RESEARCH 2003
RESEARCH 2002
RESEARCH 2001
RESEARCH 2000

Katrina Knight
Alcorn State
Summer Mentor: Dr. James Buchanan

Both chemical and electrical synapses are present in the nervous system of vertebrates, though chemical synapses are far more numerous in the adult nervous system. The possible involvement of electrical synapses in network activity of the adult has not been previously investigated. Recent studies in neonatal and embryonic vertebrate nervous systems have shown that electrical synapses contribute to the generation of respiratory and locomotor activities. In our research, we have used common gap junctional blockers (carbenoxolone and 1-octanol) on the isolated spinal cord of the adult lamprey to determine whether electrical synapses are involved in the generation of locomotor activity in the adult vertebrate nervous system. 

First, to show that carbenoxolone blocks electrical synapses in the lamprey spinal cord, an intracellular microelectrode was used to record the depolarizing response in the reticulospinal axon to ventral root stimulation because motor neurons are known to have gap junctions with these axons. Carbenoxolone (0.2mM) eliminated the response. 

To test the gap junctional blockers on swimming activity, the experimental chamber containing the isolated spinal cord was perfused with D-glutamate (0.5mM) to induce locomotor activity (fictive swimming) and extracellular electrodes were used to record the rhythmic bursts of action potentials of motor neurons in the ventral roots. Then either carbenoxolone (n=6) or 1-Octanol (n=2) was added to the bath. Analysis of the ventral root bursting showed that the cycle period of fictive swimming was altered, indicating that gap junctions contribute to locomotor rhythm generation, Furthermore, the results showed that the propagation of the bursting down the spinal cord (phase lag) was also altered, indicating that gap junctions contribute to the coupling of locomotor networks along the spinal cord.

While these results suggest that electrical synapses contribute to the generation of locomotor activity in the adult lamprey spinal cord, further experiments will be required to define the exact role that electrical synapses play in the locomotor networks.