Conditioned effects of kindling three different sites in the hippocampal complex of the rat

Epileptiform synchronization in the rat insular and perirhinal cortices in vitro

The hippocampus plays a primary role in temporal lobe epilepsy, a common form of partial epilepsy in adults. Recent studies, however, indicate that extrahippocampal areas such as the perirhinal and insular cortices represent important participants in this epileptic disorder. By employing field potential recordings in the in vitro 4-aminopyridine model of temporal lobe epilepsy, we have investigated here the contribution of glutamatergic and GABAergic signaling to epileptiform activity in these structures. First, we provide evidence of epileptiform synchronicity between the perirhinal and insular cortices, and resolve some pharmacological and network mechanisms involved in sustaining the interictal- and ictal-like discharges recorded there. Second, we report that in the absence of ionotropic glutamatergic transmission, GABAergic networks produce synchronous potentials that spread between the perirhinal and insular cortices. Finally, we have established that such activity is modulated by activating micro-opioid receptors. Our findings support clinical and experimental evidence concerning the involvement of the perirhinal and insular cortex networks in temporal lobe epilepsy, and provide observations that may impact research focussing on the role of the insular cortex in nociception.

Effects of expectation on amygdala‐kindled convulsions and interictal behaviour in rats: confirmation of a Pavlovian mechanism

We found evidence that the effects of exposure to the stimulation environment on the convulsions and interictal behaviour of basolateral amygdala (BA)-kindled rats are the result of Pavlovian conditioning. In Experiment 1, the rats first received 45 BA stimuli in one environment (CS+) and 45 sham stimuli in another environment (CS-). During this first phase of the experiment, the CS+ and CS- began to exert differential effects on interictal behaviour and convulsions. Then, during the second phase, rats received 45 stimuli and 45 sham stimuli, either as before in their original CS+ and CS- (nonreversal rats) or with their original CS+ and CS- interchanged (reversal rats). During the second phase, the CS+ and CS- continued to exert the same pattern of differential effects on the interictal behaviour and convulsions of the nonreversal rats, whereas the reversal rats began to display the reverse pattern. In Experiment 2, rats received 60 sham stimuli in one environment (CS1). Then, half of the rats received 30 stimuli in a second environment (CS2) and 30 sham stimuli in CS1 (no-pre-exposure rats), whereas the other half (pre-exposure rats) received 30 stimuli and 30 sham stimuli in CS1. Pre-exposure to the stimulation environment attenuated the kindled convulsions. These findings confirm that the conditioned effects of kindling are mediated by a Pavlovian mechanism.