A physiological and pharmacological analysis of the electrodermal response in the rat

Electrodermal responses (EDR) of the sympathetic-cholinergic sudomotor system were elicited in the footpads of the hindpaws of anesthetized rats. The most reactive CNS loci were caudal to the region of the posterior hypothalamus. Peripherally evoked responses were elicited by electrical stimulation of the decentralized tibial nerve. The amplitude of these evoked EDR was stable over time and both the centrally and peripherally elicited responses were frequency-dependent. Atropine (200 micrograms/kg) depressed the EDR elicited by both peripheral and central stimulation whereas hexamethonium (20 mg/kg) only inhibited the central EDR. Clonidine had no effect on the EDR evoked at the periphery but produced a significant dose-dependent depressant effect on the centrally evoked EDR; this effect was partially antagonized by yohimbine (0.75 mg/kg). It is suggested that the rat is a suitable species for the use of the sudomotor system in the investigation of adrenergic agents which are thought to have a central sympatho-inhibitory action.