Synaptic activity-independent persistent plasticity in endogenously active mammalian motoneurons

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Motor Control

Background:

• Synaptic plasticity in hippocampal, cerebellar, and cortical neurons underlies learning and memory.
• Persistent synaptic functional changes in mammalian motoneurons for motor behaviors remain largely uncharacterized.
• Hypoglossal (XII) motoneurons control tongue muscles crucial for upper airway function.

Purpose of the Study:

• To investigate adaptive changes in motoneuron synaptic function.
• To identify mechanisms of synaptic plasticity in hypoglossal motoneurons.
• To explore potential cellular mechanisms for long-term facilitation and obstructive sleep apnea.

Main Methods:

• Electrophysiological recordings in neonatal rodent hypoglossal motoneurons.
• Selective activation of postsynaptic serotonin type 2 (5-HT(2)) receptors.
• Pharmacological manipulation using metabotropic glutamate receptor antagonists.

Main Results:

• Episodic, but not continuous, 5-HT(2) receptor activation induced long-lasting increases in AMPA receptor-mediated currents in XII motoneurons.
• This plasticity enhanced XII nerve motor output and respiratory drive.
• Group-I metabotropic glutamate receptor antagonism blocked the induction of 5-HT-mediated plasticity.

Conclusions:

• Activity-independent postsynaptic serotonin-mediated plasticity occurs in hypoglossal motoneurons.
• This mechanism may underlie long-term facilitation and persistent increases in respiratory motor output.
• Findings offer a cellular basis for developing therapeutics for obstructive sleep apnea.