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Regional Differentiation of the Medial
Prefrontal Cortex in Regulating Adaptive
Responses to Acute Emotional Stress
Radley, Arias, Sawchenko
Salk Institute, La Jolla California
Journal of Neuroscience 2006
Radley, J. J. et al. J. Neurosci. 2006;26:12967-12976
Sawchenko?
Intro
• mPFC:
– Processing cognitive and emotional info
– Modulation attention states
– Regulating stress response
• Influence on HPA axis
• Autonomic (sympathoadrenal)
Intro.
• HPA (hypothalamic-pituitary-adrenal) axis
– Paraventricular nucleus (PVN or PVH)
• CRF neurosecretory neurons
– ACTH release from anterior Pituitary
– Corticosterone from adrenal cortex
• Projections to CNS cell groups involved in autonomic
– Sympathetic preganglionic neurons (ACh release)
– Stimulates adrenaline and noradrenalin from adrenal medulla
Regional specialization?
• mPFC lesion = inhibitory control of HPA
– Lesions mainly dorsal; prelimbic (PL) (as opposed
to infralimbic IL)
– Large lesions may alter basal, but not stress
induced HPA response in rats
– IL may preferentially modulate autonomic
– Suggestions that PL and IL differ in both nature of
influence and underlying circuitry
Schematic of mPFC regions
• Current study compares:
– Dorsal vs. ventral (mPFCd vs mPFCv) lesions
– Acute restraint stress
– Hormonal (B & ACTH)
– Histochemical (fos, CRF mRNA)
Rats and Drugs
• Adult male s.dawley 275-325g, indvidually
housed, free access to food and H2o
• Bilateral excitotoxic lesions (ibotenic acid) into
either v or d mPFC, with a sham surgery group
• 14 day recovery; 30 min restraint stress in
plastic tubes, returned to cage for 2 hours
• All animals were terminated within the same
time period of the day
Lesions
• Amanita muscaria
and Amanita
pantherina
• 10 mg/ml ibotenic
acid in saline (60-90
nL per side were
injected)
• Extent of lesion
reconstructed from
Nissel stained slides
Labeling of structures
• To measure extent of stress induced Fos
immunoreactivity
– Fast blue crystals into rostral ventrolateral medulla
to be transported by axons of passage to provide
maximal labeling of PVH pre-autonomic cell
groups projecting to both dorsal vagal complex
and preganglionic neurons in spinal cord
– Fast blue fluid in T1-T2 level of spinal cord
– Tracer injected during lesion surgery
– Dual IR for fos and fast blue
CRF mRNA
• In situ hybridization
• Probe built for CRF identification
• Allows visualization of mRNA in very small
amounts, localized to individual cells (as little
as 10-20 mRNA copies per cell)
Hormone assays
• In-dwelling jugular catheters implanted 2d
before stress exposure (12 d following
surgery)
– Blood samples collected before stress and again
immediately following stress and 30, 60 and 90
mins after
– B and ACTH measured using RIA kit
Lesion placement
Acd = dorsal anterior cingulate
Figure 2. Rostrocaudal extent of mPFCd lesion placements
Figure 2. Rostrocaudal extent of mPFCv lesion placements
Lesion effect on PVH activation
following stress
Dp= dorsal parvicellular
Mpd= hypophysiotropic
Mpv= medial parvicellular
Pm= posterior magnoceullular
Mpd is richest in CRF cell bodies
Figure 3. sham control vs sham stress
Stress = sig increased Fos in mpd, dp and mpv
Dorsal lesion = increase Fos in Mpd
Ventral lesion attenuates Mpd increase, while increasing Fos in dp and mpv
Ventral lesion is similar to sham lesion, both higher than controls
Lesion effects on PVH activational
responses to acute restraint stress
• mPFCd lesions
– Overt enhancement
• mPFCv
– Mild attenuation
– Tendency toward increased response in
preautonomic cell groups (dorsal, Vmedial)
• Of stress induced Fos-IR in the PVH mpd
region
What the fos?
