Associative learning down-regulates PKC beta 2- and gamma-immunoreactivity in astrocytes

Area of Science:

• Neuroscience
• Cell Biology
• Learning and Memory

Background:

• Previous research indicated associative learning increases protein kinase C gamma-immunoreactivity (PKC gamma-ir) in CA1 pyramidal neurons.
• Subicular neurons showed no change in PKC gamma-ir following associative learning.

Purpose of the Study:

• To investigate the impact of associative learning on protein kinase C (PKC)-positive astrocytes.
• To determine the numerical density of PKC-positive astrocytes in the CA1 region and subiculum of rabbits undergoing different conditioning protocols.

Main Methods:

• Rabbits were subjected to naive, pseudoconditioned, or trace eyeblink conditioning.
• The numerical density of PKC alpha-, beta 1-, beta 2-, and gamma-positive astrocytes was quantified in the CA1 region and subiculum.

Main Results:

• Associative learning caused a significant 70-80% reduction in PKC beta 2- and gamma-positive astrocytes within the CA1 region.
• No significant changes were observed in the number of PKC alpha- or beta 1-positive astrocytes in either the CA1 region or subiculum.
• A downregulation of PKC beta 2 and gamma in astrocytes was specific to the CA1 region and associated with associative learning.

Conclusions:

• Associative learning induces a specific downregulation of PKC beta 2 and gamma in a subset of CA1 astrocytes.
• These astrocytic changes occur concurrently with alterations in neuronal PKC gamma in the same brain region.
• The findings suggest a complex interplay between neuronal and astrocytic protein kinase C modulation during associative learning.