Journal of Neuroscience, Vol 13, 2939-2945, Copyright © 1993 by Society for Neuroscience
Role of glucocorticoids in the cholinergic degeneration in rat hippocampus induced by ethylcholine aziridinium (AF64A)
H Hortnagl, ML Berger, L Havelec and O Hornykiewicz
Institute of Biochemical Pharmacology, University of Vienna, Austria.
Glucocorticoids potentiate hippocampal damage induced by various noxious
insults in vivo and in vitro and are implicated in age-related loss of
neurons in the hippocampus of various species. The cholinergic innervation
of the hippocampus appears to be especially prone to the endangering effect
of glucocorticoids, since corticosterone, like acute stress or ACTH,
induces a rapid activation of the cholinergic septo- hippocampal pathway.
We now report the influence of glucocorticoids on the degeneration of this
pathway induced by the cholinergic neurotoxin ethylcholine aziridinium
(AF64A). The toxic effect of a submaximal dose of AF64A on cholinergic
neurons was evaluated in rats during exposure to glucocorticoids or vehicle
as well as in adrenalectomized or sham- operated rats. Daily treatment with
either corticosterone or dexamethasone, starting 7 d before the bilateral
intracerebroventricular injection of AF64A (1 nmol/ventricle),
significantly increased the AF64A-induced loss of ChAT activity in the
whole hippocampus, whereas bilateral adrenalectomy 7 d prior to AF64A-
injection attenuated the effect of AF64A. Short-term exposure to
corticosterone starting 24 hr before AF64A was as effective as the 7 d
pretreatment. Dexamethasone exacerbated the AF64A-induced cholinergic
lesion in the hippocampal subregions CA1, CA3, and dentate gyrus, and
adrenalectomy protected all subregions against the action of AF64A. Along
the longitudinal axis of the hippocampus a comparable influence was seen in
the dorsal and ventral parts. The subregional pattern in the response to
glucocorticoid suggests the involvement of mineralocorticoid type I
receptors.(ABSTRACT TRUNCATED AT 250 WORDS)