Characterization of 5-HT2A receptor desensitization and the effect of cycloheximide on it in C6 cells.
Effect of prolonged pretreatment with serotonin (5-HT) on 5-HT2A receptor desensitization was examined by the measurement of intracellular calcium ([Ca2+]i) mobilization in C6 cells. 5-HT-induced desensitization of [Ca2+]i mobilization was in a time and dose dependent manner and reached a plateau after 3 hr. After 1 and 3 hr 5-HT pretreatment, 5-HT concentration in the medium little changed. 5-HT pretreatment with cycloheximide, a protein synthesis inhibitor, produced an enhancement of the desensitization for 3 and 6 hr pretreatment. However, 5-HT pretreatment for 3 and 6 hr caused no marked change in the 5-HT2A receptor mRNA level or Galphaq/11 protein in this study, suggesting that 5-HT may decrease 5-HT-induced [Ca2+]i mobilization independent of 5-HT2A receptor mRNA or G-proteins. Endothelin-1-induced [Ca2+]i mobilization did not alter after 5-HT and/or cycloheximide pretreatment. These results showed that activation of the 5-HT2A receptor induced homologous desensitization and pretreatment with 5-HT and/or cycloheximide did not change the efficacy of the second messenger pathway from Gq to a [Ca2+]i rise.
Miyoshi
I
I
Department of Psychiatry and Neurosciences, Hiroshima University School of Medicine, Japan.
Kagaya
A
A
Kohchi
C
C
Morinobu
S
S
Yamawaki
S
S
D000818:Animals; D001932:Brain Neoplasms; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D003513:Cycloheximide / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions / Q000502:physiology*; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D005910:Glioma; D020962:Heterotrimeric GTP-Binding Proteins / Q000187:drug effects / Q000378:metabolism; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000187:drug effects; D051381:Rats; D044402:Receptor, Serotonin, 5-HT2A; D017466:Receptors, Endothelin / Q000187:drug effects / Q000378:metabolism; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects* / Q000378:metabolism
D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D044402:Receptor, Serotonin, 5-HT2A; D017466:Receptors, Endothelin; D011985:Receptors, Serotonin; D012701:Serotonin; D003513:Cycloheximide; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins; D002118:Calcium