Neuropharmacological actions of the superactive agonist analog D-TRP-6-LH-RH after peripheral injection into mice

The neuropharmacological actions of the agonist analog D-Trp-6-LH-RH were investigated in several tests after subcutaneous administrations to male mice. The doses applied were in the range 1-1000 micrograms/kg. D-Trp-6-LH-RH doses of 10 micrograms/kg and higher induced significant analgesic effects in the hot-plate and tail-flick tests, and decreased the open-field parameters (ambulation, rearing, grooming). The 100 and 1000 micrograms/kg doses increased the latencies of picrotoxin-induced seizures, significantly inhibited apomorphine-induced cage climbing and also exerted a cataleptogenic effect. The results indicate that this agonist analog of LH-RH has an inhibitory effect on the central nervous system, and the mechanism of its action may involve dopaminergic transmission and/or endogenous opiates.