Behavioural brain research
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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.
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Current anxiety tests do not provide, individually, a pure and complete picture of an animal's emotional profile. Therefore, many authors test their experimental hypotheses using a series of anxiety-related tests, which are thought to reflect different facets of emotionality. The objective of this study was to investigate the potential usefulness of integrating three widely used behavioral tests, the open field (OF), elevated plus maze (EPM), and light/dark box (LDB), to assess a wider range of emotional and non-emotional behaviors within one single trial. ⋯ Under both conditions, each test produced its own anxiety-related factor. Two benzodiazepines, chlordiazepoxide (at 5 and 10mg/kg) and midazolam (at 0.75mg/kg), facilitated the approach towards the EPM open arms, whereas pentylenetetrazole (10mg/kg) specifically inhibited exploration of the three aversive areas (OF center, EPM open arms, LDB light compartment). Together, these results suggest that the new integrated apparatus may contribute to the study of anxiety, by providing a rapid, comprehensive and reliable method of assessing emotionality-related behaviors and its underlying components.
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The molecular site of action for volatile anesthetics remains unknown despite many years of study. Members of the K(2P) potassium channel family, whose currents are potentiated by volatile anesthetics have emerged as possible anesthetic targets. In fact, a mouse model in which the gene for TREK-1 (KCNK2) has been inactivated shows resistance to volatile anesthetics. ⋯ Knockout mice (KCNK7-/-) displayed no difference in MAC for the three volatile anesthetics compared to heterozygous (+/-) or wild-type (+/+) littermates. Because inactivation of KCNK7 does not alter MAC, KCNK7 may play only a minor role in normal CNS function or may have had its function compensated for by other inhibitory mechanisms. Additional studies with transgenic animals will help define the overall role of the K(2P) channels in normal neurophysiology and in volatile anesthetic mechanisms.