Enhancement of peripheral nerve regeneration due to treadmill training and electrical stimulation is dependent on androgen receptor signaling

Moderate exercise in the form of treadmill training and brief electrical nerve stimulation both enhance axon regeneration after peripheral nerve injury. Different regimens of exercise are required to enhance axon regeneration in male and female mice (Wood et al.: Dev Neurobiol 72 (2012) 688–698), and androgens are suspected to be involved. We treated mice with the androgen receptor blocker, flutamide, during either exercise or electrical stimulation, to evaluate the role of androgen receptor signaling in these activity‐based methods of enhancing axon regeneration. The common fibular (CF) and tibial (TIB) nerves of thy‐1‐YFP‐H mice, in which axons in peripheral nerves are marked by yellow fluorescent protein (YFP), were transected and repaired using CF and TIB nerve grafts harvested from non‐fluorescent donor mice. Silastic capsules filled with flutamide were implanted subcutaneously to release the drug continuously. Exercised mice were treadmill trained 5 days/week for 2 weeks, starting on the third day post‐transection. For electrical stimulation, the sciatic nerve was stimulated continuously for 1 h prior to nerve transection. After 2 weeks, lengths of YFP+ profiles of regenerating axons were measured from harvested nerves. Both exercise and electrical stimulation enhanced axon regeneration, but this enhancement was blocked completely by flutamide treatments. Signaling through androgen receptors is necessary for the enhancing effects of treadmill exercise or electrical stimulation on axon regeneration in cut peripheral nerves. © 2013 Wiley Periodicals, Inc. Develop Neurobiol 74: 531–540, 2014     

Estrogen signaling is necessary for exercise‐mediated enhancement of motoneuron participation in axon regeneration after peripheral nerve injury in mice

Thousands of people each year suffer from peripheral nerve injury. Treatment options are limited, and recovery is often incomplete. Treadmill exercise can enhance nerve regeneration; however, this appears to occur in a sex‐dependent manner. Females respond best to short duration, high speed interval training; whereas, males respond best to slower, continuous training. Previous studies have shown a role for testosterone in this process, but the role of estrogen is unknown. To evaluate the role of estrogen signaling in treadmill exercise, we blocked estrogen receptor (ER) signaling during treadmill exercise in males and female wild type mice. The right common fibular (CF) branch of the sciatic nerve was cut and repaired with fibrin glue that contained the ER antagonist ICI 182,780. Estradiol‐filled or blank Silastic capsules were implanted subcutaneously at the time of nerve transection. Starting three days post‐transection, exercised mice received treadmill training using the paradigm appropriate to their sex 5 days a week for 2 weeks. Fourteen days after the initial nerve transection, motoneurons whose axons had regenerated at least 1.5 mm distal to the original cut sites were labeled with a retrograde tracer. Regeneration was quantified by counting the number of fluorescent labeled motoneurons in the lumbar region of the spinal cord. Both treadmill training and estradiol administration increased the number of motoneurons participating in axon regeneration, but these effects were blocked by ER antagonist treatment. Estrogen signaling is important for the enhancing effects of treadmill exercise on motoneuron participation after peripheral nerve cut. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1133–1143, 2017     

Testosterone and estrogen differently effect Th1 and Th2 cytokine release following trauma-haemorrhage.

