Impairment of serotoninergic transmission is followed by adaptive changes in 5HT1B binding sites in the rat suprachiasmatic nucleus.
Serotonin1B (5-HT1B) receptor binding in the suprachiasmatic nucleus (SCN) following impairment of serotoninergic transmission was studied by quantitative autoradiography. Serotonin (5-HT) denervation with 5,7-dihydroxytryptamine (5,7-DHT) caused a significant increase in the density of 5-HT1B receptors in both the ventral (62%) and dorsal (53%) parts of the SCN as early as 3 days after axotomy. The magnitude of this increase did not differ 3, 15 or 21 days post-lesion. An up-regulation of 5-HT1B receptors with similar magnitude was obtained in the two parts of the SCN after inhibition of 5-HT synthesis by chronic parachlorophenylalanine treatment. In this case, up-regulation was shown to be reversible after restoration of 5-HT synthesis with L-5-hydroxytryptophan. These results indicate that 5-HT1B receptor density in the SCN was inversely correlated with 5-HT levels. These plastic properties exhibited by 5-HT1B receptors in the SCN are discussed in relation to the mode of 5-HT transmission and possible localization of the receptors onto the main chemically defined cell populations of the nucleus.
Manrique
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Laboratoire de Neuroendocrinologie Expérimentale, INSERM U297, Institut Fédératif Jean Roche, Faculté de Médecine Nord, Marseille, France.
François-Bellan
A M
AM
Segu
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Becquet
D
D
Héry
M
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Faudon
M
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Héry
F
F
D015116:5,7-Dihydroxytryptamine / Q000008:administration & dosage / Q000633:toxicity; D006916:5-Hydroxytryptophan / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000378:metabolism*; D002552:Cerebral Ventricles / Q000187:drug effects / Q000502:physiology; D004151:Dipeptides / Q000378:metabolism; D010134:Fenclonine / Q000494:pharmacology; D005625:Frontal Lobe / Q000378:metabolism; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D007031:Hypothalamus / Q000378:metabolism; D007263:Infusions, Parenteral; D007457:Iodine Radioisotopes; D007700:Kinetics; D008297:Male; D009928:Organ Specificity; D051381:Rats; D017207:Rats, Sprague-Dawley; D044302:Receptor, Serotonin, 5-HT1B; D011985:Receptors, Serotonin / Q000096:biosynthesis*; D012701:Serotonin / Q000031:analogs & derivatives / Q000378:metabolism*; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects; D013997:Time Factors; D015854:Up-Regulation
D004151:Dipeptides; D007457:Iodine Radioisotopes; D044302:Receptor, Serotonin, 5-HT1B; D011985:Receptors, Serotonin; C072128:serotonin-O-carboxymethyl-Gly-Tyr; D015116:5,7-Dihydroxytryptamine; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D006916:5-Hydroxytryptophan; D010134:Fenclonine