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A threshold concentration of hexamethylenetetramine salt of 2-chloroethyl-phosphonic acid by influence on water taste is 1 mg/l. This substance slightly accumulates in animal body. Its maximum permissible concentration in water is 1 mg/l.
Preliminary evidence in man has suggested that 6-azauridine triacetate (6-AzUrdTA) might adversely affect taste acuity. The production of measurable serum concentrations of homocysteine in rabbits treated with 6-AzUrdTA further suggested a mechanism for the possible adverse effects of this drug on taste, since administration of other thiol-containing drugs in man and animals had been shown to decrease taste acuity. Since changes in preferences for NaCl solutions have been shown to reflect changes in taste acuity in the rat, preference for NaCl solutions in rats treated with 6-AzUrdTA were measured in a two-bottle test. Detection and recognition thresholds were also measured in patients with scleroderma before and after the administration of 6-AzUrdTA. Serum copper and zinc concentrations were measured in both rats and man. Rats given 6-AzUrdTA exhibited a significantly greater intake of 0.30-M NaCl than control rats, who avoided this solution. This change was accompanied by a significant decrease in serum zinc concentrations. No significant changes in taste acuity occurred in the patients. These data suggest that administration of 6-AzUrdTA affects taste acuity in rats either through the addition of thiols or the depletion of zinc.
The main objective of this study was to establish the degree of influence of various illicit drugs, taken into the body in different ways, on the senses of smell and taste. Other possible factors, that might have caused disturbances in normal functioning of both senses, were outlined. The studied group consisted of 48 drug addicts, between the age of 16 and 48 years, addicted to various illicit drugs for several years. Olfactory testing included two methods. First quantitative method described by Elsberg and Levy, modified by Pruszewicz, was used to establish the smell detection threshold. Then the University of Pennsylvania Smell Identification Test was used as a method for odor identification. The sense of taste was tested with the use of method described by Krarup and modified by Pruszewicz. The results showed disturbances in olfactory performance (combined in both method) in 52.1% of all drug abusers, and 16.7% of them were diagnosed with ageusia when the sense of taste was tested. The route of administration of illicit drugs proved to be a statistically significant factor that might have caused disturbances of smell perception and identification in the study group. Drug abusers who were taking drugs intravenously and those who smoked and inhaled various drugs had the most significant olfactory problems. Both means for assessing smell function were statistically compared and the results showed that approximately 75% of drug users with olfactory disturbances had olfactory problems in both tests.
Internal or motivational factors and external or signal factors were assessed to determine their role in motor-food response during conditioning in cats and dogs. Under experimental water-salt dysbalance visceral signalling was shown to be an essential factor involved in a goal-directed response. In addition to dominant motivation, a conditioned food signal seems to be this factor. In search for neurophysiological correlates of food motivation, we studied responses of n. tractus solitaris in rats to adequate chemical stimulation of the tongue receptors and viscerochemoreceptors. 3 groups of neurons were distinguished: those responding to the stimulation of only one receptive zone (taste and viscerochemical neurons) and neurons responding to the stimulation of both receptive areas ("convergence" units). Under salt deprivation, threshold concentrations of salt for responses from n. solitaris decreased and the response from a convergence neuron to viscerochemical stimulation diminished following application of sodium chloride on the tongue receptor.
It is universally accepted that saliva plays an important role in taste sensations. However, interactions between constituents of whole saliva and the five basic taste modalities are still poorly understood. The aim of the present study was to evaluate possible relationship between endogenous glutamate (Glu) levels in whole saliva and taste responses to a prototypic umami substance, monosodium glutamate (MSG; 0.03-10.0%). Rated intensity and pleasantness of MSG taste was studied in healthy volunteers divided into a high glutamate (HG) in saliva (HG; n = 19) and low glutamate in saliva (LG; n = 18) group based on the median split level of salivary Glu. The HG and LG group did not differ in terms of electrogustometric thresholds, rated intensity of the MSG samples and pleasantness of distilled water and the lower MSG concentrations (0.03-1.0%). Perceived intensity of water taste was significantly (P < 0.05) higher in the LG subjects. The LG group rated the higher MSG concentrations (3.0-10.0%) as more unpleasant (P < 0.01). The difference remained significant after controlling for a between-group difference in age. The present results suggest that individual differences in salivary Glu levels may alter hedonic responses to suprathreshold MSG concentrations.
