L-histidine provokes a state-dependent memory retrieval deficit in mice re-exposed to the elevated plus-maze

Abstract

0.05, Kruskal-Wallis test), or at the dose of 500 mg/kg (OAE: 5.27 ± 0.73, 4.87 ± 0.66; OAT: 63.93 ± 11.72, 63.58 ± 10.22; P > 0.05, Fisher LSD test). At T2, LH-LH animals did not reduce open-arm activity (OAE and OAT) at the dose of 200 mg/kg (T1: 4.87 ± 0.66, T2: 5.47 ± 1.05; T1: 63.58 ± 10.22; T2: 49.01 ± 8.43 for OAE and OAT, respectively; P > 0.05, Wilcoxon test) or at the dose of 500 mg/kg (T1: 4.80 ± 1.60, T2: 4.70 ± 1.04; T1: 51.55 ± 12.10, T2: 43.88 ± 10.64 for OAE and OAT, respectively; P > 0.05, Fisher LSD test), showing an inability to evoke memory 24 h later. These data suggest that LH does not act on anxiety but does induce a state-dependent memory retrieval deficit in mice.]]>

Low-dose thioperamide injected into the cerebellar vermis of mice immediately after exposure to the elevated plus-maze impairs their avoidance behavior on re-exposure to the apparatus

“…Gianlorenço et al (14) and Serafim et al (4) also found inhibitory effects of ip injection of L-histidine, a histamine precursor, on emotional memory using the same experimental protocol. Another study conducted by Gianlorenço et al.…”

“…The conventional measurements recorded were the number of enclosed-arm entries (EAE; arm entry = all four paws into an arm), the percentage of open-arm entries [%OAE = (open/total)×100] and the percentage of time spent (%OAT) in the open arms of the maze [(time open/300 s)×100]. An increase in open-arm avoidance with repeated maze exposure has been observed in several studies and has been used as a measure of learning and memory evaluated by Trial 1/Trial 2 (test/retest) protocols (4,9). …”

“…Central histamine, together with its neurons and connections, as well as its four types of receptors (H 1 -H 4 ), comprise the histaminergic system (2). Significant evidence indicates that this system is related to processes of learning and emotional memory (3,4). Furthermore, an interesting approach to altering the central histamine concentration has been to activate or block the H 3 receptor, since this receptor modulates the synthesis and release of histamine (1).…”

“…In this context, the elevated plus-maze (EPM) is an experimental model that has been developed primarily to evaluate anxiety (8). It has also been used to infer learning and memory processes by including an additional day of testing, and then comparing the animal's behavioral profile during both tests (4,9). …”

H1 but not H2 histamine antagonist receptors mediate anxiety-related behaviors and emotional memory deficit in mice subjected to elevated plus-maze testing

“…For each drug tested there was a corresponding control group in T1, resulting in the following paired groups: SAL (n = 20) and ZOL (n = 21), SAL (n = 20) and 8 mg/kg CPA (n = 20), and SAL (n = 20) and 16 mg/kg CPA (n = 22). Forty minutes after the injections (6, 18), the mice were exposed to the EPM (T1). In T2 (24 h later), each group was subdivided into two new groups, and the animals from each group were re-injected with SAL or one of the drugs prior to conducting T2.…”