The object of the study was to determine whether male and female sex steroids produce divergent effects on Th1 and Th2 cytokine release following trauma-haemorrhage. Recent studies indicate that androgens are responsible for the depressed splenocyte Th1 cytokine release in males following trauma-haemorrhage. In contrast, female mice maintain their Th1 cytokine release capacity following trauma-haemorrhage. Nonetheless, the effect of male and female sex steroids on Th1 and Th2 cytokine release following trauma-haemorrhage remains unknown. Male C3H/HeN mice were castrated and treated with pellets containing either vehicle, 5alpha-dihydrotestosterone (DHT), 17beta-estradiol (estradiol), or a combination of both steroid hormones, for 14 days prior to soft-tissue trauma (i.e. laparotomy) and haemorrhagic shock (35+/-5 mmHg for 90 min followed by adequate fluid resuscitation) or sham operation. Untreated male and female mice, as well as DHT treated female mice, served as control groups. Twenty-four hours later the animals were sacrificed, plasma obtained and splenocytes harvested. Plasma DHT and estradiol levels in treated animals were comparable with intact male and female mice, respectively. A significant depression of splenocyte Th1 cytokines, i.e. IL-2, IFN-gamma, was observed in DHT treated castrated animals, DHT treated females, and untreated males following trauma-haemorrhage, as opposed to maintained Th1 cytokine release in estradiol treated and estradiol/DHT treated castrated animals and females. The release of the anti-inflammatory cytokine IL-10 was markedly increased in DHT treated mice and males subjected to trauma-haemorrhage compared to shams, but decreased in estrogen treated mice and females under such conditions. These results suggest that male and female sex steroids differentially affect the release of Th1 and Th2 cytokines following trauma-haemorrhage and should be further studied for their potential to modulate splenocyte function in trauma victims.     

Sex hormone-dependent brain maturation and sexual behaviour in rats.

In male and female rats the endogenous steroid and gonadotrophin secretion was inhibited by injecting high doses of chlormadinone acetate (CmAc) from day 14 to 24 of life, i. e. during the period of brain maturation. In adulthood the males treated prepubertally with CmAc exhibited reduced sexual activity and fertility, whereas the females did not differ from the controls. More complete sex hormone deficiency during brain maturation was achieved by castration on day 14 of life. Controls were castrated at normal puberty time (40--60 days). Both groups were then substituted with androgens or oestrogens. In the females castrated on day 14 no impairment of sexual behaviour was observed as compared to the later castrated controls. In contrast, the early castrated males showed delayed onset of mounting behaviour. At autopsy, the weights of their sex organs were found to be lower than in the controls despite equal testosterone replacement for several months. These findings speak in favour of a permanently diminished responsiveness to androgens in males having been exposed to more or less severe androgen deficiency during sex specific brain maturation. Hence, the maturation of a male hypothalamus as well as the differentiation appears to depend at least in part on the presence of androgens, whereas in females it runs without hormonal influence.     

Gonadal hormones modulate the display of conditioned defeat in male Syrian hamsters

It has been widely reported that gonadal hormones influence the display of aggression in Syrian hamsters; conversely, much less is known about whether gonadal hormones modulate submissive/defensive behaviors in these animals. Following social defeat, male hamsters no longer display normal territorial aggression but instead display submissive/defensive behavior in the presence of a smaller opponent, a phenomenon we have termed conditioned defeat (CD). The purpose of the present study was to examine the effect of gonadal hormones on the display of CD in male hamsters. In Experiment 1, males were castrated or sham-operated. The castrated males were significantly more submissive following social defeat relative to their intact counterparts. The increased submissive behavior in the castrated males during CD testing was particularly surprising, given the fact that they were attacked significantly less during CD training. In Experiment 2a, males were castrated and given hormone replacement. Castrated males treated with testosterone or dihydrotestosterone displayed significantly less submissive behavior following social defeat than did those treated with cholesterol or estradiol. Finally, in Experiment 2b, there was no effect of hormone replacement on aggressive behavior in non-defeated hamsters suggesting that the decrease in submissive behavior in males treated with dihydrotestosterone or testosterone is specific to being previously defeated. Taken together the data indicate that the presence of androgens reduces the display of submission in defeated male hamsters. More importantly, these findings suggest that androgens may have a protective effect against the development of depression-like or anxiety-like behaviors following exposure to an ethologically relevant stressor.     

