Agonist- and antagonist-induced plasticity of rat 5-HT1A receptor in hippocampal cell culture.
We examined the response and regulation of 5-HT1A receptor on hippocampal cultured fetal neurons grown in the absence of serotonin and steroids using three experimental designs: 1) functional response using an antibody against phosphorylated cyclic adenosine monophosphate response element binding protein (pCREB); 2) transcriptional regulation using in situ hybridization; and 3) translational expression using antipeptide 5-HT1A receptor antibody. Pretreatment of cultured hippocampal cells with the agonist 8-hydroxy-2-(di-N-propylamino)-tetralin (8-OH-DPAT) (10(-8) M) or ipsapirone (IPS) (10(-9) M) for 10 min blocked the forskolin-stimulated increase in pCREB immunoreactivity. In situ hybridization radioautography revealed that IPS (10(-9) M) decreased the 5-HT1A receptor mRNA expression (-33%) after a 24-h treatment. The decrease in 5-HT1A receptor mRNAwas accompanied by a change in protein immunoreactivity using a 5-HT1A receptor antipeptide antibody. Computer-assisted morphometric analyses showed a reduction in the 5-HT1A receptor immunoreactive (IR) intensity as compared to control 24 h after treatment with 8-OH-DPAT (10(-7)-10(-12) M) and IPS (10(-9) M). Thus, fetal hippocampal neurons have a functional 5-HT1A receptor that is downregulated at both the transcription and translation levels. In addition, we found increased 5-HT1A receptor-IR intensity (+17% approximately +39%) 24 h after treatment with the antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl) cyclohexane carboxamide (WAY 100635) (10(-7)-10(-12) M). Our results indicate that the 5-HT1A receptor is sensitive to both agonists (downregulation) and antagonists (upregulation) in hippocampal fetal neurons grown in the absence of serotonin and steroids.
Department of Biology, New York University, New York 10003, USA. nmayumi@koto.kpu-m.ac.jp
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D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects*; D017403:In Situ Hybridization; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009473:Neuronal Plasticity / Q000187:drug effects*; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000235:genetics; D012702:Serotonin Antagonists / Q000494:pharmacology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*
D017362:Cyclic AMP Response Element-Binding Protein; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D005576:Colforsin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin