The Effects of Temperature on the Extracellular Firing Rate of Action Potentials in the Ventral Nerve Cord of the Periplaneta Americana Andrew Goldsmith (andrew. [email protected] edu), Tuesdays 1-4PM Section: 2 (Partner: Ana Charalambides) Abstract In polikiotherms it is known that the amount of locomotion varies based on the environmental temperature. We believe that this is caused by differences in the neural activity.
We therefore investigated how temperature changes affect the extracellular neural activity in the ventral nerve cord of the Periplaneta Americana cockroach. It was hypothesized that the frequency of extracellular action potentials was directly dependant on temperature. It was also thought that any changes in the neural activity during temperature changes were caused by morphological differences among the different nerve cords. This was investigated by applying three different temperature treatments (12? C +/- 3? C, 35? C +/- 3? C and 22?
C +/- 3? C) to the ventral nerve cord. Since it was possible that extreme temperature changes could damage the ventral nerve cord, only one treatment was done on one cockroach (N=4). A constant triggered puff of air was used as the stimulus when collecting the data. A cobalt backfill showed no clear morphological differences among the nerve cords of different temperature treatments. It was demonstrated that there was a significant linear relationship between the frequency of action potentials and the temperature of the ventral nerve cord (p0. 5). Since the warm treatment’s recovery temperature did not recover we could not perform the same analysis therefore we will assume that if it had more time it would have. This allows us to assume that warms normal and recovery frequencies would not have been statistically different when doing our analysis. Therefore our data will be analyzed using a scatter plot in Microsoft Excel. A regression analysis will be used to test for statistical differences in slope.
The anatomy portion will be analyzed by observing for morphological differences between the three treatments in the nerve cord and terminal ganglion. Results A scatter plot graph was made to visualize the two clusters of frequencies for the warm and the cold treatments compared to the normal (figure 3). The treatments frequencies are normalized to the normal treatment frequencies using the equation (average frequency of treatment)/ (average frequency of normal).
Therefore each dot represents one animal’s normalized frequency. A best fit line was then created resulting in the equation y=0. 0206x + 1. 0349. Since the slope is positive, the line shows a positive correlation between the change in temperature and the frequency of action potentials (figure 3). As one increases the temperature by 1°C the frequency increases by 2%. The best fit line was further analyzed using a regression analysis and found that there is a significant linear relationship between frequency and temperature (p