Effects of the alpha-2 adrenoceptor agonist guanfacine on attention and working memory in aged non-human primates.

Alpha-2 adrenergic receptors are potential targets for ameliorating cognitive deficits associated with aging as well as certain pathologies such as attention deficit disorder, schizophrenia and Parkinson's disease. Although the alpha-2 agonist guanfacine has been reported to improve working memory in aged primates, it has been difficult to assess the extent to which these improvements may be related to drug effects on attention and/or memory processes involved in task performance. The present study investigated effects of guanfacine on specific attention and memory tasks in aged monkeys. Four Rhesus monkeys (18-21 years old) performed a sustained attention (continuous performance) task and spatial working memory task (self-ordered spatial search) that has minimal demands on attention. Effects of a low (0.0015 mg/kg) and high (0.5 mg/kg) dose of gunafacine were examined. Low-dose guanfacine improved performance on the attention task [i.e. decreased omission errors by 50.8 ± 4.3% (P = 0.001) without an effect on commission errors] but failed to improve performance on the spatial working memory task. The high dose of guanfacine had no effects on either task. Guanfacine may have a preferential effect on some aspects of attention in normal aged monkeys and in doing so may also improve performance on other tasks, including some working memory tasks that have relatively high attention demands.