UHealth - University of Miami Health System

John N. Barrett, Ph.D.

General Information

John N. Barrett, Ph.D.


  • .(JavaScript must be enabled to view this email address)


  • English


  • Professor, Physiology and Biophysics

Research Interests

  • Mitochondrial function in healthy and diseased motor neuron cell bodies and motor terminals: effects of stimulation and different energy substrates
  • Measurements of mitochondrial respiration (O2 consumption) in small cell samples 
  • Mechanisms underlying hyperthermia-induced damage to developing neurons


1972 Ph.D., Physiology and Biophysics
University of Washington (Seattle)
1965 B.A., Chemistry, Biology and Math
St. Mary's College, Minnesota



Dr. Barrett’s research includes studies of motor neurons and axons, studies of trophic factor requirements and responses to stress in mammalian neurons, and metabolism (especially mitochondrial properties) in normal neurons and mouse models of neurodegenerative disease. 

Research in his lab has demonstrated (1) chemotropism in developing axons (sensory axons growing toward nerve growth factor), (2) proliferation of neuronal progenitors in culture, (3) the importance of calcium influx and calcium-activated potassium channels in regulating the discharge properties of motor neurons, and (4)  the importance of a selenium-binding serum protein for neuronal growth in culture.  In collaboration with Drs. Gavriel David and Ellen Barrett he has also studied responses of motor nerve terminal mitochondria to stimulation, using fluorescent indicators.

Currently he is developing a method for measuring mitochondrial respiration in small neuronal tissue samples for studies of normal neuronal respiration and respiratory defects in neurodegenerative diseases including amyotrophic lateral sclerosis.   He is also investigating mechanisms underlying stimulation of neurons by infrared pulses in collaboration with Dr. Suhrud Rajguru. 

Another current research interest is the effect of neonatal hyperthermia on the developing nervous system.  Prenatal exposure to hyperthermia early during development is known to produce gross neuronal deformities; current studies indicate that hyperthermia at later developmental stages produces more subtle neuronal deficits, manifested as learning abnormalities, hypothesized to be due to damage of late-developing interneurons.  Cleared whole mount brain preparations with deep immunostaining are used to test for early damaging effects of the hyperthermia, and measurements of cellular respiration are employed to test for mitochondrial functional defects.