Evidence for the independent role of GABA synapses of the zona incerta-lateral hypothalamic region in haloperidol-induced catalepsy.
Bicuculline (0.5-50 ng), injected bilaterally into the zona incerta-lateral hypothalamus (ZI-LH) of the rat, inhibited catalepsy evoked by haloperidol (1 mg/kg s.c.) in a dose-dependent manner. The same effect was obtained by injections of bicuculline directed towards the ventromedial thalamic nucleus (Vm), but then higher doses of the drug were necessary (10-50 ng). Muscimol (10-50 ng), injected into the ZI-LH, evoked a state of catalepsy almost identical to that of haloperidol. Bicuculline (50 ng) abolished the catalepsy evoked by muscimol (25 ng). Bicuculline injected into ZI-LH in doses of 0.5-2.5 ng did not change locomotor activity of rats as measured in photoresistor actometers, whereas it had a slightly stimulating effect at a dose of 5 ng. A comparison between the doses of bicuculline injected into the ZI-LH and Vm suggests that, irrespective of Vm synapses, GABA synapses of this region are involved in the mediation of haloperidol-induced catalepsy. A similar conclusion regarding the catalepsy and rigidity induced by morphine was drawn previously. It seems, therefore, that the catalepsy antagonism of bicuculline is independent of the action of the drug which promotes the locomotor stimulation.
Wardas
J
J
Department of Neuro-Psychopharmacology, Institute of Pharmacology, Polish Academy of Sciences, Kraków.
Ossowska
K
K
Wolfarth
S
S
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology*; D002375:Catalepsy / Q000139:chemically induced / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006220:Haloperidol / Q000494:pharmacology*; D007026:Hypothalamic Area, Lateral / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009118:Muscimol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism / Q000502:physiology*
D009118:Muscimol; D005680:gamma-Aminobutyric Acid; D006220:Haloperidol; D001640:Bicuculline