The Adrenal Medullae Autotransplanted into the Thalami Still Produce Enkephalins

Abstract

Enkephalin, an endogenous opioids, plays an important role in pain modulation. As enkephalin is produced by the adrenal medulla, a possible treatment for reduction of refractory pain is by adrenal medullary transplantation. One possible target for this transplantation is within the thalamus, a major site for processing ascending and descending nociceptive information. In the present study, quantitative estimates of L-enkephalin and M-enkephalin contents were determined in homogeneous adrenal medullae transplants. Male guinea pigs and Wistar rats (8 weeks old) were used. Right adrenal medullae were used as control. Following a two month survival time, animals were perfused with Zamboni's fixative. Thirty micron section were cut through the thalamic grafts and the left adrenal medulla and the tissue processed immunocytochemically for L-enkephalin and M-enkephalin. A micro-imaging analytic system was used to semi-quantitate the amount of L-enkephalin and M-enkephalin through the grey degrees of the immunostains. A students t-test was used to determine if the differences between the experimental and control groups were statistically significant. The results indicated that, following a two month survival time, there was a significant increase in the contents of L-enkephalin and M-enkephalin in the grafts of the thalami of both the guinea pigs and rats in comparison to control. This result suggests that L-enkephalin and M-enkephalin were produced by the grafts transplanted into the thalamus.