Low Intensity Repetitive Transcranial Magnetic Stimulation Does Not Induce Cell Survival or Regeneration in a Mouse Optic Nerve Crush Model

Low intensity repetitive Transcranial Magnetic Stimulation (LI-rTMS), a non-invasive form of brain stimulation, has been shown to induce structural and functional brain plasticity, including short distance axonal sprouting. However, the potential for LI-rTMS to promote axonal regeneration following neurotrauma has not been investigated. This study examined the effect of LI-rTMS on retinal ganglion cell (RGC) survival, axon regeneration and levels of BDNF in an optic nerve crush neurotrauma model. Adult C57Bl/6J mice received a unilateral intraorbital optic nerve crush. Mice received 10 minutes of sham (handling control without stimulation) (n=6) or LI-rTMS (n = 8) daily stimulation for 14 days to the operated eye. Immunohistochemistry was used to assess RGC survival (β-3 Tubulin) and axon regeneration across the injury (GAP43). Additionally, BDNF expression was quantified in a separate cohort by ELISA in the retina and optic nerve of injured (optic nerve crush) (sham n = 5, LI-rTMS n = 5) and non-injured mice (sham n = 5, LI-rTMS n = 5) that received daily stimulation as above for 7 days. Following 14 days of LI-rTMS there was no significant difference in mean RGC survival between sham and treated animals (p>0.05). Also, neither sham nor LI-rTMS animals showed GAP43 positive labelling in the optic nerve, indicating that regeneration did not occur. At 1 week, there was no significant difference in BDNF levels in the retina or optic nerves between sham and LI-rTMS in injured or non-injured mice (p>0.05). Although LI-rTMS has been shown to induce structural and molecular plasticity in the visual system and cerebellum, our results suggest LI-rTMS does not induce neuroprotection or regeneration following a complete optic nerve crush. These results help define the therapeutic capacity and limitations of LI-rTMS in the treatment of neurotrauma.     

Sex differences in adrenal function in the lizard Cnemidophorus sexlineatus: II. Responses to acute stress in the laboratory.

Circulating concentrations of plasma corticosterone and gonadal steroids were measured in intact and gonadectomized male and female lizards (Cnemidophorus sexlineatus) following acute stress (handling) in the laboratory. There was a significant increase in plasma corticosterone after stress. Whereas intact females exhibited greater concentrations of corticosterone relative to intact males, ovariectomized females exhibited lower concentrations of corticosterone relative to castrated males. In addition to sex differences in corticosterone responses to gonadectomy, progesterone was elevated by stress in both intact and ovariectomized females but not in males. Corticosterone adjusted for castration and handling in males was negatively correlated with the plasma androgen level. The adrenal responsiveness of males to acute stress may be attenuated by androgens presumably secreted by the testis. Not only does adrenal function influence reproduction, but adrenal responses differ between males and females, and appear to be influenced by the gonadal axis. The sex differences in adrenal responses to stress likely reflect different reproductive strategies and nutritional requirements of males and females during the breeding season.     

Sex differences in pectoral muscles but not in pectoral fins in the three‐spined stickleback Gasterosteus aculeatus

The pectoral muscle index ( I _PM)( I _PM = 100 M _PM M⁻¹, where M _PM and M are the pectoral muscle and body masses, respectively) fin‐area and fin ray length were studied over a year in male and female three‐spined stickleback Gasterosteus aculeatus from a marine population (Öresund, Sweden) kept under simulated natural light and temperature conditions. A castration‐replacement experiment was used to test androgen effects on the I _PM, fin‐area and fin ray length. Non‐breeding males were castrated or sham‐operated in winter ( i.e . the fish had low levels of androgens). Castrated control and sham‐operated fish were implanted with empty Silastic capsules and castrated groups with capsules containing the androgens testosterone or 11‐ketoandrostenedione into the abdominal cavity. The experiment was terminated after 41 days, when the controls had matured. No morphological differences were found in pectoral fins between sexes during the year, except during the peak breeding season (May), where females showed larger fin‐area and longer fin ray in length compared to males. No effects of androgens treatment or of castration on pectoral fin‐area or fin ray length was observed. Breeding and non‐breeding males showed higher I _PM compared to females. The lower I _PM in females than in males could not be explained by the larger gonads in the former alone, as a sex difference in I _PM was still present after deduction of the ovaries from the female body mass. The I _PM was higher in sham‐operated compared to castrated fish. No effects of androgens treatment on I _PM was observed.     

