Water deprivation increases Fos expression in hypothalamic corticotropin-releasing factor neurons induced by right atrial distension in awake rats

Atrial mechanoreceptors, sensitive to stretch, contribute in regulating heart rate and intravascular volume. The information from those receptors reaches the nucleus tractus solitarius and then the paraventricular nucleus (PVN), known to have a crucial role in the regulation of cardiovascular function. Neurons in the PVN synthesize CRF, AVP, and oxytocin (OT). Stimulation of atrial mechanoreceptors was performed in awake rats implanted with a balloon at the junction of the superior vena cava and right atrium. Plasma ACTH, AVP, and OT concentrations and Fos, CRF, AVP, and OT immunolabeling in the PVN were determined after balloon inflation in hydrated and water-deprived rats. The distension of the balloon increased the plasma ACTH concentrations, which were higher in water-deprived than in hydrated rats (P < 0.05). In addition, the distension in the water-deprived group decreased plasma AVP concentrations (P < 0.05), compared with the respective control group. The distension increased the number of Fos- and double-labeled Fos/CRF neurons in the parvocellular PVN, which was higher in the water-deprived than in the hydrated group (P < 0.01). There was no difference in the Fos expression in magnocellular PVN neurons after distension in hydrated and water-deprived groups, compared with respective controls. In conclusion, parvocellular CRF neurons showed an increase of Fos expression induced by stimulation of right atrial mechanoreceptors, suggesting that CRF participates in the cardiovascular reflex adjustments elicited by volume loading. Activation of CRF neurons in the PVN by cardiovascular reflex is affected by osmotic stimulation.     

Vasopressin cell groups exhibit strongly divergent responses to copulation and male-male interactions in mice

Arginine vasopressin (AVP) and its nonmammalian homolog arginine vasotocin influence social behaviors ranging from affiliation to resident-intruder aggression. Although numerous sites of action have been established for these behavioral effects, the involvement of specific AVP cell groups in the brain is poorly understood, and socially elicited Fos responses have not been quantified for many of the AVP cell groups found in rodents. Surprisingly, this includes the AVP population in the posterior part of the medial bed nucleus of the stria terminalis (BSTMP), which has been extensively implicated, albeit indirectly, in various aspects of affiliation and other social behaviors. We examined the Fos responses of eight hypothalamic and three extra-hypothalamic AVP-immunoreactive (-ir) cell groups to copulation, nonaggressive male-male interaction, and aggressive male-male interaction in both dominant and subordinate C57BL/6J mice. The BSTMP cells exhibited a response profile that was unlike all other cell groups: from a control baseline of ∼ 5% of AVP-ir neurons colocalizing with Fos, colocalization increased significantly to ∼ 12% following nonaggressive male-male interaction, and to ∼ 70% following copulation. Aggressive interactions did not increase colocalization beyond the level observed in nonaggressive male mice. These results suggest that BSTMP neurons in mice may increase AVP-Fos colocalization selectively in response to affiliation-related stimuli, similar to findings in finches. In contrast, virtually all other cell groups were responsive to negative aspects of interaction, either through elevated AVP-Fos colocalization in subordinate animals, positive correlations of AVP-Fos colocalization with bites received, and/or negative correlations of AVP-Fos colocalization with dominance. These findings greatly expand what is known of the contributions of specific brain AVP cell groups to social behavior.     

Courtship Sounds Advertise Species Identity and Male Quality in Sympatric Pomatoschistus spp. Gobies

Acoustic signals can encode crucial information about species identity and individual quality. We recorded and compared male courtship drum sounds of the sand goby Pomatoschistus minutus and the painted goby P. pictus and examined if they can function in species recognition within sympatric populations. We also examined which acoustic features are related to male quality and the factors that affect female courtship in the sand goby, to determine whether vocalisations potentially play a role in mate assessment. Drums produced by the painted goby showed significantly higher dominant frequencies, higher sound pulse repetition rates and longer intervals between sounds than those of the sand goby. In the sand goby, male quality was predicted by visual and acoustic courtship signals. Regression analyses showed that sound amplitude was a good predictor of male length, whereas the duration of nest behaviour and active calling rate (i.e. excluding silent periods) were good predictors of male condition factor and fat reserves respectively. In addition, the level of female courtship was predicted by male nest behaviour. The results suggest that the frequency and temporal patterns of sounds can encode species identity, whereas sound amplitude and calling activity reflects male size and fat reserves. Visual courtship duration (nest-related behaviour) also seems relevant to mate choice, since it reflects male condition and is related to female courtship. Our work suggests that acoustic communication can contribute to mate choice in the sand goby group, and invites further study.     

