Lick triggered intracranial stimulation interferes with retrieval of conditioned taste aversion

Abstract

The effect of brain stimulation on retrieval of conditioned taste aversion (CTA) to 0.15 M LiCl was investigated in 15 overtrained rats. The photoelecttrically detected licks at two drinking spouts delivering water or salt solutions, respectively, were used to trigger single electrical pulses, applied through implanted electrodes to basolateral amygdala or lateral hypothalamus. Current intensities not interfering with licking increased the number of licks required for recognition of the aversive fluid after spout switching from 1 or 2 to more than 5 and occasionally blocked gustatory discrimination completely. Discrimination was disrupted both by amygdalar and lateral hypothalamic stimulation of the same intensity, but amygdalar stimulation was more effective: interference was obtained from all amygdalar (n=21) but from only half of hypothalamic (n=17) stimulation points. The disruptive effects were cumulative. They were almost independent of the lick stimulus delay (1 to 100 ms) and often outlasted the period of stimulation for several min. The interfering effects of electrical stimulation are in accordance with the results of lesion studies indicating that the amygdala and the lateral hypothalamus participate in CTA retrieval, probably by mediating stimulus recognition and/or interruption of consummatory behavior.