar to that of female rats. The key difference was that in the prairie voles the long primary dendrites extended considerably further than those observed in rats. Although most female voles paired with males exhibited sexual activation, some females did not. These two groups displayed specific differences in their VMH dendrites. In particular, the long primary dendrites were longer in the reproductively active females compared with those in the non-activated females. Overall, dendrite lengths were positively correlated with plasma estradiol levels in females exposed to males, but not in unpaired females. Although causal relationships between the neuroendocrine events, dendrite length, and the outward, behavioral manifestation of reproductive activation cannot be determined from this study, these results suggest an association between ventrolateral VMH dendrite morphology and female mating behavior in prairie voles, akin to what has been observed in female rats.

Oxytocin and dendrite remodeling in the hypothalamus.

For most people, their quality of life depends on their successful interdependence with others, which requires sophisticated social cognition, communication, and emotional bonds. Across the lifespan, new bonds must be forged and maintained, and conspecific menaces must be managed. The dynamic nature of the human social landscape suggests ongoing specific alterations in neural circuitry across several brain systems to subserve social behavior. To discover the biological mechanisms that contribute to normal social activities, animal models of social behavior have been developed. One valuable model system has been female rat sexual behavior, which is governed by cyclic variation of ovarian hormones. This behavior is modulated by the neuropeptide oxytocin (OT) through its actions in the hypothalamic ventromedial nucleus (VMH). The fluctuation of this behavior is associated with dendrite remodeling, like several other examples of behavioral plasticity. This review compares hormone-induced plasticity in the VMH with other examples of dendrite plasticity across the mammalian nervous system, namely the neurobehavioral paradigms of environmental enrichment, chronic stress, and incentive sensitization, which affect the neocortex, hippocampal formation, and ventral striatum, respectively. This comparison suggests that the effects of ovarian hormones on VMH neurons in rats, given the simple dendritic arbor and short time course for dendrite remodeling, provide a dual opportunity for mechanistic and functional studies that will shed light on i) the neural actions of OT that regulate social behavior and, ii) behaviorally relevant dendrite regulation in a variety of brain structures. This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.

Sex differences in the neural circuit that mediates female sexual receptivity.

Female sexual behavior in rodents, typified by the lordosis posture, is hormone-dependent and sex-specific. Ovarian hormones control this behavior via receptors in the hypothalamic ventromedial nucleus (VMH). This review considers the sex differences in the morphology, neurochemistry and neural circuitry of the VMH to gain insights into the mechanisms that control lordosis. The VMH is larger in males compared with females, due to more synaptic connections. Another sex difference is the responsiveness to estradiol, with males exhibiting muted, and in some cases reverse, effects compared with females. The lack of lordosis in males may be explained by differences in synaptic organization or estrogen responsiveness, or both, in the VMH. However, given that damage to other brain regions unmasks lordosis behavior in males, a male-typical VMH is unlikely the main factor that prevents lordosis. In females, key questions remain regarding the mechanisms whereby ovarian hormones modulate VMH function to promote lordosis.

Ovarian hormone-induced reorganization of oxytocin-labeled dendrites and synapses lateral to the hypothalamic ventromedial nucleus in female rats.

Central oxytocin (OT) modulates many social behaviors, including female rat sexual receptivity, quantified as the copulatory stance known as lordosis. The expression of the lordosis response is modulated by OT action in the ventromedial nucleus of the hypothalamus (VMH), as demonstrated by behavioral pharmacology experiments. However, the subcellular localization of OT in this brain region has been unclear. We tested the hypothesis that ovarian hormones reorganize OT-labeled pre- or postsynaptic elements in the fiber complex lateral to the VMH by using immunoelectron microscopy. OT immunolabeling occurred in axonal boutons identified by the presence of small, clear synaptic vesicles and double labeling with the presynaptic markers synaptophysin and vesicular glutamate transporter 2. OT immunoreactivity also was observed in dendritic profiles, verified with double labeling for the dendrite-specific marker microtubule-associated protein 2. Ovarian hormones did not alter the density of axonal boutons; however, estradiol treatment reduced the density of dendritic profiles by 34%. This effect was reversed when progesterone was given subsequent to estradiol. The effect of estradiol treatment was specific to dendrites that lacked OT immunostaining; the density of OT-labeled dendritic profiles remained constant during estradiol treatment. With the estradiol-induced exit of non-OT-labeled dendritic profiles, the remaining OT-labeled dendritic profiles experienced an increase in their number of synaptic contacts. Thus, hormone treatments that mimic the 4-day rat estrous cycle provoke a chemically coded reorganization of dendrite innervation in the fiber plexus lateral to the VMH that may underlie the hormone-specific effect of OT on reproductive behavior.

Genetic and dietary effects on dendrites in the rat hypothalamic ventromedial nucleus.

Both genetic and environmental factors contribute to individual differences in body weight regulation. The present study examined a possible role for the dendritic arbor of hypothalamic ventromedial nucleus (VMH) neurons in a model of diet-induced obesity (DIO) in male rats. Rats were screened and selectively bred for being either susceptible, i.e., exhibiting DIO, or diet resistant (DR) when exposed to a 31% fat diet. A 2x2 experimental design was used, based on these two strains of rats and exposure to rat chow versus the 31% fat diet for seven weeks. Golgi-impregnated neurons were measured for soma size and dendrite parameters, including number, length, and direction. As previously observed, each VMH neuron had a single long primary dendrite. Genetic background and diet did not affect soma size or the number of dendrites of VMH neurons. However, genetic background exerted a main effect on the length of the long primary dendrites. In particular, the long primary dendrites were approximately 12.5% shorter on the VMH neurons in the DIO rats compared with DR rats regardless of diet. This effect was isolated to the long primary dendrites extending in the dorsolateral direction, with these long primary dendrites 19% shorter for the DIO group compared with the DR group. This finding implicates the connectivity of the long primary dendrites on VMH neurons in the control of energy balance. The functional significance of these shortened dendrites and their afferents warrants further study.

Sex differences in the dendritic arbor of hypothalamic ventromedial nucleus neurons.

The hypothalamic ventromedial nucleus (VMH) displays sexual dichotomies in its overall size, neurochemistry, and neuronal morphology. These differences may underlie the sex differences observed in functions mediated by the VMH, such as reproductive behaviors and energy balance. A previous Golgi impregnation analysis of VMH dendrites reported sex differences in total dendrite length in the ventrolateral region of the VMH. The present study tested the hypothesis that this sex difference is localized to a specific dendrite type. VMH neurons were visualized with Golgi impregnation. Overall, male rats displayed significantly longer dendrites than females for VMH neurons. This sex difference was apparent in both the dorsomedial and the ventrolateral subdivisions of the VMH. When dendrites were classified based on dendrite type, namely long primary, short primary and secondary dendrites, the increased length for males was observed for all dendrite types. Furthermore, when long primary dendrites were categorized according to whether they extended in the dorsomedial, ventrolateral, ventromedial or dorsolateral direction, the sex difference in length occurred for all directions. These results indicate that the previously identified dendrite categories for VMH neurons are integral to VMH circuitry for both males and females. Given that the sex difference in dendrite length applied to all dendrite types, the elongated male VMH dendrites may provide additional sites to process input from both local interneurons and extranuclear afferents.

Estradiol and progesterone differentially regulate the dendritic arbor of neurons in the hypothalamic ventromedial nucleus of the female rat (Rattus norvegicus).

The ventromedial nucleus of the hypothalamus (VMH), with its major subdivisions, the dorsomedial and ventrolateral VMH (dmVMH and vlVMH, respectively), has been studied extensively for its role in female sexual behavior. This behavior is controlled by the vlVMH through the cellular actions of estradiol combined with progesterone. Although the effects of treatment with estradiol alone on neuronal morphology in the vlVMH have been examined, much less is known about the combined effects of estradiol and progesterone on neuronal structure. The present study employed Golgi impregnation to investigate the effects of estradiol treatment alone vs. estradiol combined with progesterone treatment on dendritic arbor of VMH neurons. The dendritic arbor of VMH neurons was somewhat different in the vlVMH vs. the dmVMH, with longer and more dendrites in the vlVMH. Estradiol treatment alone caused a marked reduction in the length of long primary dendrites in the vlVMH, but not in the dmVMH. The estradiol-induced retraction of long primary dendrites in the vlVMH was reversed within 4 hours of progesterone treatment. The differences in the dendritic arbors of dmVMH and vlVMH provide further support for the notion that these two regions have different patterns of neural connectivity. In addition, this study is the first to report opposing effects of estradiol alone vs. estradiol plus progesterone on the dendritic arbor of neurons in the vlVMH. These results suggest a structural mechanism for estradiol alone to have a modest effect on mating behavior while setting the stage for its ample expression.

Food restriction alters neuronal morphology in the hypothalamic ventromedial nucleus of male rats.

Several lines of evidence have implicated the hypothalamic ventromedial nucleus (VMH) in the control of caloric homeostasis. For example, the activity of VMH neurons depends on energy availability. We tested the hypothesis that energy balance may involve the remodeling of the dendritic arbor of VMH neurons. We compared two groups of animals: one group had ad libitum access to food, and the other experienced 10-d restricted access to food. As expected, the food-deprived group lost body weight and had reduced levels of glucose, insulin, and leptin. VMH neurons were visualized after Golgi impregnation, and dendrite length was measured. Food deprivation had differential effects on VMH neurons. In particular, within the ventrolateral VMH, for neurons with long primary dendrites (LPDs) that extended in the lateral, but not medial, direction, the LPDs were 31% shorter. These same neurons exhibited a 32% reduction in the number of other dendrites without a change in soma size. In contrast, within the dorsomedial VMH, for neurons with medially, but not laterally, extended LPDs, the soma area was reduced by 28%. However, neurons in the dorsomedial VMH did not display a change in the length or number of dendrites, regardless of LPD direction. Thus, although structural changes during calorie depletion occur in both the dorsomedial and ventrolateral VMH, only the latter exhibits a remodeled dendritic arbor. These results also suggest that the direction of the LPD may be an important marker of neuronal function in the VMH.

