Houghten, RA, Johnson, N, Pasternak, GW. (1984). [3H]-β-endorphin binding in rat brain
. JOURNAL OF NEUROSCIENCE, 4(10), 2460-2465. 10.1523/jneurosci.04-10-02460.1984
Houghten, RA, Johnson, N, Pasternak, GW. (1984). [3H]-β-endorphin binding in rat brain
. JOURNAL OF NEUROSCIENCE, 4(10), 2460-2465. 10.1523/jneurosci.04-10-02460.1984
The binding of [3H]-β-endorphin to rat brain homogenates is complex. Although Scatchard analysis of saturation studies yield a straight line, detailed competition studies are multiphasic, suggesting that even at low concentrations of the compound, the 3H-ligand is binding to more than one class of site. A portion of [3H]-β-endorphin binding is sensitive to low concentrations of morphine or D-Ala2-Leu5-enkephalin (<5 nM). The inhibition observed with each compound alone (5 nM) is the same as that seen with both together (each at 5nM). Thus, the binding remaining in the presence of both morphine and the enkephalin does not correspond to either μ or σ sites. The portion of [3H]-β-endorphin binding that is inhibited under these conditions appears to be equally sensitive to both morphine and the enkephalin and may correspond to μ1 sites. Treating membrane homogenates with naloxonazine, a μ1 selective antagonist, lowers [3H]-β-endorphin binding to the same degree as morphine and D-Ala2-Leu5-enkephalin alone or together. This possible binding of [3H]-β-endorphin to μ1 sites is consistent with the role of μ1 sites in β-endorphin analgesia and catalepsy in vivo.
