Sex differences in the influence of social context, salient social stimulation and amphetamine on ultrasonic vocalizations in prairie voles

Prairie voles(Microtus ochrogaster)are a socially monogamous rodent species and their cooperative behaviors require extensive communication between conspecifics.Rodents use ultrasonic vocalizations(USVs)to com­municate and because a prairie vole breeder pair must engage in extensive cooperation for successful repro­duction,auditory communication may be critical for this species.Therefore,we sought to characterize USVs in adult male and female prairie voles,and to determine how these calls are influenced by social context,salient social stimuli and the psychostimulant drug of abuse amphetamine(AMPH).Here,we characterize prairie vole USVs by showing the range of frequencies of prairie vole USVs,the proportion of various call types,how these call types compare between males and females,and how they are influenced by social stimulation and AMPH.AMPH caused a robust increase in the number of USVs in both males and females and there was a dramatic sex difference in the complexity of call structures of AMPH-induced USVs,with males emitting more elaborate calls.Moreover,we show that novel(i.e.salient)social cues evoked differential increases in USVs across sex,with males showing a much more robust increase in USV production,both with respect to the frequency and complexity of USV production.Exposure to an estrous female in particular caused an extraordinary increase in USVs in male subjects.These data suggest that USVs may be a useful measure of social motivation in this spe­cies,including how social behaviors can be impacted by drugs of abuse.

Species recognition and the divergences in the chemical and ultrasonic signals between two coexisting Rattus species

The ability to recognize and differentiate between conspecifics and heterospecifics as well as their signals is critical for the coexistence of closely related species.In the genus Rattus,species are morphologically similar and multiple species often coexist.Here,we investigated the interspecific recognition and signal differentiation of two sympatric rat species,the brown rat(Rattus norvegicus,RN)and the Asian house rat(Rattus tanezumi,RT).In a two-way choice test,both RN and RT females showed a preference for conspecific male rats to heterospecific ones.RT females showed a significant preference for accessible urine of males of same species to those of other species,but not for the inaccessi-ble urine.On the other hand,there were significant differences in the structural characteristics of the ultrasonic vocalization emitted by males of these two rat species.Sodium dodecyl sulphate-polyacrylamide gel electrophoresis(SDS-PAGE)and isoelectric focusing electrophoresis unveiled that major urinary proteins(MUPs)in voided urine were more highly expressed in RN males versus RT males.The interspecific dif-ferences of urinary volatile compounds were also discussed.In conclusion,female rats had the ability to distinguish between males of either species.

Acoustic complexity of pup isolation calls in Mongolian hamsters: 3-frequency phenomena and chaos

Studying pup isolation calls of wild rodents provides background for developing new early-life animal models for biomedical research and drug testing.This study discovered a highly complex acoustic phenotype of pup isolation calls in 4–5-day-old Mongolian hamsters Allocricetulus curtatus.We analyzed the acoustic structure of 5,010 isolation calls emitted in the broad range of frequencies(sonic,below 20 kHz,and ultrasonic,from 20 to 128 kHz)by 23 pups during 2-min isolation test trials,1 trial per pup.In addition,we measured 5 body size parameters and the body weight of each pup.The calls could contain up to 3 independent fundamental frequencies in their spectra,the low(f0),the medium(g0),and the high(h0),or purely consisted of chaos in which the fundamental frequency could not be tracked.By presence/absence of the 3 fundamental frequencies or their combinations and chaos,we classifed calls into 6 distinctive categories(low-frequency[LF]-f0,LF-chaos,high-frequency[HF]-g0,HF-h0,HF-g0+h0,and HF-chaos)and estimated the relative abundance of calls in each category.Between categories,we compared acoustic parameters and estimated their relationship with pup body size index.We discuss the results of this study with data on the acoustics of pup isolation calls reported for other species of rodents.We conclude that such high complexity of Mongolian hamster pup isolation calls is unusual for rodents.Decreased acoustic complexity serves as a good indicator of autism spectrum disorders in knockout mouse models,which makes knockout hamster models prospective new wild animal model of neurodevelopmental disorders.

Medial Preoptic Area Modulates Courtship Ultrasonic Vocalization in Adult Male Mice

Adult male mice emit highly complex ultrasonic vocalizations(USVs)in response to female conspecifics.Such US Vs,thought to facilitate courtship behaviors,are routinely measured as a behavioral index in mouse models of neurodevelopmental and psychiatric disorders such as autism.While the regulation of US Vs by genetic factors has been extensively characterized,the neural mechanisms that control USV production remain largely unknown.Here,we report that optogenetic activation of the medial preoptic area(mPOA)elicited the production of USVs that were acoustically similar to courtship US Vs in adult mice.Moreover,mPOA vesicular GABA transporter-positive(Vgat +)neurons were more effective at driving USV production than vesicular glutamate transporter 2-positive neurons.Furthermore,ablation of mPOA Vgat+ neurons resulted in altered spectral features and syllable usage of USVs in targeted males.Together,these results demonstrate that the mPOA plays a crucial role in modulating courtship USVs and this may serve as an entry point for future dissection of the neural circuitry underlying USV production.

Female mice exhibit both sexual and social partner preferences for vocalizing males

Acoustic signals are widely used as courtship signals in the animal kingdom.It has long been known that male mice emit ultrasonic vocalizations(USVs)in the presence of female mice or in response to female secretions.This observation led to the hypothesis that male USVs play a role in courtship behavior.Although previous studies showed that female mice have a social partner preference for vocalizing males,it is not known if they exhibit a sexual partner preference when given a choice.To address this issue,we examined the copulatory behaviors of female mice with either devocalized males(with or without the playback of the USVs)or sham-operated males in 2 different behavioral paradigms:the no-choice paradigm in the home cage of a male mouse(without choice of mating partners)or the mate-choice paradigm in a 3-chambered apparatus(with choice of mating partners).In the no-choice paradigm,female mice exhibited comparable sexual receptivity with sham-operated and devocalized males.In addition,we found that female mice showed more approach behavior to-wards devocalized males when male USVs were played back.In the mate-choice paradigm,female mice visited more frequently and stayed longer with sham-operated than devocalized males.Furthermore,we showed that female mice received more intromissions from sham-operated males than devocalized males.In summary,our results suggested that,although female mice can copulate equally with both devocalized and vocalizing males when given no choice of mating partner,female mice exhibit both sexual and social partner preferences for vocalizing males in the mate-choice paradigm.