Effects of Maternal Care on Spinal Cord Development and

Reproductive Behavior in Male Rats

Joy Garrett

Katy Lenz

Aaron Wilber

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

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

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

Maternal licking alters SNB motoneuron number

Graph from Moore et al. (1992)

Adult dendritic length is affected by maternal licking

Control Reduced Licking

Adult dendritic length per motoneuron is regionally reduced by approximately 50% in the reduced licking offspring

Control Reduced Licking

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Experimental Set-Up

•Zinc sulfate reduces maternal licking by reducing olfactory acuity

P1, 2, 3, 5, 8, 11, 14

ZINC SULFATE

SALINE

1)HRP injection: P28 or P492)Hormone Assay: P1, P7, or P143)Immunohistochemistry: P49 4)Gene Array: P49

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

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

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)

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