DEPLETION OF ATRIAL NOREPINEPHRINE INDUCED BY RESERPINE IN VITRO

概要

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Previous reports from this laboratory have indicated that reserpine inhibits and eventually abolishes rhythmic contractions of isolated rabbit atria despite only 20% decrease in norepinephrine levels, whereas atria from rabbits pretreated with reserpine in vivo and depleted of norepinephrine continue to contract long after isolation (1-4). The ability of reserpine to release serotonin in vitro is highly dependent upon temperature (5). On the other hand, the release of adrenal catecholamines following reserpine is mediated at least in part by activity of the sympathetic nervous system (6, 7). Thus it is possible that the slight decrease in atrial norepinephrine levels caused by reserpine in vitro is due to low environmental temperature and/or no impingement of nerve impulses on the pacemaker area of the isolated atrial preparation. The primary aim of this study, was to determine whether altering the temperature of bath fluid and electrical stimulation of the pacemaker area promote the release of atrial norepinephrine by reserpine in vitro. The results show that modifications in experimental conditions do not result in a promotion of the norepinephrine release due to reserpine and that reserpine in vitro releases norepinephrine via a mechanism different from that of catecholamine depleting agents acting in vivo, such as reserpine and guanethidine.
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