A possible cardiovascular effect of lithium.

Heart rate rises associated with performance of mental arithmetic tasks were compared in 22 euthymic manic-depressive patients receiving lithium carbonate and 17 drug-free normal controls. The lithium-treated subjects showed a markedly lower heart rate response to the mental arithmetic stimulus. No effect was observed on basal heart rate. The results are consistent with lithium's reported inhibition of noradrenaline-induced rises in adenylate cyclase activity but lack of inhibition of basal adenylate cyclase activity. The biochemical and psychophysiological findings may parallel lithium's unique ability to calm excited behavior without sedating normal behavior.