Current Research

Our lab is interested in the neurobiology of visceral sensory integration. Our work deals with a portion of the brain that regulates vital organ function called the nucleus of the solitary tract (NTS). Peripheral afferents from the vital organs (e.g. heart, lungs, gut) directly contact the brain at NTS.

Arterial baroreceptors (BR) encode stretch of arteries with each cardiac cycle. This dynamic information  is transmitted to second order neurons in the NTS. We study these NTS neurons and synaptic transmission in brain slices using dyes to visualize the central terminal boutons of BRs within NTS.

Our major technical focus is electrophysiology (patch clamp recording) combined with optical approaches to neurons in slices and dispersed single cells (see additional information on our lab website). Our unusual slice preparation allows selective activation of single afferent axons that synapse on the recorded cell and affords near ideal conditions for quantal analysis of neurotransmitter release mechanisms. Currently, we use fluorescent tracers to identify and probe single neurons.  Combined fluorescence and infrared microscopy enables visual identification and study of specific cell types by patch recordings. Mechanically isolated cells facilitate study of miniature synaptic events originating from attached native boutons. Current major projects focus on use dependent depression of sensory synaptic transmission, accessory co-transmission (ATP, purines, peptides), and the unique, non-nociceptive role of vanilloid receptors (TRPV1). We are interested in roles played by intrinsic cellular differences in myelinated and unmyelinated axons that influence information transfer to the CNS.

Appleyard, S.M., Marks, D.; Kobayashi, K., Okano, H., Low, M.J., Andresen, M.C. Visceral afferents directly activate catecholamine neurons in the solitary tract nucleus. J. Neuroscience 27: 13292-13302. 2007. PMID: 18045923

Bailey, T.W.; Jin, Y.-H.; Appleyard, S.M., Andresen, M.C. Organization and properties of GABAergic neurons in solitary tract nucleus (NTS). J. Neurophysiology 99: 1712-1722, 2008. PMID: 18272881

Peters, J.H.; McDougall, S.J.; Kellet, D; Jordan, D.; Llewellyn-Smith, I.; Andresen, M.C.  Oxytocin enhances excitatory synaptic transmission to the solitary tract nucleus. J. Neuroscience 28(45): 11731-11740, 2008 PMID: 18987209

 Education

• Ph.D. 1978, University of Texas Medical Branch
• M.S. 1973, San Diego State University
• B.S. 1971, University of California, Irvine

Preceptor Rotations

Faculty Mentorship

Dr. Andresen is available as a mentor for 2009-2010.