Neuromodulatory actions of substance P on the muscarinic receptors of the vas deferens of the rat

The response of post-synaptic neurokinin receptors to SP were not changed by pirenzepine or N-methyl-scopolamine. Atropine led to a slight increase in the EC 50 of SP for its post-synaptic neurokinin (NK-A) receptor. In the presence of neostigmine no changes in the Emax and EC 50 values of SP for its post- and pre-synaptic receptor site were observed. Only the muscarinic receptor site were observed. Only the muscarinic receptor antagonists, atropine and NMS, elicited statistically significant increases in the Emax of SP st its pre-synaptic receptor (NK-A). Addition of 7.4–740 nM SP resulted in a decrease in the EC 50 and Emax values of ACh for its post-synaptic muscarinic receptor (M1). Conversely, 740 nM SP produced an increase in the EC 50 and Emax values of ACh at its pre-synaptic muscarinic receptor (M2). Concentrations of 7.4 and 74 nM SP did not produce statistically significant changes in the Emax of ACh for its pre-synaptic M2 receptor.