Identification of the sexually dimorphic gastrin‐releasing peptide system in the lumbosacral spinal cord that controls male reproductive function in the mouse and Asian house musk shrew (Suncus murinus)

Abstract

Several regions of the brain and spinal cord control male reproductive function. We previously demonstrated that the gastrin-releasing peptide (GRP) system, located in the lumbosacral spinal cord of rats, controls spinal centers to promote penile reflexes during male copulatory behavior. However, little information exists on the male-specific spinal GRP system in animals other than rats. The objective of this study was to examine the functional generality of the spinal GRP system in mammals using the Asian house musk shrew (Suncus murinus; suncus named as the laboratory strain), a specialized placental mammal model. Mice are also used for a representative model of small laboratory animals. We first isolated complementary DNA encoding GRP in suncus. Phylogenetic analysis revealed that suncus preproGRP was clustered to an independent branch. Reverse transcription-PCR showed that GRP and its receptor mRNAs were both expressed in the lumbar spinal cord of suncus and mice. Immunohistochemistry for GRP demonstrated that the sexually dimorphic GRP system and male-specific expression/distribution patterns of GRP in the lumbosacral spinal cord in suncus are similar to those of mice. In suncus, we further found that most GRP-expressing neurons in males also express androgen receptors, suggesting that this male-dominant system in suncus is also androgen-dependent. Taken together, these results indicate that the sexually dimorphic spinal GRP system exists not only in mice but also in suncus, suggesting that this system is a conserved property in mammals. J. Comp. Neurol. 525:1586-1598, 2017. © 2016 Wiley Periodicals, Inc.

Comparative Anatomy of Gastrin-releasing Peptide Pathways in the Trigeminal Sensory System of Mouse and the Asian House Musk Shrew <i>Suncus murinus</i>

“…Therefore, we focused on suncus as a laboratory small animal model that may possess a well developed trigeminal sensory system unique to subterranean eutherians. Recently, we cloned cDNA encoding GRP in suncus (accession number: suncus Grp ; LC138361) [29]. The mature GRP in suncus is similar to human rather than rodent GRP.…”

A sexually dimorphic peptidergic system in the lower spinal cord controlling penile function in non-human primates

“…[10][11][12] Recently, we reported that this sexually dimorphic system has been identified not only in rodents but also in the Asian house musk shrew (Suncus murinus) (order of Eulipotyphla; formerly Insectivora). 13 These results suggest that the sexually dimorphic spinal GRP system is general in mammals. However, little information exists on the spinal GRP system controlling male sexual function in primates, although it is clinically important to know whether the GRP system exists and has similar functions in the lower spinal cord in primates.…”

“…We performed an immunocytochemical analysis according to our established methods using cryosections. 10,11,13 In brief, tissue sections were first rinsed five times with PBS to remove the cryoprotectant. Endogenous peroxidase activity was eliminated by incubation in 1% H 2 O 2 in absolute methanol for 20 min followed by three 5-min rinses with PBS.…”

“…The GRP antiserum used in this study has previously been shown to be specific for GRP in the spinal cord of rats, mice and Asian house musk shrews. 13,[15][16][17] Immunoreactive products were detected with a streptavidin-biotin kit (Nichirei, Tokyo, Japan), followed by diaminobenzidine (DAB) development according to our previous method. 10,18 GRP immunoreactivities in the spinal cord were localized using an FSX100 microscope (Olympus, Tokyo, Japan).…”

“…To determine the projection site of GRP-containing fibers, doubleimmunofluorescence staining for GRP (1:1000 dilution) and neuronal nitric oxide synthase (1:5000 dilution) (nNOS; A-11; a mouse monoclonal antibody raised against amino acids 2-300 of nNOS of human origin, Santa Cruz Biotechnology, Santa Cruz, CA, USA), a marker protein for neurons in the sacral autonomic nucleus (SAN), was performed in a similar way described previously in rats, mice and Asian house musk shrews. 10,11,13 Alexa Fluor 546linked anti-mouse IgG (Molecular Probes) and Alexa Fluor 488-linked antirabbit IgG, both raised in goats, were used at a 1:1000 dilution for detection. Immunostained sections were imaged with a confocal laser scanning microscope (FluoView FV1000, Olympus).…”