Responses of single receptor units of the rat mammary gland parenchyma to tactile stimulation.

Slowly adapting mechanoreceptor units with regular and irregular discharges were found in the mammary gland parenchyma. The receptive fields of both types of receptor units had a diameter of 1-1.5 mm. In some cases the receptor units had spontaneous activity at rest (0.5-3 spikes/sec). During stimulation by sawtooth mechanical stimuli with different rates of rise the momentary frequency of the receptor units was a linear function of amplitude of the mechanical stimulus. The threshold of afferent action potentials of the receptor units increased with an increase in the rate of rise of the mechanical stimulus.