Functional neuroanatomy and plasticity of the hypothalamic circuits regulating autonomic responses to stress Krisztina J. Kovács Laboratory of Molecular Neuroendocrinology Institute of Experimental Medicine Budapest, Hungary

ACUTE STRESS Heart rate Blood pressure Muscle tension Respiratory rate Plasma glucose Gastrointestinal actvity HPA Sympato-medullar activity Sympato-adrenal Metabolic X syndrome Mood swings Anxiety Depression Confusion / forgetfulness Burnout Eating disorders Sleeping disorders Social withdrawal / aggression Drug abuse CHRONIC or UNRESOLVED

Selye explains STRESS – induced activation of HPA axis Nature, July 4, A Syndrome produced by Diverse Nocuous Agents “…. a typical response appears, the symptoms of which are independent of the nature of the damaging agent… and represent rather a response to damage as such” H. Selye

PARAVENTRICULAR NUCLEUS Magnocellular part Parvocellular part HypophyseotropicAutonom projection Medial parvocellular dorsal Periventricular Medial parvocellular ventral Dorsal parvocellular Lateral parvocellular

BAT HEART SKIN SUDOMOTOR ADRENAL MEDULLA VASCULAR TONE AVPOXYCRH CRH & AVP AVP & OXY PVN Brain stem & spinal cord HPA AXIS ACTIVATION OSMOREGULATION CARDIOVASCULAR REGULATION

Afferent connections of the hypothalamic PVN “Blood borne” Acustic Nociceptive Visceral Somatosensory Visual Corticosterone

Challenge-induced Activation of PVN Neurons c-Fos-ir 90 min after stress* Kovács et al, 2005

MAGNOCELLULAR PARVOCELLULAR CRHVASOPRESSIN Dynorphin Angiotensin II Enkephalin Dopamine Galanin VIP/PHI OXYTOCIN CRH CCK Enkephalin TRH Enkephalin CCK Angiotensin II Neurotensin Galanin VIP/PHI Vasopressin Colocalization of neuropeptides in the hypothalamic PVN ? Oxytocin CRH Vasopressin Somatostatin Dynorphin Enkephaline

Functional plasticity in the PVN - adrenalectomy Control Adrenalectomy ADX + DEX/PVN

Vasopressin potentiates CRH action at the corticotropes Rivier et al, 1984

ETHER STRESS-INDUCED VASOPRESSIN TRANSCRIPTION IN THE PARAVENTRICULAR NUCLEUS

Autonomic projection neurons in the PVN Approx neurons in 3 different parvocellular subdivisions: (dorsal-, ventral aspect of medial parvocellular- and lateral-) Neurochemical specificity of these neurons is less known: (Oxytocin, vasopressin, corticotropin-releasing hormone, somatostatin, dynorphin, enkephalin, dopamine…..) Efferent connections: to medullar and spinal preganglionic cells for both divisions (sympathetic and parasympathetic) of the ANS- spinal cord (intermediolateral cell column) - predominantly OXY dorsal vagal complex - predominantly AVP Express ER-beta, MC4R, IRS-2 etc Physiological evidences for mediation of sympatoexcitation...

FUNCTIONAL PLASTICITY OF HYPOTHALAMIC AUTONOMIC-RELATED NEURONS

Laugero et al, Endocrinology, 2001

+ sucrose + / - sucrose 1. wk 2. wk3.wk4.wk5. wk Record body weight, fluid and food consumption Blood sampling perfusion ADX / SHAM adaptation Adult male Wistar rats 1M sucrose, 0.5% NaCl, water 6. wk CRH mRNA in situ AVP mRNA in situ

Sucrose ingestion results in neuronal activation in neuroendocrine and autonomic-related neurons

Hypothalamus coordinates autonomic responses in part through AVP, released in NTS. AVP inhibits afferent synaptic transmission in the NTS: 1. By decreasing glutamate release probability (V1a receptor) 2. By inducing synaptic failures and increased conduction times

How to study complex autonomic circuits ?

Trans synaptic tracing using pseudorabies virus (PRV) PRV: pseudorabies virus, Bartha strain “self-amplifying transsynaptic tracer”. Trans-synaptic spread)

Virus-infected neurons in the PVN following inoculation into the kidney

Virus-infected neurons in the dorsal parvocellular subdivision

PRV-ir neurons after virus inoculation into a peripheral target 1.Spinal cord, intermediolateral cell column 2. Rostral ventrolateral medulla 3. A5 noradrenergic cell group 4. Hypothalamus, PVN 5. Insular cortex

Comparison of autonomic innervation of WAT and BAT Double-virus infection WAT BAT

PRV injections Ba-Dup-Lac (red)- iWATBa-Dup-Green- BAT

Outline of the brain circuit that provides sympathetic innervation of different target tissues Target organ Five cell groups in the brain appear to regulate the entire sympathetic outflow: the paraventricular hypothalamic nucleus (PVH), A5 noradrenergic cell group, caudal raphe region, rostral ventrolateral medulla, and ventromedial medulla.

CORTEX LIMBIC CORTEX PVN Medial parvo MagnoAuton. related BNSTAmygdala A5 Parabrachial PREGANGLIONIC NEURONS IMLDVC PITUITARY APPP ADRENAL CORTEXMEDULLA ACTH VP, OXY CRH, VP AUTONOMICENDOCRINEBEHAVIORAL OXY, VP, CRH DYN, ENK