Non-adrenergic inhibitory and non-cholinergic excitatory neural involvement in DMPP and nicotine action of fowl rectum.

Pharmacological analysis of the mechanical responses of fowl rectum to DMPP and nicotine showed that nicotinic stimulation produced varied responses on different segments. On the whole/distal segment DMPP and nicotine induced relaxations. On the proximal segment, DMPP induced relaxation whereas nicotine produced biphasic response. Termination of the adrenergic function converted the relaxatory responses of DMPP and nicotine to biphasic ones, the contractile component of which was potentiated by neostigmine and partially inhibited by atropine. This response was completely abolished by ganglion blockers. On cooled tissue preparations, neither nicotinic nor electrical stimulations elicited any response. These findings implicate the participation of non-adrenergic inhibitory and non-cholinergic excitatory neural elements besides the adrenergic and cholinergic ones to nicotinic stimulation.