A Friedman check at each time point revealed significant effects of ANI when it was injected at time points I [2(2) = 15.94, p .0001] and III [2(2) = 13.15, p .01], and subsequent post-hoc test revealed that the number of errors under the higher dose of ANI was higher than that of Rin (p .01) in time points I and III. Fig 4C shows the mean quantity of within-half errors defined as reentering arms ERK1 that had already been visited within the second-half performance. impaired overall performance in the second-half. This disruptive effect of ANI was successfully replicated by EME. However, DRB administered before the first-half overall performance did not impair the second-half overall performance, while it did impair it if injected before the second-half. None of these drugs caused amnesic effects during the short (5 min)/non-delayed conditions in either testmRNA and protein synthesis for the memory consolidation process, by which encoded short-term memory is transferred into long-term memory, is widely accepted. This has been repeatedly proven in many spatial tasks through the demonstration of the disruptive effects of mRNA synthesis inhibitors (mRNA-SIs) or protein synthesis inhibitors (PSIs) on overall performance in long, but not short, delay-interposed memory tasks [1C4]. However, the functions of mRNA and protein synthesis in other memory processes, including retention and retrieval, are poorly Adarotene (ST1926) understood. In previous studies, they have been examined only in the water maze task [5C7], the findings of which have led to the suggestion that hippocampal protein synthesis is not associated with retrieval process. Previous research around the neural basis of various processes involved in spatial memory suggests that the necessity for plasticity-related membrane receptor activity (e.g. -amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptors) in each memory process can vary depending on the type of spatial memory task employed [8C11]. Considering these reports, the role of intra-hippocampal mRNA and protein synthesis in each memory process might also be task-dependent. However, this has not been examined in previous studies. To test this hypothesis, it is necessary to examine and compare the functions of mRNA and protein synthesis in each memory process systematically, using multiple kinds of spatial memory tasks. In the present study, we chose to investigate this using two different kinds of spatial memory assessments: the spontaneous place acknowledgement (SPR) test and the delay-interposed radial arm maze (dRAM) task. These tasks are suitable for our study objective because they both consist of three different phases: acquisition, delay, and test phases. Therefore, each memory process can be separately investigated Adarotene (ST1926) along the time axis . However, it should be noted that these assessments have different properties; SPR overall performance depends on incidental, non-associative learning/memory, and training or rule learning is not required, while dRAM overall performance largely depends on working memory, and training repetitions are required. The present study investigated the functions of hippocampal mRNA and protein synthesis in various processes of spatial memory. For this purpose, we adopted analogous task protocols for the two assessments (SPR test and dRAM task), using the same delay length (6 h) and four time points for drug infusion (I: before acquisition phase, II: immediately (IIa) and 2 h (IIb) after acquisition phase, Adarotene (ST1926) III: before test phase). This allowed for the comparison of the effects of intra-hippocampal administration of the broadly used PSIs, anisomycin (ANI) and emetine (EME), on overall performance. Additionally, we also tested the effect of an mRNA-SI, 5,6-dichlorobenzimidazole 1–D-ribofuranoside (DRB), at the time points at which ANI caused disruptive effects. Materials and methods Subjects One hundred and eight male Wistar-Imamichi rats (Institute for Animal Reproduction, Ibaraki, Japan; 7C8 weeks) were used as subjects. Their mean body weight at the start of experiments was 274 g. Fifty-eight rats were assigned to the SPR test (experiment 1), and 50 rats were assigned to the dRAM task (experiment 2). In both experiments, animals were housed in individual cages on a 12:12 h lightCdark cycle (light on: 0800C2000) with free access to water throughout the experiment. Feeding condition was different between the two experiments. Rats were kept with free access to food in experiment 1, while.