Story Transcript
MECANISMOS MOLECULARES DE LA RECONSOLIDACIÓN Y LA EXTINCIÓN
Consolidación celular / molecular Activación y reactivación de la memoria Reconsolidación Extinción en memorias asociativas y posible participación de mecanismos tipo LTD
Contextual memory retieval may induce either RECONSOLIDATION or EXTINCTION depending on the length of context re-exposure Behavioral output
Retrieval by short reexposure (5 min)
Retrieval by prolonged reexposure (30 min)
reconsolidation
extinction
Original memory
Extinction memory
Testing session
Untrained or Amnesic Animal
Trained Animal
La extinción is una inhibición temporaria del comportamiento de freezing
La recuperación expontánea ocurre algunos días después
Miedo Condicionado (fear conditioning)
Tanto la reconsolidación como la extinción dependen de la síntesis de novo de proteínas durante un período crítico Contextual fear conditioning Inyección de anisomicina
Suzuki et al., 2004
Tanto la reconsolidación como la extinción dependen de la síntesis de novo de proteínas durante un período crítico Contextual fear conditioning Inyección de anisomicina
Suzuki et al., 2004
Reconsolidación: ¿Cómo se labiliza la memoria reactivada? ¿Cómo se re-estabiliza? Extinción: ¿La consolidación de la extinción es un proceso igual o similar al de la memoria original? ¿Es un nuevo circuito que inhibe temporariamente la expresión del original? ¿Es un debilitamiento temporario del mismo circuito? ¿Ambas cosas?
¿Cuál es el mecanismo que determina si la memoria va a reconsolidación o extinción después de la evocación?
1- NF-kB en la consolidación
Curso temporal de la actividad de NF-kB en el hipocampo durante la consolidación
NF-B Inhibition by B Decoy DNA Intrahipocampal injection of ds DNA oligonucleotide containing the NF-B consensus sequence : B Decoy : 5’-GAGGGGACTTTCCCA-3’ -CTCCCCTGAAAGGGTmutated B Decoy : 5’-GAGGCGACTTTCCCA-3’ -CTCCGCTGAAAGGGT-
Fluorescein - B Decoy entra en las neuronas 15 min después de la inyeción
B Decoy, pero no mDecoy, inhibe NF-B
Boccia et al., J. Neurosci., 2007
La inhibición de NF-B en el hipocampo impide la consolidation de la memoria
2- NF-kB en la reconsolidación
Actividad de NF-B durante la reconsolidación
***
*
de la Fuente et al, J. Neurosci. 2011
R
La inhibición de NF-B en el hipocampo impide la reconsolidación
de la Fuente et al, J. Neurosci. 2011
NoR
La inhibición de NF-kB no impide la “short-term reactivated memory”
3- NF-kB en la extinción
La inhibición de NF-B en el hipocampo retarda la recuperación expontánea E
NoE
de la Fuente et al, J. Neurosci. 2011
Curso temporal de la actividad de NF-B en el hipocampo durante y después de la extinción
de la Fuente et al, J. Neurosci. 2011
Evidencias previas sugieren que la fosfatasa calcineurina está involucrada en la extinción
La calcineurina es activada por Ca2+ - Calmodulina
P
Phosphatase activity
La calcineurina está presente en espinas dendriticas
Evidencias previas
Evidencias previas
Lin et al., J. Neurosci., 2003
Postulamos que calcineurina está involucrada en el hipocampo en la memoria de extinción
La inhibición de calcineurina por el FK506 impide la extinción
E
NoE
de la Fuente et al, J. Neurosci. 2011
La inhibición de calcineurina no impide la reconsolidación
Hipothesis: durante la re-exposición prolongada (extinction) la calcineurina es activada y bloquea la activación de NF-B
La inhibición de calcineurina permite la activación de NF-B después de la extinción (como si fuera reconsolidación)
de la Fuente et al, J. Neurosci. 2011
Hay un target nuclear de calcineurina para la memoria de extinción?
