Analysis of the modulating effect of catecholamines on electrogenesis in an isolated mechanoreceptor

Perfusion of isolated Pacinian corpuslces in the cat mesentery with solutions of dibutyryl-cAMP or theophylline caused an increase in spike activity against the background of a reduction in amplitude of receptor potentials and lowering of the threshold for spike generation. The opposite effect on mechanoreceptor electrical responses was found when catecholamines were used. It was postulated on the basis of these findings that the action of catecholamines on Pacinian corpuscles is accompanied by a fall in the cAMP level in the sensory nerve terminal. Noradrenalin caused a decrease in adenylate cyclase activity in receptor homogenates. The activating effect of noradrenalin on Na+, K+-ATPase, abolished by phentolamine but unchanged by propranolol, was demonstrated. The possible role of α-adrenoreceptors in the modulating effect of catecholamines on electrical activity of Pacinian corpuscles is discussed.