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.
Nishi
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Department of Biology, New York University, New York 10003, USA. nmayumi@koto.kpu-m.ac.jp
Azmitia
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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