Sex-specific activity and function of hypothalamic nonapeptide neurons during nest-building in zebra finches

Vertebrate species from fish to humans engage in a complex set of preparatory behaviors referred to as nesting; yet despite its phylogenetic ubiquity, the physiological and neural mechanisms that underlie nesting are not well known. We here test the hypothesis that nesting behavior is influenced by the vasopressin–oxytocin (VP–OT) peptides, based upon the roles they play in parental behavior in mammals. We quantified nesting behavior in male and female zebra finches following both peripheral and central administrations of OT and V_1a receptor (OTR and V1aR, respectively) antagonists. Peripheral injections of the OTR antagonist profoundly reduce nesting behavior in females, but not males, whereas comparable injections of V1aR antagonist produce relatively modest effects in both sexes. However, central antagonist infusions produce no effects on nesting, and OTR antagonist injections into the breast produce significantly weaker effects than those into the inguinal area, suggesting that antagonist effects are mediated peripherally, likely via the oviduct. Finally, immunocytochemistry was used to quantify nesting-induced Fos activation of nonapeptide neurons in the paraventricular and supraoptic nuclei of the hypothalamus and the medial bed nucleus of the stria terminalis. Nest-building induced Fos expression within paraventricular VP neurons of females but not males. Because the avian forms of OT (Ile⁸-OT; mesotocin) and VP (Ile³-VP; vasotocin) exhibit high affinity for the avian OTR, and because both peptide forms modulate uterine contractility, we hypothesize that nesting-related stimuli induce peptide release from paraventricular vasotocin neurons, which then promote female nesting via peripheral feedback from OTR binding in the oviduct uterus.     

A Small Subset of Fruitless Subesophageal Neurons Modulate Early Courtship in Drosophila

We show that a small subset of two to six subesophageal neurons, expressing the male products of the male courtship master regulator gene products fruitless^Male (fru^M), are required in the early stages of the Drosophila melanogaster male courtship behavioral program. Loss of fru^M expression or inhibition of synaptic transmission in these fru^M(+) neurons results in delayed courtship initiation and a failure to progress to copulation primarily under visually-deficient conditions. We identify a fru^M-dependent sexually dimorphic arborization in the tritocerebrum made by two of these neurons. Furthermore, these SOG neurons extend descending projections to the thorax and abdominal ganglia. These anatomical and functional characteristics place these neurons in the position to integrate gustatory and higher-order signals in order to properly initiate and progress through early courtship.     

Corticotropin-releasing factor (CRF) receptor subtypes in mediating neuronal activation of brain areas involved in responses to intracerebroventricular CRF and stress in rats

Corticotropin-releasing factor (CRF) plays an important role in stress responses through activation of its receptor subtypes, CRF1 receptor (CRF₁) and CRF2 receptor (CRF₂). The parvocellular paraventricular nucleus of the hypothalamus (PVNp), the central nucleus of the amygdala (CeA), and the oval nucleus of the bed nucleus of the stria terminalis (BNSTov), which are rich in CRF neurons with equivocal expression of CRF₁ and CRF₂, are involved in stress-related responses. In these areas, Fos expression is induced by various stimuli, although the functions of CRF receptor subtypes in stimuli-induced Fos expression are unknown. To elucidate this issue and to examine whether Fos is expressed in CRF or non-CRF neurons in these areas, the effects of antalarmin and antisauvagine-30 (AS-30), CRF₁- and CRF₂-specific antagonists, respectively, on intracerebroventricular (ICV) CRF- or 60 min-restraint-induced Fos expression were examined in rats. ICV CRF increased the number of Fos-positive CRF and non-CRF neurons in the PVNp, with the increases being inhibited by antalarmin in CRF and non-CRF neurons and by AS-30 in CRF neurons. Restraint also increased Fos-positive CRF and non-CRF neurons in the PVNp, with the increases being inhibited by antalarmin in the CRF neurons. ICV CRF also increased Fos-positive non-CRF neurons in the CeA and the BNSTov, which was inhibited by AS-30 in both areas, and inhibited by antalarmin in the BNSTov only. Restraint increased Fos-positive non-CRF neurons in the CeA and BNSTov, with the increases being almost completely inhibited by either antagonist. These results indicate that both ICV CRF and restraint activate both CRF and non-CRF neurons in the PVNp and non-CRF neurons in the CeA and BNSTov, and that the activation is mediated by CRF₁ and/or CRF₂. However, the manner of involvement for CRF₁ and CRF₂ in ICV CRF- and restraint-induced activation of neurons differs with respect to the stimuli and brain areas; being roughly equivalent in the CeA and BNSTov, but different in the PVNp. Furthermore, the non-CRF_1&2-mediated signals seem to primarily play a role in restraint-induced activation of non-CRF neurons in the PVNp since the activation was not inhibited by CRF receptor antagonists.     