• Effects of mPFC lesions on restraint-induced
CRF mRNA expression
– Directly related to HPA activity
• Stress increases mpd mPFC CRF mRNA 46%
compared to unstressed controls
• mPFCd lesion enhanced this effect by 34%
• mPFCv lesion n.s. diff compared to sham
stress and no stress groups
Figure 4. Effects of mPFC lesions on acute restraint-induced CRF mRNA expression in the
PVH
Figure 4. Effects of mPFC lesions on acute restraint-induced CRF mRNA expression in the
PVH
What about blood?
• HPA secretory response to 30 min restraint
• ACTH response:
– SHAM- stress = sig increase in ACTH
– mPFCv lesion = no increase compared to basal
– mPFCd lesion = sig increase compared to basal,
sham and mPFCv lesion
Figure 5. Effects of mPFC lesions on ACTH response to acute restraint
697 +- 164 pg/mL
267 +-
84 pg/mL
CORT
•
•
•
•
Similar basal levels of cort among groups
Similar elevation following stress (671-792 pg)
BUT…..
mPFCd lesion remains elevated from baseline
for 90 mins post stress
• mPFCv lesion returns to baseline faster than
sham and d lesion groups
Figure 5. Effects of mPFC lesions on CORT response to acute restraint
Whats the deal with mPFCv
• mPFCv involvment in stress-induced HPA
output is subtle compared to mPFCd
– mPFCv may preferentially modulate autonomic
outputs
– Tracer injections into 2 locations
• Rostral ventrolateral medulla
• Upper thoracic T1-T2
– Stress, then look for double labeling
Figure 6. Acute restraint stress increases activation of preautonomic PVH after mPFCv
lesions
VLM
Stress group
Brown = fast blue
Black = fos
Figure 6. Acute restraint stress increases activation of preautonomic PVH after mPFCv
lesions
Dual labelling indicates stress-sensitive preautonomic neurons, and they are localized
primarily in dorsal, ventral and lateral parvicellular
Also injected tracer into T1-T2 thoracic spinal cord to more specifically label
PVH outputs relevant to sympathetic control. Stress + mPFCv lesion in this group
led to 63% more dbl labeled neurons in PVH
Discussion: talk freely amongst
yourselves
• Support regional differentiation of mPFC
within its capacity to modulate stress-related
PVH outputs
• Stress induced HPA activity was greater
following mPFCd lesion, suppressed w/ mPFCv
• mPFCv lesion selectively enhanced stressinduced recruitment of PVH pre-autonomic
neurons
• Limitations and difficulties comparing studies
– Lesion placement, extent, stressor, duration,
methods used to characterize HPA response, etc
• mPFCv or IL: projects to brainstem cell groups
involved in central autonomic control,
including NTS (primary central terminus of
inputs carried by the vagus and
glossopharyngeal nerves)
• PVH innervates both NTS and motor nuclei of
vagus and glossopharyngeal nerves
Fight or flight…
• This innervation pattern puts IL in a position
to modulate concurrently both cardiac and
adrenal medullary activity
– “command neurons” for the F or F response
Peri-PVH
• Diencephalic mPFC projections distribute near
the PVH, but not within the nucleus proper
– Peri-PVH regions are rich in GABA interneurons
• Inhibitory control over HPA response
– mPFC projections are primarily excitatory (glu)
• while its effects on HPA is inhibitory
Figure 7. Separate pathways from mPFC may differentially regulate PVH responses to
stress
• mPFCd inhibitory mPFCv facilitates HPA
• d/v involvment in autonomic output does not
adhere to this scheme
• pPVT (posterior para-vent nuc of thalamus)
– Implicated in habituation and facilitation
• Hab: repeated exposure to same stressor = response
• Fac: exaggerated response to novel challenge
– pPVT-mPFC connection targets IL preferentially
• Implications for chronic stress adaptation
Post Traumatic Stress Disorder
• PTSD patients: functional impairment and
shrinkage of mPFC
– Correlated with dendritic atrophy and synapse
loss following chronic emotional stress in rodents
• PTSD: HPA axis dysregulation and consistent
increases in cardiovascular reactivity
• In the future
• Finer grained analysis of mPFC should foster
clarification of functional circuits underlying
stress adaptation, and their involvement in
affective disorders
This is the end.