Role of forebrain catecholamines in amygdaloid kindling

The rate and pattern of seizure development provoked by repeated electrical stimulation of the amygdala (kindling) was assessed in rats that had been pretreated with intracerebral injections of the selective catecholaminergic neurotoxin 6-hydroxy-dopamine. Rats with selective depletion of forebrain noradrenaline displayed a highly significant facilitation of both primary-site and secondary-site kindling, whereas no such effect occurred in rats with selective depletion of forebrain dopamine. The facilitative effects of noradrenaline depletion were apparently related to disinhibition of the spread of seizure discharge from the stimulated site rather than to increased epileptogenicity in the stimulated site itself. These results are consistent with previous evidence that noradrenaline reduces the susceptibility of the central nervous system to epileptiform activity, and they suggest that a lessening of seizure-suppressant noradrenergic function in the forebrain might be part of the mechanism underlying kindling.