Alterations in epididymal sperm maturation caused by ageing.

The epididymis is an organ that performs all the biochemical changes responsible for sperm maturation. During ageing, histological alterations in the epididymis and decreased protein synthesis have been found. This might affect the sperm maturation process. The aim of this study was to determine if the changes in the epididymis during ageing might cause alterations in sperm maturation. Wistar rats of 3-4months old (young) and 18-21months old (old) were used. The testosterone concentration was determined and the epididymides were dissected and divided in three regions: caput, corpus, and cauda. The tissues were used for histological processing and sperm extraction. Testosterone concentration decreased 34% in the old animals compared to the young ones. The distribution of mannose, sialic acid, and N-acetylglucosamine in the glycocalyx of the sperm membrane of old animals was different from that of young animals. The same occurred with phosphatidylserine externalisation and protein phosphorylation at tyrosine residues. Epididymis histology in old animals showed tubular and cellular degeneration. Our results suggest that ageing affects maturational markers, likely due to alterations in the epididymis as a result of the testosterone decrease associated with ageing.

Electrical activity of sensory pathways in female and male geriatric Rhesus monkeys (Macaca mulatta), and its relation to oxidative stress.

Synapses loss during aging has been related to decreased neuronal excitability and reduced electrophysiological activity in the nervous system, as well as to increased brain damage. Those physiological and biochemical alterations have been related to the oxidative stress increase associated with old age. The main substrate of lipid peroxidation (LPX) in the central and peripheral nervous systems are the myelin sheaths, and their damage generates a delayed nerve conduction velocity. However, studies in which the neural conduction velocity is related to changes in the redox state are still lacking. Therefore, our aim was to correlate the sensory neural pathways delay in healthy geriatric Rhesus monkeys (Macaca mulatta) with the oxidative stress associated with physiological aging. Twenty-four monkeys were divided into four groups according to age and gender. Auditory, visual, and somatosensory evoked potentials were obtained. Superoxide dismutase, catalase, and glutathione peroxidase enzymatic activity, as well as LPX, were determined from blood samples. Our results showed significant differences between the older and younger age groups in all neural generators of the different sensory pathways evaluated, along with an increase in LPX and the antioxidant enzymatic activities. It suggests that, even though the enzymatic activity was found to be higher in older monkeys, probably as a compensatory effect, it was not enough to avoid LPX damage and the declined electric activity associated with age.

Visual, auditive and somatosensory pathways alterations in geriatric rhesus monkeys (Macaca mulatta).

BACKGROUND: Synapses loss during aging is associated to neurophysiologic alterations that impair organism's health span, thus making the study and prevention of sensory decline relevant for healthy aging and welfare. Therefore the aim of this study was to obtain normative data related to the electrophysiological responses of the different neurosensory components in the visual, auditory and somatosensory pathways in healthy geriatric rhesus monkeys in captivity. METHODS: Twenty-four rhesus monkeys were divided in two groups: (i) Geriatric monkeys, 20-30 years of age, and (ii) Young monkeys, 7 years of age. Evoked potentials were obtained from the visual, auditory and somatosensory pathways. RESULTS: Regardless the sensory pathways evaluated, a significant delay in nerve conduction was observed in the geriatric group in comparison to the young group. CONCLUSIONS: Evoked potentials allowed identifying changes generated during aging in rhesus monkeys and normative data for this species were obtained.

Mesquite pod extract modifies the reproductive physiology and behavior of the female rat.

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.

Orchiectomy modifies the antidepressant-like response of nicotine in the forced swimming test.

Several studies have demonstrated that nicotine (NIC) exhibits antidepressant-like effects. In addition, it has been suggested that sexual hormones participate in the antidepressant actions of antidepressives. The present study was designed to analyze the effect of orchiectomy and the supplementation of testosterone propionate (TP) or 17ß-estradiol (E(2)) on the antidepressant properties of NIC using the forced swimming test (FST), as well as to determine possible changes in the FST during different time periods after orchiectomy. In order to evaluate the influences of orchiectomy on the effects of NIC, the study first evaluated the effects of different time periods on orchiectomized rats (15, 21, 30, 45 and 60 days) that were subjected to the FST. Then, different doses of NIC (0.2, 0.4, 0.8, 1.6 mg/kg, sc) were administered for 14 days to both intact and orchiectomized rats (after 21 day) which were then also subjected to the FST. Finally, the influence of the TP or E(2) supplementation on the antidepressant-like effect of NIC on orchiectomized rats (after 21 days) was also analyzed. Results reveal that orchiectomy significantly increased immobility behavior and decreased swimming and climbing up to 60 days after castration. In contrast, NIC decreased immobility behavior and increased swimming in intact rats; whereas orchiectomy suppressed this antidepressant effect of NIC. Only with E(2) supplementation was it possible to restore the sensitivity of the castrated rats to NIC. These results suggest that E(2) was able to facilitate the antidepressant response of NIC in orchiectomized rats.

Circadian activity of corticosterone in an animal model of depression: response to muscarinic cholinergic stimulation.

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; 5mg/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 12h, respectively). Results showed an increase in basal plasma levels of corticosterone in CMI-treated rats at time point zero and at 6h 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 12h). 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.

Testosterone, androstenedione, and 5alpha-dihydrotestosterone on male sexual behavior and penile spines in the hamster.

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.

Different functionality of the medial and orbital prefrontal cortex during a sexually motivated task in rats.

