Functional discrimination of postganglionic neurones to the cat's hindpaw with respect to the skin potentials recorded from the hairless skin.

Abstract

1. Functional characteristics of postganglionic neurones innervating the hairless skin of the cats hindpaw have been analyzed with respect to the skin potentials recorded from the surface of the hair-less skin in chloralose anaesthetized, immobilized, and artificially ventilated animals. 2. Postganglionic neurones of which the activity was closely correlated with the fast transient negative atropine-sensitive skin potentials were called SM (sudomotor) neurones. Other, spontaneously active, postganglionic neurones whose activity was not correlated with these potentials were called VC (vasoconstrictor) neurones. 3. The SM neurones have low resting activity of 0.2±0.1 imp/s (mean±S.D.) or are silent; their axons conduct with 0.77±0.11 m/s. These neurones are activated by vibrational stimuli (tapping on the experimental frame), by noxious cutaneous stimuli, by systemic hypoxia and systemic hypercapnia. Their activity shows respiratory modulation, but no cardiac modulation. 4. The VC neurones have resting activity of 1.1±0.4 imp/s; their axons conduct with 0.52±0.11 m/s. These neurones are inhibited by noxious cutaneous stimuli, by systemic hypoxia and by systemic hypercapnia. Vibrational stimuli inhibit part of these neurones or are without effect. The activity in the VC neurones shows respiratory and cardiac modulations. These functional properties of the VC neurones to the hairless skin are largely identical to those innervating the hairy skin which were investigated recently in our laboratory. 5. The activity of the VC neurones is correlated with slow transient skin potentials which are atropine resistant. Decrease of the activity in these neurones is accompanied by slow transient skin potentials with positive polarity.