AIMTo determine whether serotonin, a major neurotransmitter in brain, can modulate the production of secretory beta-amyloid protein precursor (sAPP) by activation of serotonin 5-HT2C receptor.

METHODSThe hippocampal slices of rats were incubated with various concentrations of serotonin, M-110, or L-107. sAPP released into the incubation medium were assayed by Western blot analysis assay with monoclonal antibody 22C11 for 2 h.

RESULTSVarious concentrations of serotonin (1.0 x 10(-2) - 1.0 x 10(3) micromol x L(-1)), M-110, a serotonin 5-HT2C agonist (1.5 x 10(-6) - 1.5 x 10(3) micromol x L(-1)), showed positive effect on the production of sAPP while L-107, a serotonin 5-HT2C antagonist (1.0 x 10(-9) - 1.0 x 10(3) micromol x L(-1)), showed negative effect on the production of sAPP over controls.

CONCLUSIONSerotonin modulates production of secretory amyloid beta-protein precursor through serotonin 5-HT2C receptor in incubated rat hippocampal slices.

Amyloid beta-Protein Precursor ; secretion ; Animals ; Hippocampus ; metabolism ; In Vitro Techniques ; Male ; Peptide Fragments ; secretion ; Rats ; Rats, Sprague-Dawley ; Receptor, Serotonin, 5-HT2C ; Serotonin ; pharmacology ; Serotonin 5-HT2 Receptor Agonists ; Serotonin 5-HT2 Receptor Antagonists

AIMTo explore the modulation of 5-HT on GABA-activated current (I(GABA)) in the membrane of rat dorsal root ganglion (DRG) neurons and its mechanism.

METHODSRat DRG neurons were isolated mechanically and enzymatically, on which whole-cell patch clamp recording and repatch technique for intracellular dialysis were performed.

RESULTSIn the majority of neurons examined (92.0%, 69/75) GABA induced a concentration-dependent inward current. In neurons sensitive to GABA preapplication of 5-HT produced potentiation effect (82.6% , 57/69) on I(GABA). Preapplication of 5-HT at concentrations of 1 x 10(-6), 1 x 10(-5), 1 x 10(-4) and 1 x 10(-3) mol x L(-1) potentiated I(GABA) by (35 +/- 8)% (n=8), (47 +/- 11)% (n=10), (65 +/- 17)% (n=9) and (75 +/- 18)% (n=11), respectively. This effect was mimicked by alpha-methyl-5-HT (1 x 10(-6) mol x L(-1)), a specific 5-HT2 receptor agonist, and reversed by cyproheptadine, a selective 5-HT2 receptor antagonist. The potentiation of I(GABA) by 5-HT was irrespective to whether the I(5-HT) presents or not in a subset of neurons. The concentration-response curves for GABA before and after pretreatment with 5-HT manifested the same threshold value and similar EC50 (2.0 x 10(-5) and 1.9 x 10(-5) mol x L(-1), respectively) , while the maximal value of I(GABA) for the latter was 33.6% higher than that for the former. Intracellular dialysis with GDP-beta-S or H-7 abolished the potentiation of I(GABA) by 5-HT, while H-9 did not.

CONCLUSION5-HT can potentiate GABA-activated current via PKC-dependent phosphorylation of GABA(A) receptor following the activation of 5-HT2 receptor.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine ; pharmacology ; Animals ; Cyproheptadine ; pharmacology ; Female ; Ganglia, Spinal ; cytology ; physiology ; Male ; Membrane Potentials ; drug effects ; Neurons ; physiology ; Patch-Clamp Techniques ; Protein Kinase C ; antagonists & inhibitors ; Rats ; Rats, Sprague-Dawley ; Receptors, Serotonin, 5-HT2 ; Serotonin ; analogs & derivatives ; pharmacology ; Serotonin 5-HT2 Receptor Agonists ; Serotonin 5-HT2 Receptor Antagonists ; Signal Transduction ; gamma-Aminobutyric Acid ; pharmacology

BACKGROUND AND OBJECTIVES: This study was aimed to explore the effects of the 5-hydroxytryptamine (5-HT) on potassium currents in rat vestibular nuclear neurons. MATERIALS AND METHOD: Sprague-Dawley rats aged 14 to 16 days were anesthetized with ether and decapitated. After enzymatic digestion, the portion of medial vestibular nucleus neuron was removed by micropunching and gently agitated. The dissociated neurons were transferred into a recording chamber mounted on an inverted microscope and whole-cell membrane currents were recorded at room temperature by using standard patch-clamp techniques. RESULTS: When cells were held at -70 mV and depolarized from -60 mV to +40 mV in 10 mV increments, sustained outward potassium currents were evoked. The response of medial vestibular nuclear neurons to 5-HT was not uniform. The outward potassium currents were increased in 17 of 40 cells and decreased in 23 of 40 cells. 5-carboxamidotryptamine, 5-HT1 agonist increased the outward potassium currents of the medial vestibular nuclear cell. alpha-methyl-5-hydroxytryptamine, 5-HT2 agonist decreased the outward potassium currents of the medial vestibular nuclear cell. CONCLUSION: These results suggest that 5-HT affects the potassium currents of the cell with different effects according to the receptor subtype on which it acts.
Animals ; Digestion ; Dihydroergotamine ; Ether ; Membranes ; Neurons* ; Patch-Clamp Techniques ; Potassium Channels ; Potassium* ; Rats* ; Rats, Sprague-Dawley ; Serotonin 5-HT1 Receptor Agonists ; Serotonin 5-HT2 Receptor Agonists ; Serotonin* ; Vestibular Nuclei

5-Hydroxytryptamine 2C (5-HT) receptor is one of the major targets of anti-obesity agents, due to its role in regulation of appetite. In the present study, the 70% EtOH extract of the roots of Bupleurum chinense was revealed to have agonistic activity on 5-HT receptor, and the subsequent bioassay-guided isolation led to identification of several saikosaponins as the active constituents with 5-HT receptor agonistic activity in vitro and anti-obesity activity in vivo. The new compound, 22-oxosaikosaponin d (1), was determined by extensive spectroscopic analyses (HR-ESI-MS, IR, and 1D and 2D NMR). The primary structure-activity relationship study suggested that the intramolecular ether bond between C-13 and C-28 and the number of sugars at C-3 position were closely related to the 5-HT receptor agonistic activity. Saikosaponin a (3), the main saponin in B. chinense, showed obviously agonistic activity on 5-HT receptor with an EC value of 21.08 ± 0.33 μmol·Lin vitro and could reduce food intake by 39.1% and 69.2%, and weight gain by 13.6% and 16.4%, respectively, at 3.0 and 6.0 mg·kgin vivo. This investigation provided valuable information for the potential use of B. chinense as anti-obesity agent.
Animals ; Anti-Obesity Agents ; chemistry ; isolation & purification ; pharmacology ; Biological Assay ; Bupleurum ; chemistry ; Male ; Oleanolic Acid ; analogs & derivatives ; chemistry ; isolation & purification ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Saponins ; chemistry ; isolation & purification ; pharmacology ; Serotonin 5-HT2 Receptor Agonists ; chemistry ; isolation & purification ; pharmacology ; Structure-Activity Relationship