These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Pharmacological analysis of the effects of Bay K 8644 and organic calcium antagonists on the mouse isolated distal colon.
    Author: Fontaine J, Lebrun P.
    Journal: Br J Pharmacol; 1988 Aug; 94(4):1198-205. PubMed ID: 2463025.
    Abstract:
    1. Bay K 8644 (10(-8) to 10(-6) M) induced concentration-related contractions of the longitudinal muscle of the mouse distal colon. The maximal responses were enhanced and the EC50 was lowered in the presence of tetrodotoxin (TTX; 1.5 x 10(-7) M). The responses were not affected by atropine (10(-7) M), mepyramine (2.5 x 10(-7) M), methysergide (5 x 10(-7) M), propranolol (10(-6) M), phentolamine (10(-6) M) or naloxone (4 x 10(-7) M). By contrast, the contractile responses were inhibited by Ca2+ entry blockers (verapamil, nifedipine) and abolished in Ca2+-free EGTA solution. These observations indicate that the contractile effects of Bay K 8644 are dependent on its ability to promote Ca2+ influx. 2. At 10(-4) M, Bay K 8644 provoked a slow relaxation of the preparation. Moreover, from 10(-5) M, Bay K 8644 markedly reduced the contractile responses to ACh and K+ depolarization. These inhibitory effects were comparable with those produced by nifedipine. Such data suggest that, at high concentrations, Bay K 8644 could act in part as a dihydropyridine Ca2+ channel antagonist. 3. Bay K 8644 (10(-9) M) preferentially enhanced, while nifedipine (10(-10) to 10(-8) M) as well as verapamil (3 x 10(-9) to 10(-6) M) preferentially inhibited, the tonic component of the contractile response evoked by K+ depolarizing solution. This may indicate that different populations of voltage-sensitive Ca2+ channels are involved in the biphasic response to K+ depolarization. 4. The biphasic contractile activity induced by ACh was barely enhanced by Bay K 8644 (10-9M) and was less sensitive to Ca2+ entry blockers than the responses to KCl. These findings are discussed in terms of receptor-operated channels and mobilization of bound calcium.
    [Abstract] [Full Text] [Related] [New Search]