AJP - Endocrinology and Metabolism, Vol 258, Issue 5 E894-E897, Copyright © 1990 by American Physiological Society
Hippocampal glutamine synthetase: insensitivity to glucocorticoids and stress
G. C. Tombaugh and R. M. Sapolsky
Department of Biological Sciences, Stanford University, California 94305.
Glucocorticoids enhance the neurotoxic potential of several insults to the
rat hippocampus that involve overactivation of glutamatergic synapses.
These hormones also stimulate the synthesis of glutamine synthetase (GS) in
peripheral tissue. Because this enzyme helps regulate glutamate metabolism
in the central nervous system, glucocorticoid induction of GS in the brain
may underlie the observed synergy. We have measured GS activity in the
hippocampus and skeletal muscle (plantaris) of adult rats after bilateral
adrenalectomy (ADX), corticosterone (Cort) replacement, or stress. No
significant changes in GS were observed in hippocampal tissue, whereas
muscle GS was significantly elevated after Cort treatment or stress and was
reduced after ADX. These results suggest that Cort-induced shifts in GS
activity probably do not explain Cort neurotoxicity, although the
stress-induced rise in muscle GS may be relevant to certain types of
myopathy.
