Amygdala Kindling in the Classical Conditioning Paradigm

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Abstract
Hypothetically, epileptiform alterations of brain excitability may be elicited by a conditioning stimulus (CS) in a classical conditioning paradigm. Male albino rats (15) were chronically implanted with electrodes in the amygdala and over the visual cortex. A train of 6 stroboscopic flashes served as the CS and the unconditioned stimulus was the amygdaloid electrical stimulation, delivered together with the 6th flash in the course of the kindling procedure. Rats were randomly assigned to 2 groups. Rats in group 1 were exposed to 1 or 2 kindling sessions per day, and those in group 2 were exposed to 10 such sessions every day. All rats in group 1 showed fully mature seizures within 15 .+-. 5.5 sessions; none of those in group 2 displayed kindled seizures. There was no evidence of amygdaloid afterdischarges or enhanced spiking as a response to the CS. A gradual selective suppression of the visual evoked potentials (VEP) secondary components, i.e., slow negative wave and sensory afterdischarge, paralleled kindling in group 1. This effect was weak in group 2. There was no change in the primary response of VEP in either group. No recovery of VEP followed the extinction of conditioning.