Research Projects in Progress
Role of magnocellular oxytocin and vasopressin neurons in appetite regulation. Oxytocin is an anorexic agent, and the magnocellular neurons robustly express insulin receptors as well as glucokinase, the hallmark of glucose sensitive cells. Thus, we are examining the hypothesis that the magnocellular neurons participate in appetite regulation by monitoring nutrient availability.
Neurotransmitter interactions. Following our demonstration of prominent potentiation of vasopressin and oxytocin release by co-administration of ATP and phenylephrine (to mimic the action of norepinephrine on ?1-adrenergic receptors), we initiated studies to understand the cellular mechanisms underlying the potentiated responses. We are using live cell imaging techniques for monitoring intracellular calcium and confocal microscopy to study receptor trafficking in vasopressin and oxytocin neurons. Since ATP activates a family of ionotropic purinergic receptors (P2X-R) that differ relative to ligand-induced desensitization as well as the ability to form membrane pores large enough to allow efflux of neuroactive compounds, this opens intriguing possibilities for identification of new mechanisms regulating cell excitability. Since neurotransmitters and neuropeptides are co-released at many (perhaps all) synapses, these studies have wide implications for CNS physiology and pathophysiology.
Effects of temperature and ‘Ecstasy’ on vasopressin and oxytocin release. Maintenance of a constant body temperature is essential in homeotherms. This requires adequate hydration, because evaporative heat loss is essential for preventing hyperthermia in warm to hot environments. ‘Ecstasy’ (methylene-dioxymethamphetamine or MDMA) is a widely abused recreational drug that can induce lethal hyperthermia and hyponatremia. We are working to identify the physiological and molecular mechanisms that integrate thermal and osmotic information to induce appropriate behavioral and hormonal responses to maintain hydration. We will test the hypothesis that ‘Ecstasy’ corrupts these mechanisms.
Ligand-induced nuclear translocation of the Neurokinin-3 receptor (NK3-R). Our observation that the G-protein coupled, NK3-R translocates from the plasma membrane to the cell nucleus upon activation opens another intriguing research direction. Does this represent a mechanism for direct regulation of gene expression by G-protein receptor ligands? Does the entire receptor enter the nucleus and if so, how does it escape the membrane? How widespread is the phenomenon in the CNS? Since NK3-R are broadly expressed in the brain and have been implicated in disorders ranging from movement disorders, to psychiatric disorders, and hypertension, does this nuclear translocation represent a mechanism that can be manipulated to alter these disease processes?
Past Research Projects
Molecular and cellular regulation of vasopressin and oxytocin secretion. My laboratory identified a number of extracellular signals (osmolality, neurotransmitters and steroid hormones) that are important in the regulation of vasopressin release from the posterior pituitary. We used cell and tissue culture; immunocytochemistry, in situ hybridization, and image analysis; vasopressin and oxytocin radioimmunoassays; and mRNA extraction, quantification, and characterization using Northern analysis and RNA protection assays to elucidate the extra- and intracellular signals involved in the regulation of vasopressin and oxytocin gene expression. Currently our focus is on the glucose, insulin, and temperature as described above.
Role of steroid hormones in regulation of vasopressin and oxytocin secretion. We demonstrated using immunocytochemistry and in situ hybridization that estrogen receptor beta is highly expressed in magnocellular vasopressin neurons and is down regulated during chronic stimulation of hormone release. Since ER-? is primarily localized in the nucleus and the classic steroid receptors are known to function as transcription factors, experiments are underway to determine which genes are regulated by ER-??in VP neurons. Viral transfection of antisense or siRNA constructs is being explored as a mechanism to knockdown ER-? expression. Immunocytochemistry, in situ hybridization, and microarray technology will be used to characterize changes in gene expression.
Physiological actions of vasopressin and oxytocin in the body. New roles for vasopressin have emerged as new information is generated about its actions in the cardiovascular system, its potential role as a neurotransmitter both centrally and peripherally, and its production in peripheral organs. These observations have spawned studies in my laboratory on the role of vasopressin in hypertension, the role of vasopressin and oxytocin in feeding behavior, and the role of vasopressin release from the suprachiasmatic nucleus in generating circadian rhythms.
Impact of aging on the vasopressin secretion. This has been a recurring focus of research in the laboratory, and remains a salient interest. The neurohypophyseal system provides an excellent model system for studying neurosecretion and as new tools and theories arise, they can be applied to this system to assess the impact of aging on neuronal systems.
