title: H₁ but not H₂ histamine antagonist receptors mediate anxiety-related behaviors and emotional memory deficit in mice subjected to elevated plus-maze testing.
abstract: This study investigated the role of H₁ and H₂ receptors in anxiety and the retrieval of emotional memory using a Trial 1/Trial 2 (T1/T2) protocol in an elevated plus-maze (EPM). Tests were performed on 2 consecutive days, designated T1 and T2. Before T1, the mice received intraperitoneal injections of saline (SAL), 20 mg/kg zolantidine (ZOL, an H2 receptor antagonist), or 8.0 or 16 mg/kg chlorpheniramine (CPA, an H1 receptor antagonist). After 40 min, they were subjected to the EPM test. In T2 (24 h later), each group was subdivided into two additional groups, and the animals from each group were re-injected with SAL or one of the drugs. In T1, the Student t-test showed no difference between the SAL and ZOL or 8 mg/kg CPA groups with respect to the percentages of open arm entries (%OAE) and open arm time (%OAT). However, administration of CPA at the highest dose of 16 mg/kg decreased %OAE and %OAT, but not locomotor activity, indicating anxiogenic-like behavior. Emotional memory, as revealed by a reduction in open arm exploration between the two trials, was observed in all experimental groups, indicating that ZOL and 8 mg/kg CPA did not affect emotional memory, whereas CPA at the highest dose affected acquisition and consolidation, but not retrieval of memory. Taken together, these results suggest that H₁ receptor, but not H₂, is implicated in anxiety-like behavior and in emotional memory acquisition and consolidation deficits in mice subjected to EPM testing.
authors.affiliation: Laboratório de Neurociências, Departamento de Fisioterapia, Centro de Ciências Biológicas e da Saúde, Universidade Federal de São Carlos, São Carlos, SP, Brasil.
authors.forename: K R
authors.initials: KR
authors.lastname: Serafim
authors.forename: M S
authors.initials: MS
authors.lastname: Kishi
authors.forename: A
authors.initials: A
authors.lastname: Canto-de-Souza
authors.forename: R
authors.initials: R
authors.lastname: Mattioli
mesh_terms: D000818:Animals; D001007:Anxiety / Q000139:chemically induced*; D052160:Benzothiazoles / Q000494:pharmacology*; D002744:Chlorpheniramine / Q000494:pharmacology*; D006634:Histamine H1 Antagonists / Q000494:pharmacology*; D006635:Histamine H2 Antagonists / Q000494:pharmacology*; D008297:Male; D018782:Maze Learning; D008569:Memory Disorders / Q000139:chemically induced*; D051379:Mice; D008845:Microinjections; D050198:Phenoxypropanolamines / Q000494:pharmacology*; D010880:Piperidines / Q000494:pharmacology*; D011969:Receptors, Histamine H1 / Q000187:drug effects*
chemical_list: D052160:Benzothiazoles; D006634:Histamine H1 Antagonists; D006635:Histamine H2 Antagonists; D050198:Phenoxypropanolamines; D010880:Piperidines; D011969:Receptors, Histamine H1; D002744:Chlorpheniramine; C055302:zolantidine