Enkephalin Release from the Globus Pallidus: In Vitro and in Vivo Studies
The presence of the opioid peptides [5-methionine] -enkephalin (Met-enkephalin) and [5-leucine] -enkephalin (Leu-enkephalin) (7) in several regions of the central nervous system (17) and the immunohistochemical evidence for their location in fibers and cell bodies (6) first supported their consideration as putative central neurotransmitters. The search for a model system to study the central neurobiology of the enkephalins has led to the striatum and especially the globus pallidus because this region has the highest content of immuno-reactive enkephalin and enkephalin-containing fibers. The early studies in one of our laboratories (8) showed that during in vitro perfusion of slices from rat globus pallidus, enkephalin-like immuno-reactive material was released by 50 mM K+ in a Cat2+dependent manner. In subsequent work (1) we have analyzed the composition of these enkephalin-like substances, both in fresh and perfused tissue and in the released material, and also some aspects of the metabolic changes of enkephalins during in vitro release experiments. Based on these studies, we have explored the basic characteristics of enkephalin release from pallidal tissue in unanesthetized-freely moving animals using a push-pull cannula perfusion technique. Our results show that enkephalins can be released from the pallidum, not only by chemical stimulation of the local fibers but also, in a more physiological manner, by electrical stimulation of the caudate nucleus.
KeywordsCaudate Nucleus High Pressure Liquid Chromatography Globus Pallidus Perfuse Medium Minimum Detectable Amount
Unable to display preview. Download preview PDF.
- 1.Bayón, A., Koda, L., Battenberg, E., Azad, R., Guillemin, R., and Bloom, F.E., Regional distribution of endorphin, methionine-enkephalin and leucine-enkephalin in the pigeon brain, Neurosei. Letters, 16 (1980) 75–80.Google Scholar
- 4.Gros, C., Pradelles, P., Rougeot, C., Bepoldin, O., Dray, F., Fournie-Zaluski, M.C., Roques, B.P., Pollard H., Llorens-Cortes, C. and Schwartz, J.C., Radioimmunoassay of methionine-and leucine-enkephalins in regions of rat brain and comparison with endorphins estimated by a radio receptor assay, J. Neurochem., 31 (1978) 29–39.PubMedCrossRefGoogle Scholar
- 6.Hokfelt, T., Eide, R., Johansson, 0., Terenius, L. and Stein, L., The distribution of enkephalin immunoreactive cell bodies in the rat central nervous system, Neurosci. Letters, 5 (1977) 25–31.Google Scholar
- 10.Konig, J.F.R. and Klippel, R.A., The Rat Brain, Krieger, Huntington, New York, 1967.Google Scholar
- 12.Myers, R.D., An improved push-pull cannula system for perfusing an isolated region of the brain, Physiol. Behavior, 5 (1970) 243–246.Google Scholar