Efficient Ca2+ mobilization induced by neurokinin A in rat vas deferens.
Although both neurokinin A (NKA) and norepinephrine (NE) induced similar maximal contractions in the epididymal and the prostatic site of vas deferens, NKA affected sensitivity more potently than did NE in both sites. The NKA-induced contractions were more strongly inhibited by nicardipine, a dihydropyridine Ca2+ entry blocker, or by elimination of extracellular Ca2+ (Cao2+) in both sites. However, ryanodine, which interferes with the release of intracellular Ca2+ (Cai2+), abolished the contractions caused by NKA in the prostatic site whereas it had no effect in the epididymal site. These results suggest that NKA-induced contraction utilizes both Cai2+ and Cao2+ in the prostatic site but mobilizes only Cao2+ in the epididymal site. Cai2+ concentration [( Ca2+]i) was measured directly with a Ca(2+)-sensitive fluorescent dye, fura-2. In the epididymal site NKA induced contractions with smaller increase in [Ca2+]i compared to that necessary for NE-induced contractions. These results suggest that NKA utilizes Ca2+ more efficiently than does NE and plays a role as a neuromodulator in rat vas deferens.
Nagata
K
K
Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.
Saito
H
H
Matsuki
N
N
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002122:Calcium Chloride / Q000494:pharmacology; D004822:Epididymis; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D015288:Neurokinin A / Q000494:pharmacology*; D009529:Nicardipine / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology; D011467:Prostate; D051381:Rats; D011919:Rats, Inbred Strains; D012433:Ryanodine / Q000494:pharmacology; D013997:Time Factors; D014649:Vas Deferens / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*
D012433:Ryanodine; D015288:Neurokinin A; D009529:Nicardipine; D002122:Calcium Chloride; D002118:Calcium; D009638:Norepinephrine