Neostriatal dopaminergic terminals prevent the GABAergic involvement in the mu- and delta-opioid inhibition of KCl-evoked endogenous acetylcholine release.
Endogenous acetylcholine (ACh) release from rat neostriatal slices was inhibited by the mu-opioid agonist [D-Ala2,Gly(ol)5]-enkephalin (DAGO) both in 6-hydroxydopamine (6-OHDA)-lesioned and non-lesioned neostriatum. However, the delta-opioid agonist [D-Pen2,D-Pen5]-enkephalin (DPDPE) could not inhibit KCl-evoked ACh release in the 6-OHDA-lesioned striatum. This result suggests that delta-opioid agonists act on dopaminergic terminals to inhibit the cholinergic neurons. In unlesioned rats, GABAA or GABAB) antagonists (bicuculline or phaclofen, respectively) prevented mu- or delta-opioid inhibition of endogenous ACh release evoked by glutamate, but not by potassium. However, in the 6-OHDA-lesioned side, DAGO inhibition of KCl-evoked ACh release was antagonized by either of the GABA antagonists. Our results suggest that the dopaminergic neurotransmission, favored by KCl, blocks the GABAergic involvement in the mu- and delta-opioid inhibition of endogenous ACh release.
Departament de Biologia Cellular i Anatomia Patològica, Hospital de Bellvitge, Facultat de Medicina, Universitat de Barcelona, Spain.
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E
Arenas
J
J
Alberch
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Pérez-Navarro
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C
Solsona
J
J
Marsal
D000109:Acetylcholine / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000818:Animals; D003342:Corpus Striatum / Q000502:physiology*; D004298:Dopamine / Q000502:physiology*; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000494:pharmacology / Q000502:physiology*; D008297:Male; D009411:Nerve Endings / Q000502:physiology; D016627:Oxidopamine; D011189:Potassium Chloride / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D004745:Enkephalins; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D005680:gamma-Aminobutyric Acid; D011189:Potassium Chloride; D020881:Enkephalin, D-Penicillamine (2,5)-; D016627:Oxidopamine; D000109:Acetylcholine; D004298:Dopamine