Calcineurin – NFAT pathway NFAT es un factor de transcripción evolutivamente relacionado with NF-B
La inhibición de NFAT impide la extinción
E
NoE
de la Fuente et al, J. Neurosci. 2011
La inhibición de NFAT no impide la reconsolidación
Calcineurin y NFAT translocan al nucleo 45 min después de la sesión de extinction
de la Fuente et al, J. Neurosci. 2011
La inhibición de calcineurina impide la translocación de NFAT FK/DMSO
de la Fuente et al, J. Neurosci. 2011
Transcription factor switch between reconsolidation and extinction The transcription factor NF-kB is activated 15 min after a brief reexposure to the training context, and induces its target genes expression. This brief stimulus leads to reconsolidation. In contrast, if the stimulus is prolonged, phosphatase CaN is activated and blocks NF-kB activation. CaN also activates NFAT transcription factor by direct dephosphorylation. This, in turn, would activate its target genes expression. CaN and NFAT translocate to the nucleus as a complex, thus impeding the NFAT rephosphorylation. In this case, extinction of memory takes place.
Reconsolidation and extinction are dissociable and mutually exclusive processes: behavioral and molecular evidence. Merlo E1, Milton AL, Goozée ZY, Theobald DE, Everitt BJ. J. Neurosci 2014
At training, rats received two CS–US pairings. Twenty-four hours later, the animals were re-exposed to 1 or 10 CSs to reactivate or extinguish the fear memory (n = 8 per group). The following day at the retention test, all the animals were presented with one CS.C, The same behavioral procedure , but with the inclusion of a non-reactivated Ctr group that was trained identically to the 1CS and 10CS groups but during the re-exposure session remained in the home cage. Twenty (pERK1/2) or 60 (CaN) minutes after re-exposure, or straight from the home cage (Ctr groups), animals were killed and the cytoplasmic protein extracts from the BLA obtained (all groups, n= 8). D, E, Representative Western blot results and analysis showing the cytosolic levels of pERK1/2 (D) or CaN (E) after 1 or 10 CS presentations. Data are presented as means ± SEM. *p < 0.05, **p < 0.01.
Reconsolidation and extinction are dissociable and mutually exclusive processes: behavioral and molecular evidence. Merlo E1, Milton AL, Goozée ZY, Theobald DE, Everitt BJ. J. Neurosci 2014
A CaN increase induced by 10 CSs is required for consolidation of the fear extinction memory. A, Animals with fully consolidated fear memory received microinfusions of ASO or Scr ODN sequences in the BLA (see Fig. 2) 2.5 h before the presentation of 1 CS (n = 10 per group) or 10 CSs (Scr ODN, n = 10; ASO, n = 8). Four days later, all groups were tested for long-term fear or extinction memory retention by the presentation of one CS. *p < 0.005. B, Animals with fully consolidated fear memory were microinfused with ASO (n = 5) or Scr ODN (n = 4) 2.5 h before 10 CS presentations. One hour after the 10 CS presentations, they were killed and the BLA cytoplasmic extract was obtained. A representative result of the Western blot analysis along with the quantification of CaN levels in the BLA is shown. Data are presented as means ± SEM. *p < 0.05.
Reconsolidation and extinction are dissociable and mutually exclusive processes: behavioral and molecular evidence. Merlo E1, Milton AL, Goozée ZY, Theobald DE, Everitt BJ. J. Neurosci 2014
NMDAR agonist and antagonist treatments differentially affect the behavioral transition between reconsolidation and extinction. A, Experimental design. One day after training, the rats received an intraperitoneal injection of the NMDAR partial agonist DCS (15 mg/kg) or the antagonist MK-801 (0.1 mg/kg). B–E, One quarter of each group received 1 CS (B), 4 CS (C), 7 CS (D), or 10 CS (E) presentations (line graphs). Twenty-four hours later, freezing behavior was measured in all groups by the presentation of one CS (bar graphs). Data are presented as means ± SEM. MK-801 groups: 1 CS, n = 12; 4 CSs, n = 9; 7 CSs, n = 9; and 10 CSs, n = 11. DCS groups: 1 CS, n = 7; 4 CSs, n = 8; 7 CS, n = 8; and 10 CSs, n = 8. *p < 0.05, **p < 0.01.
Models of the transition from reconsolidation to extinction of fear memories. A, Gradual model. B, Step function model. C, Three-phase model. R, Reconsolidation process; E, extinction process; y-axis, sensitivity to NMDAR activity manipulations; x-axis, number of CS presentations.