Docosahexaenoic acid (DHA) improves the age-related impairment of the coupling mechanism between neuronal activation and functional cerebral blood flow response: a PET study in conscious monkeys

The regional cerebral blood flow (rCBF) response to vibrotactile stimulatio n was compared in conscious young (5.9+/-1.8 years old) and aged (18.0+/-3. 3 years old) monkeys using [O-15]H2O and high-resolution positron emission tomography (PET). In addition, the effects of docosahexaenoic acid (DAH), a n n-3 polyunsaturated fatty acid (PUFA), on the rCBF response to stimulatio n were evaluated in aged monkeys. Soybean milk (SBM) or DHA-containing SBM (DHA/SBM) was supplied to aged monkeys for 1 and 4 weeks. Under control con ditions, vibrotactile stimulation elicited an increase in the rCBF response in the contralateral somatosensory cortices of both young and aged monkeys , but the degree of increase in the rCBF response was significantly lower i n aged monkeys (116% of corresponding 'rest' condition) than that in young animals (141%). The regional cerebral metabolic rate of glucose (rCMRglc) r esponse to the stimulation, an index of neuronal activation, was not signif icantly different between young and aged monkeys as measured by [F-18]-2-fl uoro-2-deoxy-D-glucose (FDG). Supply of DHA/SBM at a dose of 150 mg/kg/day as DHA for 1 week resulted in a significant increase in rCBF response to st imulation (127%) in aged monkeys, and LC-week supply of DHA induced further facilitation of the rCBF response (133%). In contrast, the reduced rCBF re sponse in the aged monkeys was not affected by SBM alone for either 1 or 4 weeks. The neuronal activation itself elicited by the stimulation, as measu red by [F-18]FDC, was not affected by SBM or DHA/SBM. These results suggest ed the involvement of DHA in the coupling mechanism between the neuronal ac tivation and rCBF response, possibly by modulation of cholinergic neuronal transmission. (C) 2000 Elsevier Science B.V. All rights reserved.