Nerve growth factor preserves a critical motor period in rat striatum

The use of the puzzle box as a means of assessing the efficacy of environmental enrichment

Environmental enrichment can dramatically influence the development and function of neural circuits. Further, enrichment has been shown to successfully delay the onset of symptoms in models of Huntington's disease (1-4), suggesting environmental factors can evoke a neuroprotective effect against the progressive, cellular level damage observed in neurodegenerative disorders. The ways in which an animal can be environmentally enriched, however, can vary considerably. Further, there is no straightforward manner in which the effects of environmental enrichment can be assessed: most methods require either fairly complicated behavioral paradigms and/or postmortem anatomical/physiological analyses. This protocol describes the use of a simple and inexpensive behavioral assay, the Puzzle Box (5-7) as a robust means of determining the efficacy of increased social, sensory and motor stimulation on mice compared to cohorts raised in standard laboratory conditions. This simple problem solving task takes advantage of a rodent's innate desire to avoid open enclosures by seeking shelter. Cognitive ability is assessed by adding increasingly complex impediments to the shelter's entrance. The time a given subject takes to successfully remove the obstructions and enter the shelter serves as the primary metric for task performance. This method could provide a reliable means of rapidly assessing the efficacy of different enrichment protocols on cognitive function, thus paving the way for systematically determining the role specific environmental factors play in delaying the onset of neurodevelopmental and neurodegenerative disease.

Activity-dependent reduction of dopamine D2 receptors during a postnatal critical period of plasticity in rat striatum is not affected by prenatal haloperidol treatment

Motor activity induced in the Circling Training test (CT) during a postnatal (PN) critical period of plasticity (PN30-37) produces a long-lasting decrease in the number of binding sites and mRNA expression levels of the dopamine D2 receptor (D2R) in rat striatum. Prenatal exposure to the antipsychotic haloperidol also decreases postnatal levels of the striatal D2R in the offspring. We examined whether such fetal exposure to haloperidol could affect the activity-dependent reduction of the D2R system during the critical period. Half of the male offspring exposed to either haloperidol (2.5 mg/kg/day), i.p.) or saline during gestational days 5-18 were subjected to the CT during the critical period, while the remaining represented CT control animals. The adult number of binding sites and mRNA expression levels of the striatal D2R at PN90 were not changed by prenatal haloperidol treatment alone. On the other hand, only pups subjected to the CT during the critical period showed decreases in both studied parameters, regardless the prenatal treatment. These findings indicated that the postnatal reduction of the striatal D2R binding induced prenatally by haloperidol does not affect long-lasting activity-dependent plastic changes on the same receptor system elicited by motor activity in an ontogenetic critical period of plasticity in rat striatum.

Delayed and bilateral changes of GAP-43/B-50 phosphorylation after circling training during a critical period in rat striatum

During the critical period of activity-dependent plasticity in rat striatum (30-37 days after birth) physiological circling behavior induces delayed modifications in GAP-43/B-50 phosphorylation by PKC. Postexercise, ipsi- and contralateral striatum to the circling direction show a similar temporal pattern of GAP-43/B-50 phosphorylation, with an initial decrease followed by a subsequent increase. However, there is a lag between initiation of the phosphorylation response in this asymmetrical task which does not occur when animals are subjected to exercise under conditions of symmetrical motor activity.