Changes in reactivity of the digital artery of the fallow deer, Dama dama,in summer and winter

The vasoreactivity of the digital artery of the fallow deer, Dama dama, has been examined. The artery was constricted by adrenoceptor agonists such as noradrenaline and L-phenylephrine, and dilated by histamine in an endothel ium dependent, L-NAME sensitive manner. No evidence could be found for musc arinic receptors using acetylcholine and carbachol. Arteries collected in t he cold winter of 1995/96 were either insensitive, or had a reduced sensiti vity to the vasodilator action of histamine, compared with arteries collect ed in summer or in the mild winters of 1997/98 ana 1998/99. The vasodilator response to forskolin was considerably reduced in the cold winter arteries compared with the warm winter arteries, whereas the vasoconstrictor action of ODQ was unchanged. It is considered that the changes seen in the cold w inter arteries were triggered by the external temperature and not by season al changes. (C) 2000 Elsevier Science Ltd. All rights reserved.