During the refractory period that follows ejaculation, the male rat regularly emits 22-kilohertz vocalizations. These cease after about three-fourths of the total period has elapsed, and this corresponds to an "absolute refractory period" during which the male cannot spontaneously initiate copulation. Similar 22-kilohertz vocalizations occur in other social contexts, and in general they appear to be desist-contact signals.

After ejaculation, the male rat emits an ultrasonic (22-kHz.) vocalization. This sound is produced repeatedly until about three fourths of the postejaculatory interval has elapsed. In this study, the occurrence of the vocalization was described, and physiological and behavioral evidence was presented that the postejaculatory vocalization reflects an inhibitory state that underlies the postejaculatory refractory period. The vocalization period was characterized by a predominance of slow-wave, spindling, sleep-like electroencephalographic activity. Electrical shock was able to stimulate mating responses only after the cessation of the vocalization period. It was concluded that an absolute refractory period of the postejaculatory interval lasts until the end of the vocalization period and that the time from the termination of the vocalization until the resumption of mating is a relative refractory period.

ULTRASONIC vocalisations commonly occur during social interactions among rodents. During mating, adult male and female rats (Rattus norvegicus) emit brief 50-60 kHz ultrasonic calls1; however, the function of these vocalisations is not known. In this study, we demonstrate that these mating calls have a precise function for communication. Specifically, 50-kHz vocalisations elicit sexual activity in female rats. Female rats exhibit a series of solicitation patterns during sexual behaviour, including orientation, darting and ear wiggling. These movements excite the male and enhance the likelihood of mounting, thereby facilitating copulation2-4. (Beach has emphasised the importance of solicitation by the female during mating and has suggested the term 'proceptivity' to include the female's behaviour in the initiation and maintenance of copulation.) Although the presence of an intact male is usually a prerequisite for solicitation behaviour, the specific sensory cues which elicit it are not known. Isolated oestrous female rats exposed to ultrasonic vocalisations from a male exhibited a shorter latency to, and higher rate of darting when subsequently placed in a mating situation5. Although the auditory cues primed oestrous females to display increased solicitation behaviour when later confronted with an intact male, there was no indication that these ultrasonic vocalisations had a direct function for communication in the induction of these behaviour patterns. The objective of the present report was to determine if ultrasonic mating calls of rats have a direct function for communication during copulation. © 1978 Nature Publishing Group.

Solitary estrous female Long-Evans rats were presented with ultrasonic vocalizations and/or urine of males to determine their effects on the females' subsequent copulatory behavior. Following exposure to ultrasounds, females exhibited a shorter latency to dart and a higher rate of darting when a male was presented. The vocalization effect was enhanced when male urine was present, but urine alone had no effect. The rate of copulation was also increased by the vocalization priming of the female. For a few individual females, ultrasounds elicited darting in the absence of a male. Results indicate that auditory cues, particularly in association with appropriate olfactory cues, prime estrous females for proceptive behavior. This increases both the likelihood and the rate of sexual performance and, therefore, the probability of successful mating. (17 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1978 American Psychological Association.