Chlorpromazine metabolism in chronic schizophrenics.
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Biomedical subjects
Publications and source records attributed to A Perales.
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The effects of Ca2+ removal and of the calcium entry blockers, nicardipine and nifedipine, on contractions of isolated human umbilical arteries, elicited with KCl and 5-hydroxytryptamine, were investigated. Withdrawal of Ca2+ caused inhibition of both KCl and 5-hydroxytryptamine responses, but the maximum effect of KCl in Ca2(+)-free medium was recuperated by increasing the KCl concentration. The maximum effect of 5-hydroxytryptamine, however, was recuperated only when Ca2+ was restored to the medium. Consistently with an inhibition in Ca2(+)-free medium, calcium entry blockers produced a concentration-dependent relaxation of human umbilical artery strips precontracted with KCl and 5-hydroxytryptamine, and inhibited the concentration-dependent contraction elicited by these stimuli. Our results indicate that contractile responses of the human umbilical arteries are dependent on extracellular Ca2+ for both KCl and 5-hydroxytryptamine. Although Ca2+ entry was sensitive to both nicardipine and nifedipine, the differences between the effects of these dihydropyridines with the two experimental approaches we used were not always conclusive.