Noradrenaline release in rats during prolonged cold-stress and repeated swim-stress.
1 Plasma noradrenaline concentration in rats was measured during prolonged cold-stress and repeated swim-stress. 2 Cold exposure for 6 h caused a rise in plasma noradrenaline which reached a peak at 4 h. 3 Administration of desmethylimipramine and normetanephrine to block neuronal and extra-neuronal uptake of noradrenaline raised plasma noradrenaline concentration without changing the pattern of the response to cold exposure. 4 Repeated cold exposure on subsequent days produced no change in the pattern of plasma noradrenaline concentration. 5 Five successive 1-min swims at 30-min intervals caused a rise in plasma noradrenaline concentration which was maximal after the third swim. 6 It is suggested that prolonged and repeated activation of sympathetic nerve terminals leads to a decline in noradrenaline release.
D000818:Animals; D003080:Cold Temperature / Q000009:adverse effects*; D003891:Desipramine / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000097:blood / Q000378:metabolism*; D009647:Normetanephrine / Q000494:pharmacology; D051381:Rats; D013312:Stress, Physiological / Q000378:metabolism*; D013550:Swimming; D013564:Sympathetic Nervous System / Q000502:physiology
D009647:Normetanephrine; D003891:Desipramine; D009638:Norepinephrine