Differential effects of nifedipine and verapamil on non-adrenergic non-cholinergic relaxations at different levels of active tone: assessment of the contribution of nerve-derived hyperpolarizing factor
Author: Ergün, Y.
Source: Autonomic & Autacoid Pharmacology, Volume 25, Number 3, July 2005 , pp. 105-112(8)
1 The objective was to investigate a possible contribution of a nerve-derived hyperpolarizing factor to the differences between non-adrenergic non-cholinergic (NANC) nerve-mediated relaxations in different states of active tone in the rat gastric fundus.
2 NANC relaxations induced by electrical field stimulation (ES: 0.1, 0.5 and 1 Hz; 25 V; 1 ms; 10 s) in 40% contracted strips (S40) were greater when compared with those in 80% contracted strips (S80).
3 ES-induced relaxations were effectively attenuated by N-nitro-l-arginine (l-NNA; 100 m) in S40 and S80. Percentage reduction of the responses obtained in the presence ofl-NNA in S40 group was less than that of S80.
4 In S40 group, nifedipine (0.5–1 m) and verapamil (0.5–1 m) inhibited the responses to 0.1 and 0.5 Hz. Nifedipine (1 m) and verapamil (0.5 m) caused no change in the responses to ES in S80.
5 In S40, whenl-NNA (100 m) and nifedipine or verapamil, either in 1 mconcentration, were administered together, the inhibition on the electrical relaxations were more than that of each drug alone.
6 In conclusion, NANC nerve-mediated relaxations are increased when studied in an active state of 40%, and a factor, sensitive to nifedipine seems to be responsible for this distinction.
Document Type: Research Article
Publication date: July 1, 2005