| Abstract: | Blood sludging or intravascular erythrocyte aggregation was induced in male, hooded rats by intravenous injection of the high molecular weight polysaccharide, Dextran 500 (mean mol. wt.=370,000). Analysis of blood sludging produced by dextran, using erythrocyte sedimentation rate (ESR), showed profound sludging after doses of 300 mg/kg, which persisted for several days. In contrast to the effects on ESR, a second study showed that Dextran 500 had no effect upon the accuracy of short-term memory (STM) in rats trained on a delayed spatial alternation task. The behavioral effects of dextran under these procedures were limited to a general, dose-dependent suppression of responding. Finally, the incidence and extent of blood sludging in behaviorally impaired, aged Rhesus monkeys was compared with that of normal, young monkeys using ESR. No significant difference in sludging between the two age groups was found. Thus, blood sludging was not associated with the STM impairment present in old monkeys. These results, taken together, do not support the notion that age related cognitive impairments (specificially in STM), are due to gross changes in blood sludging. The clinical reports of salutary effects in senile patients resulting from long-term anticoagulant therapy may therefore be due to factors unrelated to the antisluding properties of those drugs. |
