SELECTIVE BLOCK BY GLYCERYL NONIVAMIDE OF INWARDLY RECTIFYING K-PITUITARY GH(3) CELLS( CURRENT IN RAT ANTERIOR)

The effects of glyceryl nonivamide (GLNVA) on ionic currents were comp ared and examined in rat pituitary GH(3) cells. Hyperpolarization-acti vated K+ currents in GH(3) cells bathed in high-K+ Ca2+-free external solution were studied to assess effects of GLNVA on the an inwardly re ctifying K+ current (I-K(IR)). GLNVA is very potent in blocking I-K(IR ) in a concentration-dependent manner, with a half maximal concentrati ons of 0.1 mu M. The complete block of I-K(IR) achieved with concentra tions greater than or equal to 1 mu M revealed the presence of a non-i nactivating current. We also found that GLNVA at a concentration above 30 mu M inhibited L-type voltage-dependent Ca2+ current and two compo nents of K+ outward currents, while GLNVA (less than or equal to 3 mu M) did not have any effect on them. This study shows that GLNVA, in ad dition to retaining the capability of eliciting peptidergic neurons, i s a selective block of I-K(IR) in GH(3) cells and will provide a usefu l tool for characterizing I-K(IR) and understanding its physiological function. In addition, the carefulness should be taken about the inter pretation of GLNVA-mediated responses in vivo or in vitro. (C) 1998 El sevier Science Inc.