The A1 and A2 adenosine receptor agonists (5'-(N-ethylcarboxamido)-adenosine, 2-chloroadenosine, adenosine (ADO) and N6-cyclohexyladenosine) were topically appled to 30- to 60-μm arterioles in the s.c. microcirculation of hamsters at different skin temperatures. Vasoconstrictor responses evoked by nanomolar concentrations of ADO and N6-cyclohexyladenosine were enhanced when local skin temperature (T(s)) was increased, but unchanged when T(s) was decreased. All these responses were antagonized by 8-phenyltheophylline, which suggests that temperature-sensitive vasoconstrictions were mediated by A1 receptors. In contrast, norepinephrine (10-7 M) caused vasoconstrictions that were not enhanced at high T(s) and were markedly reduced at low T(s), while angiotensin II (10-8 M) caused vasoconstrictions that were temperature-insensitive. Vasodilator responses evoked by micromolar concentrations of ADO, 2-chloroadenosine and 5'-(N-ethylcarboxamido)-adenosine were temperature-insensitive. All these responses were antagonized by 8-phenyltheophylline, except those mediated by 10-6 to 10-4 M ADO, which can be explained by simple override of the receptor blockade. Thus, A1, but not A2, receptors show temperature-dependent actions in vivo, which suggests that temperature sensivitity could be an additional criterion for classification of ADO receptors.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Pharmacology and Experimental Therapeutics|
|State||Published - 1990|
ASJC Scopus subject areas
- Molecular Medicine