Corticotropin-releasing factor (CRF) receptor subtypes in mediating neuronal activation of brain areas involved in responses to intracerebroventricular CRF and stress in rats

Corticotropin-releasing factor (CRF) plays an important role in stress responses through activation of its receptor subtypes, CRF1 receptor (CRF₁) and CRF2 receptor (CRF₂). The parvocellular paraventricular nucleus of the hypothalamus (PVNp), the central nucleus of the amygdala (CeA), and the oval nucleus of the bed nucleus of the stria terminalis (BNSTov), which are rich in CRF neurons with equivocal expression of CRF₁ and CRF₂, are involved in stress-related responses. In these areas, Fos expression is induced by various stimuli, although the functions of CRF receptor subtypes in stimuli-induced Fos expression are unknown. To elucidate this issue and to examine whether Fos is expressed in CRF or non-CRF neurons in these areas, the effects of antalarmin and antisauvagine-30 (AS-30), CRF₁- and CRF₂-specific antagonists, respectively, on intracerebroventricular (ICV) CRF- or 60 min-restraint-induced Fos expression were examined in rats. ICV CRF increased the number of Fos-positive CRF and non-CRF neurons in the PVNp, with the increases being inhibited by antalarmin in CRF and non-CRF neurons and by AS-30 in CRF neurons. Restraint also increased Fos-positive CRF and non-CRF neurons in the PVNp, with the increases being inhibited by antalarmin in the CRF neurons. ICV CRF also increased Fos-positive non-CRF neurons in the CeA and the BNSTov, which was inhibited by AS-30 in both areas, and inhibited by antalarmin in the BNSTov only. Restraint increased Fos-positive non-CRF neurons in the CeA and BNSTov, with the increases being almost completely inhibited by either antagonist. These results indicate that both ICV CRF and restraint activate both CRF and non-CRF neurons in the PVNp and non-CRF neurons in the CeA and BNSTov, and that the activation is mediated by CRF₁ and/or CRF₂. However, the manner of involvement for CRF₁ and CRF₂ in ICV CRF- and restraint-induced activation of neurons differs with respect to the stimuli and brain areas; being roughly equivalent in the CeA and BNSTov, but different in the PVNp. Furthermore, the non-CRF_1&2-mediated signals seem to primarily play a role in restraint-induced activation of non-CRF neurons in the PVNp since the activation was not inhibited by CRF receptor antagonists.     

Different signaling molecules responsible for IL-1beta-induced oxytocinergic and vasopressinergic neuron activation in the hypothalamic paraventricular nucleus of the rat

It has been well known that oxytocin (OT)-ergic and arginine vasopressin (AVP)-ergic neurons located in the hypothalamic paraventricular nucleus (PVN) and super optic nucleus (SON) are two kinds of neuroendocrine cells with diverse functions. It has also been demonstrated that immune stimuli can activate these neurons to secret OT and AVP. However, the intracellular signal transduction molecules responsible for the activation of these OT-ergic and AVP-ergic neurons in PVN by immune stimuli are still unclear. In this experiment, the roles of Fos, a protein product of immediate early gene c-fos, and extracellular signal-regulated protein kinase (ERK) 1/2, a signal transduction molecule of mitogen-activated protein kinase (MAPK) family, in these processes were studied in the PVN of the rat following IL-1beta stimulation. The Sprague-Dawley rats were received either 750 ng/kg IL-1beta or equal volume normal saline (NS) injection intravenously (i.v.), and perfused transcardially by 4% paraformaldehyde 3h later. Fos and phosphorylated ERK1/2 (pERK1/2)-immunoreactivity (-ir) was observed in PVN by ABC immunohistochemical staining. Meanwhile, the double staining for OT/Fos, AVP/Fos, OT/pERK1/2 and AVP/pERK1/2 were also processed. The ABC immunohistochemical staining results showed that after an i.v. injection of IL-1beta, the expressions of Fos and pERK1/2 increased evidently in the PVN. Double-staining results showed that a large number of OT-ir cells contained strong Fos-ir products in their nuclei, while only a few of OT cells were double labeled with pERK1/2. As to AVP neurons, great quantities of AVP cells were strongly double labeled with pERK1/2 while there were nearly no Fos-ir nuclei in AVP-ir cells. We conclude from these results that the intracellular IL-1beta-induced events in OT and AVP neurons in PVN are quite different. The OT neurons are mainly activated via Fos without involvement of ERK1/2 pathway, while the latter, but not Fos, involves the intracellular event in AVP neurons activated by IL-1beta.     

