Properties of mechanosensitive neurons within Auerbach's plexus of the small intestine of the cat.

Three different kinds of mechanosensitive neurons were detected by direct electrical recording from Auerbach's plexus. Neurons classified as fast-adapting mechanoreceptors discharged spikes at the onset of stimulation, and the discharge stopped during a sustained stimulus of constant intensity. Slowly-adapting mechanoreceptors maintained during sustained stimulation, a steady discharge at a frequency that was a direct function of the intensity of the stimulus. Tonic type neurons responded to mechanical stimulation with a prolonged train of spikes which had a consistent pattern from preparation to preparation. Once the tonic-type cells were triggered, the discharge followed a characteristic time course that was unchanged by further increase or decrease in stimulus intensity. Tonic-type neurons are probably not first order sensory neurons, but they may be activated by input derived from primary mechanoreceptors. Frequency of discharge of slowly-adapting mechanoreceptors was increased by histamine. This appeared to be secondary to histamine-induced contractile activity of the musculature.