Release of sensory neuropeptides from dural venous sinuses of guinea pig

Substance P- and calcitonin gene-related peptide-like immunoreactivities (SP-LI and CGRP-LI, respectively) were measured in superfusates of either superior sagittal sinus and transverse sinuses and attached dura mater or dura mater alone of guinea pig. Exposure of cerebral venous sinuses to capsaicin (1 microM) evoked the release of both SP-LI and CGRP-LI, which was no longer observed upon second challenge with the drug. Neuropeptide release was induced by 80 mM K+ either at the first or second administration. Bradykinin (10 microM) increased the outflow of CGRP-LI, but not of SP-LI, from cerebral venous sinuses. In vitro capsaicin pretreatment (10 microM) or incubation with 10 microM indomethacin completely abolished the bradykinin-evoked CGRP-LI release. Capsaicin (1 microM) failed to evoke release from dura mater without major intracranial venous vessels. Sensory neuropeptide released from the cerebral venous sinuses may take part in certain symptoms, such as vasodilatation and inflammation accompanying the pain of the migraine attack. Bradykinin, putatively via prostanoid generation, may participate in this event.