Identification of factors that induce proliferation, survival, and differentiation of dopamine neurons. We have used cell culture approaches to identify the signals involved in promoting proliferation and subsequent differentiation of mesencephalic neuroblasts into dopamine neurons. The goal of these studies was to develop a source of dopamine neurons for transplantation in Parkinson's disease.
NIH: R21HD072428-01A1 PI, Oxytocin responses to insulin and glucose: Impact of lactation and obesity. 20% effort. Direct costs $275,000. (8% for funding), 3/1/2012-2/28/2014.
NIH: CTSA (T32 component) – Program co-director, Clinical Translational Science Ph.D. Training Track. 10% effort, 2008-2013, total new graduate training support - $1,013,000; salary and other support from U54 portion of CTSA
NIH: RO1 - NS27975-19 Principal investigator, Regulation of Vasopressin Secretion, 40% effort, 4/1/91 - 6/30/12. Direct costs for 2012 - $242,563.
AHA Grant-In-Aid #0850149Z: PI, Neurotransmitter regulation of Vasopressin Release. $66,000/yr, July 2008-2012.
NIH: R21 – NS059569 Principal investigator, Neurokinin 3 Receptor: Nuclear Localization in Supraoptic Neurons. 25% effort, 2/08-3/11, total direct costs over 2yrs - $275,000.
R01 - NS44835 Principal investigator, Neuropeptide Regulation of Vasopressin/Oxytocin Secretion. 30% effort, 3/02-2/07, direct costs for ’02-’03, $190,000.
Song, Z., S. Vijayaraghavan, and C.D. Sladek. ATP increases intracellular calcium in supraoptic neurons by activation of both P2X and P2Y purinergic receptors. Am J Physiol Regul Integr Comp Physiol. 292(1):R423-31, 2007.
Gomes, D.A.*, Z. Song*, W. Stevens, and C.D. Sladek. Switch from desensitizing to non-desensitizing P2X receptors mediates sustained stimulation of vasopressin release. Am J Physiol: Regul Integr Comp Physiology 297(4):R940-9, 2009. *Contributed equally to this work. PMC2763823
Song, Z. D.A. Gomes, W. Stevens, C.D. Sladek. Multiple ?1 Adrenergic Receptor Subtypes Support Synergistic Stimulation of Vasopressin and Oxytocin Release by ATP and Phenylephrine. Am. J. Physiol.: Regul Integr Comp Physiology 299:R1529-37, 2010. PMC3007183
Janssen, J.S., V. Sharma, U. Pugazhenthi, C. Sladek, W.M. Wood and B.R. Haugen. A Rexinoid Antagonist Increases the Hypothalamic-Pituitary-Thyroid Set Point in Mice and Thyrotrope Cells. Mol. Cell. Endocrinology 339:1-6, 2011. PMID: 21458528
Doherty, F.C., J.B. Schaack, C.D. Sladek. Comparison of the efficacy of four viral vectors for transducing hypothalamic magnocellular neurosecretory neurons in the rat supraoptic nucleus. J Neurosci Methods. 197(2):238-248, 2011. PMID: 21392530
Doherty, F.C., C.D. Sladek. Expression of NMDA receptor subunits and splice variants in the supraoptic nucleus of control and salt-loaded rats. Brain Res. 2011 (May 4) 1388:89-99 PMID: 21397592
Sladek, C.D., W. Stevens, S.R. Levinson, Z. Song, D.E. Jensen,,F.W. Flynn. Characterization of Nuclear Neurokinin 3 Receptor Expression in Rat Brain. Neuroscience, 196:535-48, 2011; http://dx.doi.org/10.1016/j.neuroscience.2011.08.044.
Book Chapters and Review Articles
Sladek, C.D. and W.E. Armstrong. The Neurohypophyseal System. Article in The New Encyclopedia of Neuroscience, a project of the Society for Neuroscience. Available online, 2008.
Sladek, C.D. and S.J. Somponpun. Estrogen Receptors: Their Roles in Regulation of Vasopressin Release for Maintenance of Fluid and Electrolyte Homeostasis. Frontiers in Neuroendocrinology 29(1):114-27, 2008. [Pub Med: NIHMS38782]
Sladek, C.D. and Z. Song. Regulation of vasopressin release by co-released neurotransmitters: Mechanisms of purinergic and adrenergic synergism. Progress in Brain Research (Advances in Vasopressin and Oxytocin – From Gene to Behavior; I.D. Neumann and R. Landgraf, eds) 170:93-107, 2008.
Sladek, C.D. and Z. Song. Diverse Roles of G-Protein Coupled Receptors in Regulation of Neurohypophyseal Hormone Secretion. J. Neuroendocrinology 24:554-565, 2012.
