Effect of blocking muscarinic receptors using atropine on thyroarytenoid muscle recruitment during swallow and breathing

Abstract

Atropine, a muscarinic acetylcholine receptor antagonist, is a commonly used drug to reduce mucous production during surgery. Because atropine blocks the parasympathetic action of acetylcholine, atropine may modulate the balance of parasympathetic and sympathetic activity. In jaw muscles, increased sympathetic drive decreases muscle contractility and reduces muscle spindle feedback. There is evidence for sympathetic innervation of laryngeal muscles, however, few studies have investigated the effects of changing sympathetic drive to laryngeal muscle recruitment during specific behaviors. As such we hypothesized that blocking parasympathetic activation would attenuate laryngeal muscle drive during swallow and breathing. To investigate, we blocked muscarinic receptors via IV infusion of atropine in a dose dependent manner (0.02, 0.07, 0.2, 0.7, 2.0, 7.0 mg/kg). Using steel wire electrodes, bipolar electromyography (EMG) recordings were made in upper airway muscles (mylohyoid, geniohyoid, thyroarytenoid and thyropharyngeus) and the costal diaphragm in Sprague Dawley rats. Swallow was induced by administering 1cc of water into the oral pharynx via syringe. Duration and amplitude of thyroarytenoid (ThAr) activity was measured during breathing and swallow for each concentration of atropine. There was a differential effect of thyroarytenoid EMG activity with a significant reduction during swallow with no change in drive during breathing. Additionally, there was no significant change in number of elicited swallows. These results suggest attenuation of parasympathetic activity on laryngeal muscles may differentially change motor recruitment during specific behaviors such as swallow and breathing.Support or Funding InformationThis work was supported by NIH grants HL 111215, HL 103415 and OT20D001983, the Craig F. Neilson Foundation Pilot Research Grant 546714, Kentucky Spinal Cord and Head Injury Research Trust, and the Commonwealth of Kentucky Challenge for Excellence.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.