Interaction of abecarnil, bretazenil, and Ro 19-8022 with diazepam-sensitive and -insensitive benzodiazepine sites in the rat cerebellum and cerebral cortex

doi:10.1016/0024-3205(95)02126-4

Life Sciences

Volume 57, Issue 24, 3 November 1995, Pages 2215-2222

https://doi.org/10.1016/0024-3205(95)02126-4 Get rights and content

Abstract

Abecarnil, bretazenil, and Ro 19-8022 inhibited the binding of [³H]Ro 15-4513 to diazepamsensitive and -insensitive sites in the rat cerebellum and cerebral cortex, but all three had a much higher affinity for the diazepam-sensitive sites in both tissues. The GABA-shift for bretazenil and Ro 19-8022 was low (< 2) for all sites studied, consistent with their partial agonistic profile. The GABA-shift for abecarnil was appreciably higher for diazepam-sensitive binding in the cerebellum than in the cerebral cortex (1.97 vs 1.18). Furthermore, the GABA-shift for abecarnil was markedly different for the diazepam-sensitive and -insensitive sites in the cerebellum (1.97 vs 0.71). All three compounds inhibited [³H]Ro 15-4513 binding to the diazepam-sensitive sites with a slope factor >1, suggestive of positive cooperativity in their binding to GABA_A receptors. Abecarnil only partially inhibited diazepam-insensitive binding of [³H]Ro 15-4513 in the cerebellum, indicating that this site can be differentiated into abecarnil-sensitive and -insensitive components.

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On the day of assay, the tissue was thawed and washed one time with buffer as before (140,000×g for 30 min at 4 °C) and then resuspended in assay buffer. [ 3H]Muscimol and [3H]Ro 15-4513 binding was measured using a filtration method as described previously (Mehta and Shank, 1995; Mehta and Ticku, 1998). Briefly, aliquots (0.1–0.2 mg protein) of membrane preparation in Tris–HCl buffer (50 mM, pH 7.4) were incubated with either [3H]Ro 15-4513 (2 nM) at 4 °C for 90 min or [3H]muscimol (3 nM) at 4 °C for 45 min in the absence and presence of different concentrations of ethanol.
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Interaction of abecarnil, bretazenil, and Ro 19-8022 with diazepam-sensitive and -insensitive benzodiazepine sites in the rat cerebellum and cerebral cortex

Abstract

Genomics

FEES Lett.

Neuron

J. Biol. Chem.

Eur. J. Pharmacol. Mol. Pharmacol. Sect.

FEBS Lett.

Trends Pharmacol. Sci.

Eur. J. Pharmacol.

Eur. J. Pharmacol.

J. Biol. Chem.

Faseb J.

J. Neurochem.

Faseb J.