Identification of the adrenoceptor subtypes expressed on GABAergic neurons in the anterior hypothalamic area and rostral zona incerta of GAD65-eGFP transgenic mice.

GABA is a major neurotransmitter in the hypothalamus. In particular, neurons in the paraventricular nucleus (PVN) of the hypothalamus receive dense GABAergic inputs from peri-PVN regions. The noradrenergic system has been reported as a modulator of GABAergic transmission to the PVN. Previous electrophysiological and morphological studies support the presence of adrenoceptors on GABAergic neurons innervating the PVN. In this study, we identified three adrenoceptors on GABAergic neurons in the peri-PVN region, focusing on the anterior hypothalamic area (AHA) and rostral zona incerta (ZIr). GABAergic neurons were identified using enhanced green fluorescent protein (eGFP), followed by single cell RT-PCR analysis of the GABA synthetic enzymes, glutamic acid decarboxylase (GAD)65 and/or GAD67. Single cell RT-PCR data revealed the expression of alpha(1A)-, alpha(1B)- and alpha(2A)-adrenoceptor mRNA on GABAergic neurons in AHA and ZIr. Additionally, immunohistochemical studies showed that the immunoreactivities of alpha(1A)-, alpha(1B)- and alpha(2A)-adrenoceptor were colocalized with eGFP-expressing neurons in AHA and ZIr. The present findings suggest the contribution of adrenoceptors to the modulation of GABAergic neurons in AHA and ZIr.