Effects of sex steroids on sensory and motor spinal mechanisms

Androgen receptors and sociosexual behaviors in mammals: The limits of generalization

Circulating testosterone is easily aromatized to estradiol and reduced to dihydrotestosterone in target tissues and elsewhere in the body. Thus, the actions of testosterone can be mediated either by the estrogen receptors, the androgen receptor or by simultaneous action at both receptors. To determine the role of androgens acting at the androgen receptor, we need to eliminate actions at the estrogen receptors. Alternatively, actions at the androgen receptor itself can be eliminated. In the present review, I will analyze the specific role of androgen receptors in male and female sexual behavior as well as in aggression. Some comments about androgen receptors and social recognition are also made. It will be shown that there are important differences between species, even between strains within a species, concerning the actions of the androgen receptor on the behaviors mentioned. This fact makes generalizations from one species to another or from one strain to another very risky. The existence of important species differences is often ignored, leading to many misunderstandings and much confusion.

Evaluation of penile vascular status in men with epilepsy with erectile dysfunction

PURPOSE

Erectile dysfunction (ED) is common in males with epilepsy, likely of multifactorial etiology, including possible systemic vascular comorbidities and medication effects. Here we examined male patients for the possibility of a vasculogenic element of ED.

METHODS

Research participants included 47 men with epilepsy (mean age=30.98 years; duration of illness=13.98 years) and 25 healthy matched men (mean age=30.36). Erectile function was assessed using the International Index of Erectile Function Questionnaire (IIEF-5). Penile blood flow was assessed using Duplex Ultrasonography (PDU) after intracavernous alprostadil injection. Penile peak systolic velocity (PSV), end-diastolic velocity (EDV) and resistance index (RI) were the functional parameters analyzed. Carotid artery intima media thickness (CA-IMT) was also measured.

RESULTS

Thirteen of the 47 men with epilepsy (23.40% versus 0% for controls) reported ED, and of these patients, 11 (84.62%) had abnormal PDU [PSV=28.23 ± 6.1cm/s, P=0.0001; EDV=2.22 ± 5.71 cm/s, P=0.004; RI=0.89 ± 0.22, P=0.071] suggesting vasculogic ED. Penile arterial insufficiency was identified in 5 (45.45%), while 6 (54.54%) had mixed arterial insufficiency and venous leak. Compared to patients with high PSV, patients with low PSV had lower IIED-5 scores, higher EDV, lower RI, higher diastolic blood pressure and higher CA-IMT values. There were no differences in depression, anxiety or concentrations of sex hormones. Significant correlations were evident between PDU variables and duration of illness, depression and anxiety scores and CA-IMT values. In multivariate analysis, the association between PDU parameters and CA-IMT values remained significant even after adjustment for other confounding variables.

CONCLUSIONS

Vasculogenic ED is frequent with epilepsy and its relationship to systemic atherosclerosis cannot be excluded.

Distribution of androgen and oestrogen receptors-α in the seminal vesicle-related spinal neurones in male rats

The seminal vesicles are male accessory sex glands that contribute much of the seminal fluid volume. Previous studies have suggested that the majority of autonomic innervations to the rat seminal vesicles originate from the bilateral major pelvic ganglia. Many preganglionic autonomic neurones innervating the pelvic ganglion were expressed androgen receptors (AR) or oestrogen receptor (ER)-α immunoreactivity. However, direct neuroanatomic data regarding the distribution of AR and ER-α in seminal vesicle related-spinal neurones are lacking. In the present study, a nonvirulent pseudorabies virus (PRV-152 strain) was used in a retrograde tracing experiment. Four days after PRV injection into the seminal vesicles of male rats, spinal cord sections were prepared. Double- and triple-fluorescence techniques using AR and ER-α with choline acetyltransferase (ChAT) and PRV were used to investigate the AR and ER-α distribution in the seminal vesicles related spinal neurones in male rats. In lamina X, 14% of the PRV-labelled neurones in the L1-L4 segments and 43% in the L5-S1 segments were double-labelled with AR. In the L1-L4 segments, 6% of PRV-labelled neurones and 26% in the L5-S1 segments were double-labelled with ER-α. In the intermedial cell column area, 10% of PRV-labelled neurones in the L1-L4 segments and 47% of PRV-labelled neurones in the L5-S1 segments were double-labelled with AR. Up to 16% of PRV-labelled neurones in the L5-S1 segments were double-labelled with ER-α. No PRV-labelled neurones in the L1-L4 segments were double-labelled with ER-α. However, for the AR and ER-α/PRV/ChAT triple-fluorescence experiments, very few seminal vesicle preganglionic neurones expressed AR or ER-α. Our data suggests that many spinal interneurones but not preganglionic neurones involved in the seminal vesicle control in male rats were double-labelled with AR or ER-α, and they were mainly located at the parasympathetic level in the spinal cord.

