Sensitization of mesolimbic brain stimulation reward after electrical kindling of the amygdala

The effects of partial kindling of the central amygdaloid nucleus on brain stimulation reward were evaluated. Intracranial self-stimulation (ICSS) rate intensity functions were determined using a two-hole nose-poke discrimination paradigm in rats implanted with electrodes in the A10 dopamine (DA) neuronal region of the ventral tegmental area (VTA), and in the medial forebrain bundle (MFB) at the level of the lateral hypothalamus. The kindling process did not influence ICSS baseline rates from either site. However, following stage 4 kindling, a low dose amphetamine challenge increased ICSS, resulted in a significant shift to the left of the rate intensity functions, and decreased reward thresholds. Analysis of the error scores which consisted of nonreinforced responses made during ICSS testing revealed that the interaction between kindling and amphetamine on ICSS was specific to changes in central reward processes, and could not be attributed to the influence of rate-enhancing performance variables. The kindling-elicited sensitization of mesolimbic DA reward functioning seen after amphetamine challenge was discussed in relation to the role of the central amygdala in the integration of stimulus-reward associations, and in the conditioning of affective emotional states.