Effects of kyotorphin and analogues on nociception and pentylenetetrazole seizures.

UNLABELLED: Kyotorphin (Kyo) is synthesized in specific brain regions where it may modulate synaptic transmission and directly excites cortical neurons, and indirectly exerts opioid actions to produce analgesia via release of met-enkephalin. Kyo is formed by specific enzyme from L-tyrosine and L-arginine in the presence of ATP and Mg2+ in the brain. Kyo and its analogues Tyr-Cav, Tyr (Cl2)-Cav exerted naloxone-reversible antinociception by paw-pressure test. Kyo exerted anticonvulsive effect on the pentylenetetrazole (PTZ) seizure model. AIM: To investigate the analgesic and the anticonvulsive effects of Kyo, Tyr-Cav and Tyr(Cl2)-Cav during acute pain and PTZ seizure model. METHODS: Changes in the nociceptive effects were examined in male Wistar rats by the tail flick (TF) and hot plate (HP) tests. Kyo, Tyr-Cav, Tyr(Cl2)-Cav were applied in rats intracerebroventricularly (i.c.v.) at a dose of 20 microg/20 microl. The anticonvulsive effects of peptides were studied on a PTZ seizure model. The peptides were applied in male mice at a dose of 20 microg/mouse (i.c.v.). RESULTS: Kyo, Tyr-Cav, Tyr(Cl2)-Cav exerted analgesic effects in both nociceptive tests used. The effects were more pronounced for L-Arg, L-Cav, Tyr-Cav and Tyr(Cl2)-Cav. In PTZ seizure model Kyo and its analogues exerted strong inhibition on seizure intensity compared with control group. CONCLUSION: Taken together, these results reveal Kyo, Tyr-Cav and Tyr(Cl2)-Cav as a behaviorally active peptide in experimental animal models.