Gender differences in murine airway responsiveness and lipopolysaccharide-induced inflammation

The roles of gender and sex hormones in lung function and disease are complex and not completely understood. The present study examined the influence of gender on lung function and respiratory mechanics in naive mice and on acute airway inflammation and hyperresponsiveness induced by intratracheal LPS administration. Basal lung function characteristics did not differ between naive males and females, but males demonstrated significantly greater airway responsiveness than females following aerosolized methacholine challenge as evidenced by increased respiratory system resistance and elastance (p < 0.05). Following LPS administration, males developed more severe hypothermia and greater airway hyperresponsiveness than females (p < 0.05). Inflammatory indices including bronchoalveolar lavage fluid total cells, neutrophils, and TNF-alpha content were greater in males than in females 6 h following LPS administration (p < 0.05), whereas whole-lung TLR-4 protein levels did not differ among treatment groups, suggesting that differential expression of TLR-4 before or after LPS exposure did not underlie the observed inflammatory outcomes. Gonadectomy decreased airway inflammation in males but did not alter inflammation in females, whereas administration of exogenous testosterone to intact females increased their inflammatory responses to levels observed in intact males. LPS-induced airway hyperresponsiveness was also decreased in castrated males and was increased in females administered exogenous testosterone. Collectively, these data indicate that airway responsiveness in naive mice is influenced by gender, and that male mice have exaggerated airway inflammatory and functional responses to LPS compared with females. These gender differences are mediated, at least in part, by effects of androgens.     

Increased fat deposition in injured skeletal muscle is regulated by sex-specific hormones

Sex differences in skeletal muscle regeneration are controversial; comparisons of regenerative events between sexes have not been rigorously defined in severe injury models. We comprehensively quantified inflammation and muscle regeneration between sexes and manipulated sex-specific hormones to determine effects on regeneration. Cardiotoxin injury was induced in intact, castrated and ovariectomized female and male mice; ovariectomized mice were replaced with low- or high-dose 17-β estradiol (E(2)) or progesterone (P4). Extent of injury was comparable between intact mice, but females were more efficient in removal of necrotic debris, despite similar tissue levels of inflammatory cells and chemokines. Myofiber size during regeneration was equivalent between intact mice and after castration or ovariectomy (OVX) but was decreased (P < 0.001) in ovariectomized mice with high-dose E(2) replacement. Intermuscular adipocytes were absent in uninjured muscle, whereas adipocyte area was increased among regenerated myofibers in all groups. Interestingly, intermuscular fat was greater (P = 0.03) in intact females at day 14 compared with intact males. Furthermore, castration increased (P = 0.01) and OVX decreased adipocyte accumulation. After OVX, E(2), but not P4, replacement decreased (P ≤ 0.03) fat accumulation. In conclusion, sex-dependent differences in regeneration consisted of more efficient removal of necrosis and increased fat deposition in females with similar injury, inflammation, and regenerated myofiber size; high-dose E(2) decreased myofiber size and fat deposition. Adipocyte accumulation in regenerating muscle was influenced by sex-specific hormones. Recovery following muscle injury was different between males and females, and sex-specific hormones contributed to these differences, suggesting that sex-specific treatments could be beneficial after injury.     

Short-term treadmill running in the rat: what kind of stressor is it?

The use of short-term (1-5 days) treadmill running is becoming increasingly common as a model to study physiological adaptations following the exercise. Although the beneficial effects of acute exercise seem clear, a paucity of data exist describing potential markers of stress in response to forced running. We subjected male and female Sprague-Dawley rats to 0, 1, 2, 5, or 10 days of treadmill running. Twenty-four to 32 h after the last bout of exercise animals were killed and examined for training-induced changes in several physiological variables. No effect of skeletal citrate synthase activity was observed in the male animals after any duration, and only at 10 days of running did females show a significant increase in citrate synthase. Myocardial heat shock protein 72 (HSP72) content was higher in male rats than female rats, and exercise led to increased HSP72 in both sexes, although the time course was different between males and females. Animals displayed several markers of systemic stress in response to the treadmill running, and this was done in a sex-dependent manner. Serum corticosterone was significantly elevated in both sexes 24 h after exercise in three of four exercise groups. Corticosterone-binding globulin was higher in females, and decreased after running in female rats. Body and spleen weights decreased in males (but not females) in response to the exercise training, and running did not alter adrenal gland weights in either sex. These data indicate that in response to short-term treadmill running both male and female rats show signs of systemic stress, but that the pattern of changes occurs in a sex-specific manner.     

