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The development, at the experimental level, of therapeutic strategies based on natural products to attenuate neurological alterations in degenerative disorders has gained attention. Antioxidant molecules exhibit both anti-inflammatory and neuroprotective properties. Alpha-mangostin (alpha-Man) is a natural xanthonoid isolated from the mangosteen tree with demonstrated antioxidant and cytoprotective properties. In this study, we investigated the antioxidant and protective properties of alpha-Man, both ex vivo and in vivo. We assessed the mitochondrial reductant capacity and oxidative damage to lipids in rat cortical slices, and several endpoints characteristic of physiological stress in the nematode, Caenorhabditis elegans (C. elegans), upon exposure to the parkinsonian neurotoxin, 6-hydroxydopamine (6-OHDA). In rat cortical slices, alpha-Man (25 and 50 mu M) reduced the 6-OHDA (100 mu M)-induced oxidative damage to lipid levels, but failed to reverse loss in cell viability. In wild-type (N2) C. elegans, alpha-Man (5-100 mu M) protected against 6-OHDA (25 mM)-induced decrease in survival when administered either as pre- or post-treatment. Protective effects of alpha-Man were also observed on survival in the VC1772 strain (skn-1 KO-) exposed to 6-OHDA, though the extent of the protection was lesser than in the wild-type N2 strain. However, alpha-Man (5-50 mu M) failed to attenuate the 6-OHDA-induced motor alterations in the N2 strain. The loss of lifespan induced by 6-OHDA in the N2 strain was fully reversed by high concentrations of alpha-Man. In addition, while 6-OHDA decreased the expression of glutathione S-transferase in the CL2166 C. elegans strain, alpha-Man preserved and stimulated the expression of this protein. alpha-Man (25 mu M) also prevented 6-OHDA-induced dopaminergic neurodegeneration in the BZ555 C. elegans strain. Altogether, our novel results suggest that alpha-Man affords partial protection against several, but not all, short-term toxic effects induced by 6-OHDA in cortical slices and in a skn-1-dependent manner in C. elegans.

Infertility is a growing worldwide public health problem, and stress is a main factor exerting detrimental effects on female reproduction. However, knowledge regarding the neuroendocrine changes caused by chronic stress in females is limited. Therefore, this study assessed the effects of stress on hormones that control female reproduction during the proestrus and diestrus stages of the estrous cycle, as well as its effects on fertility. Adult females were assigned to either a control or a stress group. Stress consisted of exposure, for 15 min, to cold-water immersion daily for 30 days. Estrous cyclicity, female sexual behavior, as well as hypothalamic kisspeptin, gonadotropin releasing hormone (GnRH) content, serum luteinizing hormone (LH), estradiol (E2), progesterone (P4), corticosterone (CORT) and fertility were assessed after chronic stress. The results show that chronically stressed females exhibited disrupted estrous cyclicity, decreased receptivity, low pregnancy rates and lower numbers of fetuses. The content of Kisspeptin and GnRH in the Anteroventral Periventricular/medial Preoptic Area decreased during proestrus, while Kisspeptin increased in the Arcuate nucleus in proestrus and diestrus. Serum LH decreased only during proestrus, whereas E2 and P4 concentrations decreased during proestrus and diestrus, with a concomitant increase in CORT levels in both stages. As a whole, these results indicate that chronic stress decreases Kisspeptin content in AVPV nucleus and GnRH in POA in females, and might induce disruption of the LH surge, consequently disrupting estrous cyclicity and fertility, leading to lower rates of pregnancy and number of fetuses.

Prenatal stress modifies the serotonergic system by altering the synthesis, metabolism, receptors and serotonin content in the hippocampus. However, it is currently unknown whether serotonin release in the ventral hippocampus of prenatally stressed rats is altered. In this study, serotonin (5-HT) and its metabolite, 5‑hydroxyindoleacetic acid (5-HIAA) levels were analysed in dialysates (in vivo) and in homogenates (in vitro) of the ventral hippocampus. This was made after the sucrose preference test and after forced swim test (FST) in male adult progeny from mothers that were stressed by immersion in cold water during the last week of gestation. Serum concentration of corticosterone was also evaluated in control and in prenatally stressed males. Sucrose preference was differently affected in prenatally stressed males: 69% showed decreased sucrose consumption, and were considered anhedonic; 31% exhibited sucrose consumption similar to control and were considered non‑anhedonic. During the FST, increased immobility and decreased swimming were observed in prenatally stressed males. After sucrose test, content and release of 5‑HT in prenatally stressed rats were similar to those in the control group, with higher metabolite. After the FST, 5-HT content increased, but its release increased slightly in anhedonic rats and did not change in non-anhedonic rats, with lower metabolite. The response of the adrenal axis to the FST was larger in anhedonic prenatally stressed males, than in control and non‑anhedonic males. These data show that behavioural disruption caused by prenatal stress is related to low release and lower metabolism of serotonin in the ventral hippocampus in adult male offspring, as well as to hyperactivity and hyperreactivity of the adrenal axis.

Prenatal stress causes learning and spatial memory deficits in adulthood by modifying hippocampal function. The dorsal hippocampus contains serotonergic and noradrenergic neuron terminals, which are related to cognitive processes. It is currently unknown whether prenatal stress modifies serotonin (5-HT) and noradrenaline (NA) content and their release in the hippocampus during cognitive performance. Therefore, we measured these variables in the dorsal hippocampus of prenatally stressed males during spatial learning and memory tests. Cognitive tests were performed in 3-month-old control and prenatally stressed male rats in the Morris Water Maze (MWM). After cognitive tests, the dorsal hippocampus was dissected to quantify 5-HT and NA content. In other males, 5-HT and NA release in the dorsal hippocampus was assessed by microdialysis, before and after cognitive tests. Prenatally stressed males showed longer latencies to reach the platform, compared to control animals. Hippocampal 5-HT content decreased during learning and memory tasks in both groups, while NA content was not modified in prenatally stressed males neither before, nor after learning and memory tests. 5-HT and NA release were significantly lower in prenatally stressed animals during spatial learning and memory tasks. Corticosterone response was greater in prenatally stressed animals compared to controls. These results show that cognitive disruption caused by prenatal stress is related to decreased 5-HT and NA release, and to higher adrenal axis response in prenatally stressed animals.

The reactive oxygen species (ROS) play an important role in various aspects of male reproductive function, for spermatozoa to acquire the ability to fertilize. However, the increase in ROS generation, both due to internal and external factors, can induce oxidative stress, causing alterations in the structure and function of phospholipids and proteins. In the nucleus, ROS attack DNA, causing its fragmentation and activation of apoptosis, thus altering gene and protein expression. Accumulating evidence also reveals that endogenously produced ROS can act as second messengers in regulating cell signalling pathways and in the transduction of signals that are responsible for regulating spermatogonia self-renewal and proliferation. In the epididymis, they actively participate in the formation of disulphide bridges required for the final condensation of chromatin, as well as in the phosphorylation and dephosphorylation of proteins contained in the fibrous sheath of the flagellum, stimulating the activation of progressive motility in epididymal spermatozoa. In this review, the role of small amounts of ROS during spermatogenesis and epididymal sperm maturation was discussed.

