Previous studies have suggested that moderate cooling increases the responsiveness of vascular alpha2-adrenoceptors. However, limited information is available documenting the influence of temperature changes on adrenoceptor responses in the microvasculature of thermoregulatory organs (e.g., the @entity1 digit and the @entity95 ear) subjected to a wide range of temperatures. In the present study, the effect of local cooling (24 degrees C) on cutaneous microvascular adrenoceptors in the ear was observed in vivo in male New Zealand White @entity95 (total: 66 ears). The @entity95 ear was studied in a temperature-controlled tissue bath; the ear preparation was pretreated with @entity7477 (an alpha1-adrenoceptor antagonist) (10(-5) M) or a combination of @entity7477 (10(-5) M) and @entity1169 (a beta-adrenoceptor antagonist) (10(-6) M). The microvascular diameter responses of the ear to @entity1063 (10(-11)-10(-4) M) then were determined at 24 or 34 degrees C, respectively, to determine the influences of low temperature on adrenoceptor responses to @entity1063 stimulation. The results demonstrated that low concentrations of @entity1063 induced vasodilation in arterioles and arteriovenous anastomoses. This vasodilation was followed by vasoconstriction with an increased concentration of @entity1063 in animals with alpha1-adrenergic blockade at 34 degrees C. Moderate tissue cooling increased the microvascular maximal response of the @entity95 ear to @entity1063 and abolished the vasodilatation induced by a low concentration of @entity1063 . There was no significant difference in the microvascular response to @entity1063 between the two temperature conditions after simultaneous blockade of alpha1-adrenoceptors and beta-adrenoceptors. Data from the present study indicate that moderate cooling does not enhance the responsiveness of alpha2-adrenoceptors to @entity1063 . In contrast, cooling reduced the beta-adrenergic activity of arterioles and arteriovenous anastomoses after @entity1063 stimulation.

Effect of cooling on cutaneous microvascular adrenoceptors in vivo in the XXXX ear.

@entity1 :: ('9606', 'Species') :: ['human'] @entity1169 :: ('MESH:D011433', 'Chemical') :: ['propranolol'] @entity95 :: ('9986', 'Species') :: ['rabbits', 'rabbit'] @entity7477 :: ('MESH:C041226', 'Chemical') :: ['terazosin'] @entity1063 :: ('MESH:D009638', 'Chemical') :: ['norepinephrine']
@entity95 :: (9986,Species) :: ['rabbit']
