title: Inhibition of glycine-induced current by morphine in nucleus tractus solitarii neurones of guinea pigs.
abstract: We studied the effect of morphine on the current induced by glycine in acutely dissociated nucleus tractus solitarii (NTS) neurones of guinea pigs, by use of the whole-cell patch clamp technique. Morphine inhibited 30 microM glycine-induced current (Igly), without affecting the current caused by 30 microM GABA. The effect of morphine was concentration-dependent, with a maximal effect at 1 mM, and reversible. The half-maximum inhibitory concentration of morphine was 30 microM. The effect of morphine was not depressed by naloxone, an opioid antagonist. Furthermore, the effect was not substantially affected by methiothepin, a 5-HT1 antagonist, ketanserin, a 5-HT2 antagonist and MDL-72222, a 5-HT3 antagonist. Morphine at 30 microM shifted the concentration-response curve for Igly to the right without affecting the maximum value. The effect of morphine on Igly showed no use-dependence. The results indicate that morphine inhibits Igly in the NTS neurones, and further suggest that morphine at the concentration used may act on the glycine receptor-ionophore complex, but not on the Cl-channel of the complex.
authors.affiliation: Department of Pharmacological Sciences, Faculty of Pharmaceutical Sciences, Kumamoto University, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Fukushima
authors.forename: S
authors.initials: S
authors.lastname: Nagayama
authors.forename: M
authors.initials: M
authors.lastname: Otsuka
authors.forename: K
authors.initials: K
authors.lastname: Takahama
authors.forename: Y
authors.initials: Y
authors.lastname: Isohama
authors.forename: H
authors.initials: H
authors.lastname: Kai
authors.forename: T
authors.initials: T
authors.lastname: Miyata
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D005998:Glycine / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D006168:Guinea Pigs; D009020:Morphine / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018408:Patch-Clamp Techniques; D012702:Serotonin Antagonists / Q000494:pharmacology; D017552:Solitary Nucleus / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
chemical_list: D012702:Serotonin Antagonists; D005680:gamma-Aminobutyric Acid; D009020:Morphine; D005998:Glycine