Behavioural brain research
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This study aims to investigate the effects of age and anxiety on behavior, learning and memory in rats. Before and after the anxiety and learning tests, locomotor activity, exploratory activity and autonomic functions of the rats were tested in open field area. At the beginning and at the end of behavior tests, urines were collected so as to determine 5-hydroxyindolaceticacid (5-HIAA) levels. ⋯ In water maze test, rats showed higher performance in reaching the platform in repetitive trials; this demonstrates that they have learned by environmental cues. Experimental group had not better performance in reaching the platform according to control group, so this supports that anxiety affects spatial learning. As a conclusion, it could be stated that especially in aged rats, anxiety that is created by elevated T-maze and cat odor and supported with 5-hydroxyindoleacetic acid and serum corticosterone, causes difficulty in emotional and spatial learning.
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Recent studies have shown that the hippocampus is critical for the context-dependent expression of extinguished fear memories. Here we used Pavlovian fear conditioning in rats to explore whether the entorhinal cortex and fornix, which are the major cortical and subcortical interfaces of the hippocampus, are also involved in the context-dependence of extinction. After pairing an auditory conditional stimulus (CS) with an aversive footshock (unconditional stimulus or US) in one context, rats received an extinction session in which the CS was presented without the US in another context. ⋯ In contrast, rats with neurotoxic lesions in the entorhinal cortex or electrolytic lesions in the fornix did not exhibit a renewal of fear when tested outside the extinction context. Impairments in freezing behavior to the auditory CS were not able to account for the observed results, insofar as rats with either entorhinal cortex or fornix lesions exhibited normal freezing behavior during the conditioning session. Thus, contextual memory retrieval requires not only the hippocampus proper, but also its cortical and subcortical interfaces.
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There have been several studies suggesting that sex hormones are involved in characterization of human mental function and behaviour. Recently, it has been reported that the -34T/C polymorphism of cytochrome P450 17 (CYP17) gene affects sex hormone dispositions. Therefore, it is possible that the CYP17 -34T/C polymorphism affects personality traits. ⋯ In males, the scores of novelty seeking, cooperativeness, and self-transcendence were higher in the group with the C allele than in that without this allele. In females, none of the seven TCI dimensions was different between the two genotype groups. The present study thus suggests that the -34T/C polymorphism of the CYP17 gene affects personality traits of healthy males, but not females, and this gender-dependent effect may be mediated by the action of sex hormones such as estradiol and testosterone.
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An early (i.e., 15min) single systemic administration of the 5-HT(1A) receptor agonist 8-OH-DPAT enhances behavioral recovery after experimental traumatic brain injury (TBI). However, acute administration of pharmacotherapies after TBI may be clinically challenging and thus the present study sought to investigate the potential efficacy of a delayed and chronic 8-OH-DPAT treatment regimen. Forty-eight isoflurane-anesthetized adult male rats received either a controlled cortical impact or sham injury and beginning 24h later were administered 8-OH-DPAT (0.1 or 0.5mg/kg) or saline vehicle (1.0mL/kg) intraperitoneally once daily until all behavioral assessments were completed. ⋯ The lower dose of 8-OH-DPAT (0.1mg/kg) enhanced motor performance, acquisition of spatial learning, and memory retention vs. both the higher dose (0.5mg/kg) and vehicle treatment (p<0.05). These data replicate previous findings from our laboratory showing that 8-OH-DPAT improves neurobehavior after TBI, and extend those results by demonstrating that the benefits can be achieved even when treatment is withheld for 24h. A delayed and chronic treatment regimen may be more clinically feasible.