Regulation of opiate receptors in mouse brain: arcuate nuclear lesion induces receptor up-regulation and supersensitivity to opiates.

Lesion of the hypothalamic arcuate nucleus of the mouse by neonatal application of monosodium glutamate (MSG) increased the binding of [3H]dihydromorphine to membranes prepared from the midbrain. A saturation curve of [3H]dihydromorphine binding indicated that MSG increased the number of the opiate receptors. The MSG-treated mice also exhibited an enhanced response to morphine and naltrexone regarding thermal pain sensitivity. The physiological implications of opiate receptors up-regulations upon arcuate nuclear lesion are discussed.