Peptide Expression in GABAergic Neurons in Rat Suprachiasmatic Nucleus in Comparison with Other Forebrain Structures: A Double Labeling In Situ Hybridization Study

Abstract

SUMMARYWe investigated the characteristics of GABAergic neurons in the rat suprachiasmatic nucleus (SCN) in normal untreated rats by examination of co-expressed peptides. We adopted double labeling in situ hybridization using a digoxigenin-labeled glutamic acid decarboxylase (GAD) riboprobe and 35 S-labeled peptide riboprobes. GAD mRNA-positive neurons were distributed throughout the SCN from the rostral to the caudal pole. In the dorsomedial part of the SCN, most GAD mRNA-positive neurons co-expressed arginine vasopressin mRNA. In the ventrolateral part of the SCN, about two thirds of GAD mRNApositive neurons co-expressed vasoactive intestinal peptide (VIP) mRNA. Co-expression of GAD and somatostatin mRNA was observed in virtually all neurons of the intermediate part of the SCN. In contrast, these peptidergic traits were poorly expressed in hypothalamic GABAergic neurons outside the SCN. Vasopressin mRNA-positive cells in the supraoptic nucleus did not express GAD mRNA, and co-expression of somatostatin mRNA and GAD mRNA was rare in the periventricular hypothalamic nucleus. Similarly, the VIP mRNA co-expression ratio of GABAergic neurons in the cerebral cortex was far lower than that in the SCN.

Subcellular distribution of 5‐HT1b and 5‐HT7 receptors in the mouse suprachiasmatic nucleus

“…VP and VIP colocalize with GABA in the SCN (Buijs et al, 1995;Tanaka et al, 1997). Thus, the similar distribution of 5-HT 7 receptor immunoreactivity in VP, VIP, and GABAergic dendrites and terminals in SCN is understandable and predictable.…”

Molecular and functional remodeling of electrogenic membrane of hypothalamic neurons in response to changes in their input

“…Sections, including the SON from the level of the preoptic area rostrally to the retrochiasmatic area caudally, were divided into six groups for detection of Na ϩ channel mRNAs. Sections from control and salt-loaded groups were hybridized in the same chamber by a free-floating method (22). Sections were deproteinized with proteinase K (2.5 g͞ml) acetylated with 0.25% acetic anhydride and 0.1 M triethanolamine and were incubated in hybridization buffer (50% formamide͞10% dextran sulfate͞20 mM Tris⅐HCl, pH 7.5͞5 mM EDTA͞0.3 M NaCl͞0.2% SDS͞500 g/ml yeast tRNA͞1ϫ Denhardt's solution͞10 mM DTT), containing digoxigenin (DIG)-UTP-labeled Na ϩ channel riboprobe (0.25 ng͞l) for 12 h at 60°C.…”

The dynamics of GABA signaling: Revelations from the circadian pacemaker in the suprachiasmatic nucleus

“…One of the very interesting features of the SCN is the high number of neuronal cell bodies that contain γ-aminobutyric acid (GABA) throughout the nucleus. Estimates of the proportion of SCN neurons containing GABA in rodents range from over 50% to virtually all neurons in the nucleus (Buijs et al, 1995; Moore and Speh, 1993; Okamura et al, 1989; Tanaka et al, 1997b; Castel and Morris, 2000; van den Pol, 1986; van den Pol and Tsujimoto, 1985; Francois-Bellan et al, 1990). GABA is found in a large number of local circuit neurons in the SCN as well as in terminals derived from projections originating from just outside the nucleus and from more distant sites (van den Pol, 1986; van den Pol and Gorcs, 1986; Kim and Dudek, 1992; Strecker et al, 1997; Morin and Blanchard, 2001; Jiang et al, 1997a; Buijs et al, 1994).…”