Background The emergence of assisted reproductive technology (ART) in humans has been an important tool for the treatment of infertility. The number of treatments performed in Latin America has been increasing, and Mexico is the third country with the most assisted reproduction cycles performed in the region. However, Mexico lacks a national regulation for assisted reproduction. Therefore, it is necessary to implement regulations that allow for a safe clinical practice based on ethics which can be available to any social group. Main body The aim of this review was to examine the existing legislation that regulates human assisted reproduction practices in Mexico, but also to examine the legal analysis of the policies, laws, and regulations in effect in some countries in Latin America, North America, and Europe. For this, seven databases were consulted, and 34 articles from 2004 to 2021 referring to the practice of ART within the legal framework and the anthropological analysis that this entails were analyzed. Eight documents were also consulted such as the Mexican General Health Law of the Official Journal of the Federation (February 7, 1984) with its last published reform (DOF 01-06-2021). And three official agency websites were also consulted. No specific legislation was found for human assisted reproduction practices in Mexico; however, assisted reproduction clinics are ruled under some agreements implemented by national organizations such as the Mexican Association of Reproductive Medicine and, at the Latin America level, the Latin America Network of Assisted Reproduction (abbreviated REDLARA in Spanish); in addition, the practice of ART is considered, although not explicitly, in the General Health Law. Conclusion In Mexico, there is no legal regulation in charge of assisted reproduction practices, which is why there is an urgent need to establish human assisted reproduction laws without incurring discriminatory and unconstitutional acts, and at the same time, be in accordance with scientific advances. This will allow a considerable reduction in the violation of human rights., Plain language summary The emergence of ART in humans has been an important tool for the treatment of infertility. It is reported that one in four couples in developing countries has fertility problems. In 2009, the International Committee for Monitoring Assisted Reproductive Technology (ICMART) established ART as "all treatments or procedures involving in vitro manipulation of oocytes, sperm or embryos for the purpose of establishing a pregnancy". The number of treatments performed in Latin America has been increasing, and Mexico is the third country with the most assisted reproduction cycles performed in the region. However, Mexico lacks a national regulation for human assisted reproduction. This has caused Mexico to become a medical tourism paradise, which increases the possibility of abuses, fraud, and clinical risks. In addition, it allows each institution offering assisted reproduction services, whether public or private, to establish arbitrary requirements for inclusion. Thus, the emergence of a regulation that allows a safe clinical practice based on ethics, which will also make this reproductive tool available to any social group, is a social need. Therefore, the aim of this review was to examine the existing legislation that regulates human assisted reproduction practices in Mexico, but also to examine the legal analysis of the policies, laws, and regulations in use in some countries in Latin America, North America, and Europe, as well as highlighting the importance of working on the establishment of regulations that allow for safe and ethically based clinical practices.

Background The evaluation of the DNA damage generated in cumulus cells after mature cumulus-oocyte complexes vitrification can be considered as an indicator of oocyte quality since these cells play important roles in oocyte developmental competence. Therefore, the aim of this study was to determine if matured cumulus-oocyte complexes exposure to cryoprotectants (CPAs) or vitrification affects oocytes and cumulus cells viability, but also if DNA damage is generated in cumulus cells, affecting fertilization and embryo development. Results The DNA damage in cumulus cells was measured using the alkaline comet assay and expressed as Comet Tail Length (CTL) and Olive Tail Moment (OTM). Results demonstrate that oocyte exposure to CPAs or vitrification reduced oocyte (75.5 ± 3.69%, Toxicity; 66.7 ± 4.57%, Vitrification) and cumulus cells viability (32.7 ± 5.85%, Toxicity; 7.7 ± 2.21%, Vitrification) compared to control (95.5 ± 4.04%, oocytes; 89 ± 4.24%, cumulus cells). Also, significantly higher DNA damage expressed as OTM was generated in the cumulus cells after exposure to CPAs and vitrification (39 ± 17.41, 33.6 ± 16.69, respectively) compared to control (7.4 ± 4.22). In addition, fertilization and embryo development rates also decreased after exposure to CPAs (35.3 ± 16.65%, 22.6 ± 3.05%, respectively) and vitrification (32.3 ± 9.29%, 20 ± 1%, respectively). It was also found that fertilization and embryo development rates in granulose-intact oocytes were significantly higher compared to denuded oocytes in the control groups. However, a decline in embryo development to the blastocyst stage was observed after CPAs exposure (1.66 ± 0.57%) or vitrification (2 ± 1%) compared to control (22.3 ± 2.51%). This could be attributed to the reduction in both cell types viability, and the generation of DNA damage in the cumulus cells. Conclusion This study demonstrates that oocyte exposure to CPAs or vitrification reduced viability in oocytes and cumulus cells, and generated DNA damage in the cumulus cells, affecting fertilization and embryo development rates. These findings will allow to understand some of the mechanisms of oocyte damage after vitrification that compromise their developmental capacity, as well as the search for new vitrification strategies to increase fertilization and embryo development rates by preserving the integrity of the cumulus cells.

Phytoestrogens are considered to be endocrine disruptors, since they can alter the endocrine system, thus disturbing many reproductive events. The intake of diets containing a high content of phytoestrogens has increased worldwide in human populations and in domestic animals. Phytoestrogens in maternal blood can pass through the placenta to the fetus in high amounts and can have long-term organizational effects. Mesquite (Prosopis sp) is a leguminous plant widely used to feed several livestock species, and is also used in the human diet. In this study we assessed the effects of exposure to mesquite pod extract during the periconception and pregnancy periods on the reproduction of male and female descendants. The females of three experimental groups received one of the following treatments: 1) vehicle injection; 2) mesquite pod extract or 3) the isoflavone daidzein during the periconception and pregnancy periods. Estrous cyclicity, sexual behavior and hormones, as well as uterine and vaginal epithelia were evaluated in the female descendants. In the males, sexual behavior and hormones, apoptosis in testicular cells and sperm quality were evaluated. In females the following was observed: alterations in estrous cycles, decreased sexual behavior, estradiol and progesterone levels, increased uterine and vaginal epithelia. In males, we observed a decrease in sexual behavior, testosterone and sperm quality, and apoptosis increased in testicular cells. All these effects were similar to those caused by daidzein. These results indicate that prenatal exposure to mesquite pod extract or daidzein, administered to females before and during pregnancy, can disrupt normal organizational-activational programming of reproductive physiology in female and male descendants.

