Matthew Ennis, Ph.D.
Simon R. Bruesch Professor and Chair
Department of Anatomy and Neurobiology
The University of Tennessee Health Science Center
855 Monroe Avenue, Suite 515
Memphis, TN 38163
Tel: (901) 448-1225
Fax: (901) 448-7193
Lab: 322 Wittenborg Anatomy Building
Email: Matthew Ennis
- Ph.D. Institution: New York University
- Postdoctoral: University of Cincinnati College of Medicine, Departments of Physiology & Biophysics and Anatomy & Cell Biology
My primary interests are centered on the functional organization and physiological properties of neural networks involved in nociception/analgesia processing and the chemical senses (i.e., olfaction and gustation). Cutting across these research areas is a more general interest in the functional role of globally-projecting neuromodulatory transmitter systems, such as norepinephrine and dopamine. My research utilizes an integrative, multidisciplinary approach combining tract tracing, immunocytochemistry, immediate early gene expression, molecular biology, optical imaging, electrophysiology and behavior to delineate cellular and circuit properties of functionally defined networks. The major current projects in my laboratory are:
- Regulation of Brainstem Opioid Analgesic Circuits. A well defined brainstem-spinal cord circuit is known to play a key role in opioid-mediated analgesia. We are investigating how higher levels of the CNS (cortical and subcortical sites) involved in emotions, motivational state and cognitive processing can regulate this brainstem analgesic circuit to allow for state-dependent modulation of pain thresholds. We are also investigating how sweet and fatty components of mother's milk produces profound opiate receptor-dependent analgesic and calming effects in newborn rats and humans. This clinically-significant phenomenon is used to manage human infant pain, yet its neurobiological underpinning are unknown.
- Synaptic Integration and Information Processing in the Olfactory Bulb. We are investigating how neuronal membrane properties and extrinsic/intrinsic neurotransmitter systems modulate information processing and output from the olfactory bulb circuit using molecular biological, functional imaging and neurophysiological approaches in vivo and in vitro. A major focus of our work is to understand how norepinephrine and dopamine transmitter systems, as well as metabotropic glutamate receptors, modulate the olfactory bulb network at cellular, synaptic, network and behavioral levels.
- Integration in the Olfactory Bulb (OB)-Piriform Cortex (PC) Circuit. Olfactory receptor neurons that express a single common odorant receptor project to one glomerulus in the OB. The glomeruli thus form a map that mirrors receptor activity. Different odors stimulate different patterns of glomerular activity. The OB and PC comprise the major components of the neural network that decipher such patterns to arrive at the recognition of an odor. The goal of this research is to understand how glomerular activity is relayed to, and processed within PC using neuroanatomical and neurophysiological approaches.
- Bendahmane M, Ogg MC, Ennis M, Fletcher ML. Increased olfactory bulb acetylcholine bi-directionally modulates glomerular odor sensitivity. Sci Rep. 2016 May 11;6:25808. doi: 10.1038/srep25808. PubMed PMID: 27165547; PubMed Central PMCID: PMC4863144.
- de Almeida L, Reiner SJ, Ennis M, Linster C. Computational modeling suggests distinct, location-specific function of norepinephrine in olfactory bulb and piriform cortex. Front Comput Neurosci. 2015 Jun 16;9:73. doi: 10.3389/fncom.2015.00073. eCollection 2015. PubMed PMID: 26136678; PubMed Central PMCID: PMC4468384.
- Dong HW, Ennis M. Activation of group I metabotropic glutamate receptors enhances persistent sodium current and rhythmic bursting in main olfactory bulb external tufted cells. J Neurophysiol. 2014 Feb;111(3):641-7. doi: 10.1152/jn.00696.2013. Epub 2013 Nov 13. PubMed PMID: 24225539; PubMed Central PMCID: PMC3921410.
- Escanilla O, Alperin S, Youssef M, Ennis M, Linster C. Noradrenergic but not cholinergic modulation of olfactory bulb during processing of near threshold concentration stimuli. Behav Neurosci. 2012 Oct;126(5):720-8. doi: 10.1037/a0030006. PubMed PMID: 23025834; PubMed Central PMCID: PMC3563246.
- Dong HW, Davis JC, Ding S, Nai Q, Zhou FM, Ennis M. Expression of transient receptor potential (TRP) channel mRNAs in the mouse olfactory bulb. Neurosci Lett. 2012 Aug 22;524(1):49-54. doi: 10.1016/j.neulet.2012.07.013. Epub 2012 Jul 20. PubMed PMID: 22820212; PubMed Central PMCID: PMC3857022.
- Linster C, Nai Q, Ennis M. Nonlinear effects of noradrenergic modulation of olfactory bulb function in adult rodents. J Neurophysiol. 2011 Apr;105(4):1432-43. doi: 10.1152/jn.00960.2010. Epub 2011 Jan 27. Review. PubMed PMID: 21273323; PubMed Central PMCID: PMC3075300.