Inhibitory effect of somatostatin on vagal motoneurons in the rat brain stem in vitro.
Effects of somatostatin-14 (SRIF) on membrane electrical properties were studied in rat brain stem slice preparations maintained in vitro. SRIF hyperpolarized the resting membrane potential and decreased the input resistance of more than two-thirds of the 85 vagal motoneurons tested in the dorsal motor nucleus of the vagus. These effects persisted under synaptic blockade caused by perfusion with a solution containing tetrodotoxin or a Ca2+-free/high-Mg2+ solution and were dependent on the extracellular SRIF concentration (5 X 10(-8) to 1 X 10(-8) M). The Hill coefficient was estimated to be 2. The reversal potential of SRIF-induced hyperpolarization was affected by changing external K+ concentration. The results suggest that, in addition to its well-known peripheral action, SRIF may inhibit secretomotor functions of visceral organs by reducing vagal output in the central nervous system.
Nabekura
J
J
Department of Physiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Mizuno
Y
Y
Oomura
Y
Y
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001933:Brain Stem / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000502:physiology; D004553:Electric Conductivity; D004558:Electric Stimulation; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013004:Somatostatin / Q000494:pharmacology*; D013569:Synapses / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology; D014630:Vagus Nerve / Q000187:drug effects / Q000502:physiology*
D013779:Tetrodotoxin; D013004:Somatostatin; D008274:Magnesium; D011188:Potassium; D002118:Calcium