Journal of Neuroscience, Vol 6, 644-649, Copyright © 1986 by Society for Neuroscience
Dynorphin- and enkephalin-like immunoreactivity is altered in limbic- basal ganglia regions of rat brain after repeated electroconvulsive shock
T Kanamatsu, JF McGinty, CL Mitchell and JS Hong
In an attempt to determine whether the opioid peptides derived from
prodynorphin participate in the effects of electroconvulsive shock (ECS),
we used radioimmunoassay and immunocytochemistry to measure dynorphin-like
immunoreactivity (DN-LI) in various rat brain regions after repeated ECS
treatments. Ten daily ECSs caused a significant increase in dynorphin A
(1-8)-LI in most limbic-basal ganglia structures, including hypothalamus
(50%), striatum (30%), and septum (30%). No significant change was found in
the frontal cortex or the neurointermediate lobe of the pituitary. In
contrast, 10 ECS treatments depleted DN-LI in hippocampal mossy fibers by
64%. A detailed time- course study revealed that a single shock caused a
small but significant increase in hippocampal DN-LI, whereas three
consecutive shocks depleted DN-LI by 30%. The maximal decrease in DN-LI was
reached after six daily ECSs. The level of DN-LI in the hippocampus partly
recovered, but remained lower than the control value 4, 7, and 14 d after
the cessation of six daily ECSs (50, 77, and 83% of control value,
respectively). In contrast with the ECS-induced depletion of hippocampal
dynorphin, 10 daily ECSs caused a significant increase (40%) in
(Met5)-enkephalin-LI in the hippocampus, as well as in other limbic-basal
ganglia structures. Immunocytochemistry revealed that enkephalin-LI was
increased in the perforant pathway, which is presynaptic to the
dynorphin-containing mossy fiber pathway in the hippocampus. These
observations suggest that different mechanisms may regulate these two
opioid peptide systems in the hippocampus.(ABSTRACT TRUNCATED AT 250 WORDS)