Summary
The responses of individual glossopharyngeal neurons of the mud puppy,Necturus maculosus, were examined over an extended concentration series of NaCl, HCl, quinine hydrochloride (QHCl) and sucrose solutions. Neuron isolation was evaluated by a computer program that sorted neural impulses according to amplitude (Fig. 1). When sufficient isolation existed, a second program counted the impulses in each test period as well as in pre- and post-stimulus periods. Response latencies were calculated independently.
The response to taste stimulation took one of three forms: 1) increased activity, 2) decreased activity, or 3) increased activity to the water rinse. For each concentration series the magnitude (SR) and latency functions of the responses were determined. These varied among stimuli and among nerve fibers (Fig. 4). However, the SR and latency functions were found in specific combinations, the most unique being one in which both functions remained constant over an entire concentration series (Fig. 4E, F).
Most neurons responded to more than one of the stimuli. Many, however, responded to at least one of the stimuli with a particular form of response and combination of SR and latency functions (Fig. 6). In this sense they may be considered chemospecific as well as multiply sensitive. Despite the many types of response, the sum of the individual SR functions closely resembled the SR functions of the whole nerve (Fig. 7) and the summed latencies produced a temporal pattern with a phasic component similar to that of the whole nerve response (Fig. 8).
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Abbreviations
- SR :
-
stimulus concentration vs response magnitude
- L :
-
latency of response
- +,0, -,I (SR orL):
-
magnitude or latency functions with positive, zero, negative or indeterminate slope
- QHCl :
-
quinine hydrochloride
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Supported in part by NIH Grant NS09168
The authors wish to thank Mr. Marc Schneider for the computer programs and his expert assistance and Mrs. G. Chapman of Florida State University for photography. We also thank Dr. David V. Smith for his critical comments. This work was submitted in partial fulfillment of the requirements for the Ph. D. degree to Michigan State University by the senior author.
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Samanen, D.W., Bernard, R.A. Response properties of the glossopharyngeal taste system of the mud puppy (Necturus maculosus). J. Comp. Physiol. 143, 151–158 (1981). https://doi.org/10.1007/BF00606079
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DOI: https://doi.org/10.1007/BF00606079