Anxiolytic and anxiogenic effects of kindling—role of baseline anxiety and anatomical location of the kindling electrode in response to kindling of the right and left basolateral amygdala

Abstract

Effects of kindling of right and left basolateral amygdala (BLA) on plus maze anxiety was studied. Using a validated retest paradigm, it was possible to retest rats in the plus maze without increasing anxiety on retest. This permitted determining prekindling baseline levels of plus maze anxiety. Right BLA kindling of high baseline anxiety rats was anxiolytic one week after kindling. Right BLA kindling of low baseline anxiety rats was anxiogenic. In addition, left BLA kindling was either anxiogenic or without effect on plus maze anxiety, depending on baseline anxiety. Effects in left BLA differ from previous work showing anxiolytic effects of left BLA kindling. The discrepancy could be explained in part by prekindling baseline anxiety. These findings require modification of the previous conclusion that left hemisphere (left BLA) kindling is anxiolytic and right BLA kindling is anxiogenic in the plus maze. Rather the hemisphere difference may be due to an interaction between baseline anxiety level and kindling. If true, anxious disposition in rodents may interact with amygdala kindling to change amygdala function differently. Kindling and baseline anxiety effects on other behaviors (such as risk assessment and resistance to capture) are also described. Present data in the light of past studies suggest both premorbid anxiety state and location of the kindling electrode contribute to the effects of kindling on behavior.