1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

425 Poster Central Taste and Chemosensory BehaviorSNIFFING PATTERNS OF RATS DURING LEARNING ANDPERFORMANCE OF ODOR DISCRIMINATION TASKSWesson D.W. 1 , Verhagen J.V. 1 , Wachowiak M. 1 1 Biology, BostonUniversity, Boston, MAOdor sampling (sniffing) is a dynamic behavior. Most earlier studieshave focused on sniffing strictly in the context of odor discrimination.In this study, we monitored sniffing behavior continuously in ratslearning and performing odor discriminations under two differentbehavioral paradigms and asked how sniffing relates to odordiscrimination as well as to other behavioral parameters. In bothparadigms, rats were habituated to head restraint and trained to performa simple lick-no-lick two odor discrimination. Sniffing, measured asintranasal pressure transients, was monitored during task acquisitionand performance. In paradigm 1, the test odorant was presented after arandom intertrial interval, with no other associated cues, while inparadigm 2 the rat was allowed to initiate each trial by pressing a barafter a tone was presented. In paradigm 1, rats sniffed at a fairlyconsistent slow frequency of 1–2 Hz. Surprisingly, sniff frequency didnot increase around the time of odor presentation. Presenting a novelodorant as a CS- induced high frequency (6–10 Hz) sniffing whichhabituated within 1–2 trials despite continued successful performance ofthe task. In paradigm 2, rats consistently showed bouts of fast sniffing.Fast sniffing began immediately following the tone and just precedingbar press, but ceased as soon as odor presentation began. Odordiscrimination difficulty did not influence the likelihood or duration offast sniffing. Thus, fast sniffing is more strongly associated with theexpectation of or search for an odor stimulus than with thediscrimination of the odor itself. Funded by NIDCD DC06441.426 Poster Central Taste and Chemosensory BehaviorOLFACTORY SENSITIVITY FOR ENANTIOMERS ANDTHEIR RACEMIC MIXTURES—A COMPARATIVE STUDY INMICE AND SPIDER MONKEYSJoshi D. 1 , Voelkl M. 2 , Shepherd G.M. 1 , Laska M. 1 1 Neurobiology, YaleUniversity, New Haven, CT; 2 Medical Psychology, University ofMunich, Munich, GermanyEnantiomers appear to be particularly valuable tools to assess odorstructure-activity relationships. Using an operant conditioningparadigm, we determined olfactory detection thresholds for the opticalantipodes of carvone and limonene as well as for their racemic mixturesin CD-1 mice. We found that (a) with few exceptions the mice wereable to detect all six stimuli at concentrations below 1 ppm, (b) allanimals were more sensitive for (–)-limonene compared to (+)-limonene, whereas no systematic difference in sensitivity was observedfor the optical antipodes of carvone, and (c) racemic mixtures of bothlimonene and carvone were not perceived at lower concentrationscompared to the single compounds. Also using an operant conditioningparadigm, five spider monkeys were tested in parallel. We found that(a) the spider monkeys were at least as sensitive for all six stimuli as themice, (b) all animals were more sensitive for (+)-limonene compared to(–)-limonene, whereas no systematic difference in sensitivity wasobserved for (+)- and (–)-carvone, and (c) racemic mixtures of bothlimonene and carvone were perceived at lower concentrations comparedto the single compounds. Possible reasons underlying the differentpatterns of sensitivity found with mice and spider monkeys arediscussed. GMS is supported by NIH grant (5 R01 DC00086-38) andthe Human Brain Project.427 Poster Central Taste and Chemosensory BehaviorBRIEF STIMULUS PRESENTATIONS PERMIT GUSTATORYDETECTION OF LINOLEIC ACID BUT NOT OLEIC ACID INRATSPittman D.W. 1 , Adamson A. 1 , Bramlett M. 1 , Evans S. 1 , Gasque L. 1 ,Lister R. 1 1 Psychology, Wofford College, Spartanburg, SCWe have shown that Sprague-Dawley rats can detect and avoid bothlinoleic and oleic acid during 15-min 2-bottle preference testingfollowing a conditioned taste aversion pairing. This study characterizedthe ability of rats to detect a variety of concentrations (44, 88, 176 µM)of linoleic, oleic, and lauric acid following a conditioned taste aversionpairing with either 88 µM linoleic or oleic acid as the conditionedstimulus. Furthermore, the role of the chorda tympani nerve wasexamined through bilateral transections in a subset of the subjects. Alltesting was conducted in the Davis Rig using 30-s stimulus durations.Rats with intact gustatory systems and a conditioned stimulus of 88 µMlinoleic acid showed significant (F 1,160 = 20.230; p < 0.01) avoidance of44, 88, and 176 µM linoleic acid and a slight generalized avoidance ofoleic acid at the 88 and 176 µM concentrations with no avoidance oflauric acid. There was a significant effect of chorda tympani nervetransection (F 1.160 = 10.381; p < 0.01) eliminating the avoidance of oleicacid and 44 µM linoleic acid with a diminished avoidance of linoleicacid at 88 and 176 µM concentrations. Rat with intact gustatory systemsand a conditioned stimulus of 88 µM oleic acid did not demonstrate anyavoidance of linoleic, oleic, or lauric acid. Based on the current studyand our previous findings, it appears that the chorda tympani nerveplays a role in the selective detection of linoleic acid but not oleic acid.Furthermore, there appears to be another mechanism of free fatty aciddetection that may be based on olfactory or post-ingestive cues.428 Poster Central Taste and Chemosensory BehaviorSALT DISCRIMINATION IN RATS WITH CROSS-REGENERATED LINGUAL GUSTATORY NERVESBlonde G. 1 , Jiang E. 1 , Garcea M. 1 , Spector A.C. 1 1 Department ofPsychology and Center for Smell and Taste, University of Florida,Gainesville, FLBecause chorda tympani nerve (CT) transection in rats severelydisrupts their performance in salt discrimination tasks, butglossopharyngeal nerve (GL) transection does not, we tested whetherrats with either the CT cross-regenerated to the posterior tongue or theGL cross-regenerated to the anterior tongue would be competent on aNaCl vs. KCl discrimination using a two-response operant procedure.In both groups of rats with cross-regenerated nerves, overallperformance decreased significantly relative to before surgery.Performance was also significantly lower than rats with intact ornormally regenerated CT nerves, and no better than rats with bilateralCT transection. With further postsurgical testing, some rats in allgroups improved their performance, seemingly learning a newdiscrimination. Amiloride treatment significantly decreasedperformance in all groups both pre- and postsurgically. Functionalconnectivity in the cross-regenerated nerves was confirmedelectrophysiologically in a subset of animals and regeneration in allanimals was verified histologically. These results suggest that neithercross-regeneration condition emulates the normally regenerated CTwith regard to this task. It is possible that the cross-regenerated nervesare capable of providing discriminable signals generated by these salttaste stimuli, however the contribution of the greater superficial petrosalnerve to the performance cannot be dismissed. We thank Drs. ScottHerness and Susan Travers for their help with the electrophysiology.Supported by NIH R01-DC01628.107