title: The effects of certain H(1)-antagonists on visual evoked potential in rats.
abstract: The present study was undertaken to clarify the effects of certain H(1)-antagonists on visual evoked potential (VEP) in rats. Pyrilamine (5 and 10 mg/kg), diphenhydramine (5 and 10 mg/kg) and chlorpheniramine (10 and 20 mg/kg) caused a significant reduction in the amplitude of late VEP components (P(3)-N(3), N(3)-P(4)), although these drugs showed no significant changes in early VEP components (P(1)-N(1), N(1)-P(2)). Cyproheptadine caused a slight enhancement of late components of VEP at a dose of 20 mg/kg. On the other hand, epinastine caused no significant effect on late VEP components even at a dose of 20 mg/kg. The reduction in the late VEP components induced by pyrilamine and diphenhydramine was significantly antagonised by pre-treatment of histidine (200 and 500 mg/kg), but not by physostigmine even at a dose of 0.01 mg/kg. The effect induced by cyproheptadine was significantly potentiated by histidine (500 mg/kg), and significantly reduced by DOI (2 mg/kg). These results indicate that an inhibition of the late VEP components induced by H(1)-antagonist pyrilamine, diphenhydramine and chlorpheniramine may be due to an inhibition of specific sensory system relating the histaminergic mechanisms. In addition, slight enhancement of these components induced by cyproheptadine may be attributable to its anti-serotonergic effects.
authors.affiliation: Department of Pharmacology, Faculty of Pharmaceutical Sciences, Okayama University, 700-8530 Okayama, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Iwamura
authors.forename: Yoko
authors.initials: Y
authors.lastname: Fujii
authors.forename: Chiaki
authors.initials: C
authors.lastname: Kamei
mesh_terms: D000284:Administration, Oral; D000818:Animals; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004569:Electroencephalography / Q000295:instrumentation / Q000379:methods; D005074:Evoked Potentials, Visual / Q000187:drug effects* / Q000502:physiology; D006634:Histamine H1 Antagonists / Q000494:pharmacology*; D006639:Histidine / Q000494:pharmacology; D007215:Indophenol / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D010775:Photic Stimulation; D010830:Physostigmine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects; D017366:Serotonin Receptor Agonists / Q000494:pharmacology
chemical_list: D002800:Cholinesterase Inhibitors; D006634:Histamine H1 Antagonists; D017366:Serotonin Receptor Agonists; C113896:dimethoxy-4-indophenyl-2-aminopropane; D006639:Histidine; D007215:Indophenol; D010830:Physostigmine