Blockade of 5-hydroxytryptamine-induced responses of rat seminal vesicle by lithium-possible mediation through calcium exchange..
Effect of lithium on the contractile responses of rat isolated seminal vesicle to 5-hydroxytryptamine (5-HT) were investigated by varying the Ca++ and Mg++ concentrations of the incubation medium in the absence and presence of EDTA. Preparations incubated in excess Ca++ (4.2 mM) or in Ca++-free Krebs solution showed decrease in sensitivity to 5-HT, whereas the responses to 5-HT were potentiated in Mg++-free incubation media and reduced in media containing excess Mg++. Rezerpinization failed to induce supersensitivity to 5-HT in any Mg++ concentration in the medium. However, reserpinized tissue in Mg++-free solution with EDTA showed increased sensitivity to 5-HT. Li+ inhibited responses to 5-HT. The inhibitory action of Li+ was augmented in medium lacking in Ca++ and was antagonized in media containing excess Ca++ (4.2mM). Li+ reduced the sensitivity and decreased maximum responses to 5-HT in any Mg++ concentration in the medium. In the presence of EDTA, the inhibition observed with Li+ in excess Mg++ (3.6 mM) medium was comparatively much less in both non-reserpinized and reserpinized preparations. Thus Li+ may be inhibiting responses to 5-Ht by block of influx of Ca++ or delayed efflux of Ca++ or inhibition of uptake of Ca++ or a combination of two or more of these effects.
D000818:Animals; D002118:Calcium / Q000502:physiology*; D008094:Lithium / Q000494:pharmacology*; D008274:Magnesium / Q000378:metabolism; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012110:Reserpine / Q000494:pharmacology; D012669:Seminal Vesicles / Q000187:drug effects; D012702:Serotonin Antagonists
D012702:Serotonin Antagonists; D012110:Reserpine; D008094:Lithium; D008274:Magnesium; D002118:Calcium; D009638:Norepinephrine