Comparison of binding of [3H]-methionine-enkephalin, [3H]-naltrexone and [3H]-dihydromorphine in the mouse vas deferens and the myenteric plexus and brain of the ginea pig.

[3H]-Methionine-enkephalin, [3H]-naltrexone and [3H]-dihydromorphine are specifically bound in homogenates of not only the brain and myenteric plexus of the guinea pig but also the vas deferens of the mouse. Brain has a ratio of methionine-enkephalin to dihydromorphine binding in favour of methionine-enkephalin binding and the myenteric plexus a ratio in favour of dihydromorphine binding, with the mouse vas deferens being intermediate.