Journal of Neuroscience, Vol 14, 4806-4814, Copyright © 1994 by Society for Neuroscience
Implantation of AtT-20 or genetically modified AtT-20/hENK cells in mouse spinal cord induced antinociception and opioid tolerance
HH Wu, GL Wilcox and SC McLoon
Department of Pharmacology, University of Minnesota, Minneapolis 55455.
AtT-20 cells, which make and release beta-endorphin, or AtT-20/hENK cells,
an AtT-20 cell line transfected with the human proenkephalin gene and
secreting enkephalin as well as presumably beta-endorphin, were implanted
in mouse spinal subarachnoid space. Cell implants did not affect the basal
response to thermal nociceptive stimuli. Administration of isoproterenol,
believed to stimulate secretion from these cells, produced antinociception
in groups receiving AtT-20 or AtT- 20/hENK cell implants but not in control
groups receiving no cells. The antinociceptive effect of isoproterenol was
dose related and could be blocked by the opioid antagonist naloxone.
Implantation of these cells offers a novel approach for the study of
tolerance. Mice receiving AtT- 20 cell implants developed tolerance to
beta-endorphin and the mu- opioid agonist DAMGO, whereas mice receiving
genetically modified AtT- 20/hENK cell implants developed tolerance to the
delta-opioid agonist DPDPE. Genetically modified AtT-20/hENK cell implants,
but not AtT-20 cell implants, reduced the development of acute morphine
tolerance in the host mice. This finding is consistent with the suggestion
that enkephalin alters development of opioid tolerance. These results
suggest that opioid-releasing cells implanted around mouse spinal cord can
produce antinociception and may provide an alternative therapy for chronic
intractable pain.