Robert W. Putnam, Ph.D. Professor Address: 011A Medical Sciences Bldg. Phone: (937) 775-2288 E-mail: robert.putnam@wright.edu University of California, Los Angeles, 1978

Research Interests:

My research focuses on the cellular neuroscience of respiratory control. We study the neurons from the brainstem of neonatal rats and their response to elevated levels of CO₂. It is believed that these neurons 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 Neorons: 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 pH and calcium sensitive fluorescent dyes to study changes of intracellular pH and intracellular calcium and their role in CO₂-induced increased firing rate of these neurons. We also employ electrophysiological techniques to study the change in electrophysiological properties of these neurons as well as using immunohistochemical and voltage clamp techniques to characterize the ion channel targets of the chemosensitive signals. We have recently begun studies to alter central chemosensitivity in rats to determine the cellular alterations that correlate with the altered central chemosensitivity. We are also developing a mathematical model of excitability in central chemosensitive neurons to determine the channels, signals and properties that make a neuron chemosensitive.

Development of Central Chemosensitivity: We have done some of the first studies to fully characterize the development of the CO₂ responsiveness of ventilation in neonatal rats. Our studies suggested a triphasic pattern of development, with an early neonatal form of chemosensitivity that gives way after 2 weeks to an adult form of chemosensitivity, and a critical window of minimal chemosenstivity at week 1. We are also studying the development of chemosensitivity in individual neurons within various chemosensitive regions. Finally, we are examining which brainstem regions are responsible for each type of chemosensitivity and the effects of chronic exposures to hypercapnia or hypoxia on these developmental patterns.

Selected Publications:

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.

Recent Funding:

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.