Brain multiparametric responses to carbon monoxide exposure in the aging rat

The multiparametric monitoring system was applied to study the effects of 2 000 ppm carbon monoxide (CO) on brain functions in vivo in the aging rat. T he vasodilatory (non hypoxic) effects of CO on CBF in normal adult rats, wh ich were shown in concentrations of 1000-2000 ppm involved the effect of ni tric oxide (NO). Energy metabolism was evaluated by optical monitoring of C BF and mitochondrial function by fluorometry of NADH. Ionic homeostasis was evaluated by monitoring the extracellular level of K+ and H+ and the DC st eady potential. Seven aging rats (24 months) were exposed to 2000 ppm for 6 0 min and 120 min of recovery, while five control rats were exposed to air under the same conditions. A comparison between the CO group and the contro l group showed that the changes in CBF, NADH and light reflectance were not statistically significant while extracellular K+ was elevated and tissue p H became more acidic. Thus, the typical CO induced increase in CBF, was not recorded in the aging rats. We concluded that the brain vasodilatory respo nse to CO was not active in the aging rat, while the ionic homeostasis resp onses were similar to those found in the adult rat. (C) 2000 Elsevier Scien ce B.V. All rights reserved.