title: Augmentation of serotonin-induced inhibition of neuronal activity in the hippocampus following repeated treatment with methamphetamine.
abstract: Electrophysiological studies were performed to determine whether or not hippocampal serotonergic modulation was affected following repeated administration of methamphetamine (MAP). Rats were i.p. administered with MAP (5 mg/kg) or saline once a day for 5 days. Hippocampal slices were prepared at 24 h, 5 and 10 days after the final MAP or saline injection. The population spikes (PS) induced by stimulation of Schaffer collateral/commissural fibers were recorded in the hippocampal CA1 region. Application of serotonin (5-HT) via a bath perfusion system inhibited the PS in a concentration-dependent manner. At 24 h after the final injection, 10-microM 5-HT-induced inhibition of PS was not affected by MAP treatment. However, 5 days after the final injection, the inhibition by 5-HT (10 microM) of PS was significantly augmented in the MAP-treated group. Ten days after the final injection, this augmentation was not statistically significant compared with that of control group. 8-OH-DPAT, a 5-HT1A receptor agonist, inhibited PS, but the inhibition was not enhanced or reduced 5 days after the final MAP treatment. However, the enhancement of PS by RS 67333, a 5-HT4 receptor agonist, was attenuated 5 days after the MAP treatment. It was found that 5-HT-induced inhibition of PS in the hippocampal CA1 region was potentiated 5 days after cessation of MAP, and this effect was suggested to be due to reduction of excitatory 5-HT4 receptor functions.
authors.affiliation: Department of Pharmacotherapy, Graduate School of Biomedical Sciences, Hiroshima University, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kimura
authors.forename: Kumatoshi
authors.initials: K
authors.lastname: Ishihara
authors.forename: Koichiro
authors.initials: K
authors.lastname: Ozawa
authors.forename: Masashi
authors.initials: M
authors.lastname: Sasa
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D004334:Drug Administration Schedule; D004357:Drug Synergism; D006624:Hippocampus / Q000187:drug effects* / Q000502:physiology; D008297:Male; D008694:Methamphetamine / Q000008:administration & dosage*; D009433:Neural Inhibition / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D044282:Receptor, Serotonin, 5-HT1A / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology*; D058829:Serotonin 5-HT1 Receptor Antagonists
chemical_list: D058829:Serotonin 5-HT1 Receptor Antagonists; D044282:Receptor, Serotonin, 5-HT1A; D012701:Serotonin; D008694:Methamphetamine; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin