Potentiation of sympathetic neuromuscular transmission mediated by muscarinic receptors in guinea pig isolated vas deferens.

In guinea-pig isolated vasa deferentia, purinergic neurogenic contractions and responses to applied adenosine 5'-triphosphate (ATP) were potentiated by carbachol; responses to adrenergic transmission and applied noradrenaline were not. Following blockade of P2 receptors and alpha-adrenoceptors, the residual neurogenic response was massively potentiated by carbachol, suggesting the presence of a non-purinergic, non-adrenergic component. In the presence of guanethidine, carbachol had no significant effect, indicating that sympathetic transmission was the only element involved. Use of oxotremorine and selective muscarinic receptor antagonists suggested that the potentiating effect of carbachol and oxotremorine was mediated via M3 muscarinic receptors without involvement of nicotinic receptors.