Vasotocin neurons in the bed nucleus of the stria terminalis preferentially process social information and exhibit properties that dichotomize courting and non-courting phenotypes

Neurons within the medial bed nucleus of the stria terminalis (BSTm) that produce arginine vasotocin (VT; in non-mammals) or arginine vasopressin (VP; in mammals) have been intensively studied with respect to their anatomy and neuroendocrine regulation. However, almost no studies have examined how these neurons process stimuli in the animals' immediate environment. We recently showed that in five estrildid finch species, VT-immunoreactive (-ir) neurons in the BSTm increase their Fos expression selectively in response to positively-valenced social stimuli (i.e., stimuli that should elicit affiliation). Using male zebra finches, a highly gregarious estrildid, we now extend those findings to show that VT-Fos coexpression is induced by a positive social stimulus (a female), but not by a positive non-social stimulus (a water bath in bath-deprived birds), although the female and bath stimuli induced Fos equally within a nearby control region, the medial preoptic nucleus. In concurrent experiments, we also show that the properties of BSTm VT-ir neurons strongly differentiate males that diverge in social phenotype. Males who reliably fail to court females (“non-courters”) have dramatically fewer VT-ir neurons in the BSTm than do reliable courters, and the VT-ir neurons of non-courters fail to exhibit Fos induction in response to a female stimulus.     

Endogenous oxytocin is necessary for preferential Fos expression to male odors in the bed nucleus of the stria terminalis in female Syrian hamsters

Successful reproduction in mammals depends on proceptive or solicitational behaviors that enhance the probability of encountering potential mates. In female Syrian hamsters, one such behavior is vaginal scent marking. Recent evidence suggests that the neuropeptide oxytocin (OT) may be critical for regulating this behavior. Blockade of OT receptors in the bed nucleus of the stria terminalis (BNST) or the medial preoptic area (MPOA) decreases vaginal marking responses to male odors; lesion data suggest that BNST, rather than MPOA, mediates this effect. However, how OT interacts with sexual odor processing to drive preferential solicitation is not known. To address this issue, intact female Syrian hamsters were exposed to male or female odors and their brains processed for immunohistochemistry for Fos, a marker of recent neuronal activation, and OT. Additional females were injected intracerebroventricularly (ICV) with an oxytocin receptor antagonist (OTA) or vehicle, and then tested for vaginal marking and Fos responses to sexual odors. Colocalization of OT and Fos in the paraventricular nucleus of the hypothalamus was unchanged following exposure to male odors, but decreased following exposure to female odors. Following injections of OTA, Fos expression to male odors was decreased in BNST, but not in MPOA or the medial amygdala (MA). Fos expression in BNST may be functionally relevant for vaginal marking, given that there was a positive correlation between Fos expression and vaginal marking for BNST, but not MPOA or MA. Together, these data suggest that OT facilitation of neuronal activity in BNST underlies the facilitative effects of OT on solicitational responses to male odors.     

