Aging potentiates the acute and chronic neurological symptoms of pyrithiamine-induced thiamine deficiency in the rodent

Abstract

The present study aimed to assess the role of advanced age in the development and manifestation of thiamine deficiency using an animal model of Wernicke-Korsakoff syndrome (WKS). Interactions between pyrithiamine-induced thiamine deficiency (PTD) and age were examined relative to working memory impairment and neuropathology in Fischer 344 rats. Young (2-3 months) and aged (22-23 months) F344 rats were assigned to one of two treatment conditions: PTD or pair-fed control (PF). Rats in the former group were further divided into three groups according to duration of PTD treatment. Working memory was assessed with an operant matching-to-position (MTP) task; after testing, animals were sacrificed and both gross and immunocytochemical measures of brain pathology were obtained. Aged rats exhibited acute neurological disturbances during the PTD treatment regime earlier than did young rats, and also developed more extensive neuropathology with a shorter duration of PTD. Aged rats displayed increased brain shrinkage (smaller frontal cortical and callosal thickness) as well as enhanced astrocytic activity in the thalamus and a decrease in ChAT-positive cell numbers in the medial septum; the latter two measures of neuropathology were potentiated by PTD. In both young and aged rats, and to a greater degree in the latter group, PTD reduced thalamic volume. Behaviorally, aged rats displayed impaired choice accuracy on the delayed MTP task. Regardless of age, rats with lesions centered on the internal medullary lamina of the thalamus also displayed impaired choice accuracy. Moreover, increased PTD treatment duration led to increased response times on the delayed MTP task. These results suggest that aging does indeed potentiate the neuropathology associated with experimental thiamine deficiency, supporting an age coupling hypothesis of alcohol-related neurological disorders.