1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

393 Poster Central Taste and Chemosensory BehaviorTASTE-INDUCED C-FOS EXPRESSION IN THE ROSTRALPORTION OF THE SOLITARY TRACT NUCLEUS OFNEONATAL RATSRubio L. 1 , Frias C. 1 , Regalado M. 1 , Torrero C. 1 , Salas M. 11 Developmental Neurobiology & Neurophysiology, UniversidadNacional Autonoma de Mexico, Queretaro, MexicoTaste-induction of Fos expression in the rostral portion of the solitarytract (NTSr) was previously examined in adults showing that Fosimmunoreactive(FI) cells were prominent in the NTSr, for quininemonohydrochloride (QHCl) in the medial zone of the nucleus while thesucrose (S) elicited FI concentrated in the lateral area, little is knowabout taste stimuli-induced activation of brainstem neurons in neonatalrats. The aim of this study was to compared the distribution of FIfollowing intraoral stimulation with, QHCl, S and NaCl in rats of 5, 15and 25 days of age. Subjects were isolated from the mother 3 h beforethe stimulation and later on the pups were stimulated with some of thefollowing solutions: H 2 0, QHCl 0.03, 0.003 M, S 0.1 M and NaCl 0.1M and 90 min after subjects were anesthetized the brain was removedand processed for Fos immunostaining. Data showed that FI wasincreased in this nucleus in QHCl stimulation at all age compared withS, NaCl and non-stimulated (ANOVA, p < 0.05). No differences werefound in the FI between H 2 0 and NaCl. In the NTSr, FI cells weredistributed mainly in the medial region after QHCl and in the lateralregion after S at all ages. The number of FI cells in the NTSr afterQHCl stimuli peaked on P15 and then decreased on day P25. Data showthat taste-specific responses distribution, are already present at birth andmay change during NTSr maturation. The number of FI in the NTSrbetween neonates and adults might partly depend to the reorganizationof the neuronal circuitry occurring early in life as a result of dietaryexperiences. Supported by: DGAPA/UNAM, IN 210903 andCONACYT 503001915.394 Poster Central Taste and Chemosensory BehaviorDIFFERENTIAL EFFECTS OF CROSS-REGENERATION OFTHE LINGUAL GUSTATORY NERVES ON QUININE-STIMULATED GAPING AND FOS-LIKEIMMUNOREACTIVITY IN THE NUCLEUS OF THESOLITARY TRACTKing C.T. 1 , Garcea M. 2 , Stolzeberg D.S. 1 , Spector A.C. 2 1 Psychology,Stetson Univ, DeLand, FL; 2 Psychology & Center for Smell and Taste,Univ of Florida, Gainesville, FLAn intact glossopharyngeal nerve (GL) is essential for normalunconditioned quinine-stimulated gaping behavior and fos-likeimmunoreactivity (FLI) in the gustatory nucleus of the solitary tract(gNST), especially in the medial-dorsal subfield (MD). Transection ofthe GL, but not the chorda tympani nerve (CT), attenuates gapingbehavior and MD-FLI in response to quinine, which is restored uponGL nerve regeneration In this study, the GL and CT were crossregenerated.Some rats had the central CT-stump sutured to theperipheral GL-stump (CT→PosteriorT); other rats received theconverse surgery (GL→AnteriorT). Histological analysis of taste budsconfirmed nerve regeneration. Numbers of gapes elicited by 3mMquinine in CT→PosteriorT (n = 5) and sham-operated (SHAM-Q, n = 5)rats were similar and significantly higher than those observed in waterstimulatedcontrols (SHAM-W, n = 6), while the number of quininestimulatedgapes in GL→AnteriorT rats (n = 6) was comparable to thatobserved in SHAM-W rats. Likewise, quinine-stimulated MD-FLI inCT→PosteriorT and SHAM-Q rats was comparable and significantlyhigher than MD-FLI in both SHAM-W and quinine-stimulated GL→AnteriorT rats at the most rostral level of the gNST. These findingssuggest that unconditioned quinine-induced gaping and MD-FLI in therostral gNST are more dependent on the taste receptor field stimulatedthan on the nerve that transmits the signal. Support: NIDCD R01-DC01628395 