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Amiloride Disrupts NaCl versus KCl Discrimination Performance: Implications for Salt Taste Coding in Rats. Alan C. Spector , Nick A. Guagliardo , and Steven J. St. John. Department of Psychology, University of Florida, Gainesville, Florida 32611.
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AmilorideDisrupts NaCl versus KCl Discrimination Performance: Implications for Salt Taste Coding in Rats Alan C. Spector, Nick A. Guagliardo, and Steven J. St. John Department of Psychology, University of Florida, Gainesville, Florida 32611 • Amiloride reduced salt discrimination performance by 50% at the highest concentrations • Narrowly tuned N-units play an important role in taste discrimination of sodium and nonsodium salts
Methods - Training • Five male rats subjected to testing in gustometer • Trained to press one of two levers • NaCl (0.05, 0.1, 0.2M) presentation - left lever • KCl (0.05, 0.1, 0.2M) presentation - right lever • Water access given as reward to correct response • 30 s time out given to punish incorrect response • After reinforcement or punishment, a 10 s dark interval was presented • Beginning of each trial was indicated by lights being turned on • Rat was given 3 s to sample the stimulus from a drinking spout, and 5 s to respond • After the 5 s response period the water spout was rotated out of the rat’s reach
Methods - Testing • Testing began with 3 control sessions using the same salt solutions as used in training • Next, amiloride was mixed with both salt solutions and the water reinforcement • Amiloride concentrations presented in the order of 100, 30, 3, 1, 10, and 100 µM • Between each concentration session another 2-3 control sessions were presented • The last session presented water against KCl
Performance disrupted by amiloride was dosage dependent • At 30 and 100 µM performance was reduced to approximately 50% • Amiloride had large effects on NaCl discrimination and only nominal effects on KCl
At Amiloride concentrations of 30 and 100 µM rats were pressing the KCl lever the most • Shows that the rats respond differently to the stimuli than they do to water
There is a significant interaction between NaCl concentration and amiloride concentration • Under control conditions NaCl concentration did not cause significant behavioral changes, but under testing conditions amiloride concentration did
There was no significant overall effect of amiloride on KCl • However, there was a significant effect on the O.2 M [KCl] alone at the 10 and 30 µM concentrations
Conclusions • NaCl discrimination was negatively correlated with amiloride concentration (dosage dependent) • At the highest amiloride concentrations, discrimination performance was reduced by 50% • As NaCl concentrations are increased, amiloride seems to have less of an effect at the same concentration • Competitive inhibition • At higher amiloride concentrations rats seemed to confuse NaCl with KCl • Amiloride had only a slight effect on KCl response in comparision to NaCl • Narrowly tuned N-units clearly play a role in sodium salt discrimination