Journal of Neurophysiology, Vol 74, Issue 1 258-272, Copyright © 1995 by APS

ARTICLES

Corticofugal influence on taste responses in the nucleus of the solitary tract in the rat

P. M. Di Lorenzo and S. Monroe
Department of Psychology, State University of New York at Binghamton 13902-6000, USA.

1. Previous work has revealed a pervasive influence of the gustatory neocortex (GN) on the electrophysiological responses to taste in the parabrachial nucleus of the pons (PbN), the second synapse in the central pathway for gustation. Subsequent experiments have further suggested that direct projections from the GN to the PbN are not sufficiently dense to account for the widespread effects of cortical input. Because the main source of input to the PbN, i.e., the nucleus of the solitary tract (NTS), also receives input from the GN, the present experiment was conducted to test the hypothesis that changes in taste responses in the PbN after temporary elimination of GN input may be a normal reaction to altered input originating in the NTS. 2. Fourty-three taste-responsive neurons in the NTS were isolated initially in urethan-anesthetized rats. Single units were then classified as "relay" (n = 12) or "nonrelay" (n = 13) on the basis of their electrophysiological response to electrical shocks delivered to the taste-responsive portion of the PbN. After histological analyses, 18 units were classified as "unknown" because the PbN stimulating electrode was found to be outside the anatomically defined taste area in the pons. 3. Electrophysiological responses to sapid solutions of the NaCl (0.1 M), HCl (0.01 M), quinineHCl (0.01 M), sucrose (0.5 M), and Na-saccharin (0.004 M) were then recorded before and after recovery from infusions of procaineHCl into the GN. Both the ipsilateral and contralateral sides of the GN, in that order, received procaine infusions separated by a recovery period of at least 45 min. 4. Analysis of across-unit patterns of response was accomplished with the use of a vector space analysis. With this approach, the response of a given neuron to a given tastant is considered as a coordinate in n-dimensional space, where n is the number of neurons tested. The responses to each stimulus generate vectors whose length relates to the overall magnitude of response across the sample and whose relative directionality indicates similarity to other across-unit patterns. Measures derived from this type of analysis were used as input in a multidimensional scaling (MDS) analysis designed to summarize the organization of the across-unit patterns of response generated by the taste stimuli. This type of analysis creates a "taste space" in which similar across-unit patterns of response are placed close together and dissimilar patterns are placed far apart.(ABSTRACT TRUNCATED AT 400 WORDS)

This article has been cited by other articles:

				J.-Y. Chen and P. M. Di Lorenzo Responses to Binary Taste Mixtures in the Nucleus of the Solitary Tract: Neural Coding With Firing Rate J Neurophysiol, May 1, 2008; 99(5): 2144 - 2157. [Abstract] [Full Text] [PDF]

				A. T. Roussin, J. D. Victor, J.-Y. Chen, and P. M. Di Lorenzo Variability in Responses and Temporal Coding of Tastants of Similar Quality in the Nucleus of the Solitary Tract of the Rat J Neurophysiol, February 1, 2008; 99(2): 644 - 655. [Abstract] [Full Text] [PDF]

				A. C. Spector and S. P. Travers The representation of taste quality in the Mammalian nervous system. Behav Cogn Neurosci Rev, September 1, 2005; 4(3): 143 - 191. [Abstract] [PDF]

				D. V. Smith, M.-K. Ye, and C.-S. Li Medullary Taste Responses are Modulated by the Bed Nucleus of the Stria Terminalis Chem Senses, June 1, 2005; 30(5): 421 - 434. [Abstract] [Full Text] [PDF]

				K. Tokita, Z. Karadi, T. Shimura, and T. Yamamoto Centrifugal Inputs Modulate Taste Aversion Learning Associated Parabrachial Neuronal Activities J Neurophysiol, July 1, 2004; 92(1): 265 - 279. [Abstract] [Full Text] [PDF]

				R. F. Lundy Jr. and R. Norgren Activity in the Hypothalamus, Amygdala, and Cortex Generates Bilateral and Convergent Modulation of Pontine Gustatory Neurons J Neurophysiol, March 1, 2004; 91(3): 1143 - 1157. [Abstract] [Full Text] [PDF]

				C.-S. Li, Y. K. Cho, and D. V. Smith Taste Responses of Neurons in the Hamster Solitary Nucleus Are Modulated by the Central Nucleus of the Amygdala J Neurophysiol, December 1, 2002; 88(6): 2979 - 2992. [Abstract] [Full Text] [PDF]

				Y. K. Cho, C.-S. Li, and D. V. Smith Gustatory Projections from the Nucleus of the Solitary Tract to the Parabrachial Nuclei in the Hamster Chem Senses, January 1, 2002; 27(1): 81 - 90. [Abstract] [Full Text] [PDF]

				J. B. Travers, K. Urbanek, and H. J. Grill Fos-like immunoreactivity in the brain stem following oral quinine stimulation in decerebrate rats Am J Physiol Regulatory Integrative Comp Physiol, August 1, 1999; 277(2): R384 - R394. [Abstract] [Full Text] [PDF]

				S. J. St. John and A. C. Spector Behavioral Discrimination between Quinine and KCl Is Dependent on Input from the Seventh Cranial Nerve: Implications for the Functional Roles of the Gustatory Nerves in Rats J. Neurosci., June 1, 1998; 18(11): 4353 - 4362. [Abstract] [Full Text] [PDF]