Effects of recombinant human interleukin 1 alpha (IL-1 alpha) on vasomotor tone of pial arterioles and cerebrospinal fluid (CSF) prostanoid levels were examined in anesthetized piglets by employing the closed cranial window method. IL-1 alpha in a dose of 10.8 micrograms infused under the window increased pial arteriolar diameter [initial size, 160 +/- 9 (SE) micrograms] significantly at 15 min postinfusion through 30 min (30-min study), exhibiting a maximum dilation of 13 +/- 1% (n = 8) over the control levels. Significant increases in levels of prostaglandin E2 (PGE2, 75%), 6-keto-PGF1 alpha (84%), and PGF2 alpha (35%) but not for thromboxane B2 (TxB2, 2%) were observed when CSF was sampled from under the window 30 min after 10.8 micrograms IL-1 alpha. A lower dose of IL-1 alpha (1.0 micrograms, n = 4) significantly increased the diameter of pial arterioles with a tendency for longer onset (25-30 min) and smaller magnitude (9-10%) than the higher dose. In IL-1 alpha time-response studies, CSF sampled 10 min after 10.8 micrograms IL-1 alpha infusion (10-min study, n = 6) under the window exhibited the same levels of PGE2, 6-keto-PGF1 alpha, PGF2 alpha, and TxB2 as those of the controls. There was no vasodilation in the 10-min study. However, when sampled 20 min after 10.8 micrograms IL-1 alpha (20-min study, n = 6), CSF levels of all prostanoids except for TxB2 significantly increased over the controls.(ABSTRACT TRUNCATED AT 250 WORDS)