title: Involvement of descending monoaminergic systems in the transmission of dental pain in the trigeminal nucleus caudalis of the rabbit.
abstract: Perfusates were taken from the superficial layers of the subnucleus caudalis of the trigeminal sensory nuclear complex (SpVc), the first relay station of dental pain, with a push-pull cannula system and were assayed for endogenous serotonin (5-HT) and catecholamines by high-pressure liquid chromatography with an electrochemical detection. Spontaneous release of 5-HT and epinephrine was observed, while that of norepinephrine was not. Tooth pulp stimulation (ST) tended to increase the level of 5-HT in the perfusates. Pretreatment with morphine at a dose of 10 mg/kg (i.v.) significantly enhanced the release of 5-HT. However, there was no significant difference in morphine effect on the 5-HT level between stimulated and non-stimulated animals. Systemic administration of morphine (10 mg/kg i.v.) completely inhibited the release of immunoreactive substance P from the superficial layers of SpVc evoked by ST, and this inhibition was antagonized by local application of methysergide (10(-4) M). These results suggest that in the superficial layers of SpVc, morphine may primarily activate the descending 5-HT pathway which serves to modulate dental pain transmission.
authors.affiliation: Department of Pharmacology, Faculty of Dentistry, Osaka University, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Yonehara
authors.forename: T
authors.initials: T
authors.lastname: Shibutani
authors.forename: Y
authors.initials: Y
authors.lastname: Imai
authors.forename: R
authors.initials: R
authors.lastname: Inoki
mesh_terms: D000818:Animals; D004837:Epinephrine / Q000378:metabolism*; D008297:Male; D009020:Morphine / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*; D011817:Rabbits; D012701:Serotonin / Q000378:metabolism*; D014070:Tooth / Q000187:drug effects / Q000294:innervation*; D014279:Trigeminal Nucleus, Spinal / Q000378:metabolism / Q000503:physiopathology*
chemical_list: D012701:Serotonin; D009020:Morphine; D004837:Epinephrine