Chapter 13 Multiple actions of noradrenaline on sympathetic preganglionic neurons of the cat studied in the spinal cord slice

Abstract

This chapter summarizes the results obtained in an analysis of catecholamines (CA) actions on sympathetic preganglionic neurons (SPNs) carried out by intracellular recording in the slice of the upper thoracic spinal cord of the cat. These data describe the actual action of CA on the SPN, and therefore permit the prediction of the effects that CA are likely to mediate in the intact animal. Several lines of evidence suggest that CA have a role as mediators, or modifiers, of synaptic actions on the SPN. The intermediolateral (IML) nucleus of the gray matter of the thoracic spinal cord is rich in CA-containing axons. Several CA-synthesizing neuron sets of brainstem and hypothalamus, some of which are located in the ventrolateral medulla, are considered as the source of this dense CA innervation of the IML column. CA-containing axons form typical synapses with identified SPNs. Binding studies show that adrenoceptors are present in the IML nucleus. The iontophoresis of CA on SPNs produces depressant effects mediated by a α 2 -adrenoreceptor.