Treatment with arginine vasotocin alters mating calls and decreases call attractiveness in male túngara frogs.

The peptide hormone arginine vasotocin (AVT) and its mammalian homolog arginine vasopressin modulate a variety of social behaviors in vertebrates. In anurans, AVT influences the production of advertisement calls, the acoustic signals that males use to attract females and repel rival males. In this study, we investigate the effects of AVT on call characteristics in the túngara frog (Physalaemus pustulosus). Túngara frogs produce a "whine" that is important for species recognition; they may also produce a second, attractive call component, the "chuck". We used a field playback experiment to determine changes in male calling behavior following treatment with AVT. A previous study showed that AVT alters call rate and the production of chucks; in the current analysis, we focus on changes in the whine. Males produce shorter whines with higher initial frequencies following treatment with AVT. Call changes do not vary with a social stimulus. We also used female phonotaxis experiments to investigate the effects of call changes on female mate choice. Females disfavor the calls produced by males treated with exogenous AVT. We suggest that AVT influences motivation to call and the motor control of call production, but that over-stimulation of the vocal system limited the production of attractive calls in this experimental context.

Arginine vasotocin promotes calling behavior and call changes in male túngara frogs.

In the túngara frog, Physalaemus pustulosus, males alter calling behavior with changes in their social environment, adding 'chucks' to their advertisement calls in response to the calls of conspecific males. Other studies demonstrate that adding chucks increases the attractiveness of calls to females but also increases the risk of bat predation. In the current study, subcutaneous injections of the neuropeptide hormone arginine vasotocin (AVT) significantly increased chuck production in male túngara frogs. The effects of AVT on chuck production did not depend on the presence of playback stimuli, suggesting that AVT increased either the males' general motivation to produce chucks or their responsiveness to the calls of distant males. Injections of AVT also increased the probability that males would call and decreased the latency to call after injection, supporting the hypothesis that AVT influences motivation to call. Finally, AVT inhibited a drop in call rate after the termination of a playback stimulus and increased call rate at a lower dose of AVT. The effects of AVT on chucks and call rate appear to be independent of each other, as there was no correlation between change in chuck production and change in call rate in individual males. We conclude that AVT may play an important role in socially-mediated call changes that result from competition for mates. The behavioral changes induced by AVT might increase a male's attractiveness to females, and also may be consistent with an aggressive response to another túngara frog male.

Paternal behavior influences development of aggression and vasopressin expression in male California mouse offspring.

Parental care has been demonstrated to have important effects on offspring behavioral development. California mice (Peromyscus californicus) are biparental, and correlational evidence suggests that pup retrieving by fathers has important effects on the development of aggressive behavior and extra-hypothalamic vasopressin systems. We tested whether retrievals affected these systems by manipulating paternal retrieval behavior between day 15 and 21 postpartum. Licking and grooming behavior affect behavioral development in rats, so we also experimentally reduced huddling and grooming behavior by castrating a subset of fathers. Experimentally increasing the frequency of paternal pup retrieving behavior decreased attack latency in resident-intruder in both male and female adult offspring, whereas experimental reduction of huddling and grooming had no effect. In a separate group of male offspring, we examined vasopressin immunoreactivity (AVP-ir) in two regions of the posterior bed nucleus of the stria terminalis (BNST): the dorsal fiber tracts (dBNST) and the ventral cell body-containing region (vBNST). Experimentally increasing retrievals led to an apparent shift in AVP-ir distribution. Specifically, offspring from the high retrieval group had more AVP-ir than offspring from the sham retrieval group in the dBNST, whereas the opposite was observed in the vBNST. Experimental reduction of paternal grooming was associated with increased AVP-ir in the paraventricular nucleus and also increased corticosterone and progesterone, similar to observed effects of maternal grooming on HPA function. This study provides further evidence that paternal behavior influences the development of aggression and associated neural substrates.