Conservation and dimorphism in androgen receptor distribution in Alston's singing mouse ( Scotinomys teguina )

Abstract

Because of their roles in courtship and intrasexual competition, sexual displays are often sexually dimorphic, but we know little about the mechanisms that produce such dimorphism. Among mammals, one example is the vocalization of Alston's singing mouse (Scotinomys teguina), which consists of a series of rapidly repeated, frequency‐modulated notes. The rate and duration of songs is sexually dimorphic and androgen responsive. To understand the neuronal mechanisms underlying this sexual dimorphism, we map the sites of androgen sensitivity throughout the brain, focusing analysis along a pathway that spans from limbic structures to vocal motor regions. We find widespread expression of AR immunoreactivity (AR‐ir) throughout limbic structures important for social behavior and vocalization, including the lateral septum, extended amygdala, preoptic area and hypothalamus. We also find extensive AR staining along previously documented vocal motor pathways, including the periaqueductal gray, parabrachial nucleus, and nucleus ambiguus, the last of which innervates intrinsic laryngeal muscles. Lastly, AR‐ir is also evident in sensory areas such as the medial geniculate, inferior, and superior colliculi. A quantitative analysis revealed that males exhibited more AR‐ir than females, a pattern that was most pronounced in the hypothalamus. Despite the elaboration of vocalization in singing mice, comparison with prior literature suggests that the broad pattern of AR‐ir may be conserved across a wide range of rodents. Together these data identify brain nuclei well positioned to shape the sexually dimorphic vocalization of S. teguina and suggest that such androgen modulation of vocalization is evolutionary conserved among rodents.

Mapping the vocal circuitry of Alston's singing mouse with pseudorabies virus

“…In another study (Zheng et al, 2021), we identify the presence of androgen receptors across this broad circuit, providing a potential mechanism for the androgen-dependence of Scotinomys song (Pasch et al, 2011). We have also found that body condition in general, and circulating leptin specifically, is associated with individual differences vocal effort.…”

“…Among singing mice, as in many other taxa, display effort is influenced by reproductive state and body condition (Burkhard et al., 2018; Giglio & Phelps, 2020; Pasch et al., 2011b). In another study (Zheng et al., 2021), we identify the presence of androgen receptors across this broad circuit, providing a potential mechanism for the androgen‐dependence of Scotinomys song (Pasch et al., 2011). We have also found that body condition in general, and circulating leptin specifically, is associated with individual differences vocal effort.…”

“…We used 16 male S. teguina outbred from a wild population caught near Quetzal Education Research Center in San Gerardo de Dota, Costa Rica. We have reported housing and husbandry previously (Zheng et al., 2021). All animal protocols were approved by the IACUC committee at The University of Texas at Austin in accordance with the National Institute of Health Guide for the Care and Use of Laboratory Animals.…”

“…Rica. We have reported housing and husbandry previously (Zheng et al, 2021). All animal protocols were approved by the IACUC committee at The University of Texas at Austin in accordance with the National Institute of Health Guide for the Care and Use of Laboratory Animals.…”

Proposing a neural framework for the evolution of elaborate courtship displays

“…More detailed studies explore the expression of these receptors in different subregions of the PAG. AR and ER, for example, can be found in the dorsal and lateral columns of PAG, as well as the ventral portions of the region ( Loyd and Murphy, 2008 ; Murphy et al, 1999 ; Zheng et al, 2021 ). Some of this work even pinpoints likely AR and ER expression to PAG neurons that project to medullary nuclei, which in turn innervate spinal motoneurons ( Loyd and Murphy, 2008 ).…”