Massey AT, Lerner DK, Holmes GL, Scott RC, Hernan AE. ACTH
Prevents Deficits
in Fear Extinction Associated with Early Life Seizures.
Front Neurol. 2016 May
2;7:65.
Abstract
OBJECTIVE:
Early life seizures (ELS) are often associated with
cognitive and psychiatric comorbidities that are detrimental to quality of
life. In a rat model of ELS, we explored long-term cognitive outcomes in adult
rats. Using ACTH, an endogeneous HPA-axis hormone given to children with severe
epilepsy, we sought to prevent cognitive deficits. Through comparisons with
dexamethasone, we sought to dissociate the corticosteroid effects of ACTH from
other potential mechanisms of action.
RESULTS:
Although rats with a history of ELS were able to acquire a
conditioned fear learning paradigm and controls, these rats had significant
deficits in their ability to extinguish fearful memories. ACTH treatment did
not alter any seizure parameters but nevertheless was able to significantly
improve this fear extinction, while dexamethasone treatment during the same
period did not. This ACTH effect was specific for fear extinction deficits and
not for spatial learning deficits in a water maze. Additionally, ACTH did not
alter seizure latency or duration suggesting that cognitive and seizure
outcomes may be dissociable. Expression levels of melanocortin receptors, which
bind ACTH, were found to be significantly lower in animals that had experienced
ELS than in control animals, potentially implicating central melanocortin
receptor dysregulation in the effects of ELS, and suggesting a mechanism of
action for ACTH.
INTERPRETATION:
Taken together, these data suggest that early treatment with
ACTH can have significant long-term consequences for cognition in animals with
a history of ELS independently of seizure cessation and may act in part through
a CNS melanocortin receptor pathway.
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