CHOLINERGIC DENERVATION OF THE RAT HIPPOCAMPUS BY 192-IGG SAPORIN - ELECTROPHYSIOLOGICAL EVIDENCE

THE consequences of intracerebroventricular injection of the toxin 192 -IgG-saporin on the electrophysiological properties of CA1 pyramidal c ells were investigated using intracellular recordings in the in vitro hippocampal slice preparation. We present the first electrophysiologic al evidence of a dysfunction of hippocampal cholinergic afferents foll owing injection of 192-IgG-saporin. The synaptic events mediated by ac etylcholine were altered in such animals: the slow cholinergic excitat ory postsynaptic potentials as well as the cholinergic activation of G ABAergic interneurones were dramatically depressed or even absent; the amplitude and duration of the afterhyperpolarization following a burs t of spikes were increased, while other neuronal properties were not m odified. These specific alterations suggest that the toxin 192-IgG-sap orin is a specific tool for the experimental study of cholinergic dene rvation in the hippocampus.