Early experience shapes the neural and behavioral development of individuals. Maternal care is one such experience, regulating development and exerting a lifelong impact on the nervous system, behavior, and disease. We have focused on the impact of early maternal licking in rats on the development of the spinal cord and male copulatory behavior. Reducing maternal licking negatively impacts both the development of motoneurons in the spinal nucleus of the bulbocavernosus (SNB), which control penile reflexes, as well as the consequent reflexes themselves. The goal of this proposal is to determine the mechanisms through which maternal licking influences the development of these motoneurons. The regional specificity of the effects of maternal licking on the SNB suggests that specific afferent populations are altered by maternal licking, thus the focus of these experiments will be on determining whether sensory or supraspinal afferents are mediating these effects. Sensory afferents from the licked perineal skin innervate the SNB dendritic field, thus it is possible that changes in local spinal cord activity mediate the effects of maternal licking on the SNB. We will use anatomical and immunohistochemical techniques to determine where sensory afferents are distributed relative to the SNB and whether licking-like tactile stimulation increases local neural activity in the spinal cord. Oxytocin is also released following maternal contact and sensory stimulation, and oxytocin afferents from the hypothalamus innervate the SNB dendritic field and regulate copulatory behavior. Thus it seems possible that maternal licking influences the development of the SNB via mediating effects on oxytocin signaling. We will use enzyme immunoassay and immuno-fluorescence to determine whether licking-like tactile stimulation increases oxytocin levels in the spinal cord, and whether such stimulation increases the activity of oxytocin-sensitive spinal neurons. Together, these experiments will give insight into the mechanisms by which maternal care regulates neural and behavioral development.
Understanding the sensitivity of the developing nervous system to maternal effects has implications for human development, giving insight into the ways in which maternal care or its absence can produce healthy or aberrant neural and behavioral development of children. Moreover, there are major sex differences in the prevalence of many neuropsychiatric and neurological disorders, from depression to autism to chronic pain disorders. This research, in uncovering the pathways through which early experience shapes sex differenfiation of the nervous system, can help understand how such disorders develop and how to intervene during development or in adulthood to prevent or treat these widespread disorders.
| Lenz, Kathryn M; Sengelaub, Dale R (2010) Maternal care effects on the development of a sexually dimorphic motor system: the role of spinal oxytocin. Horm Behav 58:575-81 |
