141. Storm-Mathisen J. (1977) Localization of transmitter candidates in the brain: the hippocampal formation as a model. Prog Neurobiol 8:119-81.

NeuronCompartmentPropertyConnectivityNotes
Hippocampus CA1 pyramidal cellDistal apical dendriteGlutamatePerforant pathway entorhinal pyramidal neuron terminals (T)Glutamate is commonly believed to be the primary excitatory neurotransmitter in the hippocampal formation generally (reviewed in Cotman et al., 1995), and in CA1 in particular (Storm-Mathisen J, 1977141 , Randall AD and Collingridge GL, 1992142 ). CA1 pyramidal neurons increase their firing (recorded extracellularly) in response to ionophoresed Glu within their apical dendritic fields or in the cell body layer (Dudar 1974 PMID#4437726). Magee JC and Cook EP, 2000183
Hippocampus CA1 pyramidal cellProximal apical dendriteI p,q.Ca fluorescence imaging shows that application of P-channel antagonists reduces the Ca influx associated with backpropagating action potentials (Storm-Mathisen J, 1977141 ). "action potential-mediated depolarization can...result in the elevation of dendritic intracellular Ca concentration (Regehr et al 1989, Jaffe DB et al, 199276 ), which is important for the induction of long term changes in synaptic strength" (Spruston N et al, 1995 [mammal ]57 ).
Hippocampus CA1 pyramidal cellProximal apical dendriteI T low threshold.Patch recordings yield an approximate channel density of 7 pS/micron^2 in juvenile rats < 4 wks of age, rising to 10 pS/micron^2 in older rats. Ca channel density was similar in other dendritic compartments, and in general lower than Na channel density (Magee JC and Johnston D, 1995 [rat ]140 ). However, in a few apical patches the channel density was increased X 3, which could indicate channel clustering. Ca fluorescence imaging shows that application of T-channel antagonists reduces the Ca influx associated with backpropagating action potentials, and has a two-fold greater effect in the dendrites than in the soma (Storm-Mathisen J, 1977141 ).
Hippocampus CA1 pyramidal cellDistal apical dendriteGaba---Labeling for glutamic acid decarboxylase (GAD), the enzyme that synthesizes GABA, is heavy in the molecular layer of CA1 (Storm-Mathisen J, 1977141 , cited in Johnston and Amaral, 1998).
Hippocampus CA1 pyramidal cellProximal apical dendriteGabaCA1 Basket Cell terminals (T)The baskets formed by inhibitory basket cells have high concentrations of glutamic acid decarboxylase (GAD), the enzyme that synthesizes GABA (Storm-Mathisen J, 1977141 ).
Hippocampus CA1 pyramidal cellSomaGabaCA1 Basket Cell terminals (T)The baskets formed by inhibitory basket cells have high concentrations of glutamic acid decarboxylase (GAD), the enzyme that synthesizes GABA (Storm-Mathisen J, 1977141 ). A 40-50% reduction in a small fraction of (peri-) somatic synapses with large or complex postsynaptic structure after kindling has been found. This functionally relevant reduction may be related to the loss of a specific class of interneurons, and could underlie the enhanced seizure susceptibility after kindling epileptogenesis (Wierenga CJ and Wadman WJ, 1999 [rat ]284 ).

References
141. Storm-Mathisen J. (1977) Localization of transmitter candidates in the brain: the hippocampal formation as a model. Prog Neurobiol 8:119-81.
142. Randall AD and Collingridge GL. (1992) Amino acid receptor-mediated synaptic currents in the CA1 region of the hippocampus. Ion Channels 3:63-81.
183. Magee JC and Cook EP. (2000) Somatic EPSP amplitude is independent of synapse location in hippocampal pyramidal neurons. Nat Neurosci 3:895-903.
76. Jaffe DB, Johnston D, Lasser-Ross N, Lisman JE, Miyakawa H and Ross WN. (1992) The spread of Na+ spikes determines the pattern of dendritic Ca2+ entry into hippocampal neurons. Nature 357:244-6.
57. Spruston N, Schiller Y, Stuart G and Sakmann B. (1995) Activity-dependent action potential invasion and calcium influx into hippocampal CA1 dendrites. Science 268:297-300.
140. Magee JC and Johnston D. (1995) Characterization of single voltage-gated Na+ and Ca2+ channels in apical dendrites of rat CA1 pyramidal neurons. J Physiol 487 ( Pt 1):67-90.
284. Wierenga CJ and Wadman WJ. (1999) Miniature inhibitory postsynaptic currents in CA1 pyramidal neurons after kindling epileptogenesis. J Neurophysiol 82:1352-62.
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