Effects of preweaning environmental stimulation on neuronal and behavioral impairment produced by undernutrition

Forced activity and environmental enrichment mildly improve manifestation of rapid cerebellar degeneration in mice

Exercise therapy represents an important tool for the treatment of many neurological diseases, including cerebellar degenerations. In mouse models, exercise may decelerate the progression of gradual cerebellar degeneration via potent activation of neuroprotective pathways. However, whether exercise could also improve the condition in mice with already heavily damaged cerebella remains an open question. Here we aimed to explore this possibility, employing a mouse model with dramatic early-onset cerebellar degeneration, the Lurcher mice. The potential of forced physical activity and environmental enrichment (with the possibility of voluntary running) for improvement of behaviour and neuroplasticity was evaluated by a series of behavioural tests, measuring BDNF levels and using stereological histology techniques. Using advanced statistical analysis, we showed that while forced physical activity improved motor learning by ∼26 % in Lurcher mice and boosted BDNF levels in the diseased cerebellum by 57 %, an enriched environment partially alleviated some behavioural deficits related to behavioural disinhibition. Specifically, Lurcher mice exposed to the enriched environment evinced reduced open arm exploration in elevated plus maze test by 18 % and increased immobility almost 9-fold in the forced swim test. However, we must conclude that the overall beneficial effects were very mild and much less clear, compared to previously demonstrated effects in slowly-progressing cerebellar degenerations.

Chronic (–)-Deprenyl Administration Attenuates Dendritic Developmental Impairment Induced by Early Social Isolation in the Rat

It has been demonstrated that postweaning social isolation alters dendritic development in the medial prefrontal cortex (mPFC) of the rat. In addition, (-)-deprenyl, a monoamine oxidase B (MAO-B) inhibitor, promotes dendritic growth in prefrontocortical pyramidal cells. This study examined whether prefrontocortical dendritic developmental impairment induced by postweaning social isolation is attenuated by chronic (-)-deprenyl administration. Weanling Sprague-Dawley male rats were randomly reared in social and isolated environments between postnatal days 21 and 51 (P21-P51). At P52, half of the animals were behaviorally evaluated in the open-field test and sacrificed for histological analysis. The remaining isolated rats were subdivided into saline- and daily (-)-deprenyl-treated animals for 30 additional days (P52-P82). Socially-reared rats remained undisturbed except for daily saline administration. At P82, all animals were behaviorally evaluated and sacrificed for histological analysis. Dendritic quantification of the Golgi-Cox-Sholl-stained neurons indicated that chronic (-)-deprenyl administration partially compensated the dendritic growth impairment induced by social isolation. In addition, both isolated-saline- and (-)-deprenyl-treated rats showed a sustained locomotor hyperactivity in the open-field test.

Role of an enriched environment on the restoration of behavioral deficits in Lurcher mutant mice

Lurcher mutant mice, characterized by massive degeneration of the cerebellar cortex, and normal littermate controls were reared from birth either in standard conditions or in an enriched environment. The effects of this manipulation on motor functions, landmark water maze learning, exploration, and anxiety were evaluated at 3 months of age. Under standard conditions, Lurcher mutants were impaired in comparison to controls on tests of sensorimotor function and had altered exploratory tendencies. The enriched housing improved the motor coordination of Lurcher mutants and decreased the number of trials before reaching criterion in the landmark water maze. In addition to its effects in Lurcher mutants, enriched rearing also increased some behavioral abilities in normal mice. It is hypothesized that enriched housing altered brain morphology or neurochemistry in both normal and cerebellar-damaged animals.