title: The role of calcium channels in substance P-induced contractile response in the rat iris.
abstract: This study was undertaken to assess the role of calcium channels in the contractile response induced by substance P in the isolated rat iris. Substance P produced graded and sustained contraction in the rat iris. Pre-incubation of preparations with thapsigargin (1 microM), verapamil (1 microM), isradipine (1 microM) or with omega-conotoxin MCIIA (0.1 microM) did not significantly inhibit substance P-mediated contraction in the isolated rat iris. However, pre-incubation of the preparations with nicardipine (1 microM) or ruthenium red (1 mM) caused parallel displacement to the right of the substance P concentration-response curve without affecting its maximal response. In contrast, amiloride (1 microM), markedly inhibited substance P-mediated contraction (73 +/- 5%), while econazole (1 mM) also significantly inhibited (44 +/- 11%) substance P-mediated contraction in the isolated rat iris. Collectively, these results suggest that substance P-mediated contractile response in the isolated rat iris depends largely on the influx of external Ca2+, by a mechanism which might involve the T-type calcium channels.
authors.affiliation: Departamento de Farmacologia, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Rua Ferrreira Lima 82, 88015-420 Florianópolis, SC, Brazil.
authors.forename: Astor
authors.initials: A
authors.lastname: Grumann Júnior
authors.forename: Ricardo V
authors.initials: RV
authors.lastname: Alves
authors.forename: João B
authors.initials: JB
authors.lastname: Calixto
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D004464:Econazole / Q000494:pharmacology; D066298:In Vitro Techniques; D007498:Iris / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009529:Nicardipine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012430:Ruthenium Red / Q000494:pharmacology; D013373:Substance P / Q000037:antagonists & inhibitors / Q000494:pharmacology*
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D012430:Ruthenium Red; D013373:Substance P; D004464:Econazole; D000584:Amiloride; D009529:Nicardipine; D002118:Calcium