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Human judgments of Gymnema sylvestre and sucrose mixtures
Physiology and Behavior. Vol. 5, pp. 945-948. Pergamon Press, 1970. Printed in Great Britain
BRIEF COMMUNICATION Human Judgments of Gymnema sylvestre and Sucrose Mixtures ''2 HERBERT
L. M E I S E L M A N
AND
B R U C E P. H A L P E R N
Pioneering Research Laboratory, United States Army Natick Laboratories, Natick, Massachussetts, U.S.A. and Department of Psychology, Section on Neurobiology and Behavior, Cornell University, Ithaca, New York, U.S.A. (Received 11 F e b r u a r y 1970)
MEISELMAN,H. L. ANDB. P. HALPERN. Humanjudgments ofGymnema sylvestre andsucrose mixtures. PHYSIOL.BEHAV. 5 (8), 945--948, 1970.--The effects of the sweet suppressant, Gymnema sylvestre (G), were studied in mixture with sucrose. Both an aqueous decoction and purified Gymnemic acid were studied. The initial impression of sweetness of the mixture of G and sucrose was not different from the sweetness of a suitable control. The lack of suppression was attributed to the relatively slow buildup of effect of G. This buildup and the following recovery were quantitatively examined. At least 30 sec were needed for the full effect of G to appear, and recovery was not complete 50 min later. Taste
Inhibition
Receptor mechanisms
Sweetness
THE GUSTATORYeffects on human judgments of the leaves of Gymnema sylvestre (G) have been studied with several different preparations of leaves, with different psychophysical procedures, and with various test compounds. Suppression o f sweetness has been reported in every case [10, 18]. Although no significant depression of sourness has been reported, depression of saltiness [11, 15] and bitterness [10,11 ] has been observed. Bartoshuk et al. [2] demonstrated that rinsing the mouth with distilled water after G extracts eliminated both the taste of the G and an effect on bitter judgments produced under their conditions through cross-adaptation. Similarly, the presence of salts in some early G preparations [11, 15] could account for the slight salty depression noted. This apparent specificity of G to sweet judgments is supported by human chorda tympani recordings in which G suppressed activity in response to sucrose and saccharin but not NaCI, citric acid, or quinine hydrochloride [4]. However, neural recordings from other human gustatory afferent nerves (cranial IX and X) are not available. The electrophysiological findings from the distal portion of cut peripheral gustatory nerves in man [4i and other mammals [1, 7] suggest that G works peripherally, probably at the distal end of the receptor [8]. Warren and Pfaffmann [17] suggested receptor site competition as the mode of action, and Dzendolet [5] has related a site competition effect to his
Gymnemasylvestre
general sweetness model, suggesting that the G straddles a receptor site, blocking entrance to the "stimulus". Recently, however, Warren et aL reported that prior presentation of sucrose or sodium saccharin did not affect the elevation of threshold produced by G without sweet additives [18]. The authors concluded that their findings argue against competition for receptor sites as a mechanism, and suggested that G might interfere with an intermediate step in nerve stimulation. In contrast, Faull et al. [6] report that data from several G experiments are fit by a competitive inhibition model. The above conflicting experiments questioned the site and mechanism of action of G. To test part of the Warren et al. proposal that G acts at a secondary step in gustatory receptor transduction, judgments of sucrose solutions were made before, during (as a mixture), and after the presentation of G or a suitable control. This tested the basic logic of their experiment, since if a prior presentation of sucrose is going to modify the effect of G, then the time required by G to reach the sucrose receptor sites must be comparable to the time required by sucrose itself. Thus, G should reduce sweet judgments when presented as a G-sucrose mixture. We conducted two such main experiments at different times using independent groups of subjects and different testers. Both experiments used the same psychophysical procedure and differed only in the form of G used: An aqueous decoction
1This work was supported by a United States Public Health Service Postdoctoral Fellowship to Dr. Meiselman, and Grant No. NB-06945 from the National Institute of Neurological Disease and Stroke, United States Public Health Service to Dr. Halpem. ~Dr. Linda Bartoshuk is thanked for the supply of Gymnema sylvestre leaves, and for reading the manuscript. Mr. John Faull also read the manuscript, and aided greatly in purifying the Gymnemasylvestre. Mr. Howard Fillet and Mr. Charles Schaninger tested the subjects. 945
946
M E I S E L M A N ,AND H A L P E R N
(GS) or gymnemic acid (HG). It will be shown that G has no immediate effect on sucrose. This lead to a brief third experiment on the time course of the G effect.
'~o
METHOD
Subjects were eleven nonsmoking male undergraduates at Cornell University, chosen from a larger group on the basis of their performance in a gustatory screening task [14]. Six subjects were used to test effects of the GS and five for the HG. All solutions were made with distilled water (conductivity < 6 × l0 -6 mhos/cm, refractive index = 1.3330). Solutions of reagent grade sucrose at 0.0, 0.1, 0.35 and 1.25 M were presented to subjects in disposable plastic beakers at 32°C. The GS or its control tea was prepared by adding 5 g of either Gymnema sylvestre leaves or orange pekoe leaves (Sahib Brand, S. S. Pierce, Boston, Massachusetts), respectively, to 75 ml distilled water, and heating in a water bath for 1 hr at 95°C. The decoction was filtered and refrigerated at 4°C for up to 2 days until use. When H G was used, it was prepared using a procedure based on that reported by Bartoshuk et al. [2], and a 0.05% solution was used. In this case, the control solution was 2 x 10-~ M quinine hydrochloride (U. S. P. grade). During any one session, the subject was presented with
5
E
4o~
0
0
Pre Mix Post Pre Mix Post Pre Mix Post Pre Mix Post HeO 0.10 0.35 1.25 Sucrose concentrotion, M
FIG. lb. Mean magnitude estimations of sweet, sour, bitter and salty for presentations of sucrose and water preceding the mixture (PRE), sucrose and HG or quinine control (MIX), and sucrose and water following the mixture (POST). The HG conditions are shown in striped lines and the quinine control in solid lines.
