DISTRIBUTION OF DOPAMINE D2-LIKE RECEPTORS IN THE RAT AMYGDALA AND THEIR ROLE IN THE MODULATION OF UNCONDITIONED FEAR AND ANXIETY

Amygdaloid dopamine D-2 receptors play an important role in the modulation of fear/anxiety. Their topographical distribution within the amygdala is however unclear, and their role in unconditioned fear/anxiety remains largely unknown. The aim of this paper was to study the intra-amygdaloid distribution of D-2 receptors and to ascertain their role in unconditioned anxiety. Chemical anatomical studies in the rat, using D-2 and D-3 in situ hybridization, quantitative receptor autoradiography with either [H-3]raclopride or [I-125]sulpiride, and D-2-like immunocytochemistry showed that the highest density of dopamine D-2 receptors is present in the central amygdaloid nucleus, particularly within its latero-capsular division, in which a D-2 but not a D-3 mRNA signal was observed. However, although at considerably reduced densities dopamine D-2 receptors were also found in other locations within the amygdala, including the basolateral nucleus. Behaviorally, the infusion of raclopride (0.75-411g/side) in the area of the central amygdaloid nucleus resulted at low doses in the appearance of anxiogeniclike effects in the Shock-Probe Burying test, whereas no effects of raclopride treatment were found at any dose in the Elevated Plus-Maze and the Open-Field test. Our results indicate that amygdaloid dopamine D-2-like receptors have a topographically differentiated distribution within the rat amygdala, the major location being in the central amygdaloid nucleus. D2-like receptors play a role in the modulation of anxiety responses involving a potential differential function of D-2-like receptors in the central amygdaloid nucleus versus the basolateral amygdaloid nucleus. (C) 2011 IBRO. Published by Elsevier Ltd. All rights reserved.