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  • Title: Efficient Ca2+ mobilization induced by neurokinin A in rat vas deferens.
    Author: Nagata K, Saito H, Matsuki N.
    Journal: Eur J Pharmacol; 1991 Nov 12; 204(3):295-300. PubMed ID: 1663458.
    Abstract:
    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.
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