Serotonergic modulation of slow inward rectification in mesencephalic trigeminal neurons

• Published in: Brain research 2019-09, Vol.1718, p.126-136
• Main Authors: Tanaka, Susumu, Tomita, Ikuo, Seki, Soju, Yamada, Saori, Kogo, Mikihiko, Furusawa, Kiyofumi
• Format: Article
• Language: English
• Subjects: 5-HT; Inward rectification; Low-frequency resonance; Mesencephalic trigeminal neuron
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2019.05.013

•5-HT suppresses the voltage sag and Ih conductance in mesencephalic V neurons.•The cAMP/protein kinase A (PKA) signaling pathway is involved in 5-HT modulation.•5-HT1A receptor activation mimics the effect of 5-HT.•5-HT suppresses low-frequency membrane resonance. Inward rectification in response to membrane hyperpolarization is a prominent feature of mesencephalic trigeminal (Mes V) neurons and the hyperpolarization-activated inward current (Ih), as the basis of this property, regulates the spike discharge characteristics and input frequency preference (resonance) in these neurons, suggesting that Ih modulation is an important regulator of oral motor activity. To examine a possible contribution of serotonin (5-HT) to the modulation of Ih activation characteristics, in the present study, we investigated the modulatory effects of 5-HT receptor activation on Ih in postnatal day (P) 2–12 rat Mes V neurons by whole-cell patch-clamp recording. Bath application of 5-HT suppressed the Ih-dependent voltage sag and Ih conductance, but induced only a modest shift in the voltage dependence of Ih activation. This 5-HT-induced suppression of Ih was greater in P10–12 than P2–4 neurons, and involved the cAMP/protein kinase A (PKA) signaling pathway but not the PKC pathway. Pharmacological activation of the 5-HT1A receptor mimicked the effect of 5-HT, while modulation of other receptor subtypes, including 5-HT1B,1D, 5-HT2, and 5-HT3, had little or no effect on Ih. Low-frequency (