Reduction of 5-hydroxytryptamine (5-HT)(1A)-mediated temperature and neuroendocrine responses and 5-HT(1A) binding sites in 5-HT transporter knockout mice.
The aim of the present study was to determine whether alterations in 5-hydroxytryptamine (5-HT)(1A) receptors would be found in knockout mice lacking the serotonin transporter (5-HTT). Hypothermic and neuroendocrine responses to the 5-HT(1A) agonist 8-hydroxy-2-(di-n-propylamino)tetraline (8-OH-DPAT) were used to examine the function of 5-HT(1A) receptors. Initial studies evaluated the dose-response and time course of 8-OH-DPAT-induced hypothermia and hormone secretion in normal CD-1 mice (the background strain of the 5-HTT knockout mice). 8-OH-DPAT dose-dependently produced hypothermic responses that peaked at 20 min postinjection. 8-OH-DPAT-induced hypothermia was blocked by the 5-HT(1A) antagonist WAY-100635. 8-OH-DPAT dose-dependently increased the concentrations of plasma oxytocin, corticotropin, and corticosterone. In the 5-HTT knockout (-/-) mice, the hypothermic response to 8-OH-DPAT (0.1 mg/kg s.c.) was completely abolished. Furthermore, 5-HTT-/- mice had significantly attenuated plasma oxytocin and corticosterone responses to 8-OH-DPAT. No significant changes in the hypothermic or hormonal responses to 8-OH-DPAT were observed in heterozygous (5-HTT+/-) mice. [(3)H]8-OH-DPAT- and [(125)I]MPPI [4-(2'-methoxyphenyl)-1-[2'-[N-(2"-pyridinyl)-iodobenzamido]ethyl] pip erazine]-binding sites in the hypothalamus and [(125)I]MPPI-binding sites in the dorsal raphe were significantly decreased in 5-HTT-/- mice. The results indicate that lack of the 5-HTT is associated with a functional desensitization of 5-HT(1A) receptor responses to 8-OH-DPAT, which may be a consequence, at least in part, of the decrease in density of 5-HT(1A) receptors in the hypothalamus and dorsal raphe of 5-HTT-/- mice.
Li
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Laboratory of Clinical Science, National Institute of Mental Health, National Institutes of Health Clinical Center, Bethesda, Maryland 20892-1264, USA. qianli@codon.nih.gov
Wichems
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Heils
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Van De Kar
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Lesch
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Murphy
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D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000631:Aminopyridines / Q000493:pharmacokinetics; D000818:Animals; D001345:Autoradiography; D001831:Body Temperature / Q000187:drug effects*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003345:Corticosterone / Q000097:blood; D004305:Dose-Response Relationship, Drug; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D051379:Mice; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins; D009490:Neurosecretory Systems / Q000187:drug effects / Q000378:metabolism*; D010121:Oxytocin / Q000097:blood; D010879:Piperazines / Q000493:pharmacokinetics / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011903:Raphe Nuclei / Q000187:drug effects / Q000378:metabolism; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000235:genetics; D044263:Receptors, Serotonin, 5-HT1; D012701:Serotonin / Q000378:metabolism*; D012702:Serotonin Antagonists / Q000494:pharmacology; D050486:Serotonin Plasma Membrane Transport Proteins; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013997:Time Factors
D000631:Aminopyridines; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D010879:Piperazines; D011725:Pyridines; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D012702:Serotonin Antagonists; D050486:Serotonin Plasma Membrane Transport Proteins; D017366:Serotonin Receptor Agonists; C493231:Slc6a4 protein, mouse; C087205:4-(2'-methoxyphenyl)-1-(2'-(N-(2''-pyridinyl)-4-iodobenzamido)ethyl)piperazine; D012701:Serotonin; D010121:Oxytocin; C090413:N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000324:Adrenocorticotropic Hormone; D003345:Corticosterone