FACILITATORY AND INHIBITORY MODULATION BY ENDOGENOUS ADENOSINE OF NORADRENALINE RELEASE IN THE EPIDIDYMAL PORTION OF RAT VAS-DEFERENS

Citation
J. Goncalves et G. Queiroz, FACILITATORY AND INHIBITORY MODULATION BY ENDOGENOUS ADENOSINE OF NORADRENALINE RELEASE IN THE EPIDIDYMAL PORTION OF RAT VAS-DEFERENS, Naunyn-Schmiedeberg's archives of pharmacology, 348(4), 1993, pp. 367-371
Citations number
31
Categorie Soggetti
Pharmacology & Pharmacy
ISSN journal
00281298
Volume
348
Issue
4
Year of publication
1993
Pages
367 - 371
Database
ISI
SICI code
0028-1298(1993)348:4<367:FAIMBE>2.0.ZU;2-U
Abstract
The present study aimed at determining the modulation by adenosine of the release of noradrenaline in the epididymal portion of the rat vas deferens. The tissues were treated with pargyline and perifused in the presence of desipramine and yohimbine. Up to four periods of electric al stimulation were applied (5 Hz, 9 min). The A1-adenosine receptor s elective agonist R-N6-phenylisopropyladenosine (R-PIA; 100-900 nmol.l- 1) reduced, whereas the A2A-receptor selective agonist thyl)phenethyla mino-5'-N-ethylcarboxamidoadenosine (CGS 21680; 3-30 nmol.l-1) increas ed the electrically-evoked noradrenaline overflow in a concentration-d ependent manner. The nonselective agonist 5'-N-ethylcarboxamidoadenosi ne (NECA; 30 - 300 nmol.l-1) reduced noradrenaline overflow, but the e ffect did not depend on the concentration. Adenosine deaminase at the concentration of 0.5 mu.ml-1 decreased but at that of 2.0 mu.ml-1 incr eased noradrenaline overflow. The inhibitors of adenosine uptake, S-(4 -nitrobenzyl)-6-thioinosine (NBTI; 50 nmol.l-1) and dipyridamole (3 mu mol.l-1), increased the electrically-evoked noradrenaline overflow. Th e A1-adenosine receptor antagonist 1,3-dipropyl-8-cy-clopentylxanthine (DPCPX; 20 nmol.l-1) caused an increase whereas the A2-adenosine rece ptor antagonist 3,7-dimethyl-1-(2-propynyl)xanthine (DMPX; 0.1 mumol.l -1) caused a decrease. NBTI (50 nmol.l-1), partially antagonized the e ffect of both DPCPX (20 nmol.l-1) and DMPX (0.1 mumol.l-1). It is conc luded that, in the epididymal portion of the rat vas deferens, endogen ous adenosine tonically modulates the release of noradrenaline evoked by electrical stimulation, through activation of both inhibitory (A1) and facilitatory (A2A) adenosine receptors.