Deforest Mellon, Jr.

Professor of Biology
288 Gilmer Hall
(434) 982-5766

Education

  • B.S., Yale University, 1957
  • Ph.D., The Johns Hopkins University, 1961
  • Postdoctoral, Stanford University, 1961-1963

Research Interests

To be optimally effective, startle behaviors depend upon the synchronized action of dedicated sensory pathways which excite central nervous targets and motor systems with minimal time delays. Among the neurophysiological adaptations that accomplish this in the central nervous system of shrimps are electrical synaptic connections between myelinated giant interneurons and myelinated giant motor neurons that galvanize contractions in the abdominal flexor muscles. Axonal conduction velocities of the myelinated medial giant interneurons (MdG) are the fastest recorded in any animal (220 m/sec @ 18o C); voltage-gated sodium ion channels in MdG nodal membrane in the vicinity of the synaptic membrane in turn have extremely fast activation and inactivation kinetics, e.g., onset to peak conductance in 100 µsec, with a maximum inward sodium current density estimated at 500 mAmp/cm2, nearly twice as steep the voltage/current transition found in mammalian axonal membrane. I am interested in characterizing the electrical and time-dependent properties of the rectifying electrical synaptic connection between MdG and MoG. Since the orthodromic synaptic transfer is undoubtedly voltage dependent, the sodium channel activation kinetics of the synaptic membrane must be at least as steep, if not more so, than that found in  MdG. We use standard two-electrode current- and voltage clamp electrophysiological techniques to determine whether the electrical properties of the MdG-MoG nexus lives up to its expectations of being the animal kingdom’s fastest synapse. 

 

Electrophysiology of startle responses in crustaceans

 

Representative Publications