Response of the Cricothyroid and Thyroarytenoid Muscles to Stereotactic Injection of Substance P into the Region of the Nucleus Tractus Solitarius in Developing Dogs

• Published in: Annals of otology, rhinology & laryngology Vol. 109; no. 12; pp. 1150 - 1156
• Main Authors: Bauman, Nancy M., Sandler, Anthony D., Wang, DeQiang, Luschei, Erich S.
• Format: Journal Article
• Language: English
• Published: Los Angeles, CA SAGE Publications 01.12.2000; Annals Publishing Compagny
• Subjects: Age Factors; Animals; Biological and medical sciences; Disease Models, Animal; Dogs; Electromyography; Ent. Stomatology; Humans; Infant, Newborn; Laryngeal Muscles - drug effects; Laryngeal Muscles - growth & development; Laryngismus - chemically induced; Laryngismus - diagnosis; Laryngismus - physiopathology; Medical sciences; Motor Activity - drug effects; Muscle Development; Non tumoral diseases; Otorhinolaryngology. Stomatology; Pharmacology. Drug treatments; Solitary Nucleus - drug effects; Stereotaxic Techniques - instrumentation; Substance P - administration & dosage; Substance P - adverse effects; Substance P - physiology; Sudden Infant Death - etiology; Upper respiratory tract, upper alimentary tract, paranasal sinuses, salivary glands: diseases, semeiology; cricothyroid muscle; thyroarytenoid muscle; electromyography; laryngospasm; nucleus tractus solitarius; substance P; dog; Fissipedia; Carnivora; Substance P; Cricothyroid muscle; Injection; Experimental study; Electrodiagnosis; Vertebrata; Chemotherapy; Mammalia; Treatment; Animal; Spasm; ENT disease; Electromyography; Larynx; Larynx disease; Biological effect; Dog
• ISSN: 0003-4894; 1943-572X
• DOI: 10.1177/000348940010901213

Substance P (SP), a putative sensory neurotransmitter, mediates reflex laryngeal adductor activity in developing dogs. Such reflex activity includes life-threatening laryngospasm induced by stimulation of distal esophageal afferent nerves. The site of SP's activity is unknown. This research was undertaken to determine whether injection of SP into the nucleus tractus solitarius (NTS) of developing beagles alters laryngeal adductor motor activity. Six animals, 57 to 78 days of age, underwent stereotactic injection of 5 to 10 μL of SP into the region of the NTS, identified by electrical stimulation of the ipsilateral superior laryngeal nerve. In 8 additional studies, SP was injected into the cerebellum (2) or brain stem (6) distant from the NTS. Cardiovascular and electromyographic (EMG) responses of the diaphragm and the cricothyroid (CT) and/or thyroarytenoid (TA) muscles were recorded in all 6 animals. Injection of SP into the region of the NTS induced a decrease in blood pressure in all animals and an increase in either ipsilateral CT or TA activity. Three of these animals experienced mixed apnea characterized by sustained EMG activity (spasm) of the ipsilateral CT or TA muscles and an absence of diaphragm EMG activity. The apnea event was fatal in 1 of these animals. In the 6 animals who underwent injections in the brain stem but outside the region of the NTS, diaphragm and laryngeal EMG activity generally did not change after injection of SP, with the exception of 1 animal who experienced a mild, short-lived increase in ipsilateral CT activity. A brief phasic increase in ipsilateral CT activity was seen in both animals who underwent injection of SP into the cerebellum. A putative sensory neurotransmitter, SP evokes ipsilateral CT and/or TA EMG activity when injected into the region of the NTS in developing beagle dogs. This research suggests that SP in the NTS may play a role in mediating life-threatening laryngeal adductor reflexes in developing mammals and may provide important information regarding therapeutic intervention.