Induced depression of single neurons in brain areas with opiate receptors
Enkephalin, applied microiontophoretically, depressed spontaneous and glutamate-induced firing of one neuron in frontal cortex, caudate nucleus, and periaqueductal gray matter, where enkephalin and high concentrations of opiate receptors are met.
More than one depressions were blocked by the specific narcotic antagonist naloxone. The results are durable with a neurotransmitter or neuromodulator role for this new brain pentapeptide.
Opium derivatives have been in medical use for the last 2000 years, and may be longer than any other class of drugs
. The brain regions which was involved in these actions have been identified in some instances by local microinjection of pmole quantities of opioids.
