TY - JOUR
T1 - Comparison of naloxonazine and β-funaltrexamine antagonism of μ1 and μ2 opioid actions
AU - Pick, Chaim G.
AU - Paul, Dennis
AU - Pasternak, Gavril W.
N1 - Funding Information:
We thank Drs. J.B. Posner and R. Hawks for their assistance with these studies. This work was supported by a grant from the American Cancer Society PDT169) and a core grant from the National Cancer Institute to MSKCC NIDA I (K02 DA00138). DP was supported by a fellowship from the CA8748). GWP is supported by a Research Scientist Development Award from
PY - 1991
Y1 - 1991
N2 - β-Funaltrexamine (β-FNA) irreversibly blocks morphine analgesia, lethality and its inhibition of gastrointestinal transit, confirming that these actions involve μ receptors. In dose-response studies, β-FNA antagonized all the actions with similar potencies (ID50 values of 12.1, 11.3 and 12.3 mg/kg, respectively). β-FNA also reduced intra-cerebroventricular and intrathecal DAMGO analgesia equally well (ID50 values of 6.09 and 7.7 mg/kg, respectively). Naloxonazine blocked systemic morphine analgesia (ID50 value 9.5 mg/kg) and supraspinal DAMGO analgesia (ID50 value 6.1 mg/kg) as potently as β-FNA. However, against spinal DAMGO analgesia, morphine's inhibition of gastro-intestinal transit or lethality, naloxonazine (ID50 values 38.8, 40.7 and 40.9 mg/kg, respectively) was significantly less active than β-FNA (p < 0.05). β-FNA remains a valuable tool in the classification of μ opioid actions. Within the μ category, actions can be defined as either μ1 (naloxonazine-sensitive) or μ2 (naloxonazine-insensitive).
AB - β-Funaltrexamine (β-FNA) irreversibly blocks morphine analgesia, lethality and its inhibition of gastrointestinal transit, confirming that these actions involve μ receptors. In dose-response studies, β-FNA antagonized all the actions with similar potencies (ID50 values of 12.1, 11.3 and 12.3 mg/kg, respectively). β-FNA also reduced intra-cerebroventricular and intrathecal DAMGO analgesia equally well (ID50 values of 6.09 and 7.7 mg/kg, respectively). Naloxonazine blocked systemic morphine analgesia (ID50 value 9.5 mg/kg) and supraspinal DAMGO analgesia (ID50 value 6.1 mg/kg) as potently as β-FNA. However, against spinal DAMGO analgesia, morphine's inhibition of gastro-intestinal transit or lethality, naloxonazine (ID50 values 38.8, 40.7 and 40.9 mg/kg, respectively) was significantly less active than β-FNA (p < 0.05). β-FNA remains a valuable tool in the classification of μ opioid actions. Within the μ category, actions can be defined as either μ1 (naloxonazine-sensitive) or μ2 (naloxonazine-insensitive).
UR - http://www.scopus.com/inward/record.url?scp=0025847117&partnerID=8YFLogxK
U2 - 10.1016/0024-3205(91)90155-5
DO - 10.1016/0024-3205(91)90155-5
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AN - SCOPUS:0025847117
SN - 0024-3205
VL - 48
SP - 2005
EP - 2011
JO - Life Sciences
JF - Life Sciences
IS - 21
ER -