UVM Theses and Dissertations
Format:
Print
Author:
Ghatak, Atreyi
Dept./Program:
Biology
Year:
2010
Degree:
MS
Abstract:
Plasma membrane Calcium ATPases (PMCAs) are one of the important calcium (Ca²) extrusion mechanisms in mammalian cells. Previous work from our laboratory showed that all four isoforms of PMCA are present in mouse olfactory sensory neurons (OSNs) (Weeraratne et al., 2006) and PMCA 2, being the most calcium calmodulin sensitive isoform, plays an important role in restoring the Ca²⁺ level back to normal in (OSNs) after depolarization. Work from our laboratory has also reported that the rate of calcium clearance from OSNs after odor stimulation is slower in the PMCA 2 Knock out (KO) mice than that of wild type mice (Saidu et al., 2009). We were interested to see the behavioral consequence of this slow calcium clearance in the PMCA2KO mice and therefore used behavioral methodologies such as fear conditioning and conditioned odor aversion in this study.
The odorants amyl acetate and geraniol were used as conditioned stimuli (CS) in olfactory fear conditioning and they were paired with mild electric foot shock, which was used as an unconditioned stimulus (US) in both wild type and PMCA 2 KO mice. The responses of the animals were recorded as motion activity using Video fear conditioning system (Med associates Inc.). Significant decrease in motton activity was considered as conditioned fear which generates as a result of forming association between the CS and the US. Our data clearly showed that the wild type mice could associate an odor CS with shock, whereas the PMCA2 KO mice could not. These data were further supported by conditioned odor aversion (COA) studies where the same odorants were used as CSs and the animals were injected with LiC1 (IP) to induce visceral illness.
The wild type mice developed clear aversion to the odorants amyl acetate and geraniol in the respective concentrations used whereas PMCA 2 KO did not develop any aversion to either. We also wanted to test whether the inability to associate the CS and US in the PMCA 2 KO mice are limited to olfactory cue mediated task only. Using light, a non-olfactory stimulus showed similar results in wild type mice whereas the PMCA 2 KO mice showed completely different behavioral responses. The wild types reduced their activity during .CS period as compared to the Pre CS period both with an odor CS and light CS, but the PMCA 2 KO showed higher activity during light CS period as compared to Pre CS period. This could be attributed to the difference in their phenotype which led them to perform differently even though learning occurred, or alternatively, due to inability to perform any cue mediated task; but further experimentations and different types of behavioral measures will be required to make a conclusive statement in that light.
The odorants amyl acetate and geraniol were used as conditioned stimuli (CS) in olfactory fear conditioning and they were paired with mild electric foot shock, which was used as an unconditioned stimulus (US) in both wild type and PMCA 2 KO mice. The responses of the animals were recorded as motion activity using Video fear conditioning system (Med associates Inc.). Significant decrease in motton activity was considered as conditioned fear which generates as a result of forming association between the CS and the US. Our data clearly showed that the wild type mice could associate an odor CS with shock, whereas the PMCA2 KO mice could not. These data were further supported by conditioned odor aversion (COA) studies where the same odorants were used as CSs and the animals were injected with LiC1 (IP) to induce visceral illness.
The wild type mice developed clear aversion to the odorants amyl acetate and geraniol in the respective concentrations used whereas PMCA 2 KO did not develop any aversion to either. We also wanted to test whether the inability to associate the CS and US in the PMCA 2 KO mice are limited to olfactory cue mediated task only. Using light, a non-olfactory stimulus showed similar results in wild type mice whereas the PMCA 2 KO mice showed completely different behavioral responses. The wild types reduced their activity during .CS period as compared to the Pre CS period both with an odor CS and light CS, but the PMCA 2 KO showed higher activity during light CS period as compared to Pre CS period. This could be attributed to the difference in their phenotype which led them to perform differently even though learning occurred, or alternatively, due to inability to perform any cue mediated task; but further experimentations and different types of behavioral measures will be required to make a conclusive statement in that light.