Article date: September 2014
By: G H Zhang, Z L Liu, B J Zhang, W Y Geng, N N Song, W Zhou, Y X Cao, S Q Li, Z L Huang, L L Shen in Volume 171, Issue 18, pages 4233-4246
Background and Purpose
Orexins have been demonstrated to play important roles in many physiological processes. However, it is not known how orexin A affects the activity of the hypoglossal motoneuron (HMN) and genioglossus (GG) muscle.
Experimental Approach
GG muscle electromyograms (GG‐EMG) were recorded in anaesthetized adult rats after orexin A or orexin receptor antagonists were applied to the hypoglossal nucleus, and in adult rats in which orexin neurons were lesioned with the neurotoxin orexin‐saporin (orexin‐SAP). HMN membrane potential and firing were recorded from neonatal rat brain slices using whole‐cell patch clamp after an infusion of orexin A or orexin receptor antagonists.
Key Results
Unilateral micro‐injection of orexin A (50, 100 or 200 μM) into the hypoglossal nucleus significantly enhanced ipsilateral GG activity in adult rats. Orexin A (4, 20, 100 or 500 nM) depolarized the resting membrane potential and increased the firing rate of HMNs in a dose‐dependent manner in the medullary slices of neonatal rats. Both SB 334867, a specific OX1 receptor antagonist and TCS OX2 29, a specific OX2 receptor antagonist not only blocked the depolarized membrane potential and the increased firing rate of HMNs by orexin A in the neonatal model but also attenuated GG‐EMG in the adult model. A significant decrease in GG‐EMG was observed in adult orexin neuron‐lesioned rats compared with sham animals.
Conclusion and Implications
Orexin A activates OX1 and OX2 receptors within the hypoglossal motor pool and promotes GG activity, indicating that orexin A is involved in controlling respiratory motor activity.
DOI: 10.1111/bph.12784
View this article