Injection of SCH 23390, but not 7-hydroxy-DPAT, into the ventral tegmental area blocks the acute motor-stimulant response to cocaine.
The present studies examined the effects of intra-ventral tegmental area (VTA) injection of SCH 23390, a dopamine (DA) D1 receptor antagonist or 7-OH-DPAT, a DA D2/3 receptor agonist, on cocaine-stimulated motor activity. Intra-VTA SCH 23390 (1.5-15 nmol/side) dose-dependently blocked cocaine-induced motor activity. Thus, 15 nmol/side SCH 23390 completely blocked, while 5 nmol/side attenuated, the motor-stimulant response to cocaine. These doses of SCH 23390 did not alter basal motor activity, suggesting the effects on the motor-stimulant response to cocaine were not the result of a generalized suppression of activity. In contrast to previous studies, intra-VTA 7-OH-DPAT did not alter basal motor activity at any of the doses tested (0.5-15 nmol/side). In addition, intra-VTA 7-OH-DPAT (1.5-15 nmol/side) pretreatment did not significantly alter the motor-stimulant response to cocaine. These data suggest that DA D1 receptors in the VTA may play a role in psychostimulant-induced motor activity. However, the role DA D2/3 receptors in the VTA may have in cocaine-induced motor activity remains unclear.
Steketee
J D
JD
Department of Pharmacology and Therapeutics, Louisiana State University Medical Center at Shreveport 71130-3932, USA.
Braswell
B C
BC
D000818:Animals; D001552:Benzazepines / Q000008:administration & dosage / Q000494:pharmacology*; D003042:Cocaine / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D018491:Dopamine Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D018765:Dopamine Uptake Inhibitors / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D007267:Injections; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013268:Stimulation, Chemical; D013764:Tetrahydronaphthalenes / Q000008:administration & dosage / Q000494:pharmacology*; D017557:Ventral Tegmental Area / Q000033:anatomy & histology / Q000502:physiology*
D001552:Benzazepines; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D018765:Dopamine Uptake Inhibitors; D013764:Tetrahydronaphthalenes; D003042:Cocaine; C031349:7-hydroxy-2-N,N-dipropylaminotetralin