Simple Summary Recently, a significant relationship between stress and reproductive failure in women was reported; being one of the possible causes of infertility. The World Health Organization recognizes infertility as a global public health issue; therefore, the interest in understanding the main causes of this issue has increased over the last few decades. Thus, many studies have reported that stress can adversely alter the functionality of the hypothalamic-pituitary-gonadal axis; as well as being one of the reasons of subfertility in patients undergoing in vitro fertilization. Therefore, it can be assumed that stress is closely related to poor in vitro fertilization outcomes. In chronically stressed female rats, irregular estrous cyclicity, increased corticosterone levels, decreased oocyte viability, and increased percentage of abnormal oocytes were obtained in all estrous cycle phases, resulting in reduced oocyte maturation during proestrus. Oocyte maturation disturbed by chronic stress is a crucial factor by which chronic stress disrupts female reproduction. Abstract Background: Stress has been considered as one of the causes of decreased reproductive function in women. However, direct evidence of the effect of chronic stress on oocytes depending on estrous cycle phases is limited. Objective: The present study aimed to evaluate the impact of chronic stress on the viability, integrity, and maturation of rat oocytes depending on estrous cycle phases, specifically proestrus, estrus, and diestrus. Methods: For this purpose, adult female rats were stressed daily by cold water immersion (15 °C) for 30 consecutive days. Results: In chronically stressed female rats, irregular estrous cyclicity, increased corticosterone levels, decreased oocyte viability, and an increased percentage of abnormal oocytes were obtained in all the estrous cycle phases, resulting in reduced oocyte maturation during proestrus. Conclusion: Oocyte maturation disturbed by chronic stress is a crucial factor by which chronic stress disrupts female reproduction

Prenatal stress disrupts reproductive function in females and males. These alterations have primarily been related to maternal corticosteroid fetal programming due to the stress response, affecting the fetus and causing long-lasting effects. The aim of this study was to investigate the influence of prenatal stress on male and female fertility. Dams were exposed to stress by immersion in cold water twice a day for the last week of gestation (days 15-21). In the adulthood, sperm quality, mature follicles, sexual hormones and fertility were assessed in female and male progeny. The results in prenatally stressed females showed lower body weight, longer estrous cycles, lower estradiol and progesterone, and lower number of pups. In prenatally stressed males, lower body weight, increased testicular cell death, as well as decreased testosterone levels, sperm quality, and fertility were observed. Aside from these effects, corticosterone levels in prenatally stressed males and females increased. These results show that prenatal stress can markedly influence infertility in adult female and male progeny. Abbreviations: 3β-HSD: 3β hydroxysteroid dehydrogenase; CRH: corticotropin releasing hormone; DEX: dexamethasone; ERα: estrogen receptor alpha; H-E: hematoxylin-eosine; HPA: hypothalamus-pituitary-adrenal; KISS: Kisspeptin; ORW: ovarian relative weight; PBS: phosphates; PS: prenatally stressed; PRW: prostatic relative weight; ROS: reactive oxygen species; SRW: seminal relative weight; TdT: terminal deoxynucleotidyl transferase; TUNEL: terminal deoxynucleotidyl transferase dUTP Nick-end labelling; TRW: testicular relative weight; URW: uterine relative weight.

Parabens (PBs) are compounds widely used in industry for food and personal care products as antimicrobials and preservatives. Their indiscriminate use has resulted in their detection in different ecosystems so that humans and other organisms are highly exposed. Methylparaben (MePB), compared with other PBs, is mostly detected in food, personal care and baby care products. PBs could be linked to the generation of hormonal disorders and fertility impairment since their recent classification as endocrine disruptors. The knowledge of the effects that MePB can exert is of great importance as, in terms of reproduction, information is limited. Therefore, the objective of the present study was to evaluate the effect of MePB on porcine oocyte viability and in vitro maturation (IVM), as well as to determine the lethal concentration at 50% (LC50 ) and the maturation inhibition concentration at 50% (MIC50 ). Oocytes were exposed to different MePB concentrations 0 (control), 50, 100, 500, 750 and 1000 μm during 44 h of IVM. Cytoplasmic alterations and reduced cumulus cell expansion were observed in oocytes exposed to MePB; however, viability was not affected. In addition, oocyte maturation decreased in a concentration-dependent manner after exposure to MePB. The estimated LC50 was 2028.38 μm, whereas MIC50 was 780.31 μm. To our knowledge, this is the first study that demonstrates that MePB altered porcine oocyte morphology, and caused a reduction in cumulus cell expansion, both of which resulted in decreased oocyte maturation. Therefore, MePB exposure may be one of the factors involved in fertility impairment in mammals, including that of humans.

Chronic stress disrupts reproductive efficiency. Yet, the manner in which stress disturbs reproduction in goats is currently unknown. The Oaxacan Mixteca region is one of Mexico's poorest, with high levels of deforestation, high ambient temperatures, and lack of water. Native goats of the Oaxacan Mixteca Region live in these stressful conditions, as well as in overcrowded and water restricted conditions. Therefore, the aim of this study was to evaluate the effects of these very stressful conditions on the reproduction of male and female goats. Control group was uncrowded, with daily water supply; stress group was overcrowded, with water restriction. The study was conducted from September 2015 to February 2016; the expression of reproductive behaviour and variations of cortisol levels were assessed. In females, oestradiol and progesterone were evaluated during the oestrous cycle. In males, testosterone levels were evaluated before and during reproductive activity. Sexual behaviour decreased in stressed goats: approaching, tail swishing, urination, vaginal discharge and flank contraction decreased in stressed females. Anogenital sniffing, licking, Flehmen reflex, bleating, mount attempts and mounts decreased in male goats. Cortisol levels in stressed animals were higher compared with control animals. Oestradiol and Progesterone levels in stressed females were significantly lower during the follicular and luteal phase, respectively, compared with control females. Testosterone levels in stressed males were lower than in control males, both before and during reproduction. These results indicate that even though goats from the Oaxacan Mixteca Region are habituated to their environmental conditions, they are still stressed by them, as shown by a higher activation of the adrenal axis in stressed goats than in control goats. High cortisol levels may induce low oestradiol levels in females and low testosterone levels in males, as well as a disruption in the expression of their reproductive behaviour.