Dehydration anorexia is attenuated in oxytocin-deficient mice

Evidence in rats suggests that central oxytocin (OT) signaling pathways contribute to suppression of food intake during dehydration (i.e., dehydration anorexia). The present study examined water deprivation-induced dehydration anorexia in wild-type and OT -/- mice. Mice were deprived of food alone (fasted, euhydrated) or were deprived of both food and water (fasted, dehydrated) for 18 h overnight. Fasted wild-type mice consumed significantly less chow during a 60-min refeeding period when dehydrated compared with their intake when euhydrated. Conversely, fasting-induced food intake was slightly but not significantly suppressed by dehydration in OT -/- mice, evidence for attenuated dehydration anorexia. In a separate experiment, mice were deprived of water (but not food) overnight for 18 h; then they were anesthetized and perfused with fixative for immunocytochemical analysis of central Fos expression. Fos was elevated similarly in osmo- and volume-sensitive regions of the basal forebrain and hypothalamus in wild-type and OT -/- mice after water deprivation. OT-positive neurons expressed Fos in dehydrated wild-type mice, and vasopressin-positive neurons were activated to a similar extent in wild-type and OT -/- mice. Conversely, significantly fewer neurons within the hindbrain dorsal vagal complex were activated in OT -/- mice after water deprivation compared with activation in wild-type mice. These findings support the view that OT-containing projections from the hypothalamus to the hindbrain are necessary for the full expression of compensatory behavioral and physiological responses to dehydration.     

Oxytocin increases heart rate variability in humans at rest: implications for social approach-related motivation and capacity for social engagement

Context

Oxytocin (OT) plays a key regulatory role in human social behaviour. While prior studies have examined the effects of OT on observable social behaviours, studies have seldom examined the effects of OT on psychophysiological markers such as heart rate variability (HRV), which provides an index of individual’s motivation for social behaviour. Furthermore, no studies have examined the impact of OT on HRV under resting conditions, which provides an index of maximal capacity for social engagement.

Objective

To examine the effects of OT on HRV measures in healthy male participants while at rest. OT was hypothesised to increase HRV, compared to placebo, and that the effects would be greatest for a non-linear measure of HRV (the detrended fluctuation scaling exponent).

Methods

Twenty-one male participants were recruited for this study. Participants were non-smokers, not on any medications and reported no history of psychiatric illness, neurological disorder, or any other serious medical condition (e.g. diabetes, cardiovascular disease). The study employed a randomised, placebo-controlled, within-subject, crossover, experimental design.

Main Outcome Measures

HRV was calculated from electrocardiography under a standardized, 10-minute, resting state condition.

Results

As hypothesised, OT increased HRV and these effects were largest using the detrended fluctuation scaling exponent, a non-linear measure. These changes were observed in the absence of any change in state mood, as measured by the profile of mood states. Importantly, participants were unable to correctly guess which treatment they had been assigned at either of the two assessments.

Conclusions

Together with the broader literature on OT and HRV, findings suggest that acute administration of OT may facilitate a fundamental psychophysiological feature of social behaviour, increasing capacity for social engagement. Findings also suggest that HRV changes may provide a novel biomarker of response to OT nasal spray that can be incorporated into research on response to treatment.     

Grin1 Receptor Deletion within CRF Neurons Enhances Fear Memory

Corticotropin releasing factor (CRF) dysregulation is implicated in mood and anxiety disorders such as posttraumatic stress disorder (PTSD). CRF is expressed in areas engaged in fear and anxiety processing including the central amygdala (CeA). Complicating our ability to study the contribution of CRF-containing neurons to fear and anxiety behavior is the wide variety of cell types in which CRF is expressed. To manipulate specific subpopulations of CRF containing neurons, our lab has developed a mouse with a Cre recombinase gene driven by a CRF promoter (CRFp3.0Cre) (Martin et al., 2010). In these studies, mice that have the gene that encodes NR1 (Grin1) flanked by loxP sites (floxed) were crossed with our previously developed CRFp3.0Cre mouse to selectively disrupt Grin1 within CRF containing neurons (Cre+/^fGrin1+). We find that disruption of Grin1 in CRF neurons did not affect baseline levels of anxiety, locomotion, pain sensitivity or exploration of a novel object. However, baseline expression of Grin1 was decreased in Cre+/^fGrin1+ mice as measured by RTPCR. Cre+/^fGrin1+ mice showed enhanced auditory fear acquisition and retention without showing any significant effect on fear extinction. We measured Gria1, the gene that encodes AMPAR1 and the CREB activator Creb1 in the amygdala of Cre+/^fGrin1+ mice after fear conditioning. Both Gria1 and Creb1 were enhanced in the amygdala after training. To determine if the Grin1-expressing CRF neurons within the CeA are responsible for the enhancement of fear memory in adults, we infused a lentivirus with Cre driven by a CRF promoter (LV pCRF-Cre/^fGrin1+) into the CeA of floxed Grin1 mice. Cre driven deletion of Grin1 specifically within CRF expressing cells in the CeA also resulted in enhanced fear memory acquisition and retention. Altogether, these findings suggest that selective disruption of Grin1 within CeA CRF neurons strongly enhances fear memory.     

