[Abstract Title]. - Society for Neuroscience

Rats were randomly assigned to one of 3 groups: trained, pseudoconditioned (pseudo), and naïve.
The trained group received 30 paired tone CS and corneal airpuff US separated by a 250ms trace
interval. Pseudo rats were given 30 CS and 30 US in an unpaired manner. Both groups had 5
training sessions (2sessions/day). Hippocampal slices were cut in ice-cold aCSF 1 d after the last
training session using a vibratome. The CA1/S was isolated from the hippocampal slice, and
SK2, hippocalcin and CaV1.2 L-type Ca 2+ channel protein levels were determined by western
blotting. Here we report an increase in SK2 and hippocalcin, but a decrease in CaV1.2 levels in
CA1/S region from rats that learned as compared to naïve and pseudo rats. These data strongly
suggest that the reduction in the amount of CaV1.2 is one source of the learning-related AHP
reduction observed in CA1 neurons after trace EBC. Although hippocalcin is proposed to be a
mediator of the slow AHP current, it does not contribute to the learning-related AHP reduction.
Rather, the increase in hippocalcin levels suggests that a compensatory mechanism may occur
after learning in response to a decreased cytosolic Ca 2+ level. The enhanced SK2 levels suggest
that a homeostatic regulation may occur after learning. The increased SK2 level in the spines
would filter out extraneous synaptic noise by establishing a higher threshold for the postsynaptic
response to occur, but a strong signal that passes the SK2 filter would be readily passed on to the
next element in the neural circuit because of the significantly reduced somatic slow AHP.
Our present findings of molecular changes that occur with trace EBC directly link the reductions
in CaV1.2 to the learning-related AHP reduction in CA1 neurons.
Disclosures: M.M. Oh, None; D.P. Srivastava, None; B.M. McKay, None; K. Schoedel,
None; P. Penzes, None; J.F. Disterhoft, None.
Poster
240. Intrinsic Membrane Properties: Modulation of Neuronal Firing Properties by Inputs
and Activity
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 240.16/E38
Topic: B.10.c. Activity-dependent plasticity of intrinsic membrane properties
Support: NIH RR-015497
NIH NS-35180
NIH MH-067564
NIH MH-074866