Chronic stress induces decreased sperm motility, viability and concentration in stressed males. Also, stress modifies oxidative status and causes apoptosis in testes, as well as a decrease in the epithelial area of seminiferous tubules. However, there are no studies that analyze the alterations caused by stress in testicular cells. Thus, in this study, alterations in the morphology of testicular germ cells caused by different days of chronic stress were assessed. Adult male rats were exposed to stress by immersion in cold water (ICW) daily for 3, 8, 20 or 50 consecutive days. Plasma testosterone and corticosterone were also assessed. Results showed that chronic stress causes loss of germ cells, and alteration of spermatogenesis. Seminiferous tubules from stressed males showed several degenerative signs, such as vacuoles in the basal epithelium, with picnotic indicia; moderate to severe exfoliation of degenerative germinal cells in the tubule lumen was also observed. These alterations were observed in all days of stress in a gradual way, from day 3-50. Testosterone levels were decreased at all those times, and corticosterone concentrations were increased on the same days. These results show that chronic stress causes severe damage to germ cells, which can account for infertility problems in males. These alterations are related to a decrease in testosterone as well as an increase in corticosterone caused by stress.

Mesquite (Prosopis sp) and Leucaena leucocephala are widespread legumes, widely used to feed several livestock species and as food source for human populations in several countries. Both mesquite and Leucaena contain several phytoestrogens which might have potential estrogenic effects. Thus, the aim of this study was to evaluate the effects of mesquite pod and Leucaena extracts on several aspects of behavior and reproductive physiology of the male rat. The effects of the extracts were compared with those of estradiol (E2) and of two isoflavones: daidzein (DAI) and genistein (GEN). The following treatments were given to groups of intact male rats: vehicle; mesquite pod extract; Leucaena extract; E2; DAI; GEN. The results indicate that mesquite pod and Leucaena extracts disrupt male sexual behavior in a similar way to DAI and GEN, but less than E2. The main disruptor of sexual behavior was E2, however after 40 and 50 days of administration, both extracts and phytoestrogens disrupted sexual behavior in a similar way to E2. The extracts also increased testicular germ cell apoptosis, decreased sperm quality, testicular weight, and testosterone levels, as phytoestrogens did, although these effects were less than those caused by estradiol. The number of seminiferous tubules with TUNEL-positive germ cells increased in extracts treated groups in a similar way to phytoestrogens groups, and E2 caused the greatest effect. The number of TUNEL-positive cells per tubule increased only in leucaena extract and E2 groups, but not in mesquite- and phytoestrogens- treated groups. Spermatocytes and round spermatids were the TUNEL-positive cells observed in all experimental groups. This effect was associated with smaller testicular weights without atrophy in experimental groups compared with control. Testicular atrophy was only observed in estradiol-treated males. Testosterone decreased in males of all experimental groups, compared with control, this androgen was undetectable in E2 treated males. These results suggest that mesquite pod and Leucaena extracts cause effects similar to those of phytoestrogens in male rat reproduction, these effects were lower than those caused by E2.

Aim of Study: Gonadal hormones exert a profound influence on the development, structure and function of the sexual organs. The testosterone is one of the androgens that plays an essential role in the development of sexual organs in male mammals. Therefore, the present study was undertaken to evaluate the testosterone levels and developmental pattern of the penile spines and seminiferous tubules during early postnatal life of Wistar rats. Methods and Materials: At 7, 14, 21, 28, 35, 42, 49, 56, 63 and 70 days after birth, penile and testicular tissues of male rats were dissected out and fixed for histological study and plasma testosterone levels were determined using high resolution chromatography. Results: An increase in the number of penile follicles, primarily in the distal region of the penis, was observed from postnatal days 14 to 42, followed by a gradual decrease. Penile spines were absent from birth until the first growth peak, which was observed at 42 postnatal days. Both testicular weight and the area of seminiferous tubules showed gradual increases before achieving their highest values at 42 postnatal days. Similarly, a gradual increase in testosterone levels was detected from day 28, with a peak at 42 postnatal days. Conclusions: These data show a temporal association between the development of the penile spines and testicular tissue with gradual increases in testosterone levels. These results may contribute to a better understanding of the behavioral, hormonal and morphological changes underlying sexual maturation in male rats.

We have previously demonstrated, that 15 days after female rats pace the sexual interaction, there is an increase in the number of new cells that reach the granular cell layer (GrL) of the accessory olfactory bulb (AOB). The aim of the present study was to evaluate, if the first sexual experience in the female rat increases cell proliferation in the subventricular zone (SVZ) and the rostral migratory stream (RMS). We also tested if this behavior promotes the survival of the new cells that integrate into the main olfactory bulb (MOB) and AOB 45 days after the behavioral test. Sexually, naive female rats were injected with the DNA synthesis marker 5′-bromo-2′-deoxyuridine (BrdU) on the day of the behavioral test. They were randomly divided into the following groups: Female rats placed alone in the mating cage (1); Females exposed to amyl acetate odor [banana scent, (2)]; Females that could see, hear, and smell the male but physical contact was not possible [exposed to male, (3)]; Female rats that could pace the sexual interaction (4); and females that mated without the possibility of pacing the sexual interaction (5). Animals were sacrificed 2 days after the behavioral test (proliferation) or 45 days later (survival). Our results show that 2 days after females were exposed to banana scent or to the male, they had a higher number of cells in the SVZ. Females, that mated in pace and no-paced conditions had more new cells in the RMS. At 45 days, no significant differences were found in the number of new cells that survived in the MOB or in the AOB. However, mating increased the percentage of new cells, that differentiated into neurons in the GrL of the AOB. These new cells expressed c-Fos after a second sexual encounter just before the females were sacrificed. No significant differences in plasma levels of estradiol and progesterone were observed between groups. Our results indicate that the first sexual experience increases cell proliferation in the RMS and mating 45 days later enhances the number of new cells that differentiate into neurons in the AOB. These new neurons are activated by sexual stimulation.

Some neurophysiological studies suggest that the cerebellum could participate in epileptic activity. Therefore, to study the participation of the main efferent projections from the cerebellum to the forebrain, we injected small doses of kainic acid (KA) into the deep cerebellar nuclei to selectively injure neighboring cells while avoiding fiber lesions. Uninjured fibers were confirmed using histological findings and by assessing the number of cells in the main cerebellar afferents, compared with controls. Under such conditions, we found that dentate and interpositus nuclei lesions interfere with seizure expression, both at early kindling acquisition and at the kindled stage. We hypothesize that the cerebellar effect on epilepsy drives skeletal motor responses, mainly in generalized seizures when the thalamus and neocortex are affected.

This study reviews the different in vivo experimental models that have been used for the study of epileptogenesis. In this review we will focus on how to replicate the different models that have led to the study of partial seizures, as well as generalized seizures and the status epilepticus. The main characteristics that participate in the processes that generate and modulate the manifestations of different models of epileptogenesis are described. The development of several models of experimental epilepsy in animals has clearly helped the study of specific brain areas capable of causing convulsions. The experimental models of epilepsy also have helped in the study the mechanisms and actions of epilepsy drugs. In order to develop experimental animal models of epilepsy, animals are generally chosen according to the kind of epilepsy that can be developed and studied. It is currently known that animal species can have epileptic seizures similar to those in humans. However, it is important to keep in mind that it has not been possible to entirely evaluate all manifestations of human epilepsy. Notwithstanding, these experimental models of epilepsy have allowed a partial understanding of most of the underlying mechanisms of this disease.