Retrograde tracing of spinal cord connections to the cervix with pregnancy in mice

In contrast to the uterus, the cervix is well innervated during pregnancy and the density of nerve fibers increases before birth. To assess neural connections between the cervix and the spinal cord, the cervix of pregnant mice was injected with the trans-synaptic retrograde neural tract tracer pseudorabies virus (PRV). After 5 days, the virus was present in nerve cells and fibers in specific areas of the sensory, autonomic, and motor subdivisions of the thoracolumbar spinal cord. In nonpregnant controls, the virus was predominantly distributed in laminae I-III in the dorsal gray sensory areas with the heaviest label in the substantia gelatinosa compared with the autonomic or motor areas. Labeled cells and processes were sparse in other regions, except for a prominent cluster in the intermediolateral column (lamina VII). Photomicrographs of spinal cord sections were digitized, and the total area with the virus was estimated. Compared with nonpregnant controls, the area with PRV was significantly decreased in all the spinal cord subdivisions in pregnant mice except in the intermediolateral column. However, areas with the virus were equivalent in mice injected with PRV at 4 days or 1 day before birth. These findings suggest that the predominant innervation of the murine cervix is from the sensory regions of the thoracolumbar spinal cord, and that these connections diminish with pregnancy. The results raise the possibility that the remaining connections from sensory and autonomic subdivisions, particularly the intermediolateral column, of the thoracolumbar spinal cord may be important for increased density of nerve fibers in the cervix as pregnancy nears term.

Physiology of penile erection and pathophysiology of erectile dysfunction

This article reviews the physiology of penile erection, the components of erectile function, and the pathophysiology of erectile dysfunction. The molecular and clinical under-standing of erectile function continues to gain ground at a particularly fast rate. Advances in gene discovery have aided greatly in working knowledge of smooth muscle relaxation/contraction pathways. The understanding of the nitric oxide pathway has aided not only in the molecular understanding of the tumescence but also greatly in the therapy of erectile dysfunction.

Evolutionary insights into the regulation of courtship behavior in male amphibians and reptiles

Comparative studies of species differences and similarities in the regulation of courtship behavior afford an understanding of evolutionary pressures and constraints shaping reproductive processes and the relative contributions of hormonal, genetic, and ecological factors. Here, we review species differences and similarities in the control of courtship and copulatory behaviors in male amphibians and reptiles, focusing on the role of sex steroid hormones, the neurohormone arginine vasotocin (AVT), and catecholamines. We discuss species differences in the sensory modalities used during courtship and in the neural correlates of these differences, as well as the value of particular model systems for neural evolution studies with regard to reproductive processes. For example, in some genera of amphibians (e.g., Ambystoma) and reptiles (e.g., Cnemidophorus), interspecific hybridizations occur, making it possible to compare the ancestral with the descendant species, and these systems provide a window into the process of behavioral and neural evolution as well as the effect of genome size. Though our understanding of the hormonal and neural correlates of mating behavior in a variety of amphibian and reptilian species has advanced substantially, more studies that manipulate hormone or neurotransmitter systems are required to assess the functions of these systems.

Evidence for the involvement of a spinal pattern generator in the control of the genital motor pattern of ejaculation

One of the hypotheses to explain the neural mechanisms underlying rhythmic behaviours suggests that the central nervous system has the intrinsic capacity to produce repetitive, rhythmic output to the muscles involved in the response by means of a neuronal circuit named central pattern generator (CPG). The occurrence of rhythmic motor patterns during ejaculatory behaviour in mammals, which includes the genital motor pattern, has been shown. A CPG might regulate the timing of the repetitive muscular responses that constitute the ejaculatory motor pattern. The objective of the present study was to evidence that a CPG at a spinal level is involved in the expression and pacing of the rhythmic motor pattern generated during ejaculation. To this purpose we used the genital reflex as a model system. Following the general principles for the study of rhythmic motor patterns, the data obtained in the present series of experiments document that: (1) a rhythmic muscular response, the genital motor pattern, is registered during the ejaculatory event (expulsion of the urethral contents); (2) this ejaculatory motor response has similar EMG characteristics in intact and in spinal urethane-anaesthetised male rats; (3) interruption of the afferent inflow (deafferentation) does not disrupt the expression of the ejaculatory motor train; (4) a change in the stimulation interval does not alter the intrinsic pacing of the ejaculatory-like response; and (5) fictive ejaculation can be induced by pharmacological means. Together, this evidence supports the notion that a CPG produces the rhythmic ejaculatory motor pattern registered during fictive ejaculation.

Characteristics of the motor and genital copulatory responses of the male hamster

The temporal and dynamic characteristics (duration, frequency, rhythmicity, and vigor) of pelvic thrusting displayed by 17 male golden hamsters during their copulatory behavioral responses: mounts, intromissions, ejaculations, and long intromissions, as well as their temporal correlation with the genital contacts established by intravaginal penile insertion, were studied by an accelerometric and polygraphic technique. Pelvic thrusting in all copulatory behavioral responses appeared as series or trains of rhythmical, synchronic, vigorous movements. The various pelvic thrusting trains lasted around 1 s on average, but those of mounts were significantly longer than the trains displayed in the other behavioral responses. The frequencies of pelvic thrusting were similar in all responses (around 15 thrusts per s) excepting mounts which had lower values. In intromission, ejaculation, and long intromission responses, when penile insertion occurred, pelvic thrusting either was interrupted or showed changes in its characteristics: penile insertion was related to a period without thrusting in intromissions, to a series of intravaginal thrusting of higher frequency (16.4 thrusts per s) and lower vigor in ejaculations, and to a prolonged period of 6 to 25 s of slow intravaginal pelvic thrusting (1-2 thrusts per s) in long intromissions. Penile insertion lasted longer in ejaculations than in intromissions and it was significantly shorter in both of these responses than in long intromissions. These results provide information about some dynamic aspects of sexual behavior in hamsters, as well as a temporal correlation between the motor and genital components of this behavior.