Male-induced puberty acceleration in young female wild mice: hormonal regulation and source of pheromonal cue

Experiments were designed to examine the influence of adult males on the rate of sexual maturation in young female wild mice. In one experiment, young females were raised in presence of adult males, adult females and in absence of any individual, while in another, they were exposed to urines of: (1) castrated males, (2) spayed females, (3) castrated and TP-treated males, (4) castrated and placebo-injected males. Female maturation as measured by age at vaginal opening and first vaginal oestrus was accelerated by presence of adult males, whereas presence of adult females considerably delayed the vaginal opening and the appearance of first oestrus in young females. In the other set of the experiments, urine from castrated or castrated and placebo-injected males was ineffective in inducing early puberty while urine from spayed females highly delayed the sexual maturation. By contrast, urine from castrated and TP-treated males accelerated the puberty more or less like normal males. The results indicate that male's chemosignal accelerating puberty in young females is present in urine and its production is under the control of androgens. However, the female-originating urinary pheromone which delays the puberty in young females is not regulated by ovarian hormones.     

Effects of castration and sex steroids on sexually dimorphic development of the mouse submandibular gland

The aims of this study were to characterize sexual dimorphism in the submandibular glands of young adult mice and to determine how sex differences arise during postnatal development. In the mouse submandibular glands, prominent sexual dimorphism was observed at 30 days of age, when the male gland was superior in both the relative occupied area (ROA) and the mitotic rate of the granular convoluted tubules (GCT) to those of the female. By neonatal castration, this sexual dimorphism was abolished, and the intraglandular structures of castrated males were similar to those of normal females. In castrated mice of both sexes, daily treatment with testosterone and 5 alpha-dihydrotestosterone for 10 days from 20 days induced only the ROA of the GCT to increase to the normal male levels but not those of the other three regions of the glands, the acini, intercalated ducts and excretory striated ducts. Testosterone responsiveness of the glands, considering both the glandular weight gain and the mitotic rate of the GCT, was significantly higher in castrated males than in castrated females. On the other hand, 17 beta-estradiol had no effect on the glands of castrated mice. Therefore, the present study suggests that the testicular hormones are responsible for the masculine development of GCT of the glands, but not the ovarian hormones, and that there is a sex difference in the responsiveness of the glands to testosterone, which is more effective in males than in females.     

Sex differences,laterality, and hormonal regulation of androgen receptor immunoreactivity in rat hippocampus

Sex differences, laterality, and hormonal regulation of androgen receptor (AR) immunoreactivity in rat hippocampal CA1 pyramidal cells were examined using the PG21 antibody. Adult male rats were either castrated or sham-operated at least 2 weeks prior to sacrifice. Gonadally intact females were sacrificed on the day of proestrus. Animals received an injection of either testosterone propionate (TP) or vehicle 2 h prior to sacrifice. Within CA1, both the intensity of staining and the number of AR+ cells were assessed. AR immunostaining was detected in all the groups with marked variation among them. The overall ranking of staining intensity was: gonadally intact males > females given TP > castrated males given TP > females > castrated males given vehicle. The number of AR+cells within subregions of CA1 showed the same basic pattern: among control-treated animals, gonadally intact males have more than females, but castrated males have the least, and acute TP treatment increases the number in both sexes. The increased level of AR immunoreactivity in CA1 of castrated males following acute TP treatment suggests that testicular androgens in adulthood normally increase AR immunoreactivity there, producing a sex difference favoring males in gonadally intact animals. We also found a higher number of AR+ CA1 cells on the left than on the right, but only in gonadally intact males and in females given TP. These results suggest that a laterality of AR distribution in the rat hippocampus may lead to lateralities in hippocampal structure and function.     

