Effect of cold exposure of the rabbit on the subsequent performance of its isolated ear artery with respect to temperature.

New Zealand white rabbits were exposed to an environmental temperature of either 20°C (control) or 5°C (cold-exposure) for periods of from one to six weeks. Ear skin temperature was around 30°C in the control environment and fell to around 15°C in the cold environment. Compared with control arteries, ear arteries from cold-exposed animals tended to have a lower optimal temperature for responses to injected noradrenaline (NOR). At 37°C, responses of control arteries exceeded those of cold-exposed arteries; at 12°C the situation was reversed. A similar "cross-over" effect was observed with responses to electrical stimulation (ES). However, in both groups of arteries, responses to ES were better preserved than were responses to NOR at low temperatures, possibly because cooling interfered with uptake into neuronal stores of NOR released by ES, thus allowing more NOR to reach the arterial muscle at these low temperatures.