title: Maternal care effects on SNB motoneuron development: the mediating role of sensory afferent distribution and activity.
abstract: Maternal licking in rats affects the development of the spinal nucleus of the bulbocavernosus (SNB), a sexually dimorphic motor nucleus that controls penile reflexes involved with copulation. Reduced maternal licking produces decreased motoneuron number, size, and dendritic length in the rostral portion of the adult SNB as well as deficits in adult male copulatory behavior. Previous research suggests that decreases in perineal tactile stimulation may be responsible for these effects. To determine whether the regional effects of maternal licking on SNB morphology are driven by sensory afferent innervation of the lumbosacral spinal cord, we used WGA-HRP to reconstruct the location of sensory afferent fibers from the perineal skin. We found that these fibers are caudally concentrated relative to the area of the SNB dendritic field, with the rostral dendritic arbor receiving little perineal afferent innervation. We also assessed Fos expression following perineal tactile stimulation to determine whether it increased local spinal cord activity in the SNB dendritic field. Sixty seconds of licking-like perineal stimulation produced a transient 115% increase in Fos expression in the area of the SNB dendritic field. This effect was driven by a significant increase in Fos in the caudal portion of the SNB dendritic field, matching the pattern of perineal afferent fiber labeling. Perineal tactile stimulation also produced significantly greater Fos expression in male pups than in female pups. Together, these results suggest that perineal sensory afferent activity mediates the effects of early maternal care on the masculinization of the SNB and resultant male copulatory behavior.
authors.affiliation: Department of Psychological and Brain Sciences and Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Lenz
authors.forename: Dale R
authors.initials: DR
authors.lastname: Sengelaub
mesh_terms: D000344:Afferent Pathways / Q000378:metabolism; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001522:Behavior, Animal; D001931:Brain Mapping; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D008297:Male; D008425:Maternal Behavior / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology*; D016761:Oncogene Proteins v-fos / Q000235:genetics / Q000378:metabolism; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D012727:Sex Characteristics; D013116:Spinal Cord / Q000166:cytology* / Q000254:growth & development*; D020521:Stroke / Q000378:metabolism; D013997:Time Factors; D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate
chemical_list: D016761:Oncogene Proteins v-fos; D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate