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Hippocampal Synaptic Expansion Induced by Spatial Experience in Rats Correlates with Improved Information Processing in the Hippocampus.

Carasatorre M, Ochoa-Alvarez A, Velázquez-Campos G, Lozano-Flores C, Ramírez-Amaya V, Díaz-Cintra SY - PLoS ONE (2015)

Bottom Line: The "catFISH" imaging method provided neurophysiological evidence that hippocampal pattern separation improved in animals treated as SC, and this improvement was even clearer in animals that experienced the WM training.By measuring the area occupied by synaptophysin staining in both the stratum oriens and the stratun lucidum of the distal CA3, we found evidence of structural synaptic plasticity that likely includes MF expansion.Finally, the measures of hippocampal network coding obtained with catFISH correlate significantly with the increased density of synaptophysin staining, strongly suggesting that structural synaptic plasticity in the hippocampus induced by the WM and SC experience is related to the improvement of spatial information processing in the hippocampus.

View Article: PubMed Central - PubMed

Affiliation: Department of "Neurobiología del Desarrollo y Neurofisiología, Instituto de Neurobiología", Universidad Nacional Autónoma de México, Querétaro, México.

ABSTRACT
Spatial water maze (WM) overtraining induces hippocampal mossy fiber (MF) expansion, and it has been suggested that spatial pattern separation depends on the MF pathway. We hypothesized that WM experience inducing MF expansion in rats would improve spatial pattern separation in the hippocampal network. We first tested this by using the the delayed non-matching to place task (DNMP), in animals that had been previously trained on the water maze (WM) and found that these animals, as well as animals treated as swim controls (SC), performed better than home cage control animals the DNMP task. The "catFISH" imaging method provided neurophysiological evidence that hippocampal pattern separation improved in animals treated as SC, and this improvement was even clearer in animals that experienced the WM training. Moreover, these behavioral treatments also enhance network reliability and improve partial pattern separation in CA1 and pattern completion in CA3. By measuring the area occupied by synaptophysin staining in both the stratum oriens and the stratun lucidum of the distal CA3, we found evidence of structural synaptic plasticity that likely includes MF expansion. Finally, the measures of hippocampal network coding obtained with catFISH correlate significantly with the increased density of synaptophysin staining, strongly suggesting that structural synaptic plasticity in the hippocampus induced by the WM and SC experience is related to the improvement of spatial information processing in the hippocampus.

No MeSH data available.


Related in: MedlinePlus

catFISH images from CA1 and CA3 from the different exploration procedures.Dorsal hippocampal tissue stained with fluorescent in situ hybridization (FISH) for Arc mRNA (in Red) revealed with Cy3 (Promega kit see Methods). Images were taken with the 40x/1.3 NA objective using a Zeiss LSM 510 or Zeiss LSM 710 confocal system with 2 different lasers either set to excite Cy3 (Arc) or SITOX-Green (Nuclear counterstaining in Green). All images were process with Image J and 40–55% of the stack was collapsed in 1 single image (using Z Project). Images then went through the median filter, using the exact same parameters for all (0.8 pixels). From A to D, the images were taken from the CA1 hippocampal network and from E to G, from the CA3 network. Images A and E were taken from a Cage control animal; B and F from an animal that underwent the AA double exploration; C and G from an animal that underwent the AA’ double exploration condition; and D and H from an animal that underwent the AB double exploration condition. Calibration bar (lower right) represents 100 μm.
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pone.0132676.g003: catFISH images from CA1 and CA3 from the different exploration procedures.Dorsal hippocampal tissue stained with fluorescent in situ hybridization (FISH) for Arc mRNA (in Red) revealed with Cy3 (Promega kit see Methods). Images were taken with the 40x/1.3 NA objective using a Zeiss LSM 510 or Zeiss LSM 710 confocal system with 2 different lasers either set to excite Cy3 (Arc) or SITOX-Green (Nuclear counterstaining in Green). All images were process with Image J and 40–55% of the stack was collapsed in 1 single image (using Z Project). Images then went through the median filter, using the exact same parameters for all (0.8 pixels). From A to D, the images were taken from the CA1 hippocampal network and from E to G, from the CA3 network. Images A and E were taken from a Cage control animal; B and F from an animal that underwent the AA double exploration; C and G from an animal that underwent the AA’ double exploration condition; and D and H from an animal that underwent the AB double exploration condition. Calibration bar (lower right) represents 100 μm.

Mentions: Image stacks from 4–6 optimally Arc-FISH-stained slides were acquired using a Zeiss LSM 510 confocal microscope (Zeiss, Mexico) with a 40×/1.3 NA oil immersion objective, using the 543-nm helium/neon laser to excite the CY3 signal, and the 488-nm argon laser to excite the Sytox green signal. Routinely, the confocal settings for the CY3 Arc signal were optimized to detect only the intranuclear and cytoplasmic staining, minimizing the noise by adjusting the laser power, the amplifier, and offset accordingly. These parameters were established on a tissue section from a cage control animal and were kept constant for imaging all other brain sections on the same slide. The pinhole, Z-sectioning interval, and gain settings were kept constant for all the imaging. About 34–50 optical Z-sections of ~0.3-μm thickness were obtained from the 20-μm-thick tissue for each CA1 and CA3 image stack (Fig 2B and 2C; Fig 3). Four image stacks were obtained from each brain region (CA1 and CA3) for a total of 8 images per section on the slide and, as mentioned before, a total of 4 to 6 optimally stained slides per block were imaged.


