To assess antagonistic properties of the nanomolar affinity GABAB receptor ligand, CGP 55845A (IC50 = 1.1 ± 0.2 nM), 3H-D-Aspartate release from synaptosomes at 22-24°C was measured in combination with the use of a fast perfusion technique, in vitro. The inhibition of high K+ elicited 3H-D-aspartate release by 250 μM (R)-baclofen was blocked by 10 μM CGP 55845A. The concomitant two-fold increase of basal aspartate release was comparable to that of freely moving rats as measured by a HPLC combined microdialysis technique, in vivo. A low concentration of CGP 55845A (250 nM) induced two release-pulses of glutamate whereas much less or no release (or release inhibition) was detected with aspartate, serine, glycine and glutamine. By contrast, one order of magnitude higher dose of CGP 55845A induced similar, double-release patterns of neurotransmitters and serine, however the relative amounts of released glutamate (15-fold) and aspartate (55-fold) were reversed in the second pulse.
|Number of pages||5|
|Journal||Pharmacology Reviews and Communications|
|Publication status||Published - dec. 1 1996|
ASJC Scopus subject areas