devazepide and naltrindole

Interactions between CCKergic and enkephalinergic systems were studied in mice using behavioral responses measured in Animex. The hyperlocomotion induced by 5 mg/kg of RB 101, a mixed inhibitor of enkephalin-degrading enzymes able to cross the blood-brain barrier, was previously shown to be mediated by delta-opioid receptor stimulation. The IP administration of a CCKA agonist, Boc-Tyr-Lys-(CONH-o-tolyl)-Asp-Phe-NH2 (0.1, 1, 10 micrograms/kg), suppressed the hyperlocomotion produced by IV injection of 5 mg/kg of RB 101. The effect of the CCKA agonist was suppressed by a selective CCKA antagonist, devazepide, injected IP at doses of 20 and 200 micrograms/kg and was potentiated by the selective delta-opioid antagonist naltrindole at the doses of 0.03 mg/kg. IP injection of the selective CCKB agonist BC 264 (0.1-1 mg/kg) did not modify the RB 101-induced hyperlocomotor effect. These results reinforce the observed physiological antagonism between the endogenous CCK and opioid systems but are at variance with the responses measured in stressful conditions. It is concluded that CCKA, but not CCKB, receptor activation counteracts the opioid-related hyperlocomotion.

Topics: Amino Acid Sequence; Animals; Benzodiazepinones; Cholecystokinin; Devazepide; Disulfides; Enkephalins; Enzyme Inhibitors; Male; Mice; Molecular Sequence Data; Motor Activity; Naltrexone; Narcotic Antagonists; Peptide Fragments; Phenylalanine; Receptors, Cholecystokinin

Published results suggest that delta-opioid agonists can modulate the mu-mediated analgesia. In this work, the antinociceptive effects produced by the mu agonist [D-Ala2,NMe-Phe4,Gly-ol5]enkephalin or the mixed inhibitor of enkephalin-degrading enzymes RB 101 (N- [(R,S)-2-benzyl-3[(S)(2-amino-4-methyl- thio)butyldithio]-1-oxopropyl]-L-phenylalanine benzyl ester) were studied after administration of the systemically active and selective delta agonist Tyr-D-Ser(O-tert-butyl)-Gly-Phe-Leu- Thr(O-tert-butyl). In the hot-plate test in mice, Tyr-D-Ser(O-tert-butyl)-Gly- Phe-Leu-Thr(O-tert-butyl) (i.v.) potentiated the antinociceptive responses elicited by [D-Ala2,NMe-Phe4,Gly-ol5]enkephalin (i.v.) or RB 101 (i.v.). These facilitatory effects were reversed not only by prior administration of the delta-selective antagonist naltrindole (0.5 mg/kg s.c.), but also unexpectedly by the selective cholecystokinin CCK-A antagonist MK-329 (20 micrograms/kg i.p.). In addition, the CCK analog [Boc- Tyr(SO3H)-Nle-Gly-Trp-Nle-Asp-Phe-NH2] (a mixed CCK-A/CCK-B agonist) increased the jump latency and this effect was blocked by MK-329 (20 micrograms/kg i.p.) and by naloxone, but not by the selective CCK-B antagonist L-365,260 (5 mg/kg i.p.). In contrast, the selective CCK-B agonist BC 264 (62 micrograms/kg i.v.) produced a hyperalgesic effect that was antagonized by L-365,260 (5 mg/kg i.p.). Taken together, these findings suggest that the potentiating effects of delta agonists on mu-mediated analgesia are due to an increase in the release of endogenous CCK interacting with CCK-A and CCK-B receptors and resulting in positive and negative regulation of the endogenous opioid system.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Amino Acid Sequence; Analgesia; Animals; Benzodiazepinones; Cholecystokinin; Devazepide; Disulfides; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalins; Male; Mice; Molecular Sequence Data; Naloxone; Naltrexone; Oligopeptides; Peptide Fragments; Phenylalanine; Receptors, Opioid, delta; Receptors, Opioid, mu; Sincalide

Topics: Amino Acid Sequence; Analgesics; Animals; Benzodiazepinones; Cholecystokinin; Devazepide; Gastric Emptying; Gastrointestinal Transit; Indoles; Male; Mice; Mice, Inbred ICR; Molecular Sequence Data; Morphinans; Naloxone; Naltrexone; Narcotic Antagonists; Peptide Fragments; Peptides; Phenylurea Compounds; Reaction Time; Receptors, Cholecystokinin; Sincalide