U. Kim et Da. Mccormick, THE FUNCTIONAL INFLUENCE OF BURST AND TONIC FIRING MODE ON SYNAPTIC-INTERACTIONS IN THE THALAMUS, The Journal of neuroscience, 18(22), 1998, pp. 9500-9516
Thalamocortical and perigeniculate (PGN) neurons can generate action p
otentials either as Ca2+ spike-mediated high-frequency bursts or as to
nic trains. Using dual intracellular recordings in vitro in monosynapt
ically connected pairs of PGN and dorsal lateral geniculate nucleus (L
GNd) neurons, we found that the functional effect of synaptic transmis
sion between these cell types was strongly influenced by the membrane
potential and hence the firing mode of both the pre- and postsynaptic
neurons. Activation of single action potentials or low-frequency spike
trains in PGN or thalamocortical neurons resulted in the generation o
f PSPs that were 0.5-2.0 mV in amplitude. In contrast, the generation
of Ca2+ spike-mediated bursts of action potentials in the presynaptic
cell increased these PSPs to an average of 4.4 mV for the IPSP and 3.0
mV for the EPSP barrage, because of temporal summation and/or facilit
ation. If the postsynaptic neuron was at a resting membrane potential
(e.g., -65 mV), these PSP barrages could result in the activation of a
low-threshold Ca2+ spike and burst of action potentials. These result
s demonstrate that the burst firing mode of action potential generatio
n is a particularly effective means by which perigeniculate and thalam
ocortical neurons may influence one another. We propose that the activ
ation of burst discharges in these cell types is essential for the gen
eration of some forms of synchronized rhythmic oscillations of sleep a
nd of epileptic seizures.