Differential effects of stress and amphetamine administration on Fos-like protein expression in corticotropin releasing factor-neurons of the rat brain

Corticotropin releasing factor (CRF) appears to be critical for the control of important aspects of the behavioral and physiological response to stressors and drugs of abuse. However, the extent to which the different brain CRF neuronal populations are similarly activated after stress and drug administration is not known. We then studied, using double immunohistochemistry for CRF and Fos protein, stress and amphetamine-induced activation of CRF neurons in cortex, central amygdala (CeA), medial parvocellular dorsal, and submagnocellular parvocellular regions of the paraventricular nucleus of the hypothalamus (PVNmpd and PVNsm, respectively) and Barrington nucleus (Bar). Neither exposure to a novel environment (hole-board, HB) nor immobilization (IMO) increased Fos-like immunoreactivity (FLI) in the CeA, but they did to the same extent in cortical regions. In other regions only IMO increased FLI. HB and IMO both failed to activate CRF+ neurons in cortical areas, but after IMO, some neurons expressing FLI in the PVNsm and most of them in the PVNmpd and Bar were CRF+. Amphetamine administration increased FLI in cortical areas and CeA (with some CRF+ neurons expressing FLI), whereas the number of CRF+ neurons increased only in the PVNsm, in contrast to the effects of IMO. The present results indicate that stress and amphetamine elicited a distinct pattern of brain Fos-like protein expression and differentially activated some of the brain CRF neuronal populations, despite similar levels of overall FLI in the case of IMO and amphetamine.     

A quantitative analysis of social interaction of the guppy, Poecilia reticulata (pisces: Poeciliidae) as a function of population density

Various controlled densities of guppies, Poecilia reticulata, wer observed in order to determine the effects of population density on frequency of courtship and agonistic interactions. Populations with single male exhibit a low level of courtship activity; the presence of a second male increases this level of activity markedly. Populations with a 1:1 sex ratio in densities greater than one pair exhibit a constant mean number of courtship interactions but, with increased crowding, an increasing variance in level of courtship activity. This results in a frequency profile of courtship interaction characteristic of each observed density. Each population density exhibits a density-dependent pattern of social interaction defined quantitatively by frequencies of courtship aggressive interactions at the population level. The contribution of the behaviour of individual males and to this patterning of social interaction in each population was partially determined.     

Vasopressinergic,Oxytocinergic, and Somatostatinergic Neuronal Activity after Adrenalectomy and Immobilization Stress

Twenty days after bilateral adrenalectomy (ADX) or immediately after the last of three 6-h long immobilization periods, the levels of hypothalamic and neurohypophyseal L-[³⁵S]Cys-labeled arginine vasopressin (AVP), oxytocin (OT), and somatostatin-14 (SRIF) (only stressed animals) were measured simultaneously in male Wistar rats, after third ventricular administration of the labeled precursor, via guide-cannulae. The acetic acid-extracted labeled peptide fractions were purified by two sequential HPLC steps. After a 4 h period of labeling, only L-[³⁵S]Cys-AVP was selectively increased in the hypothalami of ADX-ized rats, compared to the sham-operated animals, possibly reflecting a significant activation of the paraventricular parvocellular (PVC) AVP/corticotropin-releasing factor (CRF) neurons. The increased accumulation of neurohypophyseal L-[³⁵S]Cys-labeled AVP and OT in these animals, without changes in the endogenous levels of these peptides, as measured by UV absorbance, also suggests a moderate activation of the magnocellular (MGC) AVP and OT neurons, as a consequence of adrenal insufficiency. In response to immobilization stress, levels of L-[³⁵S]Cys-OT were selectively increased in the hypothalami and corresponding neurohypophyses, 2 h and 4 h after receiving the label, concomitantly with a statistically significant reduction in the stores of OT in the neural lobes. AVP and SRJF biosynthesis remained unaffected by immobilization; the neurohypophyseal AVP stores likewise remained unchanged. These observations suggest the selective activation of MGC-OT neurons in response to chronic immobilization stress. Selective increases in hypothalamic L-[³⁵S]Cys-AVP in ADX-ized rats, and in hypothalamic L-[³⁵S]Cys-OT in chronically stress-immobilized rats, are presented as a measure of PVC-AVP/CRF and MGC-OT neuronal activation, respectively.     

