DIFFERENCES IN PURINOCEPTOR MODULATION OF NOREPINEPHRINE RELEASE BETWEEN CAUDAL ARTERIES OF NORMOTENSIVE AND HYPERTENSIVE RATS

The effects of 2-chloroadenosine, a purinoceptor agonist, on the overf low of endogenous norepinephrine (NE) was examined in the electrically field-stimulated (EFS) caudal artery obtained from Wistar-Kyoto (WKY) rats and age-matched spontaneously hypertensive rats (SHRs). 2-Chloro adenosine at 10(-6) and 10(-5) M reduced the EFS-evoked release of NE from arteries of WKY rats but was without effect on the release of NE from arteries of SHRs. Methoxamine (10(-5) M), an alpha adrenoceptor a gonist, caused the release of ATP, ADP, AMP and adenosine from caudal arteries of Wistar rats, WKY rats and SHRs, and decreased the release of EFS-evoked release of endogenous NE in arteries from normotensive r ats, but not from arteries of SHRs. Thus, both exogenously applied and endogenously released purines are ineffective in reducing the evoked release of NE in this model of hypertension. The enhanced release of N E from sympathetic nerves of SHRs may be due in part to the loss of pr ejunctional modulation by purines.