Co-localization of midbrain projections, progestin receptors, and mating-induced fos in the hypothalamic ventromedial nucleus of the female rat.

In female rats, sexual behavior requires the convergence of ovarian hormone signals, namely estradiol and progesterone, and sensory cues from the male on a motor output pathway. Estrogen and progestin receptors (ER and PR) are found in neurons in the hypothalamic ventromedial nucleus (VMH), a brain region necessary for lordosis, the stereotypic female copulatory posture. A subset of VMH neurons sends axonal projections to the periaqueductal gray (PAG) to initiate a motor output relay, and some of these projection neurons express PR. Previous studies showed that VMH neurons are activated during mating, based on the expression of the immediate early gene Fos. Many of the activated neurons expressed ER; however, it is not known if such activated neurons co-express PR. Fluorogold, a retrograde tracer, was injected into the PAG of ovariectomized rats to label neurons projecting from the VMH. Hormone-treated animals then were mated, and their brains were immunohistochemically stained for PR and Fos. Of the Fos-positive neurons, 33% were double-labeled for PR, 19% were double-labeled with Fluorogold, and 5% were triple-labeled for Fos, PR, and the retrograde tracer. The majority of triple-labeled neurons were found in the rostral, rather than caudal, portion of the VMH. These results show that PR-containing neurons are engaged during sexual behavior, which suggests that these neurons are the loci of hormonal-sensory convergence and hormonal-motor integration.

Hormonal-neural integration in the female rat ventromedial hypothalamus: triple labeling for estrogen receptor-alpha, retrograde tract tracing from the periaqueductal gray, and mating-induced Fos expression.

The lordosis reflex, a stereotypic posture adopted by female rats during sexual behavior, requires the convergence of a hormonal signal, estrogen, with a descending neural pathway from the ventromedial hypothalamic nucleus (VMH). The VMH contains at least three lordosis-relevant neural populations: estrogen receptor-alpha immunoreactive (ERalpha-IR) neurons, VMH neurons that project to the periaqueductal gray (PAG), and neurons that are ERalpha-IR and project to the PAG. Expression of Fos, a marker for neuronal activation, is increased in the VMH after mating. However, it is unknown which, if any, of these lordosis-relevant populations is activated. The majority of ERalpha-IR and projection neurons were not colocalized. Of the Fos-positive neurons, 41% neither contained ERalpha nor projected to the PAG, and 35% contained ERalpha but did not project to the PAG. Only 25% of Fos-positive neurons projected to the PAG, including projection neurons that expressed ERalpha. Our results suggest that mating activates several distinct VMH neuron types. However, ERalpha-IR neurons are activated to a greater extent compared with the PAG-projecting neurons.

Hypothalamic co-localization of substance P receptor and transneuronal tracer from the lordosis-relevant lumbar epaxial muscles in the female rat.

Previous studies indicated that within the ventromedial hypothalamus (VMH), the estrogen receptor alpha (ERalpha)-containing neurons express substance P (SP), but do not comprise the majority of projection neurons. The present study tested the hypothesis that projection neurons within the VMH express SP receptors (NK1), allowing responsiveness to signals from ERalpha-containing neurons. Pseudorabies virus was transneuronally transported from the lordosis-relevant lumbar epaxial muscles to the VMH, labeling 28% of the NK1-containing neurons in the VMH and surrounding area. Thus, SP may influence sexual behavior through its release from the ERalpha-containing neurons, perhaps synaptically affecting NK1 receptor-labeled lordosis-relevant projection neurons within the VMH.

Estrogen-induced dendritic spine elimination on female rat ventromedial hypothalamic neurons that project to the periaqueductal gray.

Neurons of the ventromedial hypothalamic nucleus (VMH) that project to the periaqueductal gray (PAG) form a crucial segment of the motor pathway that produces the lordosis posture, the hallmark of female rat sexual behavior. One suggested mechanism through which estrogen facilitates lordosis is by remodeling synaptic connectivity within the VMH. For instance, estrogen alters VMH dendritic spine density. Little is known, however, about the local VMH microcircuitry governing lordosis nor how estrogen alters synaptic connectivity within this local circuit to facilitate sexual behavior. The goal of this study was to define better the neuron types within the VMH microcircuitry and to examine whether estrogen alters synaptic connectivity, as measured by dendritic spine density, on VMH projection neurons. A retrograde tracer was injected into the PAG of ovariectomized rats treated with vehicle or estradiol. Retrogradely labeled VMH neurons were filled with Lucifer yellow, then immunostained for estrogen receptor-alpha (ER alpha). VMH neurons that project to the PAG had more dendrites than functionally unidentified neurons. Additionally, VMH projection neurons could be subdivided into those located within the cluster of ER alpha-containing neurons and those medial to the cluster. Estrogen decreased spine density by 57% on the long primary dendrites of VMH projection neurons located within the ER alpha cluster but not on projection neurons medial to the cluster. Only 4% of the VMH projection neurons expressed ER alpha. These results suggest that estrogen may facilitate sexual behavior by decreasing spines selectively, via an indirect mechanism, on a subset of VMH neurons that project to the PAG.