Comparison of the effects of the cholecystokinin-B receptor antagonist, PD 134308, and the cholecystokinin-A receptor antagonist, L-364,718, on dopamine neuronal activity in the substantia nigra and ventral tegmental area.
Extracellular single-unit recording techniques were used to study the effects of the cholecystokinin-A (CCK-A) antagonist, L-364,718, and the CCK-B antagonist, PD 134308, on DA neuronal activity in chloral hydrate anesthetized rats. Neither L-364,718 (0.1-1.6 mg/kg i.v.) nor PD 134308 (0.1-6.4 mg/kg) altered the basal firing rate of substantia nigra or ventral tegmental area DA neurons. The ability of PD 134308 and L-364,718 to alter the apomorphine-induced inhibition of substantia nigra DA neurons was assessed. Pretreatment with L-364,718 (0.6 or 4.16 mg/kg i.v.) did not shift the apomorphine dose-response curve (0.5-32 micrograms/kg i.v.). In contrast, PD 134308 (0.6 or 6.4 mg/kg i.v.) produced dose-related, significant shifts to the right of the apomorphine dose-response curves. However, these effects were small in comparison to the haloperidol (0.1 mg/kg i.p.)-induced shift of the apomorphine curve. These data suggest that in the substantia nigra there may be a tonic level of CCK release that, through actions on CCK-B receptors, may modulate DA agonist-induced inhibition of DA neuronal activity.
Meltzer
L T
LT
Department of Pharmacology, Parke-Davis Pharmaceutical Research Division, Warner-Lambert Company, Ann Arbor, Michigan 48105.
Christoffersen
C L
CL
Serpa
K A
KA
Razmpour
A
A
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D001570:Benzodiazepinones / Q000494:pharmacology*; D002766:Cholecystokinin / Q000037:antagonists & inhibitors*; D020109:Devazepide; D004298:Dopamine / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D006220:Haloperidol / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology*; D008297:Male; D008536:Meglumine / Q000031:analogs & derivatives* / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011949:Receptors, Cholecystokinin / Q000037:antagonists & inhibitors*; D013378:Substantia Nigra / Q000187:drug effects / Q000502:physiology*; D013681:Tegmentum Mesencephali / Q000187:drug effects / Q000502:physiology*
D001570:Benzodiazepinones; D007211:Indoles; D011949:Receptors, Cholecystokinin; C065599:PD 134308; D008536:Meglumine; D002766:Cholecystokinin; D006220:Haloperidol; D020109:Devazepide; D001058:Apomorphine; D004298:Dopamine