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Adenosine A1 Receptor-Mediated Synaptic Depression in the Developing Hippocampal Area CA2
Douglas A Caruana1,2, Serena M Dudek2
1School of Life and Health Sciences, Aston University, Birmingham, United Kingdom.
Frontiers in Synaptic Neuroscience
|July 3, 2020
Summary
Adenosine A1 receptors (A1Rs) modulate synaptic transmission in the hippocampus. In young rats, A1R agonists depress CA2 and CA1 synapses, but this effect becomes CA2-specific in adults due to developmental changes in signaling pathways.
Area of Science:
- Neuroscience
- Receptor Pharmacology
- Synaptic Plasticity
Background:
- Adenosine A1 receptors (A1Rs) are highly expressed in the adult rat hippocampus, particularly in area CA2.
- A1R antagonists enhance synaptic responses in CA2, but this sensitivity is not present in young animals, suggesting developmental regulation beyond receptor distribution.
Purpose of the Study:
- To investigate the role of A1R-mediated postsynaptic signaling in synaptic transmission at Schaffer collateral inputs to CA2 and CA1.
- To elucidate the developmental changes underlying the differential sensitivity of CA2 synapses to A1R antagonists.
Main Methods:
- Electrophysiological recordings in rat hippocampal slices.
- Application of selective A1R agonists (CCPA), phosphodiesterase inhibitors (rolipram), and adenylyl cyclase activators (forskolin).
- Comparison of responses in juvenile (P14) and adult (P70) rats.
Main Results:
- A1R agonist CCPA induced lasting synaptic depression in both CA2 and CA1 in juvenile rats, but only in CA2 in adults.
- Phosphodiesterase inhibition (rolipram) blocked CCPA-induced depression in CA1 but not CA2.
- Adenylyl cyclase activation (forskolin) increased synaptic transmission in CA2 but had minimal effect in CA1.
Conclusions:
- A1R-mediated synaptic depression follows the postnatal development of A1R immunolabeling.
- Enhanced sensitivity to A1R antagonists in young CA2 is attributed to robust adenylyl cyclase activity and weak phosphodiesterase activity, not A1R enrichment.
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