A further contribution to the question of trophic and hormonal influences on the noradrenaline content of the male reproductive tract: effect of combined androgen and estrogen treatment of prepuberally castrated rats

Maturational and maintenance effects of testosterone on terminal axon density and neuropeptide expression in the rat vas deferens

Testosterone causes growth of many pelvic ganglion cells at puberty and their maintenance during adulthood. Here we have focused on two populations of pelvic ganglion cells that project to the rat vas deferens: noradrenergic neurons that innervate the smooth muscle and synthesize neuropeptide Y, and cholinergic neurons that primarily innervate the mucosa and contain vasoactive intestinal peptide. We have assessed the muscle innervation after pre- or postpubertal castration, using immunohistochemistry to determine axon density and radioimmunoassay to quantify levels of neuropeptides in tissue extracts. Our results show that androgen deprivation in each period causes substantial effects. Noradrenergic axons in the muscle increase in density after castration, partly due to organ size being smaller than age-matched controls. However, when corrected for target size, there is an overall decrease in total number of axons. This implies that androgen exposure at puberty has a direct effect on neurons to ensure that the adult pattern of innervation is attained, and that this is not simply by matching terminal field to target size. Similar effects of pre- and postpubertal castration imply that continued exposure to testosterone is necessary to maintain normal target innervation. Castration in both time periods increased the density of axons containing vasoactive intestinal peptide, however the effects of castration on the total number of these axons in the muscle were more variable. The concentration of vasoactive intestinal peptide increased substantially following either pre- or postpubertal castration although absolute amounts per vas deferens were decreased. Effects on neuropeptide Y concentration were less pronounced but the total amount per vas deferens was decreased after pre- or postpubertal castration. Our study shows that the action of testosterone (or a metabolite) on a pelvic ganglion cell soma is likely to reflect a change in its terminal field, but that these effects are not mediated simply by testosterone influencing the size of its target organ.

Effects of testosterone on pelvic autonomic pathways: progress and pitfalls

Testosterone has potent effects on reproductive behavior, many of which are due to actions on brain nuclei and spinal motoneurons controlling perineal muscles. The autonomic circuits involved in penile erection, ejaculation and emission, have been less commonly considered as targets for circulating androgens. This review demonstrates that many components of pelvic autonomic reflex pathways, including preganglionic neurons, autonomic ganglion cells and primary afferent neurons, are likely to be influenced by testosterone. The steroid appears to play an important role in maintaining neuronal morphology, transmitter synthesis and receptor expression throughout adulthood. Surprisingly, the effects of testosterone are not limited to neurons involved in reproductive reflexes. The challenge is now to determine the range of neuronal features influenced by androgens, and the mechanisms by which these occur. Studies of androgen receptor location indicate that in many autonomic neurons gene expression may be directly influenced by androgens, but a mismatch between receptor distribution and androgen action shows that in some cells other mechanisms must exist. It is also possible that androgens are metabolised to estrogens by some peripheral neurons. Irrespective of the mechanism, it is time to acknowledge that testosterone is an important "maintenance factor" for autonomic neurons.

The effect of long-term castration on the histochemically demonstrable catecholamines in the hypogastric ganglion of the rat

The effect of long-term castration on the hypogastric ganglion of the rat was studied using the formaldehyde-induced fluorescence (FIF) method. After castration the fluorescence intensity was lower and the size of the adrenergic neurons was smaller than in normal or in testosterone-treated castrated rats. The fluorescence profile of the ganglia of castrated rats differed from the profiles of control or testosterone-treated castrated rats. Vacuolated neurons were seen in the hypogastric ganglion of controls but not in the ganglia of castrated animals. After long-term castration the size of the ventral prostate was drastically reduced. The density of adrenergic nerves was similar in castrated, normal and testosterone-treated castrated rats. It is concluded that long-term castration has an effect on adrenergic neurons by decreasing the FIF and by producing other morphological changes. The effect can be reversed by testosterone treatment.

The formaldehyde-induced fluorescence of the developing hypogastric (main pelvic) ganglion of the rat. Short adrenergic neurons and the effect of testosterone

The development of the hypogastric ganglion of normal and testosterone-treated rats was studied using formaldehyde-induced fluorescence (FIF) method. The fluorescence intensities were recorded microspectrofluorimetrically. In normally developing rats cytoplasmic FIF decreases and cell size increases with age. In normally developing rats cytoplasmic FIF decreases and cell size increases with age. In testosterone-treated animals FIF increases during 2--6 weeks compared to the controls. The differences between control and experimental rats were significant. The diameters were significantly longer in treated animals in three and four week old groups. Vacuolated neurons were seen earlier in testosterone-treated rats. No changes in FIF or in cell size were noticed in the superior cervical ganglion. The male sex steroid, testosterone evidently influences the catecholamine turnover and cellular growth during development in the male pelvic ganglion.

Adrenergic influences on rabbit oviduct: effect of muscle size and ovarian hormones

This study attempts to distinguish between a direct action of ovarian steroids on adrenergic neurons in the oviduct and an indirect effect mediated by changes in muscle size. Mature rabbits were treated as follows: group 1, ovariectomized and a polyethylene catheter (1 mm OD) inserted into isthmus of one oviduct (CT) with contralateral oviduct as control (C); group 2, normal, estrous animals with one intubated isthmus (ET) and contralateral control (E). Fourteen days postoperatively, oviducts were removed and muscle-wall thickness, norepinephrine (NE) content, and response to nerve stimulation were measured. Although castration atrophy was prevented in CT, NE content of CT was significantly less than C, 0.032 +/- 0.07 versus 1.09 +/- 0.10 nmol. NE content of ET was also significantly less than E (1.32 +/- 0.03 versus 1.81 +/- 2.0) despite a greater wall thickness of ET. It was concluded that: a) withdrawal of ovarian hormones reduces NE contents by a direct action on nerves; b) moderate stretch, per se, increases muscle size and reduces NE content; c) nerve stimulation induces muscle contraction despite large reduction in transmitter content.

Influence of age, growth, castration and testosterone treatment on the noradrenaline levels of the ductus deferens and the auxiliary male reproductive glands of the rat

The total amount of noradrenaline (NA) in the male accessories increases with normal growth of the organs and also with the age of the rat. The ductus deferens of the old rat has about twice as high NA concentration as that of the young rat. Castration of the prepuberal rat or the puberal rat leads to retardation or cessation, respectively, of the increase in NA amount of the male genital tract. Only in the old rat does castration produce a definite decrease in NA amount of the tract. Castration always raises the NA concentration of the sex accessories. Testosterone treatment of the puberal rat or the old rat produces minor or no increase, respectively, in total amount of NA of the male sex accessories. Testosterone treatment of old prepuberally castrated rats produces a marked increase in NA content of the male organs. It is concluded that androgens have no substancial direct effect on the adrenergic innervation per se, but affects the transmitter levels of the male organs indirectly through changes in number, size and relative proportion of the target cells of the adrenergic nerves i.e. the smooth muscle cells.