Taste systems of goat geniculate ganglion.

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Abstract
Single-unit recordings were taken from chemosensory neurons in the geniculate ganglion of anesthetized goats to characterize this population neurophysiologically and to provide data for comparison with similar studies on carnivores. These units display complex spontaneous activity patterns, with most neurons exhibiting multipeaked interspike interval (ISI) histograms. Short-interval bursting discharge was common, with the interval length decreasing as a function of interval order within a burst. Burst lengths in terms of numbers of intervals were, in general, longer than those seen in the carnivore. Bursting was also a characteristic of elicited discharge from some units. The chemosensory units of the goat were divisible into 3 groups, .alpha., .delta. and .epsilon.. The measures used consisted primarily of their responses to a number of chemical solutions, including a test series developed to differentiate units in carnivores. Group .alpha. responded best to Bronsted acids, group .delta. to Na and Li salts. Group .epsilon. did not discharge consistently to any class of chemical stimuli but could be grouped together on the basis of a cluster of distinguishing features, including high degree of bursting and long latencies to electrical stimulation. Units classified as .alpha. and .delta. units were also partially distinguishable on the basis of various measures such as latency and bursting, although overlap of response measures was common for these 2 large-fiber groups. Only .alpha. units were appreciably responsive to a stimulus series containing water dilutions of plant foods and Chinese herbs. The responses of the .alpha. units to the test series were virtually identical to those of the Bronsted acid-sensitive units in carnivores, except for the sensitivity of the goat units to NaCl and KCl. Unlike the carnivore, no amino acid-(cat) or amino acid and sugar-(dog) responsive units were seen in the goat geniculate ganglion. The salt-responsive units in the goat could be tentatively identified with salt-responsive units reported by others in the chordal tympani of the rat and the hamster.

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