Selective block by glyceryl nonivamide of inwardly rectifying K⁺ current in rat anterior pituitary GH₃ cells

The effects of glyceryl nonivamide (GLNVA) on ionic currents were compared and examined in rat pituitary GH₃ cells. Hyperpolarization- activated K⁺ currents in GH₃ cells bathed in high-K⁺ Ca²⁺-free external solution were studied to assess effects of GLNVA on the an inwardly rectifying K⁺ current (I(K(IR))). GLNVA is very potent in blocking I(K(IR)) in concentration-dependent manner, with a half maximal concentrations of 0.1 μM. The complete block of I(K(IR)) achieved with concentrations ≥1 μM revealed the presence of a non-inactivating current. We also found that GLNVA at a concentration above 30 μM inhibited L-type voltage-dependent Ca²⁺ current and two components of K⁺ outward currents, while GLNVA (≤ 3 μM) did not have any effect on them. This study shows that GLNVA, in addition to retaining the capability of eliciting peptidergic neurons, is a selective block of I(K(IR)) in GH₃ cells and will provide a useful tool for characterizing I(K(IR)) and understanding its physiological function. In addition, the carefulness should be taken about the interpretation of GLNVA- mediated responses in vivo or in vitro.