Neonatal treatment with clomipramine (CMI) in rats induces multiple behavioral alterations during adulthood that resemble certain symptoms of human depression, such as impairments of pleasure-seeking behaviors. CMI may also induce permanent changes in the reactivity of the hypothalamic–pituitary–adrenocortical axis (HPA) to different stimuli; however, the endocrinal changes induced by this treatment are still a matter of debate. In the present study, we evaluated the levels of corticosterone in rats treated in the neonatal period with CMI in basal conditions (0, 6, 12 and 18 h after lights on) and after treatment with the antidepressant fluoxetine (FLX; 5 mg/kg for 14 days). To evaluate the response of the HPA axis to a cholinergic agonist, we analyzed the effect of oxotremorine administration (OXO; 0.4, 0.8 mg/kg) on plasma levels of corticosterone. Administration of OXO took place at the beginning of each one of the two phases of the light–dark cycle (time points 0 and 12 h, respectively). Results showed an increase in basal plasma levels of corticosterone in CMI-treated rats at time point zero and at 6 h after the onset of the light period. While treatment with FLX reversed the increase in corticosterone plasma levels in CMI-treated rats, the results regarding cholinergic stimulation indicate that those rats do not respond to the administration of a low dose of OXO (0.4 mg/kg) at the onset of the dark phase (time point 12 h). In conclusion, this study supports the hypothesis that neonatal treatment with CMI induces a hypersecretion of corticosterone in adulthood that was reversed through treatment with the antidepressant FLX. The CMI-treated rats showed a hyporesponse to cholinergic stimulation with OXO at low doses and at the beginning of the dark phase. Thus, the present results do not support the assumption that an increased sensitivity of the muscarinic cholinergic system is one of the possible correlates of the behavioral alterations seen in CMI-treated rats.

Chronic physical or psychological stress disrupts male reproductive function. Studies in our laboratory have shown that stress by immersion in cold water (ICW) and by electrical foot shocks (EFS) has inhibitory effects on male sexual behavior; these effects do not seem to be mediated by an increase in corticosterone, nor by a decrease in testosterone. On the other hand, it is known that endogenous opioids are released in the brain in response to these same stressors; consequently, they could be participating in the impairment of sexual behavior, as well as in the changes in corticosterone and testosterone caused by stress. The aim of this study was to analyze the effects of the opioid antagonist naltrexone (NTX) on male sexual behavior, corticosterone, and testosterone in both stressed sexually experienced and naive male rats. Sexually experienced adult male rats were assigned to one of the following groups (n=10 each): 1) control group, males without sexual evaluation; 2) control group, rats injected ip with saline, non-stressed; 3) control group, rats injected with NTX (3 mg/kg) non-stressed; 4) rats injected ip with saline, and stressed by EFS; 5) rats injected ip with NTX (1.5 mg/kg) and stressed by EFS; 6) rats injected ip with saline and stressed by ICW; 7) rats injected ip with NTX (1.5 mg/kg) and stressed by ICW; 8) rats injected ip with NTX (3 mg/kg) and stressed by ICW. Naive males were assigned to the same control groups but only stressed by ICW and the NTX dose used was 3 mg/kg. Injections were given 30 min before stress sessions. Stress was applied on 20 consecutive days. Male sexual behavior was assessed 15 min after EFS or 30 min after ICW, on days 1, 4, 8, 12, 15, and 20. Trunk blood was collected at the end of the experiments on day 20 of stress. Corticosterone and testosterone were evaluated by HPLC. Mount, intromission and ejaculation latencies were longer in control saline naive males compared to control saline sexually experienced males on the first day. NTX administration to control naive males caused a decrease in mount, intromission, and ejaculation latencies, as well as an increase in ejaculatory frequency/30 min, compared to control-saline only on day 1. Stressed naive males showed higher mount, intromission and ejaculation latencies, compared to control and stressed sexually experienced males, as well as comparable increase in corticosterone and decrease in testosterone plasma levels. NTX administration before exposure to stress prevented the modifications caused by stress in sexual parameters. Sexual behavior in control sexually-active males injected with saline or NTX was not modified. Saline stressed males showed the previously reported alterations in sexual behavior, as well as an increase in corticosterone and a decrease in testosterone plasma levels. Stressed males injected with NTX before exposure to stress showed no alterations in male sexual behavior. NTX in control non-stressed males did not modify corticosterone plasma levels, but did cause a significant increase in plasma testosterone. The increase in corticosterone and the decrease in testosterone due to stress, were attenuated with the opioid antagonist, both in naive and sexually experienced males. Prevention of ICW stress effects was more effective with higher doses of NTX (3 mg/kg). These data suggest that endogenous opioids could be participating in the effects caused by stress on male sexual behavior, corticosterone, and testosterone.

The expression of masculine sexual behavior (MSB) in male hamsters is optimally stimulated by aromatizable androgens like androstenedione (AD) and testosterone (T), while the non-aromatizable androgen, 5alpha-dihydrotestosterone (DHT), exerting potent androgenic peripheral effects, only in high doses maintains MSB after castration. No data exist on the ability of these androgens to restore long intromissions after castration. In this study, AD, T, and DHT were administered to four-week gonadectomized, sexually experienced male hamsters, for three weeks, in doses of 25 microg/day or up to 1000 microg/day to compare their potency in restoring MSB, penile size, and penile spines growth. Plasma levels of these steroids and the metabolites estrone and estradiol, were determined at the end of the treatment period. Gonadectomy completely suppressed MSB and induced a regression of penile spines. AD was more potent than T in restoring MSB, ejaculatory behavior being displayed by most castrated subjects with a lower dose of AD (50 microg/day) than of T (300 microg/day), and long intromissions being shown by all AD-treated castrated hamsters but only by 20% of T-treated ones, when doses of 1000 microg/day were given. DHT did not stimulate any copulatory response. The three androgens, even at the lowest dose, partially stimulated penis and penile epithelium growth, DHT showing the highest potency. Treatment of castrated hamsters with AD (50 microg/day), restored steroid levels to similar values as those of intact animals. These results show that AD and T restored MSB even with a partial stimulation of penile spines growth, AD being more potent than T. In contrast, DHT did not restore MSB in the hamster in spite of its peripheral androgenic potency.