_J_. g "6
o
mm
E -
g ~5 ~
o
5
o Pre Mix Post Pre Mix Post Pre Mix Post Pre Mix Post Hz 0 0.10 0.55 1.25 Sucrose concentrotion,
M
three 10 ml samples of solution. Each sample was separated from the next by 3 min rest intervals. Each solution was held in the mouth for 3 sec, and then expectorated. The first solution (PRE) was 5 ml of one of the 4 concentrations of sucrose mixed with 5 ml of distilled water. The four concentrations were presented in random order in separate sessions. The subject was asked to consider the first solution in each session a standard and assign it a value of ten. Further, he was asked to divide this total intensity among four taste categories: Sour, salty, bitter and sweet (profile). The subjects usually assigned the mixture of sucrose and water values close to sweet 10, salty 0, sour 0 and bitter 0, whereas the G and sucrose mixture received ratings fi'om more than one category. After assigning the standard a value often, subjects were asked to estimate the magnitude of the two later stimuli using numbers in proportion to the strength of the standard, according to the procedure of magnitude estimation. The subjects rated their initial impression of each stimulus and gave their magnitude estimates immediately after expectorating each solution. Three min after the first solution (PRE), 5 ml of the same sucrose concentration mixed with 5 ml of either G or control was presented, and the subject was asked for a four category profile (MIX). After 3 more rain, the standard of sucrose and water was presented again for profiling (POST).
F I G . la. M e a n magnitude estimations o f sweet, sour, bitter and salty for presentations of sucrose and water preceding the mixture
RESULTS AND mSCUSSIO~
(PRE), sucrose and GS or control tea (MIX), and sucrose and water following the mixture (POST). The GS conditions are shown in striped lines and the control tea conditions in solid lines.
and H G and their controls for the initial (PRE) ratings
Sweet ratings of sucrose solutions were s i ~ t a r for both GS
GYMNEMA SYLVESTRE AND SUCROSE MIXTURES
947
(t test p > 0.10) and comparable depressions of sweet ratings were obtained for the mixtures (MIX) (t test p > 0.10). However, sweetness measured three minutes after exposure to the mixture (POST) showed a depression of sweetness for the G conditions relative to the control conditions (t test p < 0.001). The sweetness of the H G control was approximately the same for PRE and POST conditions (t test p > 0.10) although a depression was noted with the GS control (t test p < 0.01). Both HG, GS and their controls were predominantly bitter as indicated by their profile when in combination with 0.0 M sucrose (distilled water) the GS and control tea being considerably more bitter than the H G and quinine control. F o r the GS and its tea control, the increased ratings of sweet and decreased ratings of bitter in the mixture parallel the three increasing concentrations of sucrose. F o r the H G mixture and its quinine control, the results were in the same direction but not as clear. The lack of any immediate differential effect between Gsucrose mixtures and suitable controls (MIX), considered together with the strong after-effect (POST), indicates that the presence in sucrose solutions of G does not interfere immediately with the receptor process. Also, the presence of sucrose does not prevent the subsequent G effect, as Warren et al. had reported [18]. In other words, the taste of the sucrose in the mixture is not immediately affected by the pharmacological action of G. The immediate effect of both H G and GS in mixtures is due to their sapid properties as shown by identical effects from control, having only sapid action. The delayed effect of G may be a gradual action on the receptor membrane, by either displacing the sucrose stimulus from its sites or by occupying sites when they are vacated by sucrose. It is suggested that the slight but significant after-effect on sweetness for control tea but not for quinine control resulted from the relatively intense and persisting taste of the former. Removing the strong taste, as in the quinine control, removed this after-effect. The lack of immediate differential effect by G suggested the possibility of a temporal advantage in favor of the sucrose. Kurihara [12] stated that the antisweet activity of H G reached its maximum after being held in the mouth for about 30 sec, but reported no specific data. We made a brief experiment to illuminate the time course of the effect of G. F o u r subjects from the H G mixture experiment were asked to give a fourcategory taste profile of a 0.35 M sucrose and H G mixture every 5 sec for 50 sec, during which the solution was held in the mouth. Then, 0.35 M sucrose was presented repeatedly at intervals over the next 50 min for profiling, to plot the recovery from HG. N o rinses were used.
The profile clearly indicates that sweet ratings did not reach a minimum for 20--40 sec, and that bitter ratings of the H G reached a maximum within 25 see (Fig. 2). The sweet minimum was a decrease of almost 90 per cent while magnitude estimates of aqueous sucrose held in the mouth for 5 rain decreased by only 50 per cent [13]. Although no control for
ICo
o
Sweet Bitter
Z L~ o
STD
//
I I
~
I I0
t
I I00
T i m e within session,
t
I
I
~000
sec
FIG. 2. Mean magnitude estimations of sweet and bitter of the standard (STD), the sucrose--HG mixture, and the sucrose solutions presented to measure recovery from HG.
G was run in this experiment, it is doubtful whether the temporal delay to maximum magnitude is common to other compounds with a bitter taste, since the reaction time for QHCI has been reported to be well below 5 sec [3, 9]. While the bitterness quickly returns to its initial value, sweetness has not recovered completely even after 50 min. The reciprocal nature of decreased sweet and increased bitter judgments in the development period suggest that the bitter taste parallels the blocking onset. Thus, it appears that judgments of the initial impression of sweetness in mixtures of sucrose and G are not affected by the pharmacological action of the latter because of the delay of effect of the G. Therefore, judgments of