Arachidonic acid and prostaglandin D2 cooperatively accelerate desensitization of nicotinic acetylcholine receptor channel in mouse skeletal muscles

To clarify the effects of arachidonic acid (AA) and its metabolites on desensitization of nicotinic acetylcholine (ACh) receptor channel in mouse skeletal muscle cells, we investigated the time-dependent decrease in the channel opening frequency of ACh (1 mu M)-activated channel currents by the cell-attached patch clamp technique. AA (30-100 mu M) applied to a patched membrane or to non-patched membrane accelerated the decrease in the channel opening frequency. A cyclooxygenase inhibitor, indomethacin(10 mu M), prevented the acceleration elicited by 30 mu M AA, but not by 100 mu M AA. A lipoxygenase inhibitor, nordihydroguaiaretic acid (10 mu M), and a cytochrome P-450 inhibitor, ketoconazole (3 mu M), did not affect the acceleration by 30 mu M AA. Prostaglandin (PG) D-2 at 10 mu M alone and at 25 nM in combination with 10 mu M AA accelerated the decrease in the channel opening frequency. No acceleration was observed with PGE(2) at 10 mu M alone and at 25 nM in combination with 10 mu M AA. Pretreatment with a protein kinase (PK) C inhibitor, staurosporine (10 nM), but not with a PKA inhibitor, H-89 (3 mu M), prevented the acceleration elicited by AA + PGD(2). These results suggest that AA, and PGD(2) of its metabolites, cooperatively accelerate desensitization of nicotinic ACh receptor channel. The activation of PKC by PLA and PGD(2) may be involved in the mechanism of the cooperative acceleration of desensitization. (C) 2000 Elsevier Science B.V. All rights reserved.