title: The α₁-, but not α₂-, adrenoceptor in the nucleus accumbens plays an inhibitory role upon the accumbal noradrenaline and dopamine efflux of freely moving rats.
abstract: In vivo microdialysis was used to analyse the role of the α(1)- and α(2)-adrenoceptor subtypes in the regulation of noradrenaline and dopamine efflux in the nucleus accumbens of freely moving rats. Intra-accumbal infusion of α(1)-adrenoceptor agonist methoxamine (24pmol) failed to alter the noradrenaline efflux, but decreased the dopamine efflux. The intra-accumbal infusion of α(1)-adrenoceptor antagonist prazosin (6, 600 and 6000pmol) produced a dose-related increase and decrease of the noradrenaline and dopamine efflux, respectively. An ineffective dose of prazosin (6pmol) counteracted the methoxamine (24pmol)-induced decrease of dopamine efflux. The prazosin (6000pmol)-induced increase of noradrenaline efflux, but not the decrease of dopamine efflux, was suppressed by the co-administration of an ineffective dose of methoxamine (0.024pmol). Neither the α(2)-adrenoceptor agonist clonidine (300pmol) and UK 14,304 (300pmol) nor the α(2)-adrenoceptor antagonist RX 821002 (0.6, 3, 600 and 6000pmol) significantly affected the accumbal noradrenaline and dopamine efflux. The doses mentioned are the total amount of drug over the 60-min infusion period. The present results show that (1) accumbal α(1)-adrenoceptors which are presynaptically located on noradrenergic nerve terminals inhibit the accumbal noradrenaline efflux, increasing thereby the accumbal dopamine efflux, (2) accumbal α(1)-adrenoceptors which are postsynaptically located on dopaminergic nerve terminals inhibit the accumbal dopamine efflux, and (3) accumbal α(2)-adrenoceptors play no major role in the regulation of accumbal efflux of noradrenaline and dopamine.
authors.affiliation: Department of Pharmacology, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan. saigusa@dent.nihon-u.ac.jp
authors.forename: Tadashi
authors.initials: T
authors.lastname: Saigusa
authors.forename: Yuri
authors.initials: Y
authors.lastname: Aono
authors.forename: Takuya
authors.initials: T
authors.lastname: Uchida
authors.forename: Koji
authors.initials: K
authors.lastname: Takada
authors.forename: Michel M M
authors.initials: MM
authors.lastname: Verheij
authors.forename: Noriaki
authors.initials: N
authors.lastname: Koshikawa
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Cools
mesh_terms: D058647:Adrenergic alpha-2 Receptor Agonists / Q000494:pharmacology; D058669:Adrenergic alpha-2 Receptor Antagonists / Q000494:pharmacology; D000818:Animals; D000068438:Brimonidine Tartrate; D003000:Clonidine / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D019329:Idazoxan / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D008729:Methoxamine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D009068:Movement / Q000187:drug effects; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism*; D009714:Nucleus Accumbens / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011224:Prazosin / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism*; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism*
chemical_list: D058647:Adrenergic alpha-2 Receptor Agonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D011810:Quinoxalines; D018340:Receptors, Adrenergic, alpha-1; D018341:Receptors, Adrenergic, alpha-2; D000068438:Brimonidine Tartrate; C058525:2-methoxyidazoxan; D008729:Methoxamine; D003000:Clonidine; D004298:Dopamine; D009638:Norepinephrine; D011224:Prazosin; D019329:Idazoxan