PHARMACOLOGICAL CHARACTERIZATION OF THE EFFECTS OF 5-HYDROXYTRYPTAMINE AND DIFFERENT PROSTAGLANDINS ON PERIPHERAL SENSORY NEURONS INVITRO

The excitatory and sensitizing properties of 5-HT and different prosta glandins (PGD2, PGE1, PGE2, PGF2alpha, PGI2 and PGI2-analogue, cicapro st) were characterized on an in vitro preparation of the neonatal rat spinal cord with functionally attached tail. Prolonged (10 min) perfus ion of the tail with 5-hydroxytryptamine ( 5-HT, 0.5-1 0 muM) or any o f the tested prostaglandins (0.1-5 muM) did not evoke an excitatory re sponse recorded from a lumbar ventral root, but significantly enhanced responses of peripheral nociceptors to thermal and chemical (bradykin in, capsaicin) stimuli. PGD, did not induce such an enhancement. Follo wing sensitization of peripheral nociceptors with low concentrations o f bradykinin or capsaicin, 5-HT (1-10 muM) evoked a ventral root respo nse. Using specific 5-HT-receptor agonists and antagonists, 5-HT-evoke d excitation was determined to be mediated via a 5-HT1-like receptor w hile 5-HT-induced sensitization involved 5-HT2 receptors.