Effect of amiloride on bulk flow and iontophoretic taste stimuli in the hamster

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Abstract
This investigation 1) demonstrates the effect of amiloride on various taste responses in the hamster, and 2) tests the hypothesis that its action on iontophoretic application of taste stimuli parallels its action on bulk flow delivery. Amiloride has not previously been tested in the hamster nor has its effect on iontophoretic stimuli (socalled ‘electric taste’), which is thought to behave similarly to bulk flow stimuli, been examined. Amiloride treatment (4 min of 0.0001M) of the hamster's tongue effectively inhibited chorda tympani responses to NaCl and LiCl solutions. Bulk flow (0.1M) and iontophoretic (+7 μA through 0.001M) presentations of NaCl and LiCl, which had unequal response magnitudes pre-treatment, were inhibited to the same residual response magnitude post-treatment. Recovery then proceeded along two distinct curves asymptotically returning to pre-treatment response levels. These curves could be adequately described by a simple exponential relationship. KCl responses were unaffected when presented via bulk flow techniques but significantly reduced when presented iontophoretically. HCl responses via either method were only slightly diminished. No decrement in response level was observed for the sweet stimuli sucrose (0.5M) or saccharin (−9 μA through 0.001M Na-saccharin) nor for potassium picrate, a bitter stimulus, (0.01M or −10 μA through 0.001M). Amiloride treatment of the hamster tongue was as specific in its action for sodium and lithium as reported in other species, and with the exception of KCl the action of amiloride on iontophoretic stimulation paralleled its action on bulk flow stimulation.