Sexually sluggish (S) male rats take a long time to ejaculate or sometimes they don't achieve ejaculation when tested on repeated occasions with receptive females. In order to further understand what factors might contribute to the inconsistent display of sexual behavior in these animals and determine if S and non-copulating males have a different neurobiological profile, the present study was design to characterize sex-related behaviors of S male rats. We tested their preference to physically interact between a sexually receptive female and a sexually active male. We also tested whether S males have a preference to investigate soiled bedding from females in estrous, anestrous or clean bedding. We also evaluated if the serum hormonal levels of testosterone (T) and estradiol (E) are different between copulating (C) and S male rats. Finally, we compared the neuronal activity of the vomeronasal projection pathway of C and S male rats exposed to estrous bedding. The results indicate that S male rats increased the percentage of animals displaying mounts and intromissions after repeated testing with receptive females but no increased was observed in the percentage of animals displaying ejaculations (a total of nine tests were performed). Both C and S males had a clear preference to interact with a sexually receptive female. Both groups showed a clear preference for bedding from estrous females as opposed to anestrous or clean bedding. However, the time investigating the estrous bedding was significantly lower for the S in comparison to C rats. No differences in the serum levels of T and E were found. The structures of the vomeronasal projection pathway were equally activated by estrous bedding in C and S male rats. The results indicate that S male rats do not have hormonal alterations or deficient processing of sexually relevant olfactory cues. Although S males showed a reduced preference for estrous bedding, no changes in preference for a receptive female were observed.

The expression of sleep is influenced by situations that take place during the preceding waking period, giving rise to different patterns of sleep architecture. Immobilization stress (IMB) induces an increase of both rapid eye movement (REM) and slow wave sleep (SWS). It has been suggested that these changes are mediated in part by noradrenaline and by the corticotrophin releasing factor.To determine the participation of mu receptors in the stress-induced increase of REM sleep using naltrexone (NTX).Twelve adult male rats were implanted for sleep recordings. Subjects were recorded under control conditions as well as after: a) IMB stress (1 h); b) injection of NTX (1.5 mg/kg); c) NTX plus IMB. To assess corticosterone levels, additional groups ( n=5) were decapitated at 0, 1, 3 and 6 h after vehicle injection and after immobilization. Four groups were decapitated at 0, 1, 3, and 6 h after NTX plus IMB. Corticosterone plasma levels were determined by HPLC.IMB induces an increase in REM and SWS, and a decrease in wakefulness. Administration of NTX before IMB suppresses the effects of stress on sleep. NTX administration is innocuous in non-stressed animals. However, NTX administration does not prevent the rise of corticosterone normally observed after IMB stress.These data suggest that NTX prevents the effects of IMB stress on sleep by acting outside of the hypothalamic-pituitary-adrenal axis that partially mediates the stress response.

Chronic exposure to stressors increases HPA axis activity and concomitantly reduces HPG axis activity. This antagonistic relationship between both these axes has been proposed to underlie the inhibition of reproductive function due to stress. Sexual behavior in males may be the most vulnerable aspect of male reproduction to acute and chronic stress and it has been suggested that alterations in sexual behavior during stress are due to the antagonistic relationship between testosterone and corticosteroids. However, only in a few studies has a correlation between the levels of testosterone and corticosterone, and sexual behavior been made. In this study, we evaluated the effects of different stressors, applied both acute and chronically, on masculine sexual behavior and whether or not these effects on sexual behavior are accompanied by changes in plasma levels of corticosterone and testosterone. Additionally, we evaluated the effect of testosterone treatment on the effects of stress on sexual behavior. Sexually experienced male rats were exposed to one of the following stressors: immobilization (IMB), electric foot shocks (EFS) or immersion in cold water (ICW). Sexual behavior and plasma levels of testosterone and corticosterone were assessed on days 1, 5, 10, 15, and 20 of stress. In a second experiment, males were castrated, treated with 3 different doses of testosterone propionate (TP) and exposed to ICW for 20 consecutive days. Sexual behavior was assessed on days 1, 5, 10, 15, and 20 and steroids were evaluated on day 20. Parameters of masculine sexual behavior were modified depending on the characteristics of each stressor. Mount, intromission and ejaculation latencies increased significantly, the number of mounts increased, and ejaculations decreased significantly in males exposed to EFS and to ICW but not in males exposed to IMB. Associated with these effects, testosterone decreased in the EFS and ICW groups on days 1, 15, and 20. However, corticosterone increased only in males exposed to ICW. In castrated males, TP treatment failed to block the effects of stress by ICW on sexual behavior and corticosterone. These results indicate that the effects of stress on sexual behavior depend on the characteristics of each stressor, and these effects, as well as the decrease in testosterone are not necessarily associated with the increase in corticosterone. The fact that testosterone treatment did not prevent the effects of stress on sexual behavior suggests that other mediators could be involved in the alterations of sexual behavior caused by stress.

Plasmatic levels of corticosterone display a circadian rhythm, with the higher values occurring during the dark phase in nocturnally feeding animals. Stressful situations induce a rise of corticosterone levels and this endocrine response to stress also presents circadian variations. The higher increase of corticosterone in response to stress occurs when the hormone is in its lower circadian level, and the minimum responses occurring at the peak. Since it has been shown that plasma hormones respond differently to different stressors, in the present study, we compared the acute and chronic effects of four different stressors: electric foot shocks (3 mA, 1/s, 5 min), immobilization during two hours or six hours, and immersion in cold water (15 degrees C) for 15 min. Stressors were applied, both acutely and chronically (during 4, 12 and 20 days) at the onset of the light phase as well as at the onset of the dark phase of the light/dark cycle. Body weight was assessed every day, and at the end of the manipulations plasmatic corticosterone levels were determined from the trunk blood. Adrenal and testicular weights were also assessed. Acute exposure to stressors increased plasmatic corticosterone levels significantly when the stressors were applied at the beginning of the light phase of the cycle. In the dark phase, only two hours of immobilization and immersion in cold water caused an increase in plasmatic corticosterone. With repeated exposure, electric foot shocks failed to induce significant changes in corticosterone levels in any phase of the light-dark cycle. Immobilization stress induced a significant rise in corticosterone levels only when the stressor was applied during the light phase. Immersion in cold water elicited a clear increase in plasmatic corticosterone levels in all the periods tested, regardless of the time of the cycle in which the stressor was applied. We did not observe a loss in body weight, but rather a smaller weight gain in stressed rats. Body weight gain was minimum in rats exposed to immersion and 6 hours of immobilization. Adrenal hypertrophy was observed in rats exposed to these same stressors. We conclude that: 1) the activation of the hypothalamus-pituitary-adrenal axis by stress depends mainly on the characteristics of the stressor; 2) the response of this axis to stress also depends on the time of day in which the stressor is applied.