This study was designed to analyze whether the electroencephalographic (EEG) activity of the medial (mPFC) and orbital prefrontal cortex (oPFC) was modified during the performance of male rats in a T maze under two different conditions, sexually motivated (with previous intromission and females in the goal boxes of the lateral arms) or sexually non-motivated (without previous intromission and with empty goal boxes). Relative power (RP) of three EEG band frequencies, and inter-hemispheric correlation (r) were calculated and a comparison was made between rats under motivated and non-motivated conditions. In the mPFC of sexually motivated males, an increase of the RP in the 6-7 Hz band as well as a decrease in the 8-11 Hz band was observed in relation to an awake-quiet state and during the walk in the maze stem. Similarly, an increase in the r of the 6-7 Hz band was observed during the walk in the maze stem and when remaining near to a receptive female, when compared to non-motivated males. In the oPFC, only the RP of the 6-7 Hz band was increased during the walk in the maze stem of the motivated males. These data suggest that, among sexually motivated males, the mPFC is involved both in anticipatory and motor execution during the performance of the T maze task, whereas the oPFC is only involved in the motor execution of the T maze. These results are in line with other studies suggesting that the mPFC and oPFC are functionally distinct, regions which may work together during certain behaviors and physiological conditions.

Hormonal responses to different sexually related conditions in male rats.

Plasma levels of corticosterone (C) and testosterone (T) increase after sexual activity in males of several species. However, the physiological significance of these increases has not been elucidated. In the present study, hormonal response to different conditions linked to sexual activity was assessed. In the first experiment, plasma levels of C and T were assessed both in sexually experienced and naive male rats after the following conditions: (A) control group, without sexual stimulation; (B) males exposed to ovariectomized females; (C) males exposed to intact, non-receptive females; (D) males exposed to receptive females with the vagina obstructed, to avoid intromission; (E) males exposed to receptive females: but separated by a grid that prevents physical contact; (F) males exposed to receptive females during 30 min. In a second experiment, experienced male rats were allowed to repeatedly copulate until reaching the criteria for sexual exhaustion, and 24 h later, they were allowed to copulate. Once sexually related conditions ended, males were killed and their blood was obtained. C and T plasma levels were assessed by HPLC with ultraviolet (UV) detection. Results indicate that T did not increase significantly in naive male in any sexual condition, while in the experienced males, significant increases were observed with the mere presence of a receptive female and also after ejaculation. These increases were significantly larger in experienced males. On the other hand, C also increased in all sexual conditions, both in experienced and naive rats; however, the increase observed was larger in experienced males. Regarding sexual satiety, both C and T increased after copulating ad libitum to satiety. T increased almost three-fold compared to control, while C increased two-fold. No significant changes were observed in either one of the steroids 24 h after sexual exhaustion, even though males remained with a receptive female during an hour. These results show that sexual experience has an important influence on the hormonal response to sexual activity. C rises could be directly related to sexual arousal involved in the different sexual conditions, while T rises seem to have a direct relationship with both the motivation and execution aspects of masculine sexual behavior.

Effects of hormonal replacement with androgens and estrogens on male sexual behavior and plasma levels of these steroids in gonadectomized golden hamsters (Mesocricetus auratus).

Because the endocrine control of sexual behavior in male hamsters remains controversial, this study analyzed the influence of different androgens and estrogens in the regulation of masculine, sexual behavior (MBS). Aromatizable androgens: androstenedione (A) and testosterone (T), a non-aromatizable androgen: 5alpha-dihydrotestosterone (DHT), as well as estrogens (E2 and E1) alone or in combination with DHT, were administered in gonadectomized, sexually experienced males, for 3 weeks. In addition, plasma levels of these steroids were determined. Gonadectomy completely suppressed masculine sexual behavior (MSB) after 4 weeks. Both A and T replacements restored all the sexual behavior parameters in castrated hamsters by the 3rd week of treatment, with A being more potent in restoring all copulatory series and maintaining all MSB parameters, including long intromissions. Castrated males treated with DHT showed little interest in the female and did not display any copulatory behavior. Gonadectomized males treated with estrogens alone showed active anogenital investigation and displayed some mounts, but did not ejaculate. Males treated with estrogens combined with DHT had longer latencies and less number of ejaculations than males treated with aromatizable androgens. Long intromissions were observed only in males treated with T or A. Plasma levels of A were significantly higher than T levels in intact males. In males treated with A both androgens and estrogens were present in plasma. These results support the notion that aromatizable androgens, mainly A, but not non-aromatizable androgens or even estrogens in combination with DHT, play a relevant role in the endocrine regulation of MSB in the golden hamster.

Masculine sexual activity affects slow wave sleep in Golden hamsters.

The sleep pattern is modified by events occurring during wakefulness. In rats, it has been shown that male sexual behavior has a direct influence on sleeping patterns, increasing slow wave sleep (SWS) duration. On the other hand, the sexual behavior pattern of the male Golden hamster differs from the copulatory pattern of male rats. Male hamsters copulate faster and they do not display the motor inhibition observed in rats after each ejaculation. Moreover, close to exhaustion, hamsters display a behavioral pattern known as Long Intromission, which has been linked to an sexual inhibitory process. The present study was performed to determine the effects of male sexual activity on the sleep pattern in hamsters. Subjects were allowed to copulate for 30 and 60 min. In addition, the effect of locomotor activity was also assessed. The results show that male sexual behavior induced a significant increase of SWS II, with a reduction of wakefulness. No effect was observed on REM sleep. Locomotor activity produced only a slight effect on sleep. The results are discussed in terms of the similarities between the effects observed after sexual behavior on sleep in rats and hamsters, despite the substantial differences in the behavioral pattern.