Serotonin (5-HT) activation of immortalized hypothalamic neuronal cells through the 5-HT1B serotonin receptor.
Serotonin [or 5-hydroxytryptamine or (5-HT)] has been implicated as a key modulator in energy homeostasis and a primary focus in the treatment of obesity. There is growing evidence that 5-HT, acting through the 5-HT 1B receptor (5-HT(1B)R) in the paraventricular nucleus of the hypothalamus (PVN), is important to this regulation. However, there is some contention as to whether 5-HT(1B)R action occurs directly on PVN neurons or indirectly via inhibitory inputs into the PVN. To address these questions, we used a novel clonal, hypothalamic neuronal cell model, adult mouse hypothalamic-2/30 (mHypoA-2/30), expressing a PVN-specific marker, single-minded homolog 1, as well as a complement of PVN neuropeptides, including TRH, vasopressin, ghrelin, nucleobindin-2, and galanin. Adult mouse hypothalamic-2/30 neurons were also found to express the 5-HT(1B)R and 5-HT 6 receptor, but not 2C, all previously linked to feeding regulation. Direct serotonergic stimulation (100 nm to 10 μm) of these neurons resulted in dose-dependent cFos activation. 5-HT (10 μm) suppressed forskolin-induced cAMP levels and induced a rise in intracellular Ca(2+) through ER Ca(2+) release, effects that were mimicked by the 5-HT(1B)R agonists, CGS12066B and CP93129, and that were attenuated in the presence of the 5-HT(1B)R-specific inhibitors, GR55562 and isamoltane hemifumarate. Modest transcriptional changes in ghrelin and nucleobindin-2 were also observed in response to 100 nm and 10 μm 5-HT, respectively. These findings support the model wherein 5-HT action through the 1B receptor subtype occurs directly on PVN neurons, leading to potential modification of neuronal transcriptional and secretory machinery.
Departments of Physiology, University of Toronto, Toronto, Ontario, Canada M5S 1A8.
Stephanie
S
Tung
Alexandre B
AB
Hardy
Michael B
MB
Wheeler
Denise D
DD
Belsham
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D007031:Hypothalamus / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D051379:Mice; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D044302:Receptor, Serotonin, 5-HT1B / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D044302:Receptor, Serotonin, 5-HT1B; D012701:Serotonin; D002118:Calcium