Male Sprague Dawley Rats use Deep Breaths for Ultrasonic Vocal Production

Abstract

Rodents are highly vocal organisms. Vocal production must integrate breathing movements and movements of the vocal organ. This study was designed to investigate the role of deep breaths, also known as sighing, for vocal production. Sighing is a physiologically necessary breathing behavior conserved across all mammals. In ten awake and spontaneously behaving male rats breathing and vocal behavior was monitored. A tracheal implant measured subglottal pressure. The implant was connected to a pressure transducer mounted to a rodent jacket. Animals were tethered and allowed to move freely in the home cage. Subglottal pressure and sound were simultaneously recorded during five different contexts: anesthetic sleep, rest, noxious stimuli, exposure to another male, and exposure to a female. On average, sighs were produced between 15 and 40 times per hour. Exposure to a female Sprague‐Dawley rat was the only context with a small but significant increase in the sighing rate. Vocal activity increased in three contexts (female, male, noxious stimulus). On average 24% of all sighs contained vocalizations during those contexts but the rate of vocal sighs increased with vocal activity. Those findings confirm that vocal sighs are not only a regular fixture of rodent vocal behavior, but that sighs are recruited for vocal production if vocal activity increases. Both 22 kHz and 50 kHz ultrasonic vocalizations were observed in deep breaths. Sometimes multiple vocalizations were produced during the same exhalation. Finally, the pressure signal of the inhalation phase was modified when a vocalization was produced in the subsequent exhalation. This suggests preparation leading up to vocal production. In sum, we show that awake and spontaneously behaving rats use deep breaths for vocal production, and we present evidence that vocal production uses multiple breathing patterns to generate vocal signals. These observations inform our understanding of the physiology of vocal production in mammals and illustrates the value of the rat as model system.Support or Funding InformationMidwestern University