BAM-18: analgesia, hyperalgesia and locomotor effects.
BAM-18, a proenkephalin A-derived opioid peptide, is widely distributed throughout rat CNS and displays high affinity for both mu and kappa opioid receptors. In the present study, BAM-18 was tested in two analgesia paradigms, tail-flick and hot-plate. Injections were centrally administered through a chronically implanted unilateral cannula in the lateral ventricle. In the tail-flick, low doses of BAM-18 (5 micrograms) produced a hyperalgesia while high doses of BAM-18 (50 micrograms) produced an analgesic response. Naloxone (10 mg/kg, s.c.) reversed the BAM-18-induced analgesia and unmasked a persistent hyperalgesia. Morphine-induced (1 microgram) analgesia was completely reversed by 5 micrograms BAM-18. In the hot-plate test, high doses of BAM-18 produced analgesia, with no hyperalgesia observed at any dose. Naloxone reversed the BAM-18-induced analgesia. The locomotor effects of BAM-18 did not differ from those of morphine except in effective dose (50 micrograms vs. 5 micrograms, respectively). Opioid and non-opioid effects of BAM-18 are discussed and compared with other endogenous peptides.
Stevens
K E
KE
Department of Pharmacology, University of California, Irvine 92717.
Leslie
F M
FM
Evans
C J
CJ
Belluzzi
J D
JD
Stein
L
L
D000595:Amino Acid Sequence; D000698:Analgesia; D000818:Animals; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives* / Q000032:analysis / Q000494:pharmacology; D006930:Hyperalgesia / Q000139:chemically induced*; D006941:Hyperesthesia / Q000139:chemically induced*; D007276:Injections, Intraventricular; D008124:Locomotion / Q000187:drug effects*; D008297:Male; D008969:Molecular Sequence Data; D011498:Protein Precursors / Q000032:analysis / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D011498:Protein Precursors; C053492:BAM 18P; D004744:Enkephalin, Methionine