ISSN:
1432-2072
Keywords:
Mu opioids
;
Kappa opioids
;
Opioid antagonism
;
Opioid tolerance
;
Rate-decreasing effects
;
Schedule-controlled responding
;
Morphine
;
l-Methadone
;
Bremazocine
;
U69,593
;
U50,488
;
β-FNA
;
Naltrexone
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The present study investigated the rate-decreasing effects of several mu (morphine andl-methadone) and kappa (bremazocine, U69,593 and U50,488) opioid agonists in pigeons. Mu and kappa agonists were examined alone, in combination with naltrexone or the mu-selective opioid antagonist, β-funaltrexamine (β-FNA), and in pigeons treated chronically with U50,488. Naltrexone was equipotent in shifting the morphine,l-methadone and bremazocine dose-effect curves to the right, but was less potent in shifting the U69,593 dose-effect curve and did not shift the U50,488 dose-effect curve. β-FNA shifted thel-methadone dose-effect curve to the right but did not shift the bremazocine, U69,593 or U50,488 dose-effect curves. Pigeons that developed tolerance to U50,488 following daily administration were cross-tolerant to bremazocine but not tol-methadone. Taken together, these experiments indicate that the rate-decreasing effects of morphine andl-methadone are mediated by mu opioid receptors, whereas the rate-decreasing effects of bremazocine, U69,593 and U50,488 in pigeons differ depending on the pharmacological procedures used to assess their effects.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02245223
