| Abstract No.: | C-B3026 |
| Country: | Canada |
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| Title: | THE EFFECTS OF ETHANOL ON LTD IN BOTH THE CA1 AND DENTATE GYRUS |
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| Authors/Affiliations: | 2 James Shin*; 2 Ross Petersen; 1 Brennan Eadie; 1 Timal Kannangara; 1 Andrea Titterness; 2 Brian Christie;
1 UBC, Vancouver, BC, Canada; 2 University of Victoria, BC, Canada
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| Content: | Objectives: Alcohol is a widely consumed drug that has a multitude of effects on the brain and body. While numerous studies have shown that direct application of ethanol can block long-term potentiation (LTP), a biological model of learning and memory, less is known of its effects on other forms of plasticity. In particular, some studies have shown ethanol to enhance long term depression (LTD) of synaptic efficacy (Hendricson et al., 2002), while others have found that LTD is blocked (Izumi et al., 2005). In this series of experiments, we applied ethanol in varying concentrations to determine the effects on LTD in both dentate gyrus (DG) granule cells and CA1 pyramidal cells. MATERIALS AND METHODS: Field excitatory post synaptic potentials (fEPSPs) were recorded from rat (p14-p18) hippocampal slices (400 micron) using microelectrodes of approximately 1-4MOhm. Recordings were taken in separate experiments from both CA1 and DG regions. All sectioning was performed in a sucrose based artificial cerebral spinal fluid (aCSF) at 4 degrees Celsius. Following transverse sectioning, slices were incubated for 1 hour in normal aCSF at room temperature. Hippocampal slices were recorded in normal aCSF at 30 degrees Celsius. Throughout the duration of recordings oxygenated aCSF was washed over the slices at approximately 1.5ml/minute. During the ethanol recordings oxygenated aCSF containing ethanol (50 or 100mM) was washed over the slices at the same flow rate (1.5ml/minute). When baselines were stable for at least 15 minutes, a low frequency stimulus (LFS) protocol (900 pulses at 1Hz) was applied. To determine changes in synaptic efficacy, the initial slope of the fEPSP was measured at 55-60 minutes post LFS and compared with the average of the fEPSP slope obtaining prior to the application of the conditioning stimulus.
Results: Application of 50 and 100mM ethanol reduced basal synaptic transmission. In the CA1 region, 100mM ethanol had a greater inhibition on LTD than 50mM ethanol. In contrast, LTD was more severely attenuated by 50mM ethanol than 100mM in the DG. CONCLUSION: In conclusion, we have determined that ethanol reduces LTD in both the CA1 and DG subfields of the hippocampus. In the CA1 an increase in ethanol concentration led to an increase in LTD inhibition. However, a distinct dose response was observed in the DG, with a decrease in inhibition with an increase in ethanol concentration, suggesting that the effects of ethanol have concentration dependent effects at multiple receptor proteins. |
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