Neurons are the fundamental cell of the nervous system which directs responses to stimuli, coordinates activities of other organ systems, and interprets sensory information about external conditions (Tortora and Derrickson 2012).  These neurons send information from neuron to neuron through synapses by electrical or chemical signals.  Scientists are studying how neurons do not need to synapse with other neurons to be able to send and receive information.   Neuron communications are being observed to take place without any direct connections to other neurons.

Jean-Pierre Rospars was the first to observe what is called ephaptic interactions in flies, which occurs when a neuron silences a neighboring neuron instead of sending the signal though the nervous system.  Studies by Chih Ying-Su, on Drosophila melanogaster were completed by a test on two neurons (ab3A and ab3B) which control for methyl hexanoate and 2-heptanone, respectively.  After being exposed to each of the chemicals individually, the exposed neuron would spike while the other neuron would be shut down.  This is the example of ephaptic interactions Su was looking to expose.

Su also tested these interactions by introducing synaptic blocking chemicals to Drosophila melanogaster.  The test was completed between two neurons that dealt with the flies attraction to apple cider vinegar and the distaste for carbon dioxide.  After blocking the synapses for vinegar, the flies were placed in front of two arms which both contained carbon dioxide, but only one arm also enclosed vinegar.  The flies followed down the arm with the added vinegar which gave Su a conclusion that flies were using fluid inside of the sensillum to create an electric field when the neuron was being blocked.

The phenomenon known as emphatic coupling has been discussed for a long time but it has been perceived as obscure.  A factor in the arcane observations has been the lack of evidence on the subject.  Further studies, along with the study completed by Su, show that knowledge of this occurrence might be useful for protecting crops from hungry insects, or people from disease-carrying insects.

Sources:

Tortora G.J. and B. Derrickson. 2012. Principles of Anatomy and Physiology. 13th ed., John Wiley and Sons

Su, Chih-Ying; Menuz, Karen; Reisert, Johannes; Carlson, John R. “Non-synaptic inhibition between grouped neurons in an olfactory circuit.” Nature. 21 Nov. 2012. <http://www.nature.com /nature/journa/vaop/ncurrent/full/nature11712.html?WT.ec_id=NATURE-20121122