The aim of this study was to evaluate whether continuous sexual behavior could attenuate the effects of chronic stress on spermatogenesis, sexual glands, plasma testosterone and corticosterone in sexually experienced male rats. Rats were exposed to stress by immersion in cold water (ICW) daily for 20 or 50 consecutive days. Plasma testosterone and corticosterone, masculine sexual behavior, as well as the number of offspring, the epithelial area of seminiferous, prostatic and seminal glands were assessed. In stressed males, body and testicular weights decreased, male sexual behavior was disrupted, and adrenal weights increased. In males stressed for 50 days, prostate and seminal glands had lower weights compared with controls. Prostate and seminal epithelial areas also decreased in these males. Seminiferous tubules in testes from rats stressed for 20 or 50 days showed several degenerative signs, such as vacuoles in the basal epithelium, with picnotic indicia; moderate to severe exfoliation of degenerative germinal cells in the tubule lumen was also observed. In males stressed for 50 days a significant decrease in seminiferous epithelial area was observed from stages I-VIII, regardless of copulation. The litters from females that copulated with males stressed for 50 days decreased significantly. Chronic stress caused increase in plasma levels of corticosterone, which were higher in males stressed for 20 days than in males stressed for 50 days. Testosterone decreased in stressed males and it was lower in males stressed for 50 days. In stressed males allowed to copulate, body and testicular weights were similar to controls. Adrenal, seminal glands, and prostate weights, as well as epithelial areas of males stressed for 50 days allowed to copulate were also similar to controls. Corticosterone was lower than in males stressed for 50 days, but still higher than in controls. Testosterone in males stressed for 50 days and allowed to copulate was higher than in stressed males not allowed to copulate and control males without copulation, but still lower than in control copulating males. These results show that chronic stress causes germ cell loss in testes and a decrease in prostate and seminal epithelium, possibly as a result of testosterone decrease, affecting fertility. Continuous copulation can attenuate the effects of stress on testosterone levels and on the epithelial area in male sexual glands, but not on the seminiferous epithelium after 50 days of stress.

It is well known that the activation of the hypothalamic-pituitary-adrenal (HPA) axis can induce alterations in the sleep-wake pattern. Corticotropin-releasing factor (CRF), adrenocorticotropin, and corticosterone are involved in the activation of the axis and each one of them has shown an effect on wakefulness and sleep. Nevertheless, concerning corticosterone, the picture is still controversial. In the present study, we analyzed the effects of a low (LC, 0.2 mg), medium (MC, 2 mg), and high (HC, 4 mg) dose of corticosterone on the 24-h sleep cycle in rats. Results indicate that all doses produce an initial enhancement of wakefulness with a concomitant decrease of slow-wave sleep II (SWS II). This effect was observed within the first hour in all the doses but lasted until the third hour only after the higher doses. When plasma levels of corticosterone were analyzed by high-performance liquid chromatography (HPLC), the highest levels were observed during the first 3 h, which is coincident with an increase in the percentage of wakefulness. Nevertheless, when the overall percentage of the stages was analyzed, LC seemed to induce the opposite effect (decrease of wakefulness and increase of SWS II) than that induced by the two higher doses (increased wake time, decreased SWS II). Rapid eye movement (REM) sleep was not modified at any dose. These data indicate that corticosterone exerts an alerting effect that could be important in the initial stage of the stress response.

There are apparently normal male rats that fail to initiate copulation; these animals are called non-copulating (NC) males. Several research groups have demonstrated that conversion of testosterone to oestradiol (aromatisation) in specific brain areas known to be involved in the control of masculine sexual behaviour is fundamental in the control of masculine sexual behaviour. The aim of the present study was to test the hypothesis that the concentration of aromatase activity (AA) in the brain is lower in NC males than in copulating males (C). We quantified AA in several brain nuclei and also evaluated whether NC rats have altered concentrations of testosterone in their plasma. We found that AA was reduced in the medial preoptic nuclei (MPN) of NC male rats vs C males. In addition, NC and C male rats had similar plasma levels of testosterone. These data suggest that reduced levels of AA in the MPN could be a crucial factor associated with lack of male coital behaviour in rats.

RETANA-MARQUEZ, S., H. BONILLA-JAIME AND J. VELAZQUEZ-MOCTEZUMA. Lack of effect of corticosterone administration on male sexual behavior of rats. PHYSIOL BEHAV 63(3) 367–370, 1998.—The increase in plasma levels of corticosteroids as part of the stress response has been associated with failure in the reproductive function in most vertebrate species, both in females and males. Recently, we have shown that male sexual performance in rats is readily affected by different stressors, both acutely and chronically applied. However, there are few reports that directly correlate the increase in corticosteroid levels with the behavioral effects of stress. In this study we investigated whether the administration of corticosterone, either acutely or chronically, could reproduce the effects of stress on male sexual behavior in the male rat. Four doses of corticosterone (0.5, 1, 2, and 4 mg) or the vehicle, were administered during four consecutive days to sexually experienced males. Male sexual behavior was assessed after the first and the fourth injection. After the last test, males were killed and levels of corticosterone and testosterone were measured by HPLC. We observed an increase in corticosterone plasma levels in a dose-dependent manner. None of the sexual behavior parameters, however, was modified. Plasma levels of testosterone were not modified by corticosterone administration. Both steroids were increased in response to sexual activity, though. These data show that, unlike amphibians and female mammals, corticosteroids do not alter sexual behavior in male rats and suggest that the effect of stress on male sexual behavior cannot be explained by increases in corticosterone.

It is well known that testosterone (T) plays a major role in the adequate expression of male sexual behavior. On the other hand, the stimulation of central muscarinic receptors with oxotremorine (OXO), a specific agonist, facilitates the expression of masculine sexual behavior in rats. In this study, we analyzed the relationship between T and the cholinergic system, recording the effect of OXO administration on masculine sexual behavior in gonadectomized rats, before and after receiving T treatment. Sexually experienced and unexperienced male rats were gonadectomized and periodically tested for sexual behavior. Once this behavior was absent or drastically reduced, males were treated with OXO or saline and sexual behavior was assessed. 112 or 167 days later, animals were treated daily with T during 21 days, recording the response to OXO in days 12 and 21. Sexual behavior decreased more rapidly after gonadectomy in inexperienced males. OXO administration did not improve sexual performance in either group. The administration of T rapidly restored sexual behavior of experienced males; recovery of inexperienced males was slower. In the presence of T, OXO administration exerted a facilitative effect on sexual performance of both groups. These results suggest that the facilitative effect of muscarinic stimulation on sexual behavior requires the presence of testosterone.

Masculine sexual behavior in rats can be stimulated by acutely stressing the animals. Nevertheless, little is known about the effect that different stressors could have on sexual behavior. In this work we studied the effect of different stressors applied both acutely and chronically on masculine sexual behavior. Sexually active male Wistar rats were submitted to stress by: immobilization (IMB); immersion in cold water (WIM); and electrical foot shock (EFS). These stressors were applied during 20 consecutive days and masculine sexual behavior was assessed on days 1, 4, 8, 12, 15 and 20. Motivational component, copulatory performance and copulatory potential were drastically altered by WIM. EFS produced significant alterations in almost all sexual parameters recorded but only when it was applied chronically. IMB only altered mount frequency and hit rate, although inconsistently. These results suggest that the effect of stress on sexual behavior depends on the nature and, in some conditions, on the duration of the stressor.

