Distribution of dopamine D 2-like receptors in the rat amygdala and their role in the modulation of unconditioned fear and anxiety

• Published in: Neuroscience 2012-01, Vol.201, p.252-266
• Main Authors: de la Mora, M. Perez, Gallegos-Cari, A., Crespo-Ramirez, M., Marcellino, D., Hansson, A.C., Fuxe, K.
• Format: Article
• Language: English
• Subjects: CeA (amygdaloid central nucleus); intercalated paracapsular islands; raclopride; shock-probe burying test; stress
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2011.10.045

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 [ 3H]raclopride or [ 125I]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 (0.75–4 μg/side) in the area of the central amygdaloid nucleus resulted at low doses in the appearance of anxiogenic-like 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. D 2-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. ▶D 2-like receptors within the rat amygdala are mostly restricted to the CeLC. ▶Raclopride infused in the CeA produces anxiogenic effects in defensive burying. ▶A potential differential function of D 2-like receptors in the CeA vs. the BLA.