MEDIAL PREFRONTAL CTX CONTROL OF THE PVN OF

MEDIAL PREFRONTAL CTX CONTROL OF THE PVN OF THE HYPOTHALAMUS RESPONSE TO PSYCHOLOGICAL STRESS: POSSIBLE ROLE OF THE BNST……. . Spencer et al 2005 J. Comparative Neurology

BNST Subdivisions Ac=anterior comm AL= anterior lateral AM= anterior medial DL= dorsal lateral Ic=internal capsule JXC=juxtacapsular LV=Lateral ventricle PL=posterior lateral PS=parastrial VL=ventral lateral VM=ventral medial

Abbreviations IIIV third ventricle ac anterior commissure ACTH adrenocorticotropic hormone ANOVA analysis of variance ap. PVN anterior parvocellular hypothalamic paraventricular nucleus BNST bed nucleus of the stria terminalis Ce. A central amygdala CRF corticotropin-releasing factor CRF-IR corticotropin-releasing factorimmunoreactivity CTb cholera toxin b subunit CTb-IR cholera toxin b subunitimmunoreactivity d. BNST dorsal bed nucleus of the stria terminalis DMH dorsomedial hypothalamus dp. PVN dorsal parvocellular hypothalamic paraventricular nucleus f fornix Fos-IR Fos-immunoreactivity HPA hypothalamic-pituitary-adrenal ic internal capsule IL infralimbic lp. PVN lateral parvocellular hypothalamic paraventricular nucleus LS lateral septum LV lateral ventricle Me. A medial amygdala mg. PVN magnocellular hypothalamic paraventricular nucleus m. PFC medial prefrontal cortex mp. PVN medial parvocellular hypothalamic paraventricular nucleus NTS nucleus tractus solitarius Pr. L prelimbic PVN paraventricular nucleus of the hypothalamus PVT paraventricular nucleus of the thalamus TH tyrosine hydroxylase v. BNST ventral bed nucleus of the stria terminalis VLM ventrolateral medulla VMH ventromedial hypothalamus

Hypothalamic Map

Intro PVN: role in generating adaptive autonomic, behav, & hormonal stress responses Suppressive inputs are a major target for stress related issues m. PFC: activation generates cardiac depressor responses, inhib influence on sympathetic vasomotor function, role in modulation of PVN….

Intro Anatomical studies fail to show direct projections from m. PFC to PVN Modulation must involve one or more relay through other regions Candidate regions: medial region of hypothalamus BNST, Amygdala, paraventricular nucleus of the thalamus (PVT) LS, and brainstem catecholamine groups All of the candidate regions receive m. PFC inputs and have been implicated in control of the PVN function during stress Question? Do m. PFC lesions that increase PVN responses to a psychological stressor also elicit corresponding changes in activation of any of the candidates? c-fos activity

Intro Answer! m. PFC lesion and air puff challenge causes increased c-fos activity in v. BNST, no other candidate regions ØFurther characterize role of BNST in PVN cell response to air puff ØThink in terms of integration of info from m. PFC to PVN in response to stress ØRetrograde tracing to determine if BNST directly innervates PVN ØDirect projections from m. PFC to BNST recruited by air puff stress ØExamine effects of BNST lesions on recruitment of the PVN cells to air puff stress ØDetermine specific regions of PVN involved

Methods Ø Adult male Wistar Rats Ø 250 -500 g YIKES!!! ØIndividually housed, 24 C 12 -12 light cycle, lights on at 6 am ØFood and water ad libitum ØFood intake and body weight recorded throughout Surgery: Ibotenic acid used for bilateral lesions “Excitotoxicity” Death by glutamate m. PFC lesions covered both prelimbic (Pr. L) and infralimbic (IL) regions BNST lesions covered both dorsal and ventral BNST Vascular cannulae also implanted to allow for easy collection of blood left femoral artery cannula, routed through skin up to scapulae flushed with gentamicin in heparinized saline during recovery

Methods Retrograde Tracing using the cholera toxin b subunit (CTb) ask me how this works? can be visualized using immunocytochemistry (Ctb-IR) CTb injected iontophoretically (using electric magic) into: PVN, d. BNST, both d and v. BNST 6 u. A current for 7 seconds on and 7 seconds off, 20 minutes total Plasma ACTH conc. Determined using one giant Radioimmunoassay

METHODS Headshot STRESSOR! from an air cannon Series of 27 puffs of 300 k. Pa pressurized air aimed at the head of a freely moving animal 510 cm away 15 minute period Nine blocks, each block with 3 2 -second puffs with 10 seconds between puffs and 1 minute between blocks

REMEMBER! 2 separate lesions m. PFC lesion first BNST lesion second

RESULTS: CHARACTERIZATION OF MPFC LESIONS Substantial No cell loss through all Pr. L and IL c-FOS-IR in m. PFC of air puff + lesion animals

