The effects of intraventricular/periventricular blood on cerebral 3',5'- cyclic adenosine monophosphate concentration and cerebrovascular reactivity in newborn pigs

This study investigated the effects of intraventricular/ periventricular blood on cerebral cAMP production and cortical cerebrovascular reactivity. Under halothane and N₂O anesthesia, 3 mL of either autologous blood or artificial cerebrospinal fluid (CSF) were injected into the left caudate nucleus; volume was adequate to result in extrusion of fluid or blood into the lateral ventricles of 1-2-d-old piglets. Twenty-four hours later, a closed cranial window was implanted over the left parietal cortex. Pial arteriolar responses in vasodilator and vasoconstrictor stimuli were monitored. Before the application of vasoactive agents, cortical periarachnoid CSF was collected for cAMP measurement. Pial arteriolar responses to topical application of endothelin-1 (10^-9 and 10^-8 M) and to leukotriene C₄ (10^-10 and 10^-9 M) were similar between the two groups. However, pial arteriolar responses to topical application of cAMP-mediated vasodilators, prostaglandin E₂ (10^-6 and 10^-5 M), and histamine (10^-6 and 10^-5 M), respectively, were markedly reduced in the blood group when compared with the artificial CSF (control) group. Mean CSF cAMP level in the blood group was significantly lower than the control group (199 ±31 versus 1092 ± 238 fmol/mL, p = 0.0006). We conclude that in newborn pigs intraventricular/periventricular blood results in a marked reduction of CSF cAMP concentration and attenuation of the cerebrovascular responses to cAMP- mediated vasodilators on the cortical surface remote from the site of blood or hematoma.