GABA(B) receptor inhibition causes locomotor stimulation in mice
G Colombo1, S Melis, G Brunetti
1C.N.R. Institute of Neurogenetics and Neuropharmacology, c/o Bernard B. Brodie Department of Neuroscience, University of Cagliari, S.S. 554, Km. 4.5, I-09042 Monserrato (CA), Italy. colomb@unica.it
Abstract:
The present study investigated the effect of the administration of the GABA(B) receptor antagonists, SCH 50911 [(2S)(+)-5,5-dimethyl-2-morpholineacetic acid], CGP 46381 [(3-aminopropyl)(cyclohexylmethyl)phosphinic acid] and CGP 52432 (3-[[(3,4-dichlorophenyl)methyl]amino]propyl]diethoxymethyl)phosphinic acid), on spontaneous locomotor activity in mice. All drugs were acutely administered at the doses of 10 and 30 mg/kg (i.p.). The dose of 30 mg/kg of all drugs resulted in a significant stimulation of locomotor activity. The locomotor stimulation elicited by SCH 50911 was completely blocked by haloperidol (0.1 mg/kg, i.p.), suggesting that hyperactivity induced by blockade of the GABA(B) receptor is mediated by enhanced dopamine release. These results suggest the existence of a GABA(B) receptor-mediated tonic inhibition of dopamine neurons.
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