The Journal of Neuroscience, June 15, 2000, 20(12):4497-4505
Presynaptic Protein Kinase Activity Supports Long-Term
Potentiation at Synapses Between Individual Hippocampal Neurons
Paul
Pavlidis,
Johanna
Montgomery, and
Daniel V.
Madison
Department of Molecular and Cellular Physiology, Stanford
University School of Medicine, Stanford, California 94305-5345
Simultaneous microelectrode recording from two individual
synaptically connected neurons enables the direct analysis of synaptic transmission and plasticity at a minimal synaptic connection. We have
recorded from pairs of CA3 pyramidal neurons in organotypic hippocampal
slices to examine the properties of long-term potentiation (LTP) at
such minimal connections. LTP in minimal connections was found to be
identical to the NMDA-dependent LTP expressed by CA3-CA1 synapses,
demonstrating this system provides a good model for the study of the
mechanisms of LTP expression. The LTP at minimal synaptic connections
does not behave as a simple increase in transmitter release
probability, because the amplitude of unitary EPSCs can increase
several-fold, unlike what is observed when release probability is
increased by raising extracellular calcium. Taking advantage of the
relatively short axon connecting neighboring CA3 neurons, we found it
feasible to introduce pharmacological agents to the interior of
presynaptic terminals by injection into the presynaptic soma and have
used this technique to investigate presynaptic effects on basal
transmission and LTP. Presynaptic injection of nicotinamide reduced
basal transmission, but LTP in these pairs was essentially normal. In
contrast, presynaptic injection of H-7 significantly depressed LTP but
not basal transmission, indicating a specific role of presynaptic
protein kinases in LTP. These results demonstrate that pharmacological
agents can be directly introduced into the presynaptic cell and that a
purely presynaptic perturbation can alter this plasticity.
Key words:
long-term potentiation; presynaptic; protein kinase; hippocampus; electrophysiology; synaptic transmission
Copyright © 2000 Society for Neuroscience 0270-6474/00/20124497-09$05.00/0