PT  - JOURNAL ARTICLE
AU  - P Song
AU  - D Rocchi
AU  - M Lazzarotti
AU  - E Crimi
AU  - K Rehder
AU  - V Brusasco
TI  - Postjunctional effect of pinacidil on contractility of isolated bovine trachealis
AID  - 10.1183/09031936.96.09102057
DP  - 1996 Oct 01
TA  - European Respiratory Journal
PG  - 2057--2063
VI  - 9
IP  - 10
4099  - http://erj.ersjournals.com/content/9/10/2057.short
4100  - http://erj.ersjournals.com/content/9/10/2057.full
SO  - Eur Respir J1996 Oct 01; 9
AB  - Potassium channel openers hyperpolarize the smooth muscle cell membrane and relax airway smooth muscle. In this study, pre- and postjunctional effects of pinacidil ((+/-) N-cyano-N'-(4-pyridil)-N"-(1,2,2-trimethylpropyl)-guanidine monohydrated), an adenosine triphosphate (ATP)-sensitive K(+)-channel opener, were determined in isolated bovine trachealis. The effects of pinacidil on the frequency-response to electrical field stimulation (EFS), 0.1-32 Hz, and on the concentration response to acetylcholine (ACh), 10(9)-10(-4) M, were compared in muscle strips from six animals. In addition, the effect of pinacidil on the inhibitory nonadrenergic noncholinergic (iNANC) system was evaluated in histamine-contracted muscle strips from another eight animals. Pinacidil (10(-6) or 10(-5) M) shifted both the EFS frequency-response and the ACh concentration-response curves significantly (p < 0.01) to the right. Glibenclamide (10(-7)-10(-5) M) antagonized these responses in a concentration-dependent manner. The inhibitory effects of pinacidil on contractions of the same magnitude induced by EFS or exogenous ACh were not significantly different (p = 0.11), suggesting that pinacidil had only a postjunctional effect. Pinacidil had no effect on iNANC-mediated muscle relaxation. We conclude that pinacidil attenuates the contraction of isolated bovine tracheal smooth muscle by postjunctional mechanisms.