Environmental enrichment attenuates cognitive deficits, but does not alter neurotrophin gene expression in the hippocampus following lateral fluid percussion brain injury.

Environmental enrichment attenuates neurological deficits associated with experimental brain injury. The molecular events that mediate these environmentally induced improvements in function after injury are largely unknown, but neurotrophins have been hypothesized to be a neural substrate because of their role in cell survival and neural plasticity. Furthermore, exposure to complex environments in normal animals increases neurotrophin gene expression. However, following an ischemic injury, environmental enrichment decreases neurotrophin mRNA levels. Whether these contrasting findings are attributable to differences between injured and uninjured animals or are dependent upon the specific type of brain injury has not been determined. We examined the effects of 14 days of environmental enrichment following a lateral fluid percussion brain injury on behavior and gene expression of brain-derived neurotrophic factor, its high-affinity receptor, TrkB, and neurotrophin-3 in the rat hippocampus. Environmental enrichment attenuated learning deficits in the injured animals, but neither the injury nor housing conditions influenced neurotrophin/receptor mRNA levels. From these data we suggest that following brain trauma, improvements in learning associated with environmental enrichment are not mediated by alterations in brain-derived neurotrophic factor, TrkB or neurotrophin-3 gene expression.

Patch testing with 20% Dermatophagoides pteronyssinus/farinae (Chemotechnique) antigen.

BACKGROUND: Patch testing with dust mite antigens might identify mite-sensitive individuals, particularly those with atopic dermatitis who can benefit from avoidance measures. Currently available dust mite allergens have not been well studied. OBJECTIVE: To determine the proper dilution of 20% Dermatophagoides pteronyssinus/farinae mix antigen (Chemotechnique, Malmo, Sweden) for use in closed patch testing. METHODS: Eighteen nonatopic, healthy control subjects were patch-tested to the 20% concentration, yielding 15 (83%) positive reactions, most showing a decrescendo or persistent pattern suggesting an inordinately high number of false positive reactions. Dilutions of 1.25% to 0.1% in white petrolatum were used in patch testing 8 atopic dermatitis and 11 respiratory atopy patients, and 12 nonatopic controls. RESULTS: Positive reaction rates to the 0.25% and 0.1% concentrations, respectively, were 87.5% and 62.5% for atopic dermatitis, 54% and 18% for respiratory atopy, and 33% and 8% for healthy controls. Using Fisher's exact test, the 0.1% dilution was shown to significantly differentiate rates of positivity among the 3 groups, particularly between atopic dermatitis subjects and healthy controls. CONCLUSION: We find that a 0.1% dilution of 20% D. pteronyssinus/farinae mix antigen (Chemotechnique) to be useful in identifying mite-allergic individuals with atopic dermatitis.