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The effectiveness of labellar taste input in evoking the feeding response of labellar lobe spreading in Protophormia was greatly increased by injecting flies with clonidine or DL-octopamine. This effect was suppressed when either drug was administered together with yohimbine; when injected alone, the latter determined a strong decrease in the feeding responses. Drug treatment did not determine variations in labellar taste input or evoke spontaneous activity in the denervated muscle. These results suggest that the injected substances lower the feeding-related reflex threshold at the CNS level.
Fifty-five young adult subjects and their parents were classified as alcoholic or nonalcoholic based on a standardized questionnaire (the MAST) filled out by the subjects. Subjects' thresholds for detection of 6-n-propylthiouracil (PROP; a PTC-like compound) were determined with the experimenter blind to MAST responses. There was a significantly higher proportion of nontasters of PROP among children of alcoholics than among children of nonalcoholics. There was no relationship between the child's alcoholism status and ability to taste PROP. These results are inconsistent with the view that excessive use of alcohol causes the association between nontasting and alcoholism and are consistent with the view that there is a genetic association between PROP/PTC-tasting and alcoholism.
Taste sensory responses from the chorda tympani nerve of the rat were recorded with the lingual receptive field under current or voltage clamp. Consistent with previous results (Ye, Q., G. L. Heck, and J. A. DeSimone. 1993. Journal of Neurophysiology. 70:167-178), responses to NaCl were highly sensitive to lingual voltage clamp condition. This can be attributed to changes in the electrochemical driving force for Na+ ions through apical membrane transducer channels in taste cells. In contrast, responses to KCl over the concentration range 50-500 mM were insensitive to the voltage clamp condition of the receptive field. These results indicate the absence of K+ conductances comparable to those for Na+ in the apical membranes of taste cells. This was supported by the strong anion dependence of K salt responses. At zero current clamp, the potassium gluconate (KGlu) threshold was > 250 mM, and onset kinetics were slow (12 s to reach half-maximal response). Faster onset kinetics and larger responses to KGlu occurred at negative voltage clamp (-50 mV). This indicates that when K+ ion is transported as a current, and thereby uncoupled from gluconate mobility, its rate of delivery to the K+ taste transducer increases. Analysis of conductances shows that the paracellular pathway in the lingual epithelium is 28 times more permeable to KCl than to KGlu. Responses to KGlu under negative voltage clamp were not affected by agents that are K+ channel blockers in other systems. The results indicate that K salt taste transduction is under paracellular diffusion control, which limits chemoreception efficiency. We conclude that rat K salt taste occurs by means of a subtight junctional transducer for K+ ions with access limited by anion mobility. The data suggest that this transducer is not cation selective which also accounts for the voltage and amiloride insensitive part of the response to NaCl.
Salivary secretion was evoked reflexly by taste or noxious stimulation at different body temperatures in urethane anesthetized rats. Magnitude of salivary secretion induced either by a taste stimulus or by a pinch was facilitated by increasing rectal temperature in a range of 39-40.3 degrees C. Above a threshold rectal temperature of 40.4 degrees C, copious saliva was continuously secreted without external stimulation.
