Substance P evokes slow and fast responses in cultured myenteric neurons of the guinea pig.

Intracelluar electrical recordings were made from myenteric neurons in tissue culture. Most of the neurons were found to be very sensitive to substance P (SP), which was applied by pressure from micropipettes. SP evoked two different responses: slow depolarizations with latencies of 1-5 s and durations of 1-2 min, and fast depolarizations with latencies of 30-50 ms and durations of 1-10 s. These may represent two distinct response mechanisms to SP.