High-frequency ultrasonic vocalizations index conditioned pharmacological reward in rats.
We have proposed that short (<0.5 s), high-frequency (approximately 50 kHz) ultrasonic vocalizations ("50-kHz USVs") index a positive affective state in adult rats, because they occur prior to rewarding social interactions (i.e., rough-and-tumble play, sex). To evaluate this hypothesis in the case of nonsocial stimuli, we examined whether rats would make increased 50-kHz USVs in places associated with the administration of rewarding pharmacological compounds [i.e., amphetamine (AMPH) and morphine (MORPH)]. In Experiment 1, rats made a greater percentage of 50-kHz USVs on the AMPH-paired side of a two-compartment chamber than on the vehicle-paired side, even after statistical correction for place preference. In Experiment 2, rats made a higher percentage of 50-kHz USVs on the MORPH-paired side than on the vehicle-paired side, despite nonsignificant place preference. These findings support the hypothesis that 50-kHz USVs mark a positive affective state in rats and introduce a novel and rapid marker of pharmacological reward.
Knutson
B
B
Laboratory of Clinical Studies, National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD 20892-1610, USA. knutson@odin.niaaa.nih.gov
Burgdorf
J
J
Panksepp
J
J
D000339:Affect / Q000187:drug effects*; D000661:Amphetamine / Q000494:pharmacology*; D000818:Animals; D001143:Arousal / Q000187:drug effects; D001245:Association Learning / Q000187:drug effects; D003214:Conditioning, Classical / Q000187:drug effects*; D005260:Female; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009042:Motivation; D051381:Rats; D020318:Rats, Long-Evans; D012919:Social Behavior; D012931:Social Environment; D013018:Sound Spectrography; D014465:Ultrasonics
D009020:Morphine; D000661:Amphetamine