Enhanced synaptic transmission at identified synaptic connections in the cerebral ganglion of Aplysia.
The identified A-B neuron synaptic connections in the cerebral ganglion of Aplysia exhibited a novel form of enhanced synaptic transmission. A brief high-frequency train of action potentials (2 s, 10-30 Hz) in the presynaptic A neurons produced a long-lasting increase in the amplitude of excitatory postsynaptic potentials (EPSPs) in B neurons. The increase in synaptic efficacy was termed slow developing potentiation (SDP) since the EPSP amplitude increased slowly with the peak occurring 5 min after the tetanizing train. Peak EPSP amplitudes increased relative to the initial EPSP by an average of greater than 250%. SDP decayed as a single exponential with a time constant of tau = 24 min. The enhanced transmission was neuron specific. Only the connections made by the tetanized A neuron were potentiated. However, potentiation apparently occurred at all the synapses made by the tetanized A neuron. Tetanizing the postsynaptic B neurons neither induced, nor when paired with A neuron tetanization, increased SDP. SDP appears to be primarily due to increased transmitter release by the presynaptic neuron.
Fredman
S M
SM
Department of Physiology, Meharry Medical College, Nashville, TN 37208.
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001048:Aplysia / Q000502:physiology*; D005724:Ganglia / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*