Figure 1.
Intra-LA infusions of garcinol impair training-related acetylation of histone H3 and fear memory consolidation.
(a) Schematic of the behavioral protocol. Rats were fear conditioned with three tone-shock pairings followed 1 hr later by intra-LA infusion of either vehicle (n = 7) or garcinol (500 ng/side; n = 7) and were sacrificed 30 min later. A third group did not receive conditioning and was infused with vehicle prior to sacrifice (n = 7). Separate groups of rats were fear conditioned with three tone-shock pairings followed 1 hr later by intra-LA infusion of either vehicle (n = 9) or garcinol (500 ng/side; n = 8) and tested for STM and LTM 3 and 21 hrs later, respectively. (b) Western blot analysis of acetylated and total (non-acetylated) histone H3 from LA homogenates from naïve (N)-Vehicle, fear conditioned (FC)-Vehicle and FC-Garcinol groups. * p<0.05 relative to FC-vehicle and N-Vehicle groups. Representative Western blots are depicted in the inset. (c) Mean (± SEM) percent freezing during the STM and LTM tests in vehicle and garcinol-infused groups. A third group is depicted that received infusion of either vehicle (n = 8) or garcinol (n = 6) 6 hrs following fear conditioning (‘delayed infusion’) followed by a LTM test 21 hrs later. (d) Cannula placements for rats infused with either vehicle (black circles) or garcinol (gray circles). *p<0.05 relative to vehicle-infused controls.
Figure 2.
Garcinol impairs retrieval-related acetylation of histone H3 in the LA and fear memory reconsolidation.
(a) Schematic of the behavioral protocol. Rats were fear conditioned with three tone-shock pairings. Twenty four hrs following training rats were given a memory reactivation session consisting of a single tone CS presentation followed 1 hr later by intra-LA infusions of vehicle (n = 8) or garcinol (500 ng/side; n = 7). All rats were sacrificed 30 min following infusion. A third group did not receive conditioning or retrieval testing and was infused with vehicle prior to sacrifice (n = 7). Separate groups of rats were fear conditioned followed 24 hr later by a memory reactivation session consisting of a single tone CS presentation followed 1 hr later by intra-LA infusion of vehicle (n = 9) or garcinol (500 ng/side; n = 8). Two additional groups of rats were given a ‘no-reactivation’ session followed by infusion of vehicle (n = 7) or garcinol (500 ng/side; n = 5). All rats were then tested for PR-STM and PR-LTM 3 and 21 hrs later, respectively. (b) Cannula placements for rats infused with either vehicle (black circles) or garcinol (gray circles). (c) Memory retrieval data for the Reactivated (R)-Garcinol and R-Vehicle groups used in the Western blotting experiments. *p<0.05 relative to the pre-CS period. (d) Western blot analysis of acetylated and total histone H3 from LA homogenates taken from Naïve (N)-vehicle, R-Vehicle and R-Garcinol groups. * p<0.05 relative to R-Vehicle and N-Vehicle groups. Representative Western blots are depicted in the inset. (e) Memory retrieval data for the Reactivated (R)-Garcinol and R-Vehicle groups in the behavioral experiments. *p<0.05 relative to the pre-CS period. (f) Mean (± SEM) percent freezing during the PR-STM and PR-LTM tests in R-Vehicle and R-Garcinol groups. A third group is depicted that received infusion of either vehicle (n = 9) or garcinol (n = 6) 6 hrs following retrieval (‘delayed infusion’) followed by a PR-LTM test 21 hrs later. *p<0.05 relative to vehicle-infused controls. (g) Memory retrieval data for the Non-reactivated (NR)-Garcinol and NR-Vehicle groups. (h) Mean (± SEM) percent freezing during the ‘PR’-STM and ‘PR’-LTM tests in NR-Vehicle and NR-Garcinol groups.
Figure 3.
The effect of garcinol on fear memory reconsolidation is not sensitive to spontaneous recovery, reinstatement, or to a shift in testing context.
(a) Schematic of the behavioral protocol (see text for details). (b) Memory retrieval data for rats given intra-LA infusion of vehicle (n = 6) or garcinol (n = 6). *p<0.05 relative to the pre-CS period. (c) Mean (± SEM) percent freezing during the PR-STM and PR-LTM tests in vehicle and garcinol-infused rats. *p<0.05 relative to vehicle-infused controls. (d) Mean (± SEM) percent freezing during the spontaneous recovery, reinstatement, and context shift tests. (e) Cannula placements for rats infused with either vehicle (black circles) or garcinol (gray circles). *p<0.05 relative to vehicle-infused controls.
Figure 4.
Intra-LA infusion of garcinol impairs the reconsolidation of a ‘well-consolidated’ fear memory.
(a) Rats were fear conditioned with three tone-shock pairings. Two weeks following training rats were given a memory reactivation session consisting of a single tone CS presentation followed 1 hr later by intra-LA infusion of vehicle (n = 5) or garcinol (500 ng/side; n = 6). (b) Memory retrieval data for the vehicle and garcinol-infused groups. *p<0.05 relative to the pre-CS period. (c) Mean (± SEM) percent freezing during the PR-STM and PR-LTM tests in vehicle and garcinol-infused rats. (d) Cannula placements for rats infused with either vehicle (black circles) or garcinol (gray circles). *p<0.05 relative to vehicle-infused controls.
