Korean J Physiol Pharmacol.  2019 Jul;23(4):271-279. 10.4196/kjpp.2019.23.4.271.

Potentiation of the glycine response by serotonin on the substantia gelatinosa neurons of the trigeminal subnucleus caudalis in mice

Affiliations
  • 1Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju 54896, Korea. soopark@jbnu.ac.kr
  • 2Department of Obstetrics and Gynecology, Chonbuk National University Hospital and School of Medicine, Jeonju 54896, Korea.

Abstract

The lamina II, also called the substantia gelatinosa (SG), of the trigeminal subnucleus caudalis (Vc), is thought to play an essential role in the control of orofacial nociception. Glycine and serotonin (5-hydroxytryptamine, 5-HT) are the important neurotransmitters that have the individual parts on the modulation of nociceptive transmission. However, the electrophysiological effects of 5-HT on the glycine receptors on SG neurons of the Vc have not been well studied yet. For this reason, we applied the whole-cell patch clamp technique to explore the interaction of intracellular signal transduction between 5-HT and the glycine receptors on SG neurons of the Vc in mice. In nine of 13 neurons tested (69.2%), pretreatment with 5-HT potentiated glycine-induced current (I(Gly)). Firstly, we examined with a 5-HT₁ receptor agonist (8-OH-DPAT, 5-HT(1/7) agonist, co-applied with SB-269970, 5-HT₇ antagonist) and antagonist (WAY-100635), but 5-HT₁ receptor agonist did not increase IGly and in the presence of 5-HT₁ antagonist, the potentiation of 5-HT on I(Gly) still happened. However, an agonist (α-methyl-5-HT) and antagonist (ketanserin) of the 5-HT₂ receptor mimicked and inhibited the enhancing effect of 5-HT on I(Gly) in the SG neurons, respectively. We also verified the role of the 5-HT₇ receptor by using a 5-HT₇ antagonist (SB-269970) but it also did not block the enhancement of 5-HT on I(Gly). Our study demonstrated that 5-HT facilitated I(Gly) in the SG neurons of the Vc through the 5-HT₂ receptor. The interaction between 5-HT and glycine appears to have a significant role in modulating the transmission of the nociceptive pathway.

Keyword

Glycine receptor; Patch-clamp techniques; Serotonin; Substantia gelatinosa

MeSH Terms

Animals
Glycine*
Mice*
Neurons*
Neurotransmitter Agents
Nociception
Patch-Clamp Techniques
Receptors, Glycine
Serotonin*
Signal Transduction
Substantia Gelatinosa*
Glycine
Neurotransmitter Agents
Receptors, Glycine
Serotonin
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