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

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-HT 1 receptor agonist (8-OH-DPAT, 5-HT 1/7 agonist, co-applied with SB-269970, 5-HT 7 antagonist) and antagonist (WAY-100635), but 5-HT 1 receptor agonist did not increase I Gly and in the presence of 5-HT 1 antagonist, the potentiation of 5-HT on I Gly still happened. However, an agonist (α-methyl-5-HT) and antagonist (ketanserin) of the 5-HT 2 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-HT 7 receptor by using a 5-HT 7 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-HT 2 receptor. The interaction between 5-HT and glycine appears to have a significant role in modulating the transmission of the nociceptive pathway.

Potentiation of the Glycine Response by Bisphenol A, an Endocrine Disrupter, on the Substantia Gelatinosa Neurons of the Trigeminal Subnucleus Caudalis in Mice

“…The increase in the chloride conductance hyperpolarizes the postsynaptic cell and can inhibit the neuronal firing . Many agents, such as alcohol, anesthetics, steroids, serotonin, Zn 2+ , and tropeines, have been found to have an important role in modulating the function of glycine receptors. , BPA, a component of polycarbonate plastic utilized in food and beverage containers and in some dental material, is also an endocrine disruptor and has been demonstrated to be an effector of a great number of ion channels, such as voltage-gated Ca 2+ channels, voltage-gated Na + channels, large-conductance Ca 2+ /voltage-activated K + (BK) channels, nicotinic receptors, estrogen receptor, and GABA receptors. ,,− To the best of our knowledge, this is the first report to identify a positive correlation between glycine and BPA in the SG neurons of the Vc in mice. Through electrophysiological study, we showed that BPA induced potentiation on the glycine receptor-created responses (except in the early neonatal 0–3 postnatal days) through activation of heteromeric glycine receptors.…”

“…The method to prepare the brain slices was similar to that in our previous study . ICR mice with suitable experimental ages were chosen randomly (early neonatal: 0–3 postnatal days, juvenile: 7–20 postnatal days, and adults: 45–60 postnatal days).…”

“…The method to prepare the brain slices was similar to that in our previous study. 33 ICR mice with suitable experimental ages were chosen randomly (early neonatal: 0−3 postnatal days, juvenile: 7−20 postnatal days, and adults: 45−60 postnatal days). First, the mice were decapitated, and then their brains were removed quickly and immersed in ice-cold bicarbonate-buffered artificial cerebrospinal fluid (ACSF) containing (in mM): 126 NaCl, 2.5 KCl, 2.4 CaCl 2 , 1.2 MgCl 2 , D-(+)-Glucose, 1.4 NaH 2 PO 4 , 25 NaHCO 3, and 0.5 sodium ascorbate (pH 7.3−7.4, bubbled with 95% O 2 and 5% CO 2 ).…”