Hippocampal Synaptic Expansion Induced by Spatial Experience in Rats Correlates with Improved Information Processing in the Hippocampus.

Carasatorre M, Ochoa-Alvarez A, Velázquez-Campos G, Lozano-Flores C, Ramírez-Amaya V, Díaz-Cintra SY - PLoS ONE (2015)

catFISH images from CA1 and CA3 from the different exploration procedures.Dorsal hippocampal tissue stained with fluorescent in situ hybridization (FISH) for Arc mRNA (in Red) revealed with Cy3 (Promega kit see Methods). Images were taken with the 40x/1.3 NA objective using a Zeiss LSM 510 or Zeiss LSM 710 confocal system with 2 different lasers either set to excite Cy3 (Arc) or SITOX-Green (Nuclear counterstaining in Green). All images were process with Image J and 40–55% of the stack was collapsed in 1 single image (using Z Project). Images then went through the median filter, using the exact same parameters for all (0.8 pixels). From A to D, the images were taken from the CA1 hippocampal network and from E to G, from the CA3 network. Images A and E were taken from a Cage control animal; B and F from an animal that underwent the AA double exploration; C and G from an animal that underwent the AA’ double exploration condition; and D and H from an animal that underwent the AB double exploration condition. Calibration bar (lower right) represents 100 μm.
© Copyright Policy
Related In: Results  -  Collection

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pone.0132676.g003: catFISH images from CA1 and CA3 from the different exploration procedures.Dorsal hippocampal tissue stained with fluorescent in situ hybridization (FISH) for Arc mRNA (in Red) revealed with Cy3 (Promega kit see Methods). Images were taken with the 40x/1.3 NA objective using a Zeiss LSM 510 or Zeiss LSM 710 confocal system with 2 different lasers either set to excite Cy3 (Arc) or SITOX-Green (Nuclear counterstaining in Green). All images were process with Image J and 40–55% of the stack was collapsed in 1 single image (using Z Project). Images then went through the median filter, using the exact same parameters for all (0.8 pixels). From A to D, the images were taken from the CA1 hippocampal network and from E to G, from the CA3 network. Images A and E were taken from a Cage control animal; B and F from an animal that underwent the AA double exploration; C and G from an animal that underwent the AA’ double exploration condition; and D and H from an animal that underwent the AB double exploration condition. Calibration bar (lower right) represents 100 μm.
Mentions: Image stacks from 4–6 optimally Arc-FISH-stained slides were acquired using a Zeiss LSM 510 confocal microscope (Zeiss, Mexico) with a 40×/1.3 NA oil immersion objective, using the 543-nm helium/neon laser to excite the CY3 signal, and the 488-nm argon laser to excite the Sytox green signal. Routinely, the confocal settings for the CY3 Arc signal were optimized to detect only the intranuclear and cytoplasmic staining, minimizing the noise by adjusting the laser power, the amplifier, and offset accordingly. These parameters were established on a tissue section from a cage control animal and were kept constant for imaging all other brain sections on the same slide. The pinhole, Z-sectioning interval, and gain settings were kept constant for all the imaging. About 34–50 optical Z-sections of ~0.3-μm thickness were obtained from the 20-μm-thick tissue for each CA1 and CA3 image stack (Fig 2B and 2C; Fig 3). Four image stacks were obtained from each brain region (CA1 and CA3) for a total of 8 images per section on the slide and, as mentioned before, a total of 4 to 6 optimally stained slides per block were imaged.

Bottom Line: The "catFISH" imaging method provided neurophysiological evidence that hippocampal pattern separation improved in animals treated as SC, and this improvement was even clearer in animals that experienced the WM training.By measuring the area occupied by synaptophysin staining in both the stratum oriens and the stratun lucidum of the distal CA3, we found evidence of structural synaptic plasticity that likely includes MF expansion.Finally, the measures of hippocampal network coding obtained with catFISH correlate significantly with the increased density of synaptophysin staining, strongly suggesting that structural synaptic plasticity in the hippocampus induced by the WM and SC experience is related to the improvement of spatial information processing in the hippocampus.

View Article: PubMed Central - PubMed

Affiliation: Department of "Neurobiología del Desarrollo y Neurofisiología, Instituto de Neurobiología", Universidad Nacional Autónoma de México, Querétaro, México.

ABSTRACT
Spatial water maze (WM) overtraining induces hippocampal mossy fiber (MF) expansion, and it has been suggested that spatial pattern separation depends on the MF pathway. We hypothesized that WM experience inducing MF expansion in rats would improve spatial pattern separation in the hippocampal network. We first tested this by using the the delayed non-matching to place task (DNMP), in animals that had been previously trained on the water maze (WM) and found that these animals, as well as animals treated as swim controls (SC), performed better than home cage control animals the DNMP task. The "catFISH" imaging method provided neurophysiological evidence that hippocampal pattern separation improved in animals treated as SC, and this improvement was even clearer in animals that experienced the WM training. Moreover, these behavioral treatments also enhance network reliability and improve partial pattern separation in CA1 and pattern completion in CA3. By measuring the area occupied by synaptophysin staining in both the stratum oriens and the stratun lucidum of the distal CA3, we found evidence of structural synaptic plasticity that likely includes MF expansion. Finally, the measures of hippocampal network coding obtained with catFISH correlate significantly with the increased density of synaptophysin staining, strongly suggesting that structural synaptic plasticity in the hippocampus induced by the WM and SC experience is related to the improvement of spatial information processing in the hippocampus.

No MeSH data available.


Related in: MedlinePlus