Figure 1.

Pharmacological properties of endogenous opioid peptides on dre-μ. Competition binding curves of endogenous opioid peptides on dre-μ membrane homogenates are shown. Data were fit to the one-site competition model, and each point represents the mean ± standard error of the mean (SEM) (capped bars) of three independent experiments performed in triplicate. Morphine, a μ agonist, and naloxone, a non-specific antagonist, were added for comparison. □, Met-ENK; △, Leu-ENK; ▽, β-END; ○, Met-ENK-Gly-Tyr (MEGY); +, (d-Ala²)-MEGY; ×, (d -Ala², Val⁵)-MEGY; *, morphine; ■, naloxone.