Culture and courtship in vertebrates: a review of social learning and transmission of courtship systems and mating patterns

Female and male animals often choose mates based upon the complementarity of their courtship behaviours and preferences. The importance of this fact on the evolutionary dynamics of populations has long been appreciated. What has not been appreciated is the role that social learning might play in the transmission of systems of courtship behaviour across generations. This paper addresses the social transmission of courtship behavioural traditions in vertebrates. It discusses views of culture in the context of behavioural signals and preferences in courtship. It then reviews empirical evidence for culture-like processes affecting courtship behaviour, focusing on studies of song learning in passerine birds and work on social learning of mating preferences. The paper concludes with potential future directions for research on social traditions in systems of courtship behaviour, including determining mechanisms of transmission, genetic and non-social environmental effects, and selective factors influencing the stability of behavioural traditions over time. By integrating proximate and ultimate questions for the transmission of courtship systems, this work would increase our understanding of the ways individual development, cultural processes, and population evolution influence, and are in turn influenced by, one another.     

Enhanced corticosterone concentrations and attenuated Fos expression in the medial amygdala of female oxytocin knockout mice exposed to psychogenic stress

Centrally released oxytocin (OT) is believed to attenuate the response of the hypothalamic-pituitary-adrenal (HPA) axis to psychogenic stress. To test this hypothesis, we measured plasma corticosterone concentrations and Fos-immunoreactive protein in the paraventricular nucleus of the hypothalamus (PVN) and limbic brain areas of female wild-type and OT knockout mice that were exposed to a shaker platform, a predominantly psychogenic stress. Plasma corticosterone concentrations after shaker stress were higher in female OT knockout mice than wild-type mice. Genotypic differences in the corticosterone response after shaker stress persisted across all stages of the estrous cycle and when mice were conditioned to repeated shaker stress. Shaker stress activated Fos in OT-positive neurons of wild-type mice and corticotropin-releasing hormone-positive, but not vasopressin-positive, neurons within the PVN of wild-type and OT knockout mice. Fos expression was also increased after shaker stress in the bed nucleus of the stria terminalis, medial and central nuclei of the amygdala, medial preoptic area, and the paraventricular nucleus of the thalamus of wild-type and OT knockout mice. However, Fos expression in the medial amygdala was significantly lower in female OT knockout mice than wild-type mice. Our findings indicate heightened stress-induced corticosterone release in female OT knockout mice. Therefore, the results suggest that OT pathways play a role in attenuating the HPA axis response to psychogenic stress in female mice.     

Peripheral CRF activates myenteric neurons in the proximal colon through CRF(1) receptor in conscious rats

Corticotropin-releasing factor (CRF) injected peripherally induces clustered spike-burst activity in the proximal colon through CRF(1) receptors in rats. We investigated the effect of intraperitoneal CRF on proximal colon ganglionic myenteric cell activity in conscious rats using Fos immunohistochemistry on the colonic longitudinal muscle/myenteric plexus whole mount preparation. In vehicle-pretreated rats, there were only a few Fos immunoreactive (IR) cells per ganglion (1.2 +/- 0.6). CRF (10 microg/kg ip) induced Fos expression in 19.6 +/- 2.1 cells/ganglion. The CRF(1)/CRF(2) antagonist astressin (33 microg/kg ip) and the selective CRF(1) antagonist CP-154,526 (20 mg/kg sc) prevented intraperitoneal CRF-induced Fos expression in the proximal colon (number of Fos-IR cells/ganglion: 2.7 +/- 1.2 and 1.0 +/- 1.0, respectively), whereas atropine (1 mg/kg sc) had no effect. Double labeling of Fos with protein gene product 9.5 revealed the neuronal identity of activated cells that were encircled by varicose fibers immunoreactive to vesicular acetylcholine transporter. Fos immunoreactivity was mainly present in choline acetyltransferase-IR nerve cell bodies but not in the NADPH-diaphorase-positive cells. These results indicate that peripheral CRF activates myenteric cholinergic neurons in the proximal colon through CRF(1) receptor.