The effects of castration on neurotransmission in the rat vas deferens.

1 Responses to adrenoceptor agonist drugs and to field stimulation were examined in vasa deferentia from adult castrated or intact rats. Isometric tension was recorded in vitro from whole or transversely bisected vasa. 2 After castration vasa exhibited spontaneous contraction, noradrenaline no longer produced a 'tonic' contraction but increased the 'phasic' spontaneous activity and salbutamol inhibited spontaneous activity by a beta-adrenoceptor-mediated mechanism. 3 After castration the 'adrenergic' components of the contractile responses to field stimulation were lost whereas 'non-adrenergic' responses remained, pre-junctional inhibition of field stimulation-induced contractions by either endogenous or exogenous activation was lost but adrenergic terminals could still be demonstrated microscopically. 4 Testosterone treatment partially reversed these effects of castration. 5 The relevance of these results to the nature of neurotransmission and to the genesis of spontaneous contraction in the vas deferens is discussed.