Robert W. Putnam, Ph.D.
Ph.D., University of California, Los Angeles, 1978
My research focuses on the cellular neuroscience of acid sensitive neurons within the brainstem, especially the role of these neurons in the control of breathing and in the genesis of panic disorder. We study the neurons from the brainstem of neonatal rats and mice and determine their responses to elevated CO2 and decreased pH. Many of the neurons we study are believed to play a major role in controlling ventilation and our work is thus of relevance to disorders that involve altered respiratory drive, such as sudden infant death syndrome (SIDS) and sleep apnea. There are two main thrusts of our work.
Cellular Signals and Targets in CO2-sensitive Neurons: We are looking at the cellular signaling pathways and the ion channel targets involved in the sensing of elevated CO2 by central chemosensitive neurons. This work involves the use of pH and calcium sensitive fluorescent dyes to study changes of intracellular pH and intracellular calcium and their roles in CO2-induced increased firing rate of these neurons. We simultaneously employ electrophysiological techniques, including whole cell current and voltage clamp, to study the basic electrophysiological responses to acid in these neurons and the responses of individual ion channels, especially K+ channels, to changes of CO2 and pH. We have more recently begun using immunohistochemical techniques to identify the ion channels expressed on chemosensitive neurons, to describe the 3-dimensional structure of these neurons, and to study the relationship of these neurons to capillaries and arterioles. We have described several K+ channels involved in central chemosensitive signaling, shown that calcium-activated K+channels can serve as a previously unsuspected brake on the chemosensitive response, and that there is a close association between capillaries and the cell body of chemosensitive neurons. Finally, we are developing a mathematical model of excitability in central chemosensitive neurons to determine the ion channels, cellular signals and properties that make a neuron chemosensitive. These findings have led to important changes in our concepts of central neuronal chemosensitive signaling.
The Role of a G-protein Coupled Receptor in Panic Disorder: We are now studying a knock-out mouse that exhibits reduced anxiety and panic disorder. This mouse has a G-protein coupled receptor protein, expressed in T cells, that is knocked out. This protein is the T cell death associated gene-8 (TDAG8). These mice curiously exhibit reduced anxiety, which is usually induced by exposure to high levels of CO2. We are studying the response to elevated CO2 in neurons from brain regions that express high levels of TDAG8 (predominantly in the circumventricular organs) in control and TDAG8 knock-out mice. Our hypothesis is that the neuronal response to high levels of CO2 is blunted in neurons from knock-out mice. Since the protein that is knocked out is from T cells, we also hypothesize that this effect is mediated by a change in inflammation. This work represents novel studies on a previously unexplored role for inflammation in the control of breathing.
Imber AN, Putnam RW (2012). Postnatal development and activation of L-type Ca2+ currents in locus coeruleus (LC) neurons: implications for a role for Ca2+ in central chemosensitivity. J Appl Physiol 112:1715-1726.
Kersh AE, Hartzler LK, Havlin K, Belcastro B, Nanagas V, Kalra A, Chua J, Whitesell R, Ritucci NA, Dean JB,Putnam RW (2009). pH regulating transporters in neurons from various chemosensitive brainstem regions in neonatal rats. Amer J Physiol Regul Integr Comp Physiol 297:R1409-R1420.
Putnam RW (2010). CO2 chemoreception in cardiorespiratory control. J Appl Physiol 108:1796-1802.
Gargaglioni LH, Hartzler LK, Putnam RW (2010). The locus coeruleus and central chemosensitivity. Resp Physiol Neurobiol 173:264-273.
Dean JB, Putnam RW (2010). The caudal solitary complex is a site of central CO2 chemoreception and integration of multiple systems that regulate expired CO2. Resp Physiol Neurobiol 173:274-287.
Nichols NL, Mulkey DK, Wilkinson KA, Powell FL, Dean JB, Putnam RW (2009). Characterization of the chemosensitive response of individual solitary complex (SC) neurons from adult rats. Amer J Physiol Regul Integr Comp Physiol 296:R763-R773.
Chernov MM, Daubenspeck JA, Denton JS, Pfeiffer JR, Putnam RW, Leiter JC (2007). A computational analysis of central CO2 chemosensitivity in Helix aspersa. Amer J Physiol Cell Physiol 292:C278-C291.
D'Agostino DP, Putnam RW, Dean JB (2007). Superoxide (·O2-). production in CA1 neurons of rat hippocampal slices exposed to graded levels of oxygen. J Neurophysiol 98:1030-1041.
Putnam RW, Conrad SC, Gdovin MJ, Erlichman JS, Leiter JC (2005). Neonatal maturation of the hypercapnic ventilatory response and central neural CO2 chemosensitivity. Resp Physiol Neurobiol 149:165-179.
Ritucci NA, Dean JB, Putnam RW (2005). Somatic vs. dendritic responses to hypercapnia in chemosensitive locus coeruleus neurons from neonatal rats. Amer J Physiol Cell Physiol 289:C1094-C1104.