Hormones and social behavior in the lizard, Anolis carolinensis

The purpose of this experiment was to study the effects of homologous and heterologous gonadal hormones on sexual and aggressive behavior in a reptilian species. Thirty adult male and thirty adult female lizards (Anolis carolinensis) were divided into 10 groups of six each (five groups per sex) and each group was given one of five treatments: either left intact, sham-castrated and injected with the hormone vehicle, castrated and injected with the hormone vehicle, castrated and injected with estradiol benzoate, or castrated and injected with testosterone propionate. After a week of visual isolation and daily hormone injection, animals were tested four times, twice with a stimulus animal of each sex. Females treated with estrogen were receptive, but did not court. Females treated with androgen were receptive and also courted and pursued stimulus females as frequently as males given androgen. No males in any group were receptive, and thus the female appears to be more capable of heterotypical sexual behavior than the male. Castrated males failed to court. Courtship and pursuit of stimulus females was readily stimulated in males with testosterone, and weakly stimulated by estrogen. Intact males were very aggressive, but lower levels of aggression were independent of gonadal hormones, as was subordination (head-nodding). The results for aggression and subordination are interpreted with reference to naturally-occurring Anolis behavior, and the results for sexual behavior are compared with similar experiments with mammals and birds.     

Quantitative morphology and carbohydrate histochemistry of the mouse submandibular gland following prepubertal castration.

The endocrinologic basis for morphological and biochemical sex differences in the mouse submandibular gland have not been clarified. Previous studies have emphasized the maintenance of glandular differences in adult animals, rather than considering the factors responsible for their developmental etiology. Male CD-1 mice were castrated at intervals between 10 and 50 days of age and killed at 100 days. The quantitative development of granular tubules and the carbohydrate histochemistry of the submandibular glands were compared to untreated males and females. The area of granular tubules increased with age at castration. Nested analysis of variance indicated significant differences among treatments and among sections within individual glands. No group of castrated males had a greater development of tubules than untreated females. Carbohydrate histochemistry demonstrated an increase in carboxylated mucosubstances in the acinar cells and granular tubule cells of castrated animals.     

Regulation of hormonally mediated maternal nest structure in the mouse (Mus musculus) as a function of neonatal hormone manipulation

Nest building in mice was evaluated by amount of hay used daily and type of nest constructed. Increased amounts of hay were utilized and maternal style nests constructed following treatment with appropriate ratios of oestrogen plus progesterone. This response occurred only in the female. Following neonatal injection of testosterone propionate the female no longer showed the maternal nest building response. When males were castrated on day 1, they showed a response to oestrogen and progesterone which was similar to the female response. Thus, the hormonally elicited maternal nest style is sex limited due to early exposure to androgens and therefore resembles sexual responsiveness and the ovulatory mechanism which can similarly be suppressed as a result of the presence of androgen.     

Sexual dimorphisms in a neuromuscular system regulating courtship in the green anole lizard: effects of season and androgen treatment.

During the breeding season, male green anoles (Anolis carolinensis) court females by extending a red throat fan called a dewlap. Motoneurons controlling this sexually dimorphic behavior are located in two portions of the brain stem: (a) the vagal portion of nucleus ambiguus (AmbX), and (b) the region containing the glossopharyngeal portion of nucleus ambiguus and the ventral motor nucleus of the facial nerve (AmbIX/VIImv). These motoneurons project to the ceratohyoideus muscle via the ramus pharyngo-laryngeus IX+X. To investigate the effects of season on and androgen regulation of neural and peripheral structures controlling dewlap extension, two experiments were conducted: (a) During the breeding and nonbreeding seasons, motoneuron number, soma size, and nucleus size were investigated in intact males and females and in castrated males treated with a testosterone propionate (TP) or a blank Silastic capsule. (b) Cross-sectional area of the nerve and muscle fiber size, number, and density were investigated in the four treatment groups during the breeding season only. No significant differences were found in motoneuron number. In the breeding season, subtle male-biased sex differences existed in both AmbX and AmbIX/VIImv soma size. Nerve cross-sectional area and muscle fiber size and number were substantially larger in males than females. Muscle fiber density was higher in females. No consistent effects due to season or androgen treatment were detected, although characteristics of motoneurons were in some cases slightly larger in the nonbreeding season. These results suggest that, while parallels to behavior exist between the sexes, morphological changes in adulthood in the dewlap motoneurons and muscle do not normally regulate courtship behavior in the male green anole.     

