Amygdala kindling does not change emotional responding as measured by the acoustic startle response in the rat

Human patients with limbic epilepsy are often prone to anxiety and depression. The present study investigated the effect of seizures on emotional responding in the kindling model of complex-partial seizures. Male Wistar rats received electrodes into the right basolateral amygdala and were subsequently kindled until fully generalized seizures could be elicited. These rats did not show a change in the magnitude of the acoustic startle response (ASR) compared to the response amplitude before kindling, or compared to unimplanted controls and to only partially kindled rats. Since the ASR amplitude is a sensitive measure for anxiety or fear, these findings suggest that amygdala kindling does not induce a state of anxiety or fear. However, when analyzing the time course of the ASR within a session, the normally occurring habituation of the ASR was absent in electrode implanted-rats suggesting that the physiological changes induced by electrode implantation interfere with response habituation. Kindling even tended to sensitize the ASR in electrode-implanted rats. Finally, the effect of carbamazepine which is both anticonvulsant and antipsychotic was tested. Carbamazepine significantly reduced the ASR in control and partially kindled rats while this effect was less pronounced in fully kindled rats. It is concluded that amygdala kindling does not change emotional responding as measured by the ASR in rats.