title: Breeding for 50-kHz positive affective vocalization in rats.
abstract: Adolescent and adult rats exhibit at least two distinct ultrasonic vocalizations that reflect distinct emotional states. Rats exhibit 22-kHz calls during social defeat, drug withdrawal, as well as in anticipation of aversive events. In contrast, 50-kHz calls are exhibited in high rates during play behavior, mating, as well as in anticipation of rewarding events. The neurochemistry of 22-kHz and 50-kHz calls closely matches that of negative and positive emotional systems in humans, respectively. The aim of this study was to replicate and further evaluate selective breeding for 50-kHz vocalization, in preparation for the analysis of the genetic underpinnings of the 50-kHz ultrasonic vocalization (USV). Isolate housed adolescent rats (23-26 days old) received experimenter administered tactile stimulation (dubbed "tickling"), which mimicked the rat rough-and-tumble play behavior. This stimulation has previously been shown to elicit high levels of 50-kHz USVs and to be highly rewarding in isolate-housed animals. Each tickling session consisted of 4 cycles of 15 seconds stimulation followed by 15 seconds no stimulation for a total of 2 min, and was repeated once per day across 4 successive days. Rats were then selected for either High or Low levels of sonographically verified 50-kHz USVs in response to the stimulation, and a randomly selected line served as a control (Random group). Animals emitted both 22-kHz and 50-kHz types of calls. After 5 generations, animals in the High Line exhibited significantly more 50-kHz and fewer 22-kHz USVs than animals in the Low Line. Animals selected for low levels of 50-kHz calls showed marginally more 22-kHz USVs then randomly selected animals but did not differ in the rate of 50-kHz calls. These results extend our previous findings that laboratory rats could be bred for differential rates of sonographically verified 50-kHz USVs.
authors.affiliation: J.P. Scott Center for Neuroscience, Mind and Behavior Department of Psychology, Bowling Green State University, Bowling Green, OH 43403, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Burgdorf
authors.forename: Jaak
authors.initials: J
authors.lastname: Panksepp
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Brudzynski
authors.forename: Roger
authors.initials: R
authors.lastname: Kroes
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Moskal
mesh_terms: D000339:Affect; D000818:Animals; D001947:Breeding; D005260:Female; D008297:Male; D010812:Physical Stimulation; D051381:Rats; D020318:Rats, Long-Evans / Q000235:genetics / Q000523:psychology*; D014110:Touch; D014828:Vocalization, Animal