Poster Central Taste and Chemosensory BehaviorLICKING AND GAPING ELICITED BY NSTMICROSTIMULATIONKinzeler N.R. 1 , Travers S.P. 2 1 Psychobiology & BehavioralNeuroscience, Ohio State Univ, Columbus, OH; 2 Oral Biology, OhioState Univ, Columbus, OHBitter compounds evoke a distinct distribution of Fos-likeimmunoreactive cells (FLI) concentrated in dorsomedial rNST. IXthnerve section, but not decerebration disrupts this pattern, paralleling theconsequences of these manipulations on oral rejection behavior(gaping), thus suggesting that the region of Fos expression defines anafferent trigger zone for bitter-elicited protective reflexes. We testedthis using rNST microstimulation. Microelectrodes and intraoralcannulae were implanted under electrophysiological guidance. Ratswere tested with taste (0.3 M sucrose & 3 mM quinine) and electricalstimulation (0.2 ms biphasic pulses, 100 Hz) at varying intensities (5-40µA) and durations (0.1–24.3 s), and then 30 mM quinine was infused toelicit FLI. NST microstimulation was effective for eliciting licking andgaping, and the amount of oral behavior was a positive function ofcurrent intensity and duration. Licking was elicited in most (7/8)animals with placements in rNST, but gaping was observed in half(4/8). 2/4 rats had a lower threshold for licking than gaping but thereverse was never true. Correlations between the number of gapes anddistance from the densest FLI failed to reveal a systematic relationship(r = -.25, P > 0.1). Interestingly, however, only one subject had aplacement centered in the FLI, and this was the single instance wheregaping was the dominant behavior. These results suggest that thesubstrate for gaping involves neurons with a more limited anatomicalextent and perhaps a higher threshold than for licking, but defining thecritical topography requires further investigation. Supported byDC00417 and T32-DE014320.396 Poster Central Taste and Chemosensory BehaviorMELANIN CONCENTRATING HORMONE INCREASESBRIEF-ACCESS LICKING FOR SUCROSE AND WATER BUTNOT QUININE HYDROCHOLORIDEBaird J.P. 1 , Rios C. 1 , Walsh C.E. 2 , Pecora A.L. 1 1 Psychology &Neuroscience, Amherst College, Amherst, MA; 2 Psychology, SmithCollege, Northampton, MAPreviously we showed that 3V melanin concentrating hormone(MCH) injections (5 µg) increased sucrose intake by increasing lick rateearly in the meal and the mean lick-burst size, suggesting enhancedgustatory evaluation. Therefore, we evaluated brief-access (20 s) lickingfor water, sucrose and quinine hydrochloride (QHCl) solutions afterMCH/vehicle treatment. Under vehicle, licking for sucrose increasedmonotonically with concentration (0.015 M to 1 M). Licking for weakconcentrations of QHCl (0.001 mM-0.03 mM) was comparable to thatfor water, but declined exponentially across the three strongestconcentrations (0.1 mM-1 mM). MCH uniformly increased licking forall concentrations of sucrose, and water (p < 0.001). When sucroseresponses were standardized to water, the effect was completely lost,indicating that although MCH increased avidity for the tastants, it notdid modify the concentration response function. These results areconsistent with the effects of food deprivation on licking for sucroseand water in brief access tests. MCH also increased responding forwater and weak concentrations of QHCl, but it had no effect on lickingfor the three strongest concentrations of QHCl. Therefore, MCH didnot produce non-specific increases in oromotor activity, and it did notchange the perceived intensity of the tastants. We conclude that MCHenhances the gain of responses to normally-accepted stimuli at a phaseof processing that occurs after the initial gustatory apprasial and afterthe decision to accept or reject the taste stimulus. [Supported byAmherst College, Howard Hughes Medical Institute & DC-05326]99