Role of postnatal androgens in sexual differentiation of the lordosis-inhibiting effect of central injections of cholecystokinin

The neuropeptide cholecystokinin (CCK) inhibits lordosis behavior when infused into the ventromedial nucleus of the hypothalamus (VMN) of female rats and has no effect when infused into the VMN of male rats. To test whether this sex difference develops under the control of perinatal steroids, male rats were castrated or given sham surgeries within 3 h of birth and female rats were injected with either 0 or 100 micrograms testosterone propionate on postnatal day 5. As adults, these rats were castrated as necessary, implanted with unilateral cannulae directed at the VMN, and tested for their ability to display female sexual behavior and to respond to CCK. Neonatal castration of males prevented defeminization of this response. When treated with 5 micrograms estradiol benzoate (EB), neonatally castrated males showed both lordosis behavior and a profound inhibition of that behavior after infusions of CCK. Neonatally castrated males did not display lordosis behavior when treated with 2 micrograms EB. Control males showed no lordosis behavior and, therefore, no response to CCK. Both doses of EB induced lordosis behavior in neonatally androgenized females. Significantly, these neonatally androgenized females were less responsive to CCK's inhibition of lordosis and were also anovulatory. These results imply that androgens alter the development of CCK responsive circuits as well as defeminize cyclic gonadotropin release. Levels of 125I-sCCK-8 binding in the VMN were correlated closely with an individual's ability to respond to sCCK-8. In summary, the inhibition of female sexual behavior caused by exogenously administered CCK in normal adult female rats appears to be controlled at least partially by levels of CCK receptors in the VMN and to differentiate under the control of perinatally present testosterone.     

Sex-specific p38 MAP kinase activation following trauma-hemorrhage: involvement of testosterone and estradiol

Although immune functions are markedly depressed in males and not in proestrous females following trauma-hemorrhage (T-H), the mechanisms responsible for the divergent responses remain unknown. Because sex steroids modulate the activation of p38, our aim was to determine whether differences in the activation of p38 by phosphorylation (p38-P) might contribute to the sex-dimorphic immune response following T-H. The effects of testosterone and estradiol on the activation of p38 were also examined. Intact male mice (C3H/HeN), castrated males treated with vehicle, 5alpha-dihydrotestosterone (DHT), or 17beta-estradiol, and proestrous females were subjected to trauma (i.e., midline laparotomy) and hemorrhagic shock (35 +/- 5 mmHg for 90 min and resuscitation) or sham operation. At 2 h thereafter, splenic (SMphi) and peritoneal macrophages (PMphi) were harvested and cultured (with 10 microg/ml LPS), and Western blot analysis was carried out for quantification of p38 and p38-P. Sex, testosterone and estradiol plasma levels, and T-H did not alter the constitutive expression of p38 in SMphi and PMphi. In contrast, the activated form of p38 (p38-P) was markedly increased in SMphi and PMphi from female shams compared with male shams. Moreover, the phosphorylation of p38-P increased in males after T-H, whereas it decreased in females under those conditions. Castration before T-H prevented the increase in p38-P in males. Castrated animals treated with DHT displayed increased p38-P following T-H, whereas 17beta-estradiol had no effect on p38-P in castrated mice. Thus 1) sex influences the activation of p38 MAP kinase, 2) DHT is responsible for the increased activation of p38 in male mice, and 3) this sex-specific activation of p38 might be responsible for the sexually dimorphic immune response following T-H.