A. Romano et al., ACUTE ADMINISTRATION OF A PERMEANT ANALOG OF CAMP AND A PHOSPHODIESTERASE INHIBITOR IMPROVE LONG-TERM HABITUATION IN THE CRAB CHASMAGNATHUS, Behavioural brain research, 75(1-2), 1996, pp. 119-125
A shadow passing overhead acts as a danger stimulus and elicits an esc
ape response in the crab Chasmagnathus that habituates promptly and fo
r a long period. Robust retention is shown at 24 h after 15 trials of
shadow presentation or at 120 h after 30 trials, but no significant re
tention is disclosed at 24 h after 5 trials or at 72 h after 15. A coc
ktail of the cAMP membrane permeable analog 8-(4-chlorophenylthio)-cAM
P (CPT-cAMP), plus the phosphodiesterase inhibitor isobutyl methylxant
hine (IBMX), was given by systemic administration. Pretraining injecti
on of the cocktail (25 or 50 mu M, 15 min before a 5-trial session) fa
iled to affect short-term habituation, but induced significant retenti
on when tested at 24 h. This facilitatory effect was not shown when a
lower dose (5 mu M) was used. A post-training injection of 25 mu M, im
mediately after a 5- or 15-trial session, induced retention when teste
d at 24 or 72 h, respectively. Thus, the administration of CPT-cAMP+IB
MX during acquisition of a habituated response or immediately after, i
mproves long-term habituation, a result supporting the view that an in
crease in the cAMP level is one of the steps in long-term memory conso
lidation.