Activation of periaqueductal grey pools of beta-endorphin by analgetic electrical stimulation in freely moving rats.
Electrical stimulation of the ventral midbrain periaqueductal grey (PAG) elicited an antinociception (analgesia) in freely moving rats. Stimulated animals displayed a pronounced decrease in levels of immunoreactive (ir)-beta-endorphin (beta-EP) in the midbrain PAG. This depletion was selective in that: animals placed in the chamber and not stimulated revealed neither an analgesia nor an alteration in levels of ir-beta-EP. No change in levels of ir-beta-EP was detectable in other brain regions. Both stimulated rats and rats placed in the chamber and not stimulated revealed a rise in circulating ir-beta-EP: the magnitude of this rise did not, however, differ between these groups. Levels of ir-Met-enkephalin, ir-Leu-enkephalin and ir-dynorphin A were modified neither in the PAG nor in other CNS tissues. The data demonstrate that electrical stimulation of the midbrain PAG selectively influences (presumably activates) pools of beta-EP therein. Together with our finding that destruction of PAG-localized beta-EP neurones to block stimulation-analgesia, the data suggest that an activation of intrinsic pools of beta-EP underlies stimulation-produced analgesia elicited from the PAG in the rat.
D000818:Animals; D004399:Dynorphins / Q000378:metabolism; D004599:Electric Stimulation Therapy; D004723:Endorphins / Q000378:metabolism*; D004743:Enkephalin, Leucine / Q000378:metabolism; D004744:Enkephalin, Methionine / Q000378:metabolism; D008124:Locomotion; D008297:Male; D010487:Periaqueductal Gray / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012684:Sensory Thresholds; D004561:Transcutaneous Electric Nerve Stimulation; D001615:beta-Endorphin
D004723:Endorphins; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D001615:beta-Endorphin; D004399:Dynorphins; D011388:Prolactin