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It was investigated when and how the four examined sensory systems and the behaviour performances depending on them are affected by metamorphosis and whether they develop at an uniform rate from hatching up to metamorphosis. The following conclusions were reached on the basis of the results: -- The central nervous system starts to metamorphose earlier than the habitus and the viscera. -- Motor reactions based on the new capacities of the metamorphosed sensory systems only set in after metamorphosis. -- During metamorphosis the threshold of general sensitivity for the release of motor reactions is drastically raised. -- The sense of taste does not begin to function until after metamorphosis. -- The olfactory sense is the only one of the four tested systems that functions immediately after hatching. -- The level of development of the sensory systems and motor reactions is low in the early larva. The lack of taxis is characteristic of this. -- There is a phase of accelerated development of the sensory systems and motor reactions between the early and late larval stages. -- By comparison with the situation after metamorphosis the sensory systems of the old larva are fairly simple in their structure, but the motor reactions they permit are sufficient for the larva to cope with its aquatic biotope. -- Not until after the morphological structures have attained a new level of development do the relevant motor reactions show a corresponding advance.
The excitability of the rat chorda tympani nerve following adaptation to NaCl was measured by observing the recovery of the transient portion of the integrated neural response. When a single concentration of NaCl was used as a test stimulus, recovery time was positively correlated with the concentration of the adapting solution, a relationship common to a number of other sensory systems. Adapting and testing with the same concentration of NaCl produced very little relationship between concentration and recovery time. It is suggested that the relativley extensive period of postexcitatory depression is due to a prolonged inaccessability of tast receptor sites that results in a reduction in the rate of stimulus-receptor interaction.
Cystic fibrosis is consistently accompanied by the ability to taste and smell salt, sweet, sour, and bitter substances in solution at concentrations much more dilute than those at which the substances are detectable by normal persons. These abnormal thresholds are not affected by the administration of carbohydrate-active steroids.
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When substances of similar taste are mixed, the mixture can show suppression or synergism. That is, the perceived intensity of the mixture can be less than or greater than the sum of the perceived intensities of the components. In the present study, these departures from simple additivity could be predicted from the psychophysical functions relating tast intensity to stimulus concentration of the unmixed components. Psychophysical functions are said to show compression when successive increments in concentration produce progessively smaller increments in perceived intensity and to show expansion when successive increments in concentration produce progressively larger increments in perceived intensity. Suppression resulted from mixtures of substances with compressed psychophysical functions, and synergism resulted from mixtures of substances with expanded functions.
Milk delivery through suckling lowers human newborn heart and metabolic rats. In rat and human infants pain threshold is markedly elevated and crying is arrested. These changes are induced by milk flavor or sugar taste which release central endorphins. In rats the changes are naloxone reversible; human infants born to women who were maintained on methadone during pregnancy were not quieted by sweet taste. Cholecystokinin (CCK) released during milk absorption quiets infant rats as does beta-casomorphine derived from casein hydrolysis. Through opioid and CCK mediation, milk also causes affective change that facilitates infant-mother bonding.
The importance of olfactory learning in host plant selection is well demonstrated in insects, including the heliothine moths. In the present study olfactory conditioning of the proboscis extension response was performed to determine the moths' ability to learn and discriminate three plant odorants: beta-ocimene and beta-myrcene (activating the same receptor neurone type), and racemic linalool (activating two different types). The conditioned stimulus (CS) was an air puff with each odorant blown into a constant air stream and over the antennae, and the unconditioned stimulus (US) was sucrose solution applied first to the antennal taste sensilla, then to the proboscis. Conditioning with increasing odorant concentrations induced increased learning performance. The concentration threshold for learning was 100 times lower for racemic linalool than for the two other odorants, a fact that can be correlated with a higher sensitivity of the moths' antennae to racemic linalool as shown in electroantennogram recordings. After correcting for the different odour sensitivities, the moths' ability to discriminate the odorants was studied. Differential conditioning experiments were carried out, in which moths had to distinguish between a rewarded (CS+) odorant and an explicitly unrewarded odorant (CS-), choosing odour concentrations giving the same learning rate in previous experiments. The best discrimination was found with beta-myrcene as the rewarded odorant and racemic linalool as the unrewarded. The opposite combination gave lower discrimination, indicating a higher salience for beta-myrcene than for racemic linalool. The moths could also discriminate between beta-ocimene and beta-myrcene, which was surprising, since they activate the same receptor neurone type. No difference in salience was found between these two odorants.