Identification of neurones of the brain and spinal cord involved in the innervation of the ductus deferens using the viral tracing method

From Ancient to Emerging Infections: The Odyssey of Viruses in the Male Genital Tract

The male genital tract (MGT) is the target of a number of viral infections that can have deleterious consequences at the individual, offspring, and population levels. These consequences include infertility, cancers of male organs, transmission to the embryo/fetal development abnormalities, and sexual dissemination of major viral pathogens such as human immunodeficiency virus (HIV) and hepatitis B virus. Lately, two emerging viruses, Zika and Ebola, have additionally revealed that the human MGT can constitute a reservoir for viruses cleared from peripheral circulation by the immune system, leading to their sexual transmission by cured men. This represents a concern for future epidemics and further underlines the need for a better understanding of the interplay between viruses and the MGT. We review here how viruses, from ancient viruses that integrated the germline during evolution through old viruses (e.g., papillomaviruses originating from Neanderthals) and more modern sexually transmitted infections (e.g., simian zoonotic HIV) to emerging viruses (e.g., Ebola and Zika) take advantage of genital tract colonization for horizontal dissemination, viral persistence, vertical transmission, and endogenization. The MGT immune responses to viruses and the impact of these infections are discussed. We summarize the latest data regarding the sources of viruses in semen and the complex role of this body fluid in sexual transmission. Finally, we introduce key animal findings that are relevant for our understanding of viral infection and persistence in the human MGT and suggest future research directions.

Presence of corticotrophin-releasing factor and/or tyrosine hydroxylase in cells of a neural brain-testicular pathway that are labelled by a transganglionic tracer

Our laboratory has shown that male testosterone levels are not solely controlled by the release of hypothalamic gonadotrophin-releasing hormone and pituitary luteinising hormone, but are also regulated by a multisynaptic pathway connecting the brain and the testis that interferes with the testosterone response to gonadotrophins. This pathway, which is independent of the pituitary gland, is activated by an i.c.v. injection of either the stress-related peptide corticotrophin-releasing factor (CRF) or of beta-adrenoceptor agonists, both of which alter androgen release and decrease levels of the peripheral-type benzodiazepine receptor and the steroidogenic acute regulatory protein within Leydig cells. Our original studies used the retrograde transganglionic tracer pseudorabies virus (PRV) to map progression of the virus from the testes to upper brain levels. The present study aimed to extend this work by identifying the regions where CRF and catecholamine neurones represented components of the stress-activated, brain-testicular pathway that prevents testosterone increases. To this end, anaesthetised adult male rats received an intra-testicular injection of PRV. Using immunofluorescence, we identified co-labelling of PRV and either CRF or tyrosine hydroxylase (TH), the enzyme responsible for biogenic amine synthesis. Co-labelling of PRV and CRF was found in the bed nucleus of the stria terminalis, the paraventricular nucleus of the hypothalamus (PVN) and the central amygdala. Co-labelling of PRV and TH was found in the PVN, substantia nigra, A7/Kölliker-Fuse area, area of A5, locus coeruleus, nucleus of solitary tract, area of C3, area of C2 and the area of C1/A1. These results indicate that most cell groups of the ventral noradrenergic pathway have neurones that are a part of the brain-testicular pathway. This suggests that the stress hormones CRF and catecholamines may act as neurotransmitters that signal the pathway to inhibit increases in plasma testosterone levels.

Selective impairment of noradrenergic transmission in the bisected rat vas deferens following photochemically-induced cerebral ischaemia

BACKGROUND

Cerebrovascular disease may impair the autonomic control of peripheral organs including the male urogenital tract. This study investigates the effect of cortico-parietal focal ischaemia on the adrenergic and purinergic transmission in isolated epididymal and prostatic portion of rat vas deferens.

METHODS

Focal brain ischaemia was induced in male rats by photochemical activation following rose bengal intravenous injection. Twenty-four hours following brain ischaemia, cumulative and non-cumulative concentration-response curves were obtained for noradrenaline and alpha,beta-methylene ATP in the right and left epididymal and prostatic portions of the vas deferens. Both portions were also stimulated by single-pulse or pulse trains at 2-30 Hz to produce isometric contractions.

RESULTS

In both portions from ischaemic rats the response to exogenous noradrenaline was markedly depressed compared with controls. Acute cortico-parietal ischaemia almost completely abolished the adrenergic phase of the response to single-pulse stimulation in the epididymal portion of the vas deferens. In addition, brain ischaemia deeply depressed phasic and tonic contractions of the frequency-response curve in both portions of bisected vas deferens.

CONCLUSIONS

Cortico-parietal ischaemia produces a selective noradrenergic impairment at the level of male sexual secondary organs that may contribute to sexual dysfunction after stroke.

Supraspinal connections of the reproductive organs: structural and functional aspects

Gonadal functions are governed by the hypothalamo-hypophyseal system. Other organs of the reproduction tract are under the regulatory action of gonadal steroids. In the past two decades several data have been accumulated on the involvement of fine-tuning control mechanisms which include autocrine and paracrine effects of biologically active substances produced locally and the regulatory action of nerves innervating the organs of the system. Recent studies using the viral transsynaptic technique have revealed cell groups in the central nervous system that are transneuronally connected with the male and female reproductive organs. This review summarizes neuromorphological data on the supraspinal innervation of reproductive organs and the functional significance of these brain areas in the control of reproduction.