Figure 3
A 5-HT 1 receptor antagonist but not 5HT 2 or 5HT 3 antagonists block serotonergic inhibition of neurotransmitter release from trigeminal neurons. Panels A-D illustrate glutamate or immunoreactive CGRP in the buffer measured after successive 10 minute incubations in the absence and presence of 50 mM KCl and/or drugs. Drugs were present as indicated during "Pretreat" and "50 mM KCl" incubations but not during the "Basal" incubation. Data is presented as the mean ± S.E.M. and the number of wells tested is indicated in parentheses. An asterisk indicates a significant difference (p < 0.05) between the transmitter release from control cells and from cells treated with serotonin and/or serotonin receptor antagonists. NAS-181 (1 μM), a 5-HT1 receptor antagonist, blocks the serotonergic inhibition of release of glutamate and CGRP (Panels A and B, respectively) without affecting basal or stimulated release. SB 200646 (1 μM), a 5-HT2B/2C antagonist does not block 5-HT (10 μM) inhibition of KCl-stimulated release of CGRP (Panel C) or alter basal or KCl-stimulated release. Y-25130 (500 nM), a 5-HT3 antagonist does not block 5-HT (10 μM) inhibition of KCl-stimulated release of CGRP (Panel D) or alter basal or KCl-stimulated release.