Effects of accumbens DALA microinjections on brain stimulation reward and behavioral activation in intact and 6-OHDA treated rats.
The effects of bilateral nucleus accumbens microinjections of d-ala-met-enkephalinamide (DALA) were assessed in behavioral activation and lateral hypothalamic self-stimulation (LHSS) rate-frequency curve-shift paradigms in normal and accumbens 6-OHDA (4.0 micrograms) treated rats. Microinjections of DALA (2.5 micrograms/microliters) in the behavioral activation paradigm had little effect on normal activity; however, DALA administered to 6-OHDA treated rats produced a significant overall increase in locomotion. The 6-OHDA DALA-induced locomotion effect peaked at 2 weeks after 6-OHDA treatment and then returned to baseline levels by week 5 post-treatment. Using LHSS, DALA tested over a range of doses (2.5, 5, 10, 20 micrograms/microliters) displayed a weak biphasic reward effect only at the highest dose, which was characterized by an initial suppression followed by an elevation. DALA significantly depressed initial operant motor/performance in LHSS in a dose dependent fashion. Microinjections of the normally ineffective low dose of DALA (2.5 micrograms/microliters) following accumbens 6-OHDA treatment produced a significant LHSS reward decrease 2 weeks post-treatment, while LHSS motor/performance was relatively unaffected. Results are discussed in terms of opiate-dopamine and limbic-motor interactions.
Department of Psychology, Northeastern University, Boston, MA 02115.
P L
PL
Johnson
J R
JR
Stellar
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001921:Brain / Q000502:physiology*; D003216:Conditioning, Operant / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004744:Enkephalin, Methionine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D007026:Hypothalamic Area, Lateral / Q000502:physiology; D008297:Male; D008845:Microinjections; D009043:Motor Activity / Q000187:drug effects; D009714:Nucleus Accumbens / Q000502:physiology*; D016627:Oxidopamine / Q000494:pharmacology*; D051381:Rats; D012201:Reward; D012653:Self Stimulation
D004744:Enkephalin, Methionine; C022118:enkephalinamide-Met, Ala(2)-; D016627:Oxidopamine