Intra-VTA injections of the mu-opioid antagonist CTOP enhance locomotor activity.
In this paper we report on the effects of microinjections of the mu-opioid antagonist CTOP (D-Pen-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2) into the ventral tegmental area (VTA) on activity and ingestive behavior in the rat. Intra-VTA CTOP (0.015, 0.15, and 1.5 nmol per side) dose-dependently increased activity, whereas it had no effect on feeding and drinking behavior. These results are consistent with previous reports that intra-VTA injections of CTOP enhance extracellular dopamine levels in the nucleus accumbens. Furthermore, we propose a model of VTA mu-opioid mechanisms that might account for these surprising effects of intra-VTA CTOP.
D000704:Analysis of Variance; D000818:Animals; D004327:Drinking Behavior / Q000187:drug effects*; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004745:Enkephalins / Q000494:pharmacology; D005247:Feeding Behavior / Q000187:drug effects*; D008845:Microinjections; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D017450:Receptors, Opioid, mu / Q000037:antagonists & inhibitors*; D013004:Somatostatin / Q000031:analogs & derivatives* / Q000494:pharmacology; D017557:Ventral Tegmental Area / Q000187:drug effects*
D004745:Enkephalins; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; C049352:phenylalanyl-cyclo(cysteinyltyrosyl-tryptophyl-ornithyl-threonyl-penicillamine)threoninamide; D013004:Somatostatin