title: H1-histamine receptors in the amygdala are involved in emotional memory but do not mediate anxiety-related behaviors in mice submitted to EPM testing.
abstract: This study investigated the role of amygdala H(1) receptors in state-dependent memory deficits induced by l-histidine (LH). Tests using an elevated plus-maze (EPM) were performed on two consecutive days: Trial 1 (T1) and Trial 2 (T2). Before each trial, mice were intraperitoneally (IP) injected with LH (500mg/kg). Two hours later, they were microinjected with the H(1) receptor antagonist, chlorpheniramine (CPA 0.016, 0.052, or 0.16 nmol/0.1μl), or saline (SAL) into the amygdala and submitted to the EPM. LH-CPA did not affect trial 1 performances in the EPM, which indicated that these drugs did not affect anxiety. Emotional memory, as revealed by a reduction in open arm exploration between both trials, was present in the SAL-SAL groups as well as in the SAL-CPA groups for the lower doses of CPA (0.016 and 0.052nmol). On the contrary, neither the LH-SAL group nor the LH-CPA groups exhibited this decrease in open arm activity between both trials, which reveals that LH impaired emotional memory. While intra-amygdalar CPA did not interact with LH effect, it impaired per se the emotional memory performances at the highest dose (0.16nmol). No significant changes were observed in the number of enclosed arm entries (EAE), an EPM index of general exploratory activity. These results may be attributed to a combined effect in the different nucleus of the amygdala. Taken together, these results suggest that the H(1) receptors in the amygdala are not implicated in anxiety-like behaviors but are involved in emotional states induced by the T1/T2 EPM protocol in mice.
authors: Laboratory of Neuroscience, Physiotherapy Department, Center of Biological Sciences and Health, Federal University of Sao Carlos, Rod. Washington Luis, Sao Carlos, Brazil. Kelly.serafim@hotmail.com
authors: K R
authors: KR
authors: Serafim
authors: A C L
authors: AC
authors: Gianlorenço
authors: F P
authors: FP
authors: Daher
authors: R
authors: R
authors: Mattioli
mesh_terms: D000679:Amygdala / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001007:Anxiety / Q000523:psychology*; D004644:Emotions / Q000187:drug effects / Q000502:physiology*; D006634:Histamine H1 Antagonists / Q000008:administration & dosage; D007276:Injections, Intraventricular; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology*; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008845:Microinjections; D011897:Random Allocation; D011969:Receptors, Histamine H1 / Q000502:physiology*
chemical_list: D006634:Histamine H1 Antagonists; D011969:Receptors, Histamine H1