Modulation of calcitonin gene-related peptide release from dorsal thoraco-lumbar spinal cord slices by 5-HT3 receptors.

The release of endogenous calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) from slices of dorsal and ventral thoraco-lumbar spinal cord was examined using a fixed volume incubation technique and radioimmunoassay. Incubation with potassium (25-100 mM) produced a dose-related increase in basal CGRP-LI in the supernatant of dorsal slices which was calcium dependent and release was also evoked by incubation with capsaicin (10 microM). Pre-incubation with the 5-HT3 agonist 2-methyl-5-hydroxytryptamine (10(-5) M) attenuated potassium-induced release from dorsal spinal cord slices, which was prevented by additional pre-incubation with the 5-HT3 antagonist ondansetron (10(-8) M). In contrast, the low level of CGRP-LI released from ventral spinal cord slices was not significantly enhanced by incubation with either potassium or capsaicin.