CENTRAL-NERVOUS-SYSTEM INNERVATION OF THE PENIS AS REVEALED BY THE TRANSNEURONAL TRANSPORT OF PSEUDORABIES VIRUS

Transneuronal tracing techniques were used in order to identify putati ve spinal interneurons and brainstem sites involved in the control of penile function. Pseudorabies virus was injected into the corpus caver nosus tissue of the penis in rats. After a four day survival period, r ats were perfused with fixative and virus-labelled neurons were identi fied by immunohistochemistry. Postganglionic neurons were retrogradely labelled in the major pelvic ganglia. In the spinal cord, sympathetic and parasympathetic preganglionic neurons were labelled transneuronal ly. Presumptive interneurons were also labelled in the lower thoracic and lumbosacral spinal cord in locations consistent with what is curre ntly known about such interneurons. In the brainstem, transneuronally labelled neurons were found in the medulla, pons and hypothalamus. Reg ions consistently labelled included the nucleus paragigantocellularis, parapyramidal reticular formation of the medulla, raphe pallidus, rap he magnus, A5 noradrenergic cell group, Barrington's nucleus and the p araventricular nucleus of the hypothalamus. This study confirmed previ ous studies from our lab and others concerning the preganglionic and p ostganglionic neurons innervating the penis. The number, morphology an d location of these neurons were consistent with labelling seen follow ing injection of conventional tracers into the penis. The brainstem nu clei labelled in this study were also consistent with what is currentl y known about the brainstem control of penile function. The labelling appeared to be highly specific, in that descending systems involved in other functions were not labelled. These results provide further evid ence that the pseudorabies virus transneuronal tracing technique is a valuable method for identifying neural circuits mediating specific fun ctions.