Behavioural brain research
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Comparative Study
Ontogeny of fear-, anxiety- and depression-related behavior across adolescence in C57BL/6J mice.
Adolescence is characterized by behavioral traits such as emotional lability and impulsivity that are associated with increased vulnerability to affective illness and addictions. Research in rodents has found that adolescent rats and mice differ from adults on measures of anxiety-like behavior, novelty seeking and stress-responsivity. The present study sought to extend these data by evaluating fear-, anxiety- and depression-related behaviors in male C57BL/6J mice aged four (early adolescent), six (peri-adolescent) or eight (early adult) weeks of age. ⋯ Depression-related immobility behavior in the forced swim test was lower in early adolescents than adult mice across three test exposures. Present findings in the C57BL/6J inbred strain add to growing evidence of changes in rodent fear- and stress-related behaviors across the developmental transition from juvenility through adulthood. Understanding the neural basis of these ontogenic changes could provide insight into the pathogenesis and treatment of affective disorders that have their origins in adolescence.
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Previously we reported that during protracted morphine abstinence rats show reduced conditioned place preferences (CPP) for food-associated environments, compared to non-dependent subjects. To determine the brain regions involved in this altered reward behavior, we examined neural activation (as indexed by Fos-like proteins) induced by a preference test for a food-associated environment in 5-week morphine-abstinent versus non-dependent animals. ⋯ Furthermore, the number of Fos positive neurons in these areas was found to correlate negatively with food preference in abstinent animals. These results indicate that the altered hedonic processing during protracted morphine withdrawal leading to decreased preference for cues associated with natural rewards may involve heightened activity in stress-related brain areas of the extended amygdala and their medullary noradrenergic inputs.
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Pregnancy and motherhood are life-altering events that result in a number of hormonal, neural and behavioral changes in the mother. Motherhood has been shown to influence spatial learning and memory performance of the mother. In turn new research has shown that reproductive experience (number of times pregnant and mothered) plays a significant role on spatial learning and memory performance. ⋯ Results show that regardless of error type (reference or working memory errors), primiparous rats make fewer errors compared to multi- and nulli-parous rats, with a trend to enhanced memory compared to sensitized rats. In addition, pregnant-only rats completed the task on significantly fewer days than primiparous, multiparous, nulliparous and sensitized rats. Clearly the combination of first pregnancy and first mothering experience has a significant impact on hippocampus-dependent learning and memory performance in the mother.
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Comparative Study
Elevated anxiety-like and depressive behavior in Desert hedgehog knockout male mice.
To investigate the functional role of Desert hedgehog (Dhh) gene in the nervous system, we examined motor, sensory, learning and memory functions as well as mood in Dhh knockout (KO) mice. Dhh KO male mice exhibited prolonged immobility time compared with wild-type male mice in the forced swimming test, and showed enhanced inhibition in the Vogel's conflict model. ⋯ In contrast, Dhh KO female mice did not show any significant difference compared to wild-type female mice. These behavioral abnormalities of Dhh KO male mice may be due to lower testosterone levels with abnormal development of the testes caused by Dhh-null mutation.
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Comparative Study
Protein synthesis inhibition in the basolateral amygdala following retrieval does not impair expression of morphine-associated conditioned place preference.
Conditioned place preference is an animal model used to evaluate the affective properties of natural rewards and drugs of abuse. This animal model is a kind of classical conditioning that depends on learning and memory. The basolateral amygdala (BLA) plays an important role in the consolidation and extinction of memory for this task. ⋯ Our results show that the protein synthesis inhibition in all of these experimental designs had no effect on conditioned place preference memory under conditions that would initiate reconsolidation, suggesting that if reconsolidation of a conditioned place preference task exists it is not mediated by protein synthesis in basolateral amygdala. The effect of anisomycin on consolidation of contextual fear conditioning was also investigated as a positive control to assure that the negative results were not due to methodological problems. Using the same dose of anisomycin (62.5 microg/1 microl) in morphine-associated place preference procedures, we have found that this anisomycin dose blocks the consolidation of contextual fear memory, ruling out the possibility that these negative results can be attributed to methodological problem of some sort.