Evidence for a nucleus accumbens CCK2 receptor regulation of rat ventral pallidal GABA levels - A dual probe microdialysis study

We employed dual probe microdialysis in the nucleus accumbens and ipsilater al ventral pallidum of the halothane anaesthetized rat to investigate the e ffect of intra-accumbens perfusion with the sulphated octapeptide cholecyst okinin (CCK-8S, 10-1000 nM, 60 min) alone and in the presence of the select ive CCK1 and CCK2 receptor antagonists L-364,718 (10 and 100 nM) and PD1343 08 (10 nM), tetrodotoxin (TTX, 1000 nM) and the GABA, receptor antagonist b icuculline (1000 nM),on dialysate GABA levels in the ventral pallidum. Intr a-accumbens perfusion with the 100 and 1000 nM concentration of CCK-8S was associated with a significant decrease (-16 +/- 3% and -23 +/- 3% vs basal, respectively) in ventral pallidum GABA levels. The CCK-8S (1000 nM) induce d decrease in ventral pallidal dialysate GABA levels was abolished when PDI 34308, TTX and bicuculline, but not L-364,718, were included into the perfu sion medium of the accumbens probe. The data indicate that nucleus accumben s CCK-8S exerts a CCK2 receptor mediated inhibition of ventral pallidal GAB A levers. Furthermore, the TTX and bicuculline sensitivity of this effect s uggests that this is possibly mediated via CCK2 receptors probably located on local GABA interneurons. (C) 2000 Elsevier Science Inc. All rights reser ved.