From 5 to 22 months of age, cognitive and emotional responses of nulliparous, primiparous, and multiparous rats were assessed using a dry land maze (DLM) and an elevated plus-maze (EPM) at 4-month intervals. Parous rats exhibited improved spatial memory in the probe and competitive versions of the DLM, and more exploration in the EPM and a novel stimulus test relative to nulliparous females. The nulliparous females, however, outperformed parous rats during the DLM visual cue test at 17 months of age. At 23 months, no differences in stressed corticosterone levels or Golgi-stained hippocampal neurons were observed. Thus, cognitive and emotional modifications were observed in parous rats; the neurobiological mechanisms for these enduring effects, however, remain to be identified.
The prevalence of major depression is increased in Alzheimer disease, but currently the basis of this association remains unclear. The present study examined rates of depression in four groups: (1) cognitively normal controls with no Alzheimer pathology at autopsy, (2) cognitively normal individuals with Alzheimer pathology, (3) clinical diagnoses of MCI plus Alzheimer pathology, (4) clinical diagnoses of dementia plus Alzheimer pathology. Participant data were obtained from the Baltimore Longitudinal Study of Aging. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression Scale (CES-D). Individuals with Alzheimer pathology but no cognitive decline prior to death had significantly lower rates of depression than cognitively normal controls with no Alzheimer pathology and individuals with Alzheimer pathology plus clinical diagnoses of dementia. These findings suggest that depression is a risk factor for AD in the presence of AD pathology, but depression is not a risk factor for AD pathology.
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