[Abstract Title]. - Society for Neuroscience

Authors: *T. M. SZABO 1 , T. BROOKINGS 1 , D. S. FABER 2 , T. PREUSS 2 ;
1 Biol Dept, Brandeis Univ., Waltham, MA; 2 Domick P Purpura Dept of Neurosci., Albert
Einstein Col. of Med., New York, NY
Abstract: An animal's ability to adapt and behave normally in the natural environment is crucial
to its survival, and one important factor it must adjust to is temperature. To study the effect of
temperature acclimation on intrinsic membrane properties and the integrated functioning of a
neuron in the vertebrate central nervous system we used the Mauthner (M-) cell as a model. The
M-cell can be studied both physiologically in the intact brain as well as in a behaving animal,
since it triggers a startle response when it fires. Animals acclimated for at least one month to 5°,
15° or 25°C had escape kinetics consistent with the general effects of temperature: slower in
cold, faster in warm. Probability of escape increased and directionality decreased at 25°C, results
that were also seen when acclimated animals were tested at 15°C. To examine the
neurophysiology underlying these behavioral changes, we recorded from the M-cell
intracellularly in animals acclimated under the same conditions. Some cellular properties were
directly impacted by temperature including input resistance and action potential kinetics,
although not to the extent seen in acute temperature exposure (Preuss and Faber, 2003). No
differences were seen in length constant or threshold between the three populations. At VIIIth
nerve-M-cell mixed synapses there was a reduction in the slope of the input-output relationship
over many stimulation strengths at both 5° and 25° compared to 15°C. Kinetic differences in the
coupling potential, which reflects presynaptic (VIIIth nerve) action potential kinetics, were
consistent with general temperature effects, while tau of the chemical PSP was lower at both 5°
and 25°C. An examination of feedback inhibition demonstrated a significant increase in coldacclimated
animals and decrease in warm-acclimated animals, results that are consistent with an
increased probability of escape in warm-acclimated animals. Together, these studies demonstrate
that while various aspects of the M-cell circuit are directly impacted by temperature effects in a
predictable manner even after a period of acclimation, the opposing mechanistic actions of
various systems, for example inhibition vs. input resistance, act to help the cell and animal
maintain stable levels of activity. In addition, it seems likely that any disturbance of the
excitatory/inhibitory balance produces computational problems for directional escape.
Disclosures: T.M. Szabo, None; T. Brookings, None; D.S. Faber, None; T. Preuss, None.
Poster
237. Synaptic Integration II
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 237.19/D44
Topic: B.07.c. Synaptic integration