{"title":"RH-3421, a potent dihydropyrazole insecticide, inhibits depolarization-stimulated rises in free [Ca2+] and 45Ca2+ uptake in mammalian synaptosomes.","authors":"A Zhang, R A Nicholson","doi":"","DOIUrl":null,"url":null,"abstract":"<p><p>The dihydropyrazole RH-3421 inhibits veratridine- and K(+)-induced rises in synaptosomal free Ca2+ with IC50s of 0.2 and 1 microM, respectively. The K(+)-induced rise in free synaptosomal Ca2+, which requires external Ca2+, is also blocked by RH-3421 in the presence of tetrodotoxin. The K(+)-stimulated 45Ca2+ uptake by synaptosomes is unaffected by tetrodotoxin, blocked by cobalt ions and inhibited by RH-3421 both alone (IC50 = 11 microM) and in the presence of tetrodotoxin. RH-3421 does not influence the level of free Ca2+ or basal 45Ca2+ uptake in non-depolarized synaptosomes. The results suggest RH-3421 inhibits voltage-sensitive calcium channels in nerve endings.</p>","PeriodicalId":79328,"journal":{"name":"Comparative biochemistry and physiology. Part C, Pharmacology, toxicology & endocrinology","volume":"108 3","pages":"307-10"},"PeriodicalIF":0.0000,"publicationDate":"1994-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Comparative biochemistry and physiology. Part C, Pharmacology, toxicology & endocrinology","FirstCategoryId":"1085","ListUrlMain":"","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
The dihydropyrazole RH-3421 inhibits veratridine- and K(+)-induced rises in synaptosomal free Ca2+ with IC50s of 0.2 and 1 microM, respectively. The K(+)-induced rise in free synaptosomal Ca2+, which requires external Ca2+, is also blocked by RH-3421 in the presence of tetrodotoxin. The K(+)-stimulated 45Ca2+ uptake by synaptosomes is unaffected by tetrodotoxin, blocked by cobalt ions and inhibited by RH-3421 both alone (IC50 = 11 microM) and in the presence of tetrodotoxin. RH-3421 does not influence the level of free Ca2+ or basal 45Ca2+ uptake in non-depolarized synaptosomes. The results suggest RH-3421 inhibits voltage-sensitive calcium channels in nerve endings.
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