The effects of protection by D-Pen2-D-Pen5-enkephalin or D-Ala2-NMePhe4-Gly-ol-enkephalin against beta-chlornaltrexamine in the spinal cord on the antinociception induced by beta-endorphin administered intracerebroventricularly in the mouse.
Chlornaltrexamine (beta-CNA, 0.5 micrograms) alone or beta-CNA plus either mu-agonist, D-Ala2-NMePhe4-Gly-ol-enkephalin (DAMGO, 500 ng) or delta-agonist, D-Pen2-D-Pen5-enkephalin (DPDPE, 10 micrograms) was injected intrathecally (i.t.) to protect mu- or delta-opioid receptors, respectively, for 24 h in male ICR mice. The antinociception was assessed by the tail-flick and hot-plate test. DPDPE or DAMGO injected i.t. increased inhibition of the tail-flick and hot-plate response in a dose-dependent manner. The dose-response curve for tail-flick and hot-plate response induced by DPDPE or DAMGO in i.t. saline-treated group significantly shifted to the right in i.t. beta-CNA alone treated group but returned to the control level in the group treated with i.t. beta-CNA coadministered with DPDPE or DAMGO, respectively. The effects of protection of mu- and delta-opioid receptor in the spinal cord on inhibition of the tail-flick and hot-plate response induced by beta-endorphin and morphine administered intracerebroventricularly (i.c.v.) were then studied. Intrathecal pretreatment with beta-CNA or beta-CNA coadministered with DAMGO attenuated inhibition of the tail-flick response induced by beta-endorphin administered i.c.v. However, i.t. treatment with beta-CNA coadministered with DPDPE did not affect inhibition of the tail-flick response induced by beta-endorphin administered i.c.v. Intrathecal pretreatment with beta-CNA or beta-CNA coadministered with either DPDPE or DAMGO did not alter inhibition of the hot-plate response induced by beta-endorphin administered i.c.v.(ABSTRACT TRUNCATED AT 250 WORDS)
Suh
H W
HW
Department of Pharmacology, College of Medicine, Hallym University, Chunchon, Kangwon-Do, Korea.
Lim
J S
JS
Song
D K
DK
Kim
Y H
YH
Tseng
L F
LF
D000595:Amino Acid Sequence; D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000494:pharmacology*; D007276:Injections, Intraventricular; D007278:Injections, Spinal; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D008969:Molecular Sequence Data; D009271:Naltrexone / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors; D009292:Narcotic Antagonists / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement / Q000379:methods; D013116:Spinal Cord / Q000187:drug effects*; D001615:beta-Endorphin / Q000008:administration & dosage
D000700:Analgesics; D004745:Enkephalins; D009292:Narcotic Antagonists; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D009271:Naltrexone; D001615:beta-Endorphin; C017120:chlornaltrexamine; D020881:Enkephalin, D-Penicillamine (2,5)-