Central control of ultrasonic vocalizations in neonatal rats: I. Brain stem motor nuclei.

Abstract

Neonatal rats produce ultrasonic vocalizations in response to cold stress. The rate and intensity of these vocalizations decrease dramatically as the pup reaches maturity. The laryngeal nerves controlling the production of ultrasounds and their nuclei of origin were investigated in 10-day-old rat pups. Unilateral and bilateral transections of the inferior laryngeal nerve reduced ultrasounds to undetectable levels. Transecting the superior laryngeal nerve either unilaterally or bilaterally reduced the sound pressure level, reduced the rate, and increased the fundamental frequency of the ultrasounds. Retrograde transport of horseradish peroxidase revealed that the efferent axonb in the inferior laryngeal nerve arise from the cells of the dorsal formation of the nucleus ambiguus and that efferents in the superior laryngeal nerve originate from the ventral formation of the nucleus ambiguus. Therefore, different aspects of the production of pup ultrasounds appear to be controlled by distinct neuronal subpopulations of the nucleus ambiguus.

Comparative Study on Isolation Calls Emitted from Hamster Pups.

“…On the other hand, the emission of USVs is related to the inferior laryngeal nerves, and inhibited by the section of inferior laryngeal nerves [12,19]. The inferior laryngeal nerves are branched from the vagus [18,19]. From these findings, the emission of USVs might be influenced by the activity of the autonomic nerve.…”

“…The BAT thermogenesis can be activated by cold stress via the sympathetic nervous system [9]. On the other hand, the emission of USVs is related to the inferior laryngeal nerves, and inhibited by the section of inferior laryngeal nerves [12,19]. The inferior laryngeal nerves are branched from the vagus [18,19].…”

Ultrasonic output from the excised rat larynx

“…6,8 However, it has also been reported that unilateral laryngeal denervation has no effect on the intensity, duration, or frequency of USV of adult rats. 9 These conflicting reports may be due to differences in the a͒ Author to whom correspondence should be addressed.…”

“…Therefore, it is unclear if USVs are created by a constriction at the larynx or some other location in the upper airway. While results of prior laryngeal denervation studies implicate the larynx as the site of this constriction, 6,8 direct observation of the larynx during USV production would provide more compelling evidence for the larynx as the source of USVs. Although endoscopic procedures for in vivo observation of the rat larynx have been developed, 10 these methods cannot be used to visualize laryngeal movement in the awake rat.…”

Ontogenetic Changes of Ultrasonic Vocalizations Emitted from Infant Rats

“…USV emission occurs as air passes through the constricted plate of the larynx [13]. BAT activity, which is induced by cold stress, is controlled by the autonomic nervous system [10,15], the development of which is promoted by thyroid hormones in infant rats [7]. Therefore, the increased incidences and ontogenetic changes of USVs from day 0 to day 3 might depend on the development of the laryngeal nerve in the nervous system.…”