Effect of brain-stem stimulation on renal function.

Evidence that tranquilising action of reserpine is associated with change in brain serotonin and not in brain epinephrine by B.B. A reserpine analogue, dimethylaminobenzoyl methyl reserpate (SU5171) can release half the brain nor-epinephrine in rabbits without releasing significant amounts of brain serotonin and without eliciting sedation. Larger doses release both amines and induce marked sedation. Additional strong evidence that the sedation produced bv reserpine itself is not due to the loss of brain. nor-epinephrine is provided by experiments in which rats and rabbits suhject to stress are not noticeably affected by reserpine. These results suggest that the tranquilising actions of Rauwolfia alkaloids are not related to changes in brain nor-epinephrine level. The implications of these and certain other findings in the role of serotonin in the action of reserpine are discussed. Effect of denervation and of cocaine on the action of sympathomi-metic amines by B.C. The secretory effect of sympathomimetic amines on the submaxillary gland of cat was increased after section of the chorda tympani (preganglionic parasympathetic) nerve. After sympathetic denervation, the secretory response to tyramine and phenylethylamine was absent, the response to dopa. mine and ephedrine decreased and that to adrenaline and nonadrenaline increased. Large doses of cocaine, given locally, produced changes similar to those obtained after sympathetic denervation. The sensitisation towards adrenaline and nor-adrenaline was obtained with smaller doses. Tyramine did not release catecholamines from suprarenal medulla. It is suggested that chromaffine tissue present in the adrenal medulla, or in skin, represents one type of store that can be released by nicotine. The adrenergic neurones, on which tyramine and similar substances might act as releasers, may represent a second ype of store of catechol amines.