Rittuci NA, Erlichman JS, Leiter JC, Putnam RW (2005). The response of membrane potential and intracellular pH to hypercapnia in neurons and astrocytes from rat retrotrapezoid nucleus. Ameri J Physiol Regul Intergr Comp Physiol 289:R851-R861.
Putnam RW, Filosa JA, Ritucci NA (2004). Cellular mechanisms involved in CO2 and acid signaling in chemosensitive neurons. Amer J Physiol Cell Physiol 287:C1493-C1526.
Dean JB, Mulkey DK, Henderson III RA, Potter SJ, Putnam RW (2004). Hyperoxia, reactive oxygen species, and hyperventilation: oxygen sensitivity of brain stem neurons. J Appl Physiol 96:784-791.
Mulkey DK, Henderson III RA, Ritucci NA, Putnam RW, Dean JB (2004). Oxidative stress decreases intracellular pH and Na+/H+ exchange and increases excitability of solitary complex (SC) neurons from rat brain slices. Amer J Physiol Cell Physiol 286:C940-C951.
Filosa JA, Putnam RW (2003). Multiple targets of chemosensitive signaling in locus coeruleus neurons: Role of K+and CA2+ channels. Amer J Physiol Cell Physiol 284:C145-C155.
Mulkey DK, Henderson III RA, Putnam RW, Dean JB (2003). Hyperbaric oxygen and chemical oxidants stimulate CO2/H+-sensitive neurons in rat brain stem slices. J Appl Physiol 95:910-921.
Mulkey DK, Henderson III RA, Putnam RW, Dean JB (2003). Pressure (<4 ATA). increases membrane conductance and firing rate in the rat solitary complex. J Appl Physiol 95:922-930.
Dean JB, Mulkey DK, Garcia III AJ, Putnam RW, Henderson III RA (2003). Neuronal sensitivity to hyperoxia, hypercapnia, and inert gases at hyperbaric pressures. J Appl Physiol 95:883-909.
Fiolosa JA, Dean JB, Putnam RW (2002). Role of intracellular and extracellular pH in the chemosensitive response of rat locus coeruleus neurones. J Physiol (London). 541.2:493-509.
Stundent CE, Filosa JA, Garcia AJ, Dean JB, Putnam RW (2001). Development of in vivo ventilatory and single chemosensitive neuron responses to hypercapnia in rats. Respir Physiol 127:135-155.
Putnam RW (2001). Intracellular pH regulation of neurons in chemosensitive and nonchemosensitive areas of brain slices. Respir Physiol 129:37-56.
Dean JB, Kinkade EA, Putnam RW (2001). Cell-cell coupling in CO2/H+-excited neurons in brainstem slices.Respir Physiol 129:83-100.
Mulkey DK, Henderson III RA, Olson JE, Putnam RW, Dean JB (2001). Oxygen measurements in brainstem slices exposed to normobaric hyperoxia and hyperbaric oxygen. J Appl Physiol 90:1887-1899.
Chambers-Kersh L, Ritucci NA, Dean JB, Putnam RW (2000). Response of intracellular pH to acute anoxia in individual neurons from chemosensitive and nonchemosensitive regions of the medulla. In: Oxygen sensing: molecules to man (Lahiri S, Prabhakar N, Forster II RE, eds)., pp 453-464. New York: Kluwer Academic/Plenum.
2012-2013: Acid Sensing and Panic, National Institutes of Health Research Grant (NIH R01 MH093362), PI: Renu Sah; PI on subcontract: R.W. Putnam. $251,487.
2010-2012: The Role of Calcium in Central Cardiorespiratory Control Neurons American Heart Association Great Rivers Affiliate Predoctoral Fellowship (AHA 10PRE4150123), PI: A.N. Imber; Sponsor: R.W. Putnam. $46,000.
2006-2010: Intracellular pH responses of central chemoreceptors, National Institutes of Health Research Grant (NIH RO1 HL56683); PI: RW Putnam, Co-PI : JB Dean. $1,142,693.
2001-2006: Intracellular pH Responses of Central Chemoreceptors, National Institutes of Health Research Grant (NIH R01 HL 56683); PI: R.W. Putnam; Co-PI: J.B. Dean. $1,022,400.
2003-2006: Cellular Mechanisms of Central Nervous System and Pulmonary Oxygen Toxicity, Office of Naval Research (ONR), Undersea Medicine Program (N00014-04-1-0172); PI: J.B. Dean; Co-PIs: R.W. Putnam and R.A. Henderson III. $739,705.
2005-2006: Hyperbaric Atomic Force Microscopy (AFM) Studies of Oxygen Toxicity, Office of Naval Research (ONR), Undersea Medicine Program (N00014-05-1-0519); PI: J.B. Dean; S. Higgins. $378,000.
2005-2006: Neural Plasticity during Acclimatization to Hypoxia, National Institutes of Health Research Grant (NIH R01 HL 81823); PI: F.L. Powell; PI on subcontract: R.W. Putnam. $77,278.
2005-2007: Effects of Chronic Hypercapnia on Chemosensitive Neurons, Ruth L. Kirschstein National Research Service Award (NIH F32 HL 080877); PI: L.K. Hartzler; Sponsor: R.W. Putnam. $86,044.