Characteristics of the electrodermal response. A model for analysis of central sympathetic reactivity.

Electrodermal responses (EDR) of the sympathetic-cholinergic sudomotor system were elicited in anaesthetized cats. Responses were evoked centrally from hypothalamic, medullary and spinal loci, by stimulation of the pre- and postganglionic peripheral nerves, and reflexly following stimulation of an afferent nerve. The response was found to be dependent upon innervation of both the median and ulnar nerves (approximately 40 and 60% respectively). Both the centrally and peripherally evoked responses were frequency-dependent when a maximal current was used. The EDR evoked peripherally or from the cervical cord reached its maximal amplitude at 10-16 Hz whereas the EDR evoked from the hypothalamus and medulla did not reach its maximal amplitude until 48-64 Hz. These responses are relatively independent of blood flow in that complete occlusion of the peripheral blood supply did not greatly alter the amplitude of centrally evoked responses. The results suggest that this sympathetic-cholinergic system may be a useful model system with which to study the actions of various adrenergic agents on the reactivity of central structures which regulate sympathetic nervous activity.