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In vivo assessment of the midbrain raphe nuclear regulation of serotonin release in the hamster suprachiasmatic nucleus.
- Source :
-
Journal of neurophysiology [J Neurophysiol] 1999 Apr; Vol. 81 (4), pp. 1469-77. - Publication Year :
- 1999
-
Abstract
- Serotonin (5-HT) plays important regulatory roles in mammalian circadian timekeeping; however, little is known concerning the regulation of serotonergic activity in the circadian clock located in the suprachiasmatic nuclei (SCN). By using in vivo microdialysis to measure 5-HT release we demonstrated that electrical or pharmacological stimulations of the dorsal or median raphe nuclei (DRN and MRN, respectively) can alter basal release of 5-HT in the hamster SCN. There were similar increases in SCN 5-HT release after electrical stimulation of either the MRN or DRN, indicating that both could contribute to the serotonergic activity in the SCN. Systemic pretreatment with the 5-HT antagonist metergoline abolished DRN-induced SCN 5-HT release but had little effect on MRN-induced SCN 5-HT release, suggesting different pathways for these nuclei in regulating 5-HT output in the SCN. Microinjections of the 5-HT1A autoreceptor agonist 8-OH-DPAT or antagonist WAY 100635 into the MRN caused significant inhibition and stimulation of SCN 5-HT release, respectively. Both drugs had substantially less effect in the DRN. These differential drug actions indicate that somatodendritic 5-HT1A autoreceptors on MRN neurons provide the prominent raphe autoregulation of 5-HT output in the SCN. Collectively the current results are evidence that DRN as well as MRN neurons can contribute to the regulation of 5-HT release in the hamster SCN. On the basis of the current observations and those from recent anatomic tracing studies of serotonergic projections to SCN it is hypothesized that DRN input to the SCN could be mediated by a DRN --> MRN --> SCN pathway involving a 5-HT-sensitive multisynaptic interaction between the DRN and MRN neurons.
- Subjects :
- 8-Hydroxy-2-(di-n-propylamino)tetralin pharmacology
Animals
Autoreceptors analysis
Autoreceptors physiology
Brain Chemistry drug effects
Chromatography, High Pressure Liquid
Cricetinae
Electric Stimulation
Male
Mesocricetus
Metergoline pharmacology
Microdialysis
Piperazines pharmacology
Pyridines pharmacology
Receptors, Serotonin analysis
Receptors, Serotonin physiology
Receptors, Serotonin, 5-HT1
Serotonin analysis
Serotonin Antagonists pharmacology
Serotonin Receptor Agonists pharmacology
Raphe Nuclei metabolism
Serotonin metabolism
Suprachiasmatic Nucleus metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0022-3077
- Volume :
- 81
- Issue :
- 4
- Database :
- MEDLINE
- Journal :
- Journal of neurophysiology
- Publication Type :
- Academic Journal
- Accession number :
- 10200183
- Full Text :
- https://doi.org/10.1152/jn.1999.81.4.1469