In Vivo Responses of Single Olfactory Receptor Neurons of Channel Catfish to Binary Mixtures of Amino Acids. Kang, Jiesheng and John Caprio. Department of Zoology and Physiology, Louisiana State University, Baton Rouge, LA. 70803-1725.
APStracts 3:0207N, 1996.
For the first time in any vertebrate, in vivo responses of single olfactory receptor neurons to odorant mixtures were studied quantitatively. Extracellular electrophysiological responses of 54 single olfactory receptor neurons from 23 channel catfish, Ictalurus punctatus , to binary mixtures of amino acids and to their components were recorded simultaneously with the electro-olfactogram (EOG). For 57% (73 of 128) of the tests, no significant change (N) from spontaneous activity occurred. Responses to the remaining 55 tests of binary mixtures were excitatory (E; 13%) or suppressive (S; 30%). No response type was associated with any specific mixture across the neurons sampled. Eighty-six percent of the responses of catfish olfactory receptor neurons to binary mixtures were classified similar to at least one of the component responses, a percentage comparable (i.e. 89%) to that observed for single olfactory bulb neurons in the same species to equivalent binary mixtures. The responses of single olfactory receptor neurons to component- similar binary mixtures (i.e. component responses were both E, both S and both N, respectively) were generally (80% of 59 tests) classified similar to the responses to the components. For E+N and S+N binary mixtures, the N component often (66% of 58 tests) reduced or concealed (i.e. "masked") the excitatory and suppressive responses, respectively. For the majority (6 of 11 tests) of E+S binary mixtures, null activity resulted. Responses to the remaining five tests were either excitatory (n=3) or suppressive (n=2).

Received 3 May 1996; accepted in final form 9 September 1996.
APS Manuscript Number J364-6.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 7 October 1996