Adenosine Signaling through A1 Receptors Inhibits Chemosensitive Neurons in the Retrotrapezoid Nucleus

Area of Science:

• Neuroscience
• Respiratory Physiology
• Cellular Signaling

Background:

• The retrotrapezoid nucleus (RTN) contains chemosensitive neurons crucial for respiratory control.
• Purinergic signaling, particularly involving adenosine, modulates RTN neuron activity.
• The precise mechanisms of adenosine's effects on RTN chemoreceptors are not fully understood.

Purpose of the Study:

• To investigate the effects of adenosine on chemosensitive RTN neurons.
• To elucidate the intrinsic and synaptic mechanisms underlying adenosine's modulation of RTN chemoreceptors.

Main Methods:

• Electrophysiological recordings (cell-attached and whole-cell voltage-clamp) from RTN neurons in brain slices.
• Application of adenosine and specific A1 receptor antagonists (DPCPX).
• Analysis of neuronal activity, potassium conductance, and excitatory/inhibitory postsynaptic currents (EPSCs/IPSCs).

Main Results:

• Adenosine (1 µM) inhibited RTN chemoreceptor activity through A1 receptor activation.
• Adenosine activated a G-protein-regulated inward-rectifier K+ (GIRK)-like conductance in chemosensitive RTN neurons.
• Adenosine reduced the frequency of EPSCs but not IPSCs, indicating presynaptic inhibition of excitatory input.

Conclusions:

• Adenosine inhibits chemosensitive RTN neurons via direct activation of A1 receptors and GIRK-like channels.
• Adenosine also suppresses excitatory synaptic transmission to RTN chemoreceptors.
• These findings clarify purinergic mechanisms regulating breathing control at the RTN level.