Temperature-dependent neuronal regulation of arterial blood flow in rat cranial dura mater.

Several endogenous factors such as calcitonin gene-related peptide (CGRP), nitric oxide, and histamine have been found to affect meningeal blood flow. A possible regulation of meningeal blood flow by thermosensitive neurons has not been examined so far. We monitored meningeal arterial blood flow with laser Doppler flowmetry in anesthetized rats. A vortex thermode was used to control the temperature of the exposed dura mater. After fast heating from 36 degrees C to 45 degrees C, meningeal blood flow increased slowly within 5 min. Immediately after fast cooling to 36 degrees C, the flow transiently increased before it returned to the initial basal level. After the application of lidocaine onto the dura mater, the heating-induced flow increase was greater and the transient cooling-induced flow increase was reduced, indicating the involvement of neuronal mechanisms. Furthermore, after topical application of phenylephrine, the cooling-induced response was increased, and following topical application of phentolamine the heating-induced flow increase was higher. The flow changes evoked by thermal stimulation were unaffected by high concentrations of 1) cimetidine, 2) a vasoactive intestinal polypeptide antagonist and the CGRP receptor antagonists, 3) CGRP(8-37), and 4) BIBN4096BS. We conclude that activation of temperature-sensitive meningeal afferents can regulate the dura mater blood flow by a sympathetic reflex.