Origins and projections of peptide-immunoreactive nerves in the male rat genitofemoral nerve.

Following injection of retrograde tracer to one genitofemoral nerve of male rats, motoneurones and dorsal root ganglion cells of segmental levels L1/L2 were labelled ipsilaterally. Many labelled motoneurones were calcitonin gene-related peptide- (CGRP) immunoreactive. In the ganglia, a proportion of the labelled cells were CGRP-, tachykinin- or galanin-immunoreactive (10%:6%:53% respectively). In comparison with ganglia of the contralateral side, galanin-immunoreactive cells were significantly increased in the ipsilateral ganglia. Unilateral genitofemoral nerve section induced a loss of CGRP- or tachykinin- and an increase of galanin-immunoreactive cells in the ipsilateral L1/L2 ganglia. In the ipsilateral L1/L2 dorsal horn, CGRP and tachykinin, but not galanin, immunoreactivity was reduced. In the cremaster muscle and scrotal skin of either side galanin-immunoreactive fibres were not visible and CGRP- and tachykinin-immunoreactive fibres were depleted in the ipsilateral side. Capsaicin induced a loss of CGRP- and tachykinin-immunoreactive ganglion cells and of CGRP, tachykinin or galanin immunoreactivity from the dorsal horn. In the scrotal skin, CGRP- and tachykinin-immunoreactive fibres were depleted. By contrast in the muscle, a few CGRP-immunoreactive fibres persisted. The data demonstrate that (i) the genitofemoral nerve originates at segmental levels L1/L2; (ii) CGRP- and tachykinin-immunoreactive sensory and CGRP-immunoreactive motor neurones project to the cremaster muscle and scrotal skin; and (iii) nerve pertubation induces an increase of galanin-immunoreactive sensory neurones, the significance of which remains to be elucidated.