The behavioural effects of enkephalin analogues injected into the ventral tegmental area and globus pallidus.
Two stable analogues of enkephalin D-Ala2-Met5-enkephalinamide (DAMA) and D-Ala2,D-Leu5-enkephalin (DADLE) injected bilaterally into the ventral tegmental area (VTA) induced locomotion, characterized by bursts of morphine-like activity. The response of DADLE was blocked by systemic-alpha-flupenthixol (0.2 mg/kg) and naloxone (1 mg/kg). At higher doses of enkephalins in the VTA, stereotypy behaviour involving gnawing, became apparent. When injected bilaterally into the globus pallidus (GP), both analogues induced a dose-dependent increase in locomotor activity but stereotypy was not observed. The locomotor behaviour induced by DADLE was blocked by naloxone but not by alpha-flupenthixol. These results suggest that naloxone-sensitive opiate receptors modulate, at a number of different sites, the neural pathways involved in the expression of behavioural activity.
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D004723:Endorphins / Q000494:pharmacology*; D016308:Enkephalin, Leucine-2-Alanine; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives*; D004745:Enkephalins / Q000494:pharmacology*; D005475:Flupenthixol / Q000494:pharmacology; D005917:Globus Pallidus / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology; D009928:Organ Specificity; D051381:Rats; D013681:Tegmentum Mesencephali / Q000187:drug effects / Q000502:physiology*
D004723:Endorphins; D004745:Enkephalins; D009270:Naloxone; D004744:Enkephalin, Methionine; C022118:enkephalinamide-Met, Ala(2)-; D016308:Enkephalin, Leucine-2-Alanine; D005475:Flupenthixol