Elevated temperature decreases sensitivity of P2X purinergic receptors in skeletal muscle arteries

We hypothesized that elevated temperatures would attenuate but that reduced temperatures would potentiate the tension mediated by vascular P2X purinergic receptors. The femoral arteries of 24 rats were dissected out and placed in modified Krebs-Henseleit buffer. Arteries were cut into 2-mm sections and mounted in organ tissue baths. Maximal tension (g) was measured during a KCl and norepinephrine challenge. Tension was measured during doses of α,β-methylene ATP (10^-7 to 10^-3 M), phenylephrine (10^-7 to 10^-4 M), and acetylcholine (10 ^-9 to 10^-5 M), with tissue bath temperature adjusted to 35, 37, and 41°C. Dose-response curves were fit using nonlinear regression analysis to calculate the EC₅₀ and slope. The peak tension was lower with α,β-methylene ATP during 41°C (1.49 ± 0.14 g) compared with 35°C (2.08 ± 0.09 g) and 37°C (1.94 ± 0.09 g; P < 0.05). Slope and EC₅₀ were not affected by temperature. Tension produced by phenylephrine and relaxation to acetylcholine were not affected by temperature. These data indicate that the vasoconstrictor response to α,β-methylene ATP is sensitive to temperature. Moderate cooling does not potentiate P2X-mediated vasoconstriction, but elevated temperature attenuates the vasoconstrictor response to P2X purinergic receptors.