Quantitative aspects of responses in trigeminal relay neurones and interneurones following mechanical stimulation of sinus hairs and skin in the cat

Publisher Website
Google Scholar
Abstract
Stimulus-response relationships in discharges of trigeminal relay- and interneurons were investigated in the barbiturate anesthetized cat using controlled sinus hair or skin displacements. In comparison with discharges in slowly adapting primary afferent fibers the responses in all higher order neurons were considerably reduced in firing rate and often revealed modifications suggesting the interaction of mechanisms actively modulating the afferent input. In relay neurons with or without a tonic discharge component the dynamic on response during a trapezoidal displacement of sinus hairs was determined entirely or predominantly by the movement velocity and to be independent of the deflexion angle of a stimulus. In contrast, the static response in tonic relay neurons was determined by both the movement velocity and the displacement amplitude. Spatial summation of afferent input caused either only quantitative changes in the responses of relay neurons leaving the general discharge properties unaltered or caused both qualitative and quantitative changes in the responses. Interneurons consisted of 2 functional groups. In about 25% of them the responses were not or only slightly dependent on the intensity of the applied stimulus, often burstlike and of an all or nothing character. In the 2nd group of interneurons the responses showed a quantitative dependence on the applied stimuli. In this group of interneurones responses often increased with the spatial extension of the peripheral stimulus revealing spatial summation of the afferent input.