Some breed of goats originating or adapted to subtropical latitudes display large seasonal variations of their sexual and/or reproductive activity. This seasonality causes a seasonality of milk, cheese and meat production. To solve this problem it is necessary to have a deep knowledge of the annual sexual activity of animals and to identify the environmental factor controlling the timing of the annual reproductive cycle. In this review we will describe our approach to develop sustainable techniques to control reproductive activity in goats from subtropical Mexico: (1) The characteristics of the annual breeding season in both male and female goats were determined; (2) Photoperiod was identified as the major environmental factor controlling the timing of the annual breeding season; (3) Photoperiod treatments were used to stimulate the sexual activity of bucks during the non-breeding season; (4) Male goats rendered sexually active were used to induce and synchronize the estrous behavior and ovulatory activity of anestrous does in confined or grazing conditions by the male effect; (5) We determined that nutritional supplementation during the male effect improves the reproductive response of females exposed to the sexually active males. These results constitute an original manner to control the reproductive activity of goats using photoperiod, the male effect and nutrition., Algunas razas caprinas originarias o adaptadas a las latitudes subtropicales muestran una marcada estacionalidad de su actividad sexual y/o reproductiva. Esta estacionalidad provoca que la producción de leche, queso y cabrito sea también estacional. Para resolver este problema, es necesario conocer las características del ciclo anual de actividad sexual de los animales e identificar el factor del medio ambiente que controla el desarrollo de este ciclo anual de reproducción. En este artículo describiremos las reflexiones que nos permitieron desarrollar técnicas sustentables de control reproductivo en los caprinos locales del subtrópico mexicano: 1) Determinamos que las actividades sexual y endocrina de los machos y hembras son estacionales; 2) Identificamos que el fotoperiodo es el principal factor del medio ambiente que regula la estacionalidad sexual en ambos sexos; 3) Utilizamos el fotoperiodo para estimular la actividad sexual de los machos durante el periodo de reposo; 4) Los machos cabríos sexualmente activos se utilizaron para inducir y sincronizar la actividad estral y ovulatoria de las cabras anéstricas mantenidas en condiciones extensivas o en confinamiento, a través de la técnica de bioestimulación conocida como efecto macho; 5) Determinamos que la complementación alimenticia durante el efecto macho mejora la respuesta reproductiva de las cabras expuestas a los machos cabríos sexualmente activos. Estos resultados constituyen una manera original para controlar la actividad sexual de los caprinos utilizando el fotoperiodo, el efecto macho y la nutrición.

Phytoestrogens are non steroidal compounds that can bind to estrogen receptors, mimicking some effects of estradiol (E(2)). These compounds are widespread among legumes, which are used as pasture, and their importance in animal agriculture has increased. Mesquite (Prosopis sp) is a widespread legume, widely used to feed several livestock species in Mexico. The main product of mesquite is the pod, which is considered high quality food. As a legume, it could be assumed that mesquite contains some amounts of phytoestrogens which might induce potential estrogenic effects. However, to our knowledge, there are no reports regarding the possible estrogenic activity of this legume either in livestock or in animal models such as the rat. Therefore, in this study, we evaluated the potential estrogenic effects of mesquite pod extract on several aspects of behavior and reproductive physiology of the female rat. The effects of the extract were compared with those of E(2) and two isoflavones: daidzein (DAI) and genistein (GEN). The following treatments were given to groups of intact and ovariectomized (OVX) female rats: vehicle; mesquite pod extract; E(2); GEN; DAI. Compared to vehicle groups, mesquite pod extract, DAI, GEN, and E(2) increased uterine weight and induced growth in vaginal and uterine epithelia. In intact rats, mesquite pod extract, GEN and DAI altered estrous cyclicity, decreased lordotic quotient and intensity of lordosis. In OVX rats, mesquite pod extract, DAI and GEN induced vaginal estrus, increased vaginal epithelium height, and induced lordosis, although its intensity was reduced, compared with intact rats in estrus and E2-treated rats. These results suggest that mesquite pod extract could have estrogenic activity. However, the presence of phytoestrogens in this legume remains to be confirmed.

The cholinergic system participates in the regulation of masculine sexual behavior, mainly through the muscarinic system. Recently, muscarinic receptors have been subdivided into at least two subtypes, M1 and M2, according to their differential affinity for pirenzepine. In this study, we analyzed the possible participation of the M1 muscarinic receptor subtype on masculine sexual behavior regulation. In the first experiment, trihexyphenidyl, a specific M1 antagonist, was administered to experienced adult male rats in a wide range of doses (from 0.1 to 6.4 mg/kg). No modification was observed in any of the male sexual behavior parameters recorded, with the exception of the highest dose at which an increase of the intromission frequency and a decrease of the ejaculation frequency were observed. In the second experiment, trihexyphenidyl was administered in several doses (from 0.2 to 1.6 mg/kg), before the administration of oxotremorine, a muscarinic agonist, at a dose that readily facilitates masculine sexual behavior. Trihexyphenidyl completely prevented the facilitatory effects of oxotremorine even at the smallest dose used. These results strongly suggest that the M1 muscarinic receptor subtype participates in the cholinergic facilitation of masculine sexual behavior.

In this study, the role of cholinergic systems in the regulation of male sexual behavior was analyzed by different approaches. Both muscarinic agonists and antagonists, as well as a nicotine agonist, were administered to sexually experienced male rats. In Experiment 1, oxotremorine (OXO), a muscarinic agonist, decreased the intromission frequency and ejaculatory latency in a dose-dependent way. Moreover, an increase in ejaculatory frequency was observed. In Experiment 2, the muscarinic antagonist scopolamine (SCO) produced a dose-related impairment of sexual behavior, decreasing the percentage of sexually active males. The smaller doses of SCO delayed the initiation of sexual behavior and decreased ejaculatory frequency. In an attempt to analyze the effect of muscarinic supersensitivity on sexual behavior, in Experiment 3 a long-term blockade of muscarinic receptors (SCO for 17 days) was followed by OXO administration. Animals displayed a significant increase of mount frequency, which results in the decrease of both the hit rate and ejaculatory frequency. In Experiment 4, six doses of nicotine were acutely administered. Only the higher doses (0.4, 0.8, and 1.6 mg/kg) induced a decrease in intromission frequency, although no significant differences were found in any other parameter. These results strongly suggest that cholinergic participation in masculine sexual behavior regulation is mediated mainly through muscarinic system.