Nicotinic, muscarinic and adrenergic receptors in a parasympathetic ganglion.

Transmission in submandibular ganglia of hamsters was blocked by hexamethonium and dimethylphenylpiperazinium. Dimethylphenylpiperazinium caused depolarization and decreased membrane resistance (Rm). The muscarinic agonist, bethanechol (BCh) caused depolarization of some cells and hyperpolarization of others. Regardless of the change in membrane potential, BCh always increased Rm. Since the responses to BCh persisted in the absence of [Ca++]0, it was concluded that BCh acted directly on the ganglion cells and did not depend upon a transsynaptic process. All responses to BCh were prevented by atropine. The evidence suggests that the ganglion cells possess muscarinic receptors. Like BCh, norepinephrine (NE) either depolarized or hyperpolarized the ganglion cells. There was no relationship between the blockade of transmission by NE and the effect of NE on the membrane potential. The responses to NE were prevented by dihydroergotamine, suggesting the presence of alpha adrenergic receptors on the ganglion cells.