Composition and central projections of the pudendal nerve in the rat investigated by combined peptide immunocytochemistry and retrograde fluorescent labelling

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The central distribution of the afferent and efferent projections of pelvic striated muscles, the pudendal and sciatic nerves, were systemically investigated in rats by retrograde tracing techniques combined with immunocytochemistry using antibodies to 9 neuropeptides. True Blue was injected into either the pelvic muscles, pudendal or sciatic nerves. Seven days later the spinal cord and dorsal root ganglia (L3–S2 levels) were processed for immunocytochemistry. Injection of tracer into the pelvic muscles labelled dorsomedial, ventral and dorsolateral motoneuron groups of the L6 segment and a few sensory neurons in the receptive dorsal root ganglia. Pudendal nerve injection also labelled the same motoneuron groups, 50% of neurons of the retrodorsolateral column and numerous sensory neurons of the dorsal root ganglion. Concomitant labelling of pudendal and sciatic nerves with different fluorescent tracers revealed a small number of double-labelled cells in the dorsal root ganglia but only single-labelled cells in the retrodorsolateral nucleus. Enkephalin-, somatostatin- and neuropeptide Y-containing fibres were particularly abundant in and around dorsomedial and dorsolateral groups as well as the intermediolateral cell column. We conclude that in the rat (a) the pudendal nerve has motor, sensory and autonomic (parasympathetic) components in contrast to the sciatic which is primarily motor and somatosensory, (b) some afferents from these nerves exhibit pre-spinal convergence and (c) dorsomedial and dorsolateral motoneuron groups are homologous to Onuf's nucleus in man.