TY - JOUR
T1 - Role of medullary GABA signal transduction on parasympathetic reflex vasodilatation in the lower lip
AU - Kawakami, So
AU - Izumi, Hiroshi
AU - Masaki, Eiji
AU - Kuchiiwa, Satoshi
AU - Mizuta, Kentaro
N1 - Funding Information:
This work was supported by Grants-in-Aid for Young Scientists (A) [ 20689036 (KM)] and Research Fellowships for Young Scientists [No. 163019 (KM)] from the Japan Society for the Promotion of Science .
PY - 2012/2/9
Y1 - 2012/2/9
N2 - In the orofacial area, noxious stimulation of the orofacial structure in the trigeminal region evokes parasympathetic reflex vasodilatation, which occurs via the trigeminal spinal nucleus (Vsp) and the inferior/superior salivatory nucleus (ISN/SSN). However, the neurotransmitter involved in the inhibitory synaptic inputs within these nuclei has never been described. This parasympathetic reflex vasodilatation is suppressed by GABAergic action of volatile anesthetics, such as isoflurane, sevoflurane, and halothane, suggesting that medullary GABAergic mechanism exerts its inhibitory effect on the parasympathetic reflex via an activation of GABA receptors. The aim of the present study was to determine the role of GABAA and GABAB receptors in the Vsp and the ISN in regulating the lingual nerve (LN)-evoked parasympathetic reflex vasodilatation in the lower lip. Under urethane anesthesia (1 g/kg), change in lower lip blood flow elicited by electrical stimulation of the LN was recorded in cervically vago-sympathectomized rats. Microinjection of GABA (10 μM; 0.3 μl/site) into the Vsp or the ISN significantly and reversibly attenuated the LN-evoked parasympathetic reflex vasodilatation. Microinjection of the GABAA receptor-selective agonist muscimol (100 μM; 0.3 μl/site) or the GABAB receptor-selective agonist baclofen (100 μM; 0.3 μl/site) into the Vsp or the ISN significantly and irreversibly reduced this reflex vasodilatation, and these effects were attenuated by pretreatment with microinjection of each receptor-selective antagonists [GABAA receptor selective antagonist bicuculline methiodide (1 mM; 0.3 μl/site) or GABAB receptor selective antagonist CGP-35348 (1 mM; 0.3 μl/site)] into the Vsp or the ISN. Microinjection of these antagonists alone into the Vsp or the ISN had no significant effect on this reflex vasodilatation. In addition, microinjection (0.3 μl/site) of the mixture of muscimol (100 μM) and baclofen (100 μM) into the Vsp or the ISN also significantly reduced this reflex vasodilatation. These results suggest that medullary GABA signal transduction inhibits the parasympathetic reflex vasodilatation in the rat lower lip via GABAA and GABAB receptors in the Vsp and the ISN.
AB - In the orofacial area, noxious stimulation of the orofacial structure in the trigeminal region evokes parasympathetic reflex vasodilatation, which occurs via the trigeminal spinal nucleus (Vsp) and the inferior/superior salivatory nucleus (ISN/SSN). However, the neurotransmitter involved in the inhibitory synaptic inputs within these nuclei has never been described. This parasympathetic reflex vasodilatation is suppressed by GABAergic action of volatile anesthetics, such as isoflurane, sevoflurane, and halothane, suggesting that medullary GABAergic mechanism exerts its inhibitory effect on the parasympathetic reflex via an activation of GABA receptors. The aim of the present study was to determine the role of GABAA and GABAB receptors in the Vsp and the ISN in regulating the lingual nerve (LN)-evoked parasympathetic reflex vasodilatation in the lower lip. Under urethane anesthesia (1 g/kg), change in lower lip blood flow elicited by electrical stimulation of the LN was recorded in cervically vago-sympathectomized rats. Microinjection of GABA (10 μM; 0.3 μl/site) into the Vsp or the ISN significantly and reversibly attenuated the LN-evoked parasympathetic reflex vasodilatation. Microinjection of the GABAA receptor-selective agonist muscimol (100 μM; 0.3 μl/site) or the GABAB receptor-selective agonist baclofen (100 μM; 0.3 μl/site) into the Vsp or the ISN significantly and irreversibly reduced this reflex vasodilatation, and these effects were attenuated by pretreatment with microinjection of each receptor-selective antagonists [GABAA receptor selective antagonist bicuculline methiodide (1 mM; 0.3 μl/site) or GABAB receptor selective antagonist CGP-35348 (1 mM; 0.3 μl/site)] into the Vsp or the ISN. Microinjection of these antagonists alone into the Vsp or the ISN had no significant effect on this reflex vasodilatation. In addition, microinjection (0.3 μl/site) of the mixture of muscimol (100 μM) and baclofen (100 μM) into the Vsp or the ISN also significantly reduced this reflex vasodilatation. These results suggest that medullary GABA signal transduction inhibits the parasympathetic reflex vasodilatation in the rat lower lip via GABAA and GABAB receptors in the Vsp and the ISN.
KW - GABA
KW - Inferior salivatory nucleus
KW - Lower lip
KW - Parasympathetic reflex
KW - Trigeminal spinal nucleus
KW - Vasodilatation
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U2 - 10.1016/j.brainres.2011.12.023
DO - 10.1016/j.brainres.2011.12.023
M3 - Article
C2 - 22226507
AN - SCOPUS:84856298484
SN - 0006-8993
VL - 1437
SP - 26
EP - 37
JO - Molecular Brain Research
JF - Molecular Brain Research
ER -