EXCITATORY EFFECTS OF CATECHOLAMINES IN THE C.N.S.

Abstract

This chapter describes the excitatory effects of catecholamines in the C.N.S. Excitatory effects by noradrenaline on cortical neurons have been reported. It is necessary to use acid solutions in order to expel noradrenaline by microiontophoresis, and pH has been implicated as a possible factor in the effects observed because it has been found that hydrogen ions alone can cause excitation of single neurons in the cerebral cortex. It is found that whilst pH may be a factor affecting the proportions of neurons in the cerebral cortex showing excitatory responses to iontophoretically applied noradrenaline, it is unlikely to account for all excitations observed. Another possible artefactual explanation for excitatory responses by central neurons to iontophoretically applied noradrenaline is related to the suggestion that these effects may be due to an indirect action by noradrenaline on blood vessels. The main support for this is the parallel time course of constriction of arterioles as a result of noradrenaline application, and the time course of excitatory effects on neurons in the central nervous system.