Biphasic effects of mianserin and desipramine on serotonin-evoked current and Cl- efflux in Xenopus oocytes.
Serotonin (5-HT, 1 microM) elicited two phases of Cl- inward current in Xenopus oocytes injected with rat brain mRNA: a transient current (T-current), which was generated rapidly (within 1 min), and a sustained current (S-current), which persisted for 10 min. Each type of 5-HT-evoked response was time-dependent after mRNA injection. The T-current was generated at 20-30 h and the S-current at 30-40 h. Although mianserin at 0.1 microM completely inhibited the T-current, 10 microM mianserin was required to suppress the S-current. 5-HT also caused Cl- efflux from oocytes preloaded with 36Cl-. Cl- efflux during 1 min, corresponding to the T-current, was inhibited by 0.1 microM mianserin. A higher concentration of mianserin (10 microM) was required to block the efflux for 10 min, corresponding to the S-current, as well as the current response. Desipramine selectively inhibited the T-current and Cl- efflux for 1 min. The mechanisms underlying the different sensitivity to mianserin of oocytes injected with rat brain mRNA are discussed.
Tohda
M
M
Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Nomura
Y
Y
D000818:Animals; D002712:Chlorides / Q000378:metabolism* / Q000502:physiology; D003891:Desipramine / Q000494:pharmacology*; D004594:Electrophysiology; D005260:Female; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008803:Mianserin / Q000494:pharmacology*; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000235:genetics / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology*; D013268:Stimulation, Chemical; D013997:Time Factors; D014981:Xenopus
D002712:Chlorides; D011985:Receptors, Serotonin; D008803:Mianserin; D012701:Serotonin; D003891:Desipramine