Transcript Effects of maternal care on spinal cord development and

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
Experimental Set-Up
140
•Zinc sulfate reduces
maternal licking by
reducing olfactory
acuity
Seconds/Observation
120
100
80
60
*
40
20
0
Control
Reduced Licking
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
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 lickingdeprived 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 downregulated by maternal care