Effect of sympathetic nerve stimulation on cerebral blood flow in newborn piglets

Abstract

The purpose of this study was to determine the effect of sympathetic nerve stimulation on regional cerebral blood flow during the first 3 wk of postnatal development in piglets. Forty-one piglets ranging in age from 2 to 24 days were studied while anesthetized with 30% N20, paralyzed and mechanically ventilated (PaCO2 = 35-40 mm Hg). Regional cerebral blood flow was measured with tracer microspheres (15 ± 1 µm) during electrical stimulation (15 Hz, 15 V, 3 ms) of the right cervical sympathetic trunk. Sympathetic stimulation decreased blood flow to the ipsilateral cerebrum (gray and white matter) (-15 ± 2%), hippocampus (–9 ± 2%), choroid plexus (–50 ± 5%), and masseter muscle (–93 ± 2%) compared to the contralateral side where blood flow to these regions was 74 ± 4, 45 ± 2, 258 ± 26, and 24 ± 4 ml/min/100 g, respectively (mean ± SEM; p < 0.05). The magnitude of the reduction in cerebral blood flow was not dependent on postnatal age as no significant differences were noted when the piglets were grouped according to age. Hypercapnia (PaCO2 = 64 ± 5 mm Hg) increased blood flow 2- to 4-fold above control in all brain regions except the choroid plexus. The effect of sympathetic nerve stimulation was augmented during hypercapnia where blood flow to the ipsilateral cerebrum, hippocampus, and caudate nucleus was decreased by –34 ± 4, –23 ± 5, and – 16 ± 3 %, respectively. Activation of sympathetic nerves can reduce blood flow to specific brain regions during control conditions and these effects are larger in hyperemic conditions such as hypercapnia. These data demonstrate that sympathetic nerves are present and completely developed at birth and, when sufficiently activated, capable of influencing regional cerebrovascular resistance in the newborn piglet. © 1986 International Pediatric Research Foundation, Inc.