Septohippocampal neurons after intraventricular AF64A administration in rats: an electrophysiological study

The putative cholinergic neurotoxin, ethylcholine aziridinium ion (AF64A), was injected bilaterally into the cerebral ventricles of male rats. The properties of the medial septum-nucleus of the diagonal band of Broca's area (MS-nDBB) neurons were studied 4 to 6 or 19 to 23 days following injections. The spontaneous activity of those neurons was higher in the injected animals, but their responses to glutamate and cholinergic agonists were not modified. The proportion of orthodromic responses elicited by fimbria-fornix stimulation in MS-nDBB neurons was unchanged. In contrast, the proportion of septohippocampal neurons (SHNs) identified by the antidromic stimulation of the fimbria-fornix was smaller in pretreated animals and their mean antidromic latency was shorter. These results suggest that intracerebroventricular administration of the neurotoxin AF64A is followed by changes in the properties of MS-nDBB neurons and specifically by the disappearance of a subpopulation of SHNs.