Me. Pedreira et al., CYCLOHEXIMIDE INHIBITS CONTEXT MEMORY AND LONG-TERM HABITUATION IN THE CRAB CHASMAGNATHUS, Pharmacology, biochemistry and behavior, 52(2), 1995, pp. 385-395
A shadow moving over head elicits an escape response in the crab Chasm
agnathus that habituates promptly and for a long period. The effect of
the protein synthesis inhibitor cycloheximide (CY) on this long-term
memory was analyzed. Two hours after injection, 10 mu g CY inhibited [
C-14]-amino acid incorporation into cerebral plus thoracic ganglia by
88% and 20 mu g by 92%, but no inhibition was found at 24 h. A single
injection of 10-20 mu g CY given 30 min before training, failed to aff
ect the short-term habituation. Similar doses impaired both context me
mory (CM) and long-term habituation (LTH) when tested at 72 and 120 h
but only CM at 24 h. Such a disparity was explained by an unspecific d
epressing effect upon the response, attributed to an interaction betwe
en CY and training. The hypothesis was confirmed, because CY injected
immediately after training disclosed amnestic effect at 24 h on both C
M and LTH. A similar effect was proven when animals were injected at 2
h but not at 6 h after training. Results from experiments with pretra
ining and pretesting injections put aside a state-dependence or retrie
val deficit effects of the drug. Taken together, findings of this arti
cle argue strongly for de novo protein synthesis as a mechanism of LTH
and for the close relation between CM and LTH.