Effects of somatostatin-28 on rat locus coeruleus neurons.
The effects of somatostatin-28 (SS-28) on rat locus coeruleus (LC) neurons were investigated with techniques of brain slice and intracellular recording. SS-28 was applied by micropressure ejection through a micropipette. SS-28 (500 microM, 10 or 20 psi, 1 msec - 5 sec) reversibly decreased the firing rate of all neurons of the locus coeruleus tested. In addition to inhibition of spontaneous firing, larger concentrations of SS-28 also hyperpolarized the neurons of the locus coeruleus and simultaneously decreased the input resistance. At the greatest concentration (20 psi x 5sec) applied, SS-28 produced complete inhibition of firing of all neurons tested; the inhibition was associated with a 11-mV hyperpolarization and decreased input resistance 9 percent. The voltage-current relationship of the resting cell revealed an inward-going rectification that became enhanced after the pressure application of SS-28. The reversal potential for the SS-28-induced hyperpolarization was -116 mV, which is approximately the potassium equilibrium potential. The results also showed that BaCl2 blocked the SS-28-induced hyperpolarization, but apamin did not. We conclude that the inhibitory actions of SS-28 are due to opening the inward-going rectification potassium channels and that SS-28 and somatostatin-14 exert similar electrophysiological actions on LC neurons.
Chiu
T H
TH
Department of Physiology, National Yang Ming Medical College, Taipei, Taiwan, Republic of China.
Wu
T H
TH
Yeh
M H
MH
D000818:Animals; D001030:Apamin / Q000494:pharmacology; D017609:Barium Compounds / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D066298:In Vitro Techniques; D008125:Locus Coeruleus / Q000187:drug effects* / Q000502:physiology; D008297:Male; D015221:Potassium Channels / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013004:Somatostatin / Q000494:pharmacology*; D053561:Somatostatin-28
D017609:Barium Compounds; D002712:Chlorides; D015221:Potassium Channels; C024986:barium chloride; D001030:Apamin; D013004:Somatostatin; D053561:Somatostatin-28