A REDUCED CALORIE-HIGH FIBER DIET RETARDS AGE-ASSOCIATED DECREASES INMUSCARINIC RECEPTOR SENSITIVITY

The effects of a reduced calorie-high fiber diet (RCHF) were examined on three cholinergic signal transduction (ST) parameters: (a) oxotremo rine enhancement of K+-evoked dopamine release and (b) carbachol-stimu lated low KM GTPase activity [an indicator of muscarinic receptor (mAC hR)-G protein coupling/uncoupling], and (c) [H-3]Quinuclidinyl benzila te (QNB) autoradiography. Comparisons were made among: young control ( 6 months), old normal control, old reduced calorie high fiber [both 24 months)]. The results indicated that old reduced calorie high fiber r ats (1900 kcal/kg/day, 2.4%, lipids 2.4%, fiber 28%, carbohydrates 40. 7%) as compared to the old normal control rats (3000 kcal/kg/day, 4.8% lipids, 4.2% fiber, carbohydrates 61.5%) showed a retardation of age- related deficits in dopamine release (a above) and GTPase activity (b above). These parameters were 25% higher in the old reduced calorie hi gh fiber rats as compared to old normal controls and did not differ fr om young controls, even though there was no increase in mAChR concentr ation in the restricted group. Thus, these results indicate that a red uced calorie high fiber diet as utilized in these experiments was effe ctive in retarding the age-related decrements in two of three signal t ransduction parameters. They are discussed in terms of the induction o f membrane changes (e.g., fluidity) or related decreases in oxidative stress by the restricted diet that may be involved in these signal tra nsduction effects.