Effects of phorbol esters on pial arteriolar diameter and brain production of prostanoids in piglets.

We determined the effects of phorbol 12,13-dibutyrate (PDB), which activates protein kinase C, on pial arteriolar diameter and cerebrospinal fluid (CSF) prostanoid levels in newborn pigs. A closed cranial window was implanted, and the diameter of one pial arteriole was determined by intravital microscopy. In addition, CSF was sampled from under the window, and prostanoid levels (prostaglandin [PG] E2, 6-keto-PGF1 alpha, PGF2 alpha, and thromboxane B2) were determined by radioimmunoassay. Diameter and CSF prostanoid levels were determined during application of artificial CSF containing no drugs and during application of 10(-8), 10(-7), and 10(-6) M PDB. We also determined effects of 4 alpha-phorbol 12,13-didecanoate (4 alpha-PDD), a phorbol ester that does not activate protein kinase C, and dimethyl sulfoxide, the vehicle for the phorbol esters, on pial arteriolar diameter and CSF prostanoid levels. Initial diameters were 100-200 microns. At 10(-8)-10(-6) M, PDB progressively constricted pial arterioles and increased CSF levels of prostanoids; the other phorbol ester and dimethyl sulfoxide had no such effects. Baseline arteriolar diameter was 147 +/- 17 microns (mean +/- SEM), and diameter was 140 +/- 17 microns at 10(-8) M PDB, 120 +/- 18 microns at 10(-7) M PDB (p less than 0.05), and 108 +/- 14 microns at 10(-6) M PDB (p less than 0.05) (n = 5).(ABSTRACT TRUNCATED AT 250 WORDS)