Distinct classes of low frequency ultrasonic vocalizations in rats during sexual interactions relate to different emotional states

Acta Neurobiol Exp (Wars). 2019;79(1):1-12.

Abstract

This study examined low-frequency ultrasonic vocalizations (lUSVs) in rats during two types of sexual interactions; postejaculatory interval (PEI) and barrier - noncontact (NC) test. We report distinct classes of lUSVs that can be assigned to different emotional states; relaxation vs. frustration. Totally flat, 22-kHz calls (Class A), were observed during the relaxation state following ejaculation; characterized by immobilization or grooming during the PEI. On the other hand, two-three component lUSVs (Class B) that start at a higher frequency (45-kHz: flat, upward or short signal) and then shift to 35-23-kHz (mostly to 28-23-kHz), correspond as we assume, to arousal and frustration - active states associated with sniffing a hole or exploration during the NC test. We suggest that momentary, abrupt decreases of arousal during the frustration state correspond to Class B lUSVs. The detailed spectral analysis of the high-frequency component of two-component lUSVs is crucial for establishing the relationship between such lUSVs and the corresponding behavior and emotional states. Our studies indicate that while the two-component Class B 22-kHz lUSVs may relate to the frustration state, a single component, flat, Class A lUSV relates to the relaxation state. The results of these studies support a notion that rats emit distinct vocalization patterns, reflecting their emotional states.

MeSH terms

  • Animals
  • Emotions / physiology*
  • Exploratory Behavior / physiology
  • Female
  • Grooming / physiology
  • Immobility Response, Tonic / physiology
  • Male
  • Rats
  • Rats, Long-Evans
  • Sex Characteristics*
  • Sexual Behavior, Animal / physiology*
  • Ultrasonics*
  • Vocalization, Animal / physiology*