Somatostatin inhibits the nicotinic receptor-activated inward current in guinea pig chromaffin cells.
At a holding potential of -60 mV, bath application of somatostatin produced no current response itself, but inhibited the nicotinic inward current, a concentration of about 0.01 microM being required for a half-maximal effect. This inhibition was affected neither by pretreatment with somatostatin nor by injection of guanosine-5'-0-(3-thiotriphosphate) through a patch pipette. When somatostatin (0.03-0.1 microM) produced its maximum inhibition, the proportion of plateau to peak nicotinic current was greatly reduced (to 5.3 +/- 5.7% from the control value of 34.9 +/- 4.9%, n = 5) with a facilitation of the time course of desensitization. After washout of somatostatin, the nicotinic current was restored to control level in a time-dependent, rather than an activation-dependent manner. The results suggest that somatostatin inhibits the function of the nicotinic receptor by facilitation of its desensitization or by an open-channel block.
Inoue
M
M
Department of Pharmacology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Kuriyama
H
H
D000313:Adrenal Medulla / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D005260:Female; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006168:Guinea Pigs; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009538:Nicotine / Q000494:pharmacology*; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000502:physiology*; D013004:Somatostatin / Q000494:pharmacology*
D011978:Receptors, Nicotinic; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D013004:Somatostatin; D009538:Nicotine