This investigation was conducted to test whether topical nitroprusside (NP), a cytosolic guanylate cyclase activator, would increase the level of cyclic GMP and alter O2 consumption or blood flow in the cerebral cortex of rats. Male Long-Evans rats were used in a control (n = 9), low dose NP (n = 13, 10-3 M) or high dose NP (n = 12, 10-2 M) group. Nitroprusside or saline was topically applied to the right side of the cerebral cortex and the left side was used as a control. The cyclic GMP level was determined in five rats in each group using a radioimmunoassay. In the o ther rats in each group, regional cerebral blood flow was measured by [14C]iodoantipyrine and regional arterial and venous O2 saturations were determined microspectrophotometrically. Nitroprusside significantly increased the cyclic GMP level from 21.4 ± 12.0 pmol/g (contralateral cortex) to 52.2 ± 36.7 pmol/g (NP treated cortex) in low dose nitroprusside group and from 19.9 ± 22.6 pmol/g (contralateral cortex) to 58.5 ± 15.1 pmol/g (NP treated cortex) in high dose nitroprusside group. High dose nitroprusside significantly increased cerebral blood flow from 80 ± 11 ml · min-1 · 100 g (contralateral cortex) to 114 ± 11 ml · min-1 · 100 g (NP treated cortex). However, there was no significant difference in O2 extraction and O2 consumption between the NP treated cortex and contralateral cortex in either the low or the high dose NP groups. In the high dose NP group, the O2 extraction was 8.0 ± 1.3 ml O2 · 100 ml-1 in the treated cortex and 8.8 ± 1.5 ml O2 · 100 ml-1 in the contralateral cortex, while the O2 consumptions in the NP treated cortex and contralateral cortex were 8.1 ± 1.3 ml O2 · min-1 · 100 g-1 and 7.3 ± 1.2, respectively. Thus, NP increased the cyclic GMP level without a significant change in O2 consumption in the cerebral cortex. Our data suggested that O2 consumption in the cerebral cortex was not affected by the increased level of cyclic GMP.
All Science Journal Classification (ASJC) codes
- Developmental Biology
- Molecular Biology
- Clinical Neurology