Figure 5.
Intra-LA infusion of garcinol impairs fear memory consolidation and the consolidation of training-related neural plasticity in the LA.
(a) Rats were given two baseline AEFP recording sessions on separate days followed by fear conditioning with three tone-pip-shock pairings followed 1 hr later by intra-LA infusion of either vehicle (n = 8) or garcinol (500 ng/side; n = 7). Rats in each group were then tested for STM and LTM 3 and 21 hrs later while AEFPs were recorded from the LA. (b) Mean (± SEM) percent freezing during the STM and LTM tests in vehicle and garcinol-infused groups. (c) Mean (± SEM) percent of change in AEFP amplitude during the STM and LTM tests in vehicle and garcinol-infused rats, relative to baseline. *p<0.05 relative to vehicle-infused controls. (d) Representative AEFPs recorded from the LA for each group during baseline (light gray trace), STM and LTM sessions (darker traces). Scale bar = 10 µV, 5 ms. (e) Electrode placements for rats infused with either vehicle (black circles) or garcinol (gray circles).
Figure 6.
Intra-LA infusion of garcinol impairs fear memory reconsolidation and memory-related neural plasticity in the LA.
(a) Rats were given two baseline AEFP recording sessions on separate days followed by fear conditioning with three tone-pip-shock pairings. Twenty four hrs following training rats were given a memory reactivation session consisting of a single tone-pip CS presentation followed 1 hr later by intra-LA infusions of vehicle (n = 5) or garcinol (500 ng/side; n = 7). Rats in each group were then tested for PR-STM and PR-LTM 3 and 21 hrs later while AEFPs were recorded from the LA. (b) Memory retrieval data for the vehicle and garcinol-infused groups. *p<0.05 relative to the pre-CS period. (c) Mean (± SEM) percent freezing during the PR-STM and PR-LTM tests in vehicle and garcinol-infused groups. (d) Mean (± SEM) percent of change in AEFP amplitude during the PR-STM and PR-LTM tests in vehicle and garcinol-infused rats, relative to baseline. *p<0.05 relative to vehicle-infused controls. (e) Representative AEFPs recorded from the LA for each group during baseline (light gray trace), PR-STM and PR-LTM sessions (darker traces). Scale bar = 10 µV, 5 ms. (f) Electrode placements for rats infused with either vehicle (black circles) or garcinol (gray circles).
Figure 7.
Intra-LA infusion of garcinol in the absence of fear memory retrieval has no effect on fear memory reconsolidation or memory-related neural plasticity in the LA.
(a) Rats were given two baseline AEFP recording sessions on separate days followed by fear conditioning with three tone-pip-shock pairings. Twenty four hrs following training rats were given a ‘no-reactivation’ session followed by infusion of vehicle (n = 7) or garcinol (500 ng/side; n = 6). Rats in each group were then tested for ‘PR’-STM and ‘PR’-LTM 3 and 21 hrs later while AEFPs were recorded from the LA. (b) Memory retrieval data for the vehicle and garcinol-infused groups. (c) Mean (± SEM) percent freezing during the ‘PR’-STM and ‘PR’-LTM tests in vehicle and garcinol-infused groups. (d) Mean (± SEM) percent of change in AEFP amplitude during the ‘PR’-STM and ‘PR’-LTM tests in vehicle and garcinol-infused rats, relative to baseline. *p<0.05 relative to vehicle-infused controls. (e) Representative AEFPs recorded from the LA for each group during baseline (light gray trace), ‘PR’-STM and ‘PR’-LTM sessions (darker traces). Scale bar = 10 µV, 5 ms. (f) Electrode placements for rats infused with either vehicle (black circles) or garcinol (gray circles).
Figure 8.
Systemic injection of garcinol impairs the consolidation and reconsolidation of a fear memory.
(a) Schematic of the behavioral protocol. In the consolidation experiment, rats were fear conditioned with two tone-shock pairings followed 30 min later by i.p. injection of either garcinol (10 mg/kg; n = 8) or vehicle (n = 8). STM was examined 3 hrs later and LTM 21 hrs following injections. In the reconsolidation experiment, rats were fear conditioned with two tone-shock pairings followed 24 hrs later by fear memory reactivation session and i.p. injection of either garcinol (R-Garcinol; n = 9) or vehicle (R-Vehicle; n = 9). A third group received garcinol following a no-reactivation control session (NR-Garcinol; n = 8). All rats received tests of PR-STM and PR-LTM 3 hrs and 21 hrs after injections, respectively. (b) Mean (± SEM) percent freezing during the STM and LTM tests in vehicle and garcinol-infused groups in the consolidation experiment. * p<0.05 relative to vehicle group. (c) Memory retrieval data for the R-Vehicle, R-Garcinol, and NR-Garcinol groups in the reconsolidation experiment. *p<0.05 relative to the pre-CS period. (d) Mean (± SEM) percent freezing during the PR-STM and PR-LTM tests in R-Vehicle, R-Garcinol, and NR-Garcinol groups. *p<0.05 relative to vehicle-infused controls.