Hypertension, Vol 4, 662-669, Copyright © 1982 by American Heart Association
Methionine enkephalinergic neuronal activity in cerebral nuclei of spontaneously hypertensive rats
K Nakamura and T Hayashi
The role of methionine enkephalin (ME) neurons in the development of
genetic hypertension in SHR is the subject of this study. Methionine
enkephalin-like immunoreactivity (MELI) and ME receptor binding (MERB)
levels were assayed quantitatively by microdensitometry of fluorescence
micrographs and autoradiographs of 85 cerebral nuclei and areas of both
young and adult spontaneously hypertensive rats (SHR). Normotensive Wistar
Kyoto rats (WKY) were used as controls. In young SHR, both MELI and MERB
levels were markedly higher in the n. dorsalis nervi vagi, n. amygdaloideus
medialis, and group of stria terminal nuclei than in those of young WKY,
while both levels were lower in the n. reticularis lateralis, n. corporis
mamillaris lateralis, and n. arcuatus. MELI levels in the tractus spinalis
nervi trigemini and MERB in the n. tractus spinalis nervi trigemini and
median eminence were also lower in young SHR, whereas MERB in the n.
amygdaloideus centralis was higher. Alteration in these nuclei was no
longer detectable in adult SHR. Whereas in adult SHR, both MELI and MERB
levels in the n. reticularis medialis were higher than those of adult WKY,
and MELI in the n. accumbens septi and MERB in the n. caudatus were also
higher, while MELI in the area lateralis hypothalami was lower than that in
adult WKY. The findings indicate that activation of ME neurons in the n.
dorsalis nervi vagi and limbic area and also a decrease in ME neuronal
activity in the area spinalis nervi trigemini, n. reticularis lateralis,
and n. arcuatus may be casually related to the development of hypertension
and hyperreactivity in SHR.