Distribution of type 1 cannabinoid receptor expressing neurons in the septal-hypothalamic region of the mouse. Colocalization with GABAergic and glutamatergic markers.

Hrabovszky, Erik and Wittmann, Gábor and Kalló, Imre and Füzesi, Tamás and Fekete, Csaba and Liposits, Zsolt (2012) Distribution of type 1 cannabinoid receptor expressing neurons in the septal-hypothalamic region of the mouse. Colocalization with GABAergic and glutamatergic markers. JOURNAL OF COMPARATIVE NEUROLOGY, 520 (5). pp. 1005-1020. ISSN 0021-9967

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Abstract

Type 1 cannabinoid receptor (CB1) is the principal mediator of retrograde endocannabinoid signaling in the brain. In this study, we addressed the topographic distribution and amino acid neurotransmitter phenotype of endocannabinoid-sensitive hypothalamic neurons in mice. The in situ hybridization detection of CB1 mRNA revealed high levels of expression in the medial septum (MS) and the diagonal band of Broca (DBB), moderate levels in the preoptic area and the hypothalamic lateroanterior (LA), paraventricular (Pa), ventromedial (VMH), lateral mammillary (LM) and ventral premammillary (PMV) nuclei, and low levels in many other hypothalamic regions including the suprachiasmatic (SCh) and arcuate (Arc) nuclei. This regional distribution pattern was compared to location of GABAergic and glutamatergic cell groups, as identified by the expression of glutamic acid decarboxylase 65 (GAD65) and type 2 vesicular glutamate transporter (VGLUT2) mRNAs, respectively. The MS, DBB and preoptic area showed overlaps between GABAergic and CB1-expressing neurons, whereas hypothalamic sites with moderate CB1 signals, including the LA, Pa, VMH, LM and PMV, were dominated by glutamatergic neurons. Low CB1 mRNA levels were also present in other glutamatergic and GABAergic regions. Dual-label in situ hybridization experiments confirmed the cellular co-expression of CB1 with both glutamatergic and GABAergic markers. In this report we provide a detailed anatomical map of hypothalamic glutamatergic and GABAergic systems whose neurotransmitter release is controlled by retrograde endocannabinoid signaling from hypothalamic and extrahypothalamic target neurons. This neuroanatomical information contributes to the understanding of the role that the endocannabinoid system plays in the regulation of endocrine and metabolic functions. J. Comp. Neurol., 2011. (c) 2011 Wiley-Liss, Inc.

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