Substance P depolarizes nerve terminals in an autonomic ganglion.

The effect of substance P on presynaptic nerve terminals was examined by intracellular impalements of calyciform terminals within the chick ciliary ganglion. Substance P produced a slow depolarization of the nerve terminals which was associated with an increase in input resistance. The postsynaptic ciliary neurons were unaffected by exposure to substance P, indicating that at this synapse the physiological effects of substance P may be largely presynaptic in nature.