C-FOS IR IN CORONAL SECTION OF MPFC Sham Lesion m. PFC Lesion

RESULTS: EFFECTS OF SHAM LESIONS Effects of air puff on sham lesioned animals Air puff = sig in Fos-IR in all regions Post hoc tests on those that sig. interact w/lesion m. PFC both Pr. L and IL mp. PVN CRF cells v. BNST Compared to non-stressed sham lesion control Similar Fos profile as seen with other psychological stressors (noise, restraint)

EFFECTS OF m. PFC LESION ON AIR PUFF RESPONSE Lesion Table Lesion had no effect in non-stressed animals 1 sham no stress vs m. PFC no stress + stress = Increase Sig fos in mp. PVN in the number of activated CRF cells increase in plasma ACTH with stress No difference between sham or m. PFC lesion Lesion + stress = fos in v. BNST

Sham+stress = less fos Right mp. PVN m. PFC lesion + stress = more fos

m. PFC lesion

Fos in v. BNST following m. PFC lesion Sham= less fos lesion= more fos

http: //ngm. nationalgeographic. com/your-shot/top-shots-2008 http: //www. sciencemag. org/cgi/content/full/319/5859/101/DC 1

BNST LESIONS BNST lesions vary in how much of the structure they cover BNST lesion + stress = fos compared to sham lesion + stress group Some BNST lesion + stress groups still showed high levels of fos and they were excluded from analysis as an incomplete lesion group

BNST sham injection BNST lesion

BNST LESION AND FOOD INTAKE No effect of BNST lesion on food intake No effect on body mass

EFFECT OF BNST LESION ON STRESS RESPONSE No effect in any region in non stressed groups Table 2 sham no stress vs lesion no stress Lesion+stress = fos in v. BNST, PVN, m. PFC, Me. A mp. PVN showed fos Air puff induces increased ACTH release No sig. attenuation of the ACTH response in the BNST lesion group, despite the decreased fos expression in the CRF cells of the mp. PVN

BNST lesion

EFFECT OF STRESS ON NEURONS PROJECTING TO PVN N=18: intra-PVN CTb 7 d before stress 10 have sig. tracer deposits in mp. PVN Of these 10, all showed large numbers of retrogradely labeled neurons in the v. BNST ~14% of these were co-labeled with fos mp. PVN-projecting v. BNST cells sensitive to stress No retrograde labeling in the m. PFC

Retrograde labels from CTb injections into the Mp-PVN

MPFC LABELS FROM BNST INJECTIONS d. BNST inj. d. BNST + v. BNST inj.

m. PFC labeling of fos and Ctb and co-localization From BNST injections Labeling only occurred In the v and d. BNST group

DISCUSSION m. PFC lesion enhanced recruitment of mp. PVN CRF cells by air puff stress BNST lesion + stress = decreased fos in all regions studied m. PFC and BNST important in influencing the response to a psychological stress

DISCUSSION CHOICE OF STRESSOR 2 categories of acute, unconditioned stressor Psychological: threat of a disturbance Physical: actual disturbance of tissue integrity Air cannon = moderate intensity Avoids saturation of stress response Psychological in nature (they think) <10% total CRF cell activation in mp. PVN ~25% stress of what they see w/ restraint or noise

DISCUSSION CHOICE OF STRESSOR Air puff (along w/restraint&swim stress) elicited Me. A fos activation Hemorrhage & immune challenge activate Ce. A Air puff in BNST activated only ventral portion Immune Challenge activates v and d. BNST Air puff meets criteria of psychological

ROLE OF MPFC IN CRF CELL RESPONSE m. PFC lesion increases expression of fos protein by mp. PVN CRF cells in response to air cannon Not accompanied by an increase in ACTH Could be due to altered release of other secretagogues like oxytocin or AVP CRF release could be doing other things mp. PVN bstem CRF also stim. NE synthesis & release in

ROLE OF BNST IN mp. PVN CRF CELL RESPONSE TO AIR CANNON v. BNST = increased fos following airpuff and lesion to m. PFC (only candidate region that did) v. BNST gets a direct projection from m. PFC, and projects directly to mp. PVN Difficult to lesion only v. BNST sends Glu to mp. PVN which could be a direct stimulation following a stressor

MPFC INPUTS TO THE BNST Direct projection from m. PFC to ipsalateral v. BNST (but not d. BNST) However, v. BNST tracer injections did not retrogradely label any m. PFC neurons…… May be another brain region involved

CONCLUSION Psychological stressor= increased mp. PVN CRF and v. BNST cell recruitment in m. PFC lesioned animals BNST lesion = decreased mp. PVN cell response to psychological stressor m. PFC may suppress mp. PVN CRF cell response to stress via the a BNST pathway

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