Effects of Maternal Care on Spinal Cord Development and Reproductive Behavior in Male Rats

1. Effects of Maternal Care on Spinal Cord Development and Reproductive Behavior in Male Rats Joy Garrett Katy Lenz Aaron Wilber

2. Maternal Licking Behavior • During first 2 postnatal weeks • Anogenital Licking • Dams lick male pups more than female pups • Important for brain development and behavior, including stress reactivity, emotionality, learning and memory, and sexual behavior

3. Maternal licking influences adult male sex behavior Reducing maternal licking produces deficits in male copulatory behavior: • Longer latency to ejaculation • Longer post-ejaculatory intromission latency • Longer inter-intromission intervals

4. Spinal Nucleus of the Bulbocavernosus (SNB) • Sexually dimorphic • Hormone sensitive • Controls penile reflexes during copulation • Development is activity-dependent • Dendritic development is biphasic: outgrowth until P28 retraction from P28 until P49

5. Maternal licking alters SNB motoneuron number Graph from Moore et al. (1992)

6. Control Reduced Licking Adult dendritic length is affected by maternal licking Adult dendritic length per motoneuron is regionally reduced by approximately 50% in the reduced licking offspring

7. SALINE 1)HRP injection: P28 or P49 2)Hormone Assay: P1, P7, or P14 3)Immunohistochemistry: P49 4)Gene Array: P49 ZINC SULFATE P1, 2, 3, 5, 8, 11, 14 Experimental Set-Up • Zinc sulfatereduces maternal licking by reducing olfactory acuity

8. 1. Neuroanatomy • Already know adult dendritic length is affected. We will also look at an earlier developmental timepoint (P28) to see if dendritic outgrowth is affected versus dendritic retraction • Horseradish peroxidase (HRP) retrograde labeling allows visualization of SNB motorneuron morphology • Use Neurolucida to reconstruct dendritic arbor across the population of motoneurons

9. 2. Hormone Assay • Deprivation of maternal care is a stressor: causes increases in both ACTH and CORT • SNB motoneurons highly express glucocorticoid receptors (GR) • Stress also suppresses the HPG axis production of testosterone (T), and SNB motoneuron dendrites depend on T • Perform an EIA on the plasma of control and licking-deprived rat pups on days 1, 7, and 14, to look at T and CORT levels

10. 3. Immunohistochemistry • It is possible that licking-induced changes in steroid hormone receptor expression could control the effects of licking on SNB dendritic morphology. • Both GR and androgen receptors (AR) of receptors are expressed highly in the SNB • On P49, perform immunohistochemistry on control and licking-deprived rats to look for differences in GR and AR expression Photomicrograph taken from Blanco et al. (2003)

11. 4. Gene Array • Other molecular factors affect dendritic arborization of SNB motoneurons (e.g. ciliary neurotrophic factor (CNTF) and brain derived neurotrophic factor (BDNF)). Many of these factors are target-derived. • Perfrom a gene microarray on purified RNA of the SNB muscle tissue both during the maternal licking period and in adulthood (P49) • This will demonstrate which genes are up- or down- regulated by maternal care