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Titolo:
INHIBITION OF SUBSTANTIA-NIGRA DOPAMINE CELL FIRING BY R(-)-N-N-PROPYLNORAPOMORPHINE - ELECTROPHYSIOLOGICAL AND AUTORADIOGRAPHIC STUDIES AFTER REGIONAL INACTIVATION OF DOPAMINE-RECEPTORS BY MICROINJECTION OF N-ETHOXYCARBONYL-2-ETHOXY-1,2-DIHYDROQUINOLINE
Autore:
COX RF; WASZCZAK BL;
Indirizzi:
BURROUGHS WELLCOME CO,WELLCOME RES LABS,DIV PHARMACOL,3030 CORNWALLISRD RES TRIANGLE PK NC 27709 NORTHEASTERN UNIV,BOUVE COLL PHARM & HLTH SCI,PHARMACOL SECT BOSTON MA 02115
Titolo Testata:
Brain research
fascicolo: 1, volume: 613, anno: 1993,
pagine: 32 - 42
SICI:
0006-8993(1993)613:1<32:IOSDCF>2.0.ZU;2-B
Fonte:
ISI
Lingua:
ENG
Soggetto:
VENTRAL TEGMENTAL AREA; CENTRAL NERVOUS-SYSTEM; SINGLE UNIT-ACTIVITY; H-3 YM-09151-2; PHARMACOLOGICAL CHARACTERIZATION; QUANTITATIVE AUTORADIOGRAPHY; UNILATERAL INACTIVATION; FEEDBACK PATHWAY; RAT STRIATUM; NEURONS;
Keywords:
SUBSTANTIA-NIGRA; DOPAMINE NEURON; N-ETHOXYCARBONYL-2-ETHOXY-1,2-DIHYDROQUINOLINE; RECEPTOR RESERVE; AUTORADIOGRAPHY; R(-)-N-N-PROPYLNORAPOMORPHINE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
59
Recensione:
Indirizzi per estratti:
Citazione:
R.F. Cox e B.L. Waszczak, "INHIBITION OF SUBSTANTIA-NIGRA DOPAMINE CELL FIRING BY R(-)-N-N-PROPYLNORAPOMORPHINE - ELECTROPHYSIOLOGICAL AND AUTORADIOGRAPHIC STUDIES AFTER REGIONAL INACTIVATION OF DOPAMINE-RECEPTORS BY MICROINJECTION OF N-ETHOXYCARBONYL-2-ETHOXY-1,2-DIHYDROQUINOLINE", Brain research, 613(1), 1993, pp. 32-42

Abstract

The irreversible receptor inactivator, N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ), was injected into rat striatum or substantia nigra to study potential contributions of dopamine receptors in each area to the inhibition of substantia nigra (A9) dopamine cell firing byiv. R(-)-N-n-propylnorapomorphine (NPA), a dopamine agonist. Extracellular, single unit recording studies showed that the numbers of activedopamine cells, basal firing rates and responses to i.v. R(-)-NPA were unchanged a day after striatal EEDQ injections, despite significant losses of striatal D1 and D2 receptors (confirmed by autoradiography). These results indicate that striatal receptors do not control the basal activity of A9 neurons, nor do they mediate inhibitions of firing by R(-)-NPA. Microinjections of EEDQ into substantia nigra, however, inactivated 75-78% of nigral D1 and D2 receptors and reduced the number of active dopamine cells and slightly increased firing rates. Moreover, dose-response curves to R(-)-NPA were shifted 10-fold to the right and the maximum inhibitory response was depressed. Furchgott analysis of the dose-response curves yielded a steep occupancy-response curve with maximum ( > 95%) inhibition of firing at only 24% receptor occupation (i.e., 76% reserve). Thus, the substantial (approximately 70%) receptor reserve previously shown to exist for inhibition of dopamine cellfiring by i.v. R(-)-NPA20,21 appears to be intrinsic to the nigra. Toassess contributions of nigral D1 and D2 receptors to this response, selective inactivation of each receptor subtype was achieved (confirmed autoradiographically) by treating rats with SCH 23390 (4 mg/kg) or S(-)eticlopride (2mg/kg), respectively, 30 min before intranigral EEDQ. Selective D2, but not D1, receptor inactivation produced rightward shifts and depressed the maximum of the R(-)-NPA dose-response curve in a manner like that observed after non-selective inactivation of nigraldopamine receptors. Unexpectedly, pretreatment with SCH 23390 (to protect D, receptors) also produced a modest rightward shift in the R(-)-NPA dose-response curve, suggesting a slight role for D1 receptors in this response. These results indicate that inhibition of A9 dopamine cell firing by iv. R(-)-NPA is mediated by dopamine receptors located in substantia nigra, but not striatum and confirm the predominant role of nigral D2 receptors.

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Documento generato il 01/04/20 alle ore 23:53:09