Hypocretin/Orexin Neurons Endogenously Regulate Somatic Motoneuron Excitability

• Main Author: Saleh, Asem
• Other Authors: Peever, John H.
• Language: en_ca
• Published: 2010
• Subjects: Hypocretin; 0317
• Online Access: http://hdl.handle.net/1807/25791

The role of hypocretin neurons in modulating somatic motoneuron excitability and hence muscle tone is poorly understood. We investigated whether hypocretin neurons influence the hypoglossal and trigeminal motor pools that innervate the genioglossus and masseter muscles respectively, both of which function to maintain upper airway patency. We hypothesized hypocretin neurons facilitate motor outflow at the motor pools. We pharmacologically manipulated hypocretin neuron activity in anaesthetized mice to determine their role in somatic motoneuron excitability. We also antagonized hypocretin receptors in the hypoglossal motor pool to determine the pathway through which hypocretin neurons influence motoneuron excitability. We demonstrated that hypocretin neurons potently excite somatic motoneurons and hence facilitate genioglossus and masseter muscle tone. Furthermore, we demonstrated that an endogenous hypocretinergic drive on somatic motoneurons facilitated muscle tone under anaesthesia. These studies demonstrate that hypocretin is an excitatory neuromodulator of muscle tone and contributes to the excitatory regulation of somatic motoneurons.