Muscarinic pharmacology of the spinal cord of the neonatal rat in vitro.

The pharmacology of two muscarinic responses, recorded from the ventral roots of the spinal cord in the neonatal rat, have been compared: the depolarising response and the inhibition of the monosynaptic compound action potential (CAP). Pirenzepine was more potent than AF-DX 116 in antagonising the depolarising response. However, the potencies of these compounds indicated that this response may be mediated by neither M1 nor M2 (cardiac-like) receptors. The drug AF-DX 116 (1 microM), but not pirenzepine, selectively reduced the inhibitory effect. It is concluded that the receptors mediating these two responses are different.