Rats emit a complex repertoire of 50-kHz ultrasonic vocalizations (USVs) during positive social and rewarding interactions, including rhythmic tactile stroking. These calls are increasingly recognized as reliable behavioral indicators of hedonic states and reward-related processing in the brain. While it is well established that the mesolimbic dopamine system, particularly the nucleus accumbens (NAc), plays a central role in mediating such vocalizations, the extent to which specific call subtypes are differentially regulated by dopaminergic transmission remains unclear.
This study examined how simultaneous antagonism of D1, D2, and D3 dopamine receptors in the NAc shell affects both the quantity and acoustic characteristics of 50-kHz USVs elicited by rhythmic hand stroking. Eight male Wistar/ST rats were implanted with bilateral guide cannulae targeting the NAc shell. After recovery, each animal underwent four experimental sessions across four consecutive days. On two of these days, animals received intracranial infusions of a combined solution containing SCH 23390 (500 ng/side, D1 antagonist) and raclopride (25 µg/side, D2/D3 antagonist). Control sessions involved vehicle infusion into the same site.
Stroking was administered for 30 seconds while the rat was held vertically, using gentle, repetitive palm strokes at approximately 1–1.5 Hz. USVs were recorded using a high-sensitivity microphone and analyzed using a detailed 14-subtype classification system developed by Wright et al., with special emphasis on harmonic flat calls and frequency-modulated (FM) types such as trill, complex, and step up. The results showed that DA receptor blockade significantly reduced the number of predominantly flat calls with harmonics during stimulation and diminished FM call production after stimulation. However, no significant changes were observed in mean peak frequency or call duration across conditions.
Importantly, flat calls without harmonics remained unchanged following drug administration, indicating that only specific subtypes are sensitive to dopaminergic modulation. The reduction in harmonic calls during stroking suggests their dependence on active dopaminergic signaling, possibly reflecting real-time positive affect. The suppression of post-stimulus FM calls further implies that dopamine supports the persistence of motivational states beyond the immediate stimulus.
These findings highlight a functional specificity in the regulation of 50-kHz USV subtypes by the NAc dopaminergic system. Harmonic and FM calls appear to be selectively governed by dopamine activity, whereas other acoustic features remain stable. This differential sensitivity supports the hypothesis that distinct neural circuits underlie the production of different call types—possibly reflecting separate emotional or communicative functions.2124-57-4 SMILES
Moreover, the lack of change in call amplitude and duration despite pharmacological intervention strengthens the validity of these parameters as robust indicators of affective state.58-05-9 References The stability of fundamental acoustic features suggests they may serve as baseline markers, while subtype-specific responses offer insight into dynamic neurochemical processes.PMID:30725891
In conclusion, this study demonstrates that the emission of certain 50-kHz USV subtypes—particularly those with harmonics and FM patterns—is highly dependent on intact dopaminergic transmission in the NAc shell. These findings underscore the importance of subtype-level analysis in ultrasonic vocalization research, enabling more precise investigation of the neurobiology of emotion, reward, and motivation. Future studies should explore how these patterns vary across developmental stages, social contexts, and disease models to further clarify their role in affective communication.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com
