IMMUNOHISTOCHEMICAL LOCALIZATION OF THE BETA-2 AND BETA-3 SUBUNITS OFTHE GABA(A) RECEPTOR IN THE BASOLATERAL AMYGDALA OF THE RAT AND MONKEY

The basolateral amygdala has a strong intrinsic inhibitory system medi ated by GABA(A) receptors and is the main site of the anxiolytic actio ns of benzodiazepines. In an effort to identify the anatomical substra tes for these transmitter and drug actions, immunohistochemical techni ques were used to analyse the neuronal localization of the beta(2) and beta(3) receptor subunits of the GABA(A)-benzodiazepine receptor comp lex in the rat and monkey basolateral amygdala. The overall pattern of GABA(A)-benzodiazepine receptor immunoreactivity was very similar in both species. The density of the immunoreactivity in the neuropil vari ed in different nuclei of the basolateral amygdaloid complex. In both species the neuropil of the lateral nucleus exhibited the most robust staining. Immunoreactivity was also seen in neuronal perikarya and den drites where it was localized to the cytoplasm and/or surface membrane . The cell type with the strongest immunoreactivity was a subpopulatio n of small non-pyramidal neurons that had numerous thin dendrites. Oth er larger non pyramidal neurons were also stained. Pyramidal neurons i n the rat and monkey basolateral amygdala exhibited light to moderate perikaryal staining that varied in different nuclei. The results of th is study indicate that the pattern of GABA(A)-benzodiazepine receptor immunoreactiviry in the neuropil of the rat and monkey basolateral amy gdala closely resembled the distribution of benzodiazepine receptors l ocalized in previous radioligand autoradiographic studies. The finding of intense immunoreactivity in subpopulations of non-pyramidal neuron s suggests the existence of disinhibitory mechanisms which may be impo rtant for the activation of basolateral amygdaloid projection neurons. Copyright (C) 1996 IBRO.