Song, Z. and C.D. Sladek. Phenylephrine (PE) induced increases in intracellular calcium ([Ca++]i) in supraoptic nucleus (SON) neurons are dependent on release of calcium from intracellular calcium stores. Experimental Biology ’07, April, 2007.
Gomes, D.A., C.D. Sladek, L.L.K. Elias, and J.Antunes-Rodrigues. Carbon Monoxide and Nitric Oxide Modulate Hyperosmolality-Induced oxytocin secretion from hypothalamus explant. Experimental Biology ’07, April, 2007.
Song, Z. and C.D. Sladek, Angiotensin II induced increase in intracellular calcium in supraoptic nucleus neurons. VIIth World Congress on Neurohypophyseal Hormones, Regensburg, Germany, September 2007.
Song, Z. and C.D. Sladek, P2X2 purinergic receptors are responsible for ATP stimulated calcium influx in supraoptic neucleus neurons. Experimental Biology ’08.
Gomes, D.A., Z. Song, and C.D. Sladek, Non-desensitizing purinergic receptors (P2-R) are responsible for sustained stimulation of vasopressin (VP) release by ATP and phenylephrine. Experimental Biology ’08.
Song, Z., D.A. Gomes, W. Stevens, and C.D. Sladek, The role of P2Y1 purinergic receptors (P2Y1R) in regulation of vasopressin and oxytocin release from neurohypophysis. Beijing Joint International Physiology Meeting, Beijing, China, October, 2008.
Song, Z. and C.D. Sladek, Activation of P2Y1 purinergic receptors (P2Y1Rs) increased intracellular calcium in rat supraoptic neurons by both influx and release from intracellular stores. Society for Neuroscience, 2008.
Doherty, F. and C.D. Sladek, siRNA mediated knockdown of ER? in vivo in the paraventricular nucleus of the rat. Experimental Biology 2009.
Sladek, C.D., W. Stevens, R.R. Lawson, and S.R. Levinson. Neurokinin 3 receptor immunoreactivity in supraoptic nucleus: Impact of antigen epitope on immunohistochemical localization. Experimental Biology 2009.
Sladek, C.D., W. Stevens, R.R. Lawson, and Z. Song. Molecular evidence for multiple purinergic P2X receptor subtypes in supraoptic nucleus. Experimental Biology 2009.
Song, Z., W. Stevens, and C.D. Sladek. Molecular and functional studies of P2Y1 purinergic receptors in mouse supraoptic nucleus neurons. IUPS, Japan, 2009.
Song, Z. and C.D. Sladek. Phenylephrine (PE) induced increases in intracellular calcium in supraoptic nucleus neurons are primarily mediated by a1A adrenergic receptors. VIIIth World Congress on Neurohypophyseal Hormones. Kitakyushu, Japan, September, 2009.
Sladek, C.D., Z. Song, D.A. Gomes, and W. Stevens. ?1A-adrenergic receptors are not required for sustained stimulation of vasopressin release by ATP and phenylephrine. VIIIth World Congress on Neurohypophyseal Hormones. Kitakyushu, Japan, September, 2009.
Sladek, C.D., W. Stevens, Z. Song. ?1-adrenergic receptor (?1-AR) subtypes: Involvement in regulation of supraoptic nucleus (SON) vasopressin (VP) and oxytocin (OT) neurons. Experimental Biology 2010.
Sladek, C.D., W. Stevens, S.R. Levinson, Z. Song, D.E. Jensen,,F.W. Flynn. Characterization of Nuclear Neurokinin 3 Receptor Expression in Rat Brain. Winter Conf on Brain Res., 2011.
Sladek, C.D., W. Stevens, S.R. Levinson, Z. Song, D.E. Jensen,,F.W. Flynn. Characterization of Nuclear Neurokinin 3 Receptor Expression in Rat Brain. Experimental Biology 2011.
Song, Z. and C.D. Sladek. Glucokinase and insulin receptor in supraoptic nucleus neurons: Potential role in glucose and metabolic sensing? Experimental Biology 2011.
Sladek, C.D., Z. Song, and W. Stevens, Thermal stimulation of vasopressin and oxytocin (VP/OT) release from explants of the hypothalamo-neurohypophyseal system (HNS). Experimental Biology 2012.
Buswell Fellow, University of Rochester, 1976-1977
Research Career Development Award, 1977-1982
Morris Parker Award for Excellence in Research - Chicago Medical School, 1994
Elected to Alpha Omega Alpha, Honor Medical Society, 2001
Erlanger Distinguished Lecturer, American Physiology Society, 2002
James O. Davis Distinguished Lecturer in Cardiovascular Science, 2003