My research interests include examining how animals adapt to environmental (temperature changes) and metabolic (exercise, feeding, etc.) perturbations to their acid-base status. Alterations in breathing are the primary, acute response to a metabolic acidosis or alkalosis. Current projects in my lab involve experiments designed to understand how central (brainstem) chemoreceptors sense changes in blood gases and pH. We use the combined techniques of fluorescence imaging microscopy and whole-cell electrophysiology to measure neuronal responses to changes in CO₂, O₂, and pH in brainstem neurons of poikilothermic vertebrates. I am interested in understanding how these chemoreceptors are altered by changes in the animal's environment.

Selected Publications

Simonis, Molly C., Lynn K. Hartzler, Gregory G. Turner, Michael R. Scafini, Joseph S. Johnson, and Megan A. Rúa. 2023. “Long-Term Exposure to an Invasive Fungal Pathogen Decreases Eptesicus Fuscus Body Mass with Increasing Latitude.” Ecosphere 14(2): e4426. https://doi.org/10.1002/ecs2.4426

Zubov, T., Silika, S., Dukkipati, Saihari S., Hartzler, L.K., Santin, J.M., (2021) Characterization of laryngeal motor neuron properties in the American bullfrog, Lithobates catesbeianus. Respiratory Physiology and Neurobiology. Volume 294, December 2021, 103745

Vallejo, M., Santin, J.M., and Hartzler, L.K., (2018) Noradrenergic modulation determines respiratory network activity during temperature changes in the in vitro brainstem of bullfrogs. Respiratory Physiology and Neurobiology. 258:25-31. DOI: 10.1016/j.resp.2018.10.002

Zena, L.A., Leite, Cléo A. C., Longhini, Leonardo S., Dias, Daniel P. M., da Silva, Glauber S. F., Hartzler, Lynn K., Gargaglioni, Luciane H., Bícego, Kênia C. (2017) Analysis of the respiratory component of heart rate variability in the Cururú toad Rhinella schneideri. Scientific Reports. 7(1): 16119. DOI: 10.1038/s41598-017-16350-0

Santin, J.M., Vallejo, M., and Hartzler, L.K. (2017) Synaptic up-scaling preserves motor circuit output after chronic, natural inactivity.  eLife 2017;6:e30005 doi: 10.7554/eLife.30005

Santin, J.M. and Hartzler, L.K. (2017) Activation of respiratory muscles does not occur during cold-submergence in bullfrogs, Lithobates catesbeianus. Journal of Experimental Biology. 220: 1181-1186. DOI: 10.1242/jeb.153544

Santin, J.M. and Hartzler, L.K. (2016) Environmentally-induced return to juvenile-like chemosensitivity in the respiratory control system of bullfrogs, Lithobates catesbeianus. The Journal of Physiology. 594.21: 6349-6367. DOI: 10.1113/JP272777

Santin JM, Wang T, Dukkipati SS and Hartzler LK (2016) Commentary: The Spinal Cord Has an Intrinsic System for the Control of pH. Frontiers in Physiology. 7:513. doi: 10.3389/fphys.2016.00513

Zena, L.A., Fonseca, E.M., Santin, J.M., Porto, L., Gargaglioni, L.H., Bícego, K.C., Hartzler, L.K. (2016) Effect of temperature on chemosensitive locus coeruleus neurons of Savannah monitor lizards Varanus exanthematicus. Journal of Experimental Biology. 219: 2856-2864. doi:10.1242/jeb.138800

Santin, J.M. and Hartzler, L.K. (2016) Control of lung ventilation following overwintering conditions in bullfrogs, Lithobates catesbeianus. Journal of Experimental Biology. 219: 2003-2014 doi:10.1242/jeb.136259

Santin, J.M. and Hartzler, L.K. (2016) Reassessment of chemical control of breathing in undisturbed bullfrogs, Lithobates catesbeianus, using measurements of pulmonary ventilation. Respiratory Physiology and Neurobiology. 224: 80-89.  http://dx.doi.org/10.1016/j.resp.2015.09.013

Santin, J.M. and Hartzler, L.K. (2015) Activation state of the hyperpolarization-activated current modulates temperature-sensitivity of firing in locus coeruleus neurons from bullfrogs.  Am. J. Physiol. Regul. Integr. Comp. Physiol. 308(12): R1045-61. DOI:10.1152/ajpregu.00036.2015

Patrone, L.G.A., Bícego, K.C., Hartzler, L.K., Putnam, R.W., and Gargaglioni, L.H. (2014) Cardiorespiratory effects of gap junction blockade in the locus coeruleus in unanesthetized adult rats.  Respiratory Physiology and Neurobiology. 190:86-95. DOI: 10.1016/J.RESP.2013.09.001

Santin, J.M., Watters, K.C., Putnam, R.W., and Hartzler, L.K. (2013) Temperature influences neuronal activity and CO₂/pH sensitivity of locus coeruleus neurons in the bullfrog, Lithobates catesbeianus.  American Journal of Physiology,  Regulatory, Integrative, and Comparative Physiology  305(12): R1451-1464 DOI: 10.1152/ajpregu.00348.2013

Santin, J.M., and Hartzler, L.K. (2013) Respiratory signaling of locus coeruleus neurons during hypercapnic acidosis in the bullfrog, Lithobates catesbeianus. Respiratory Physiology and Neurobiology. 185(3): 553-561. doi:10.1016/j.resp.2012.11.002

Reinert, B.L., Pohlman, R.L., and Hartzler, L.K. (2012). Correlation of Air Displacement Plethysmography with Alternative Body Fat Measurement Techniques in Men and Women. International Journal of Exercise Science 5(4): 367-378.

Sheehan, K.M. and Hartzler, L.K. (2011).  Effects of XS® Energy Drink on Aerobic Exercise Capacity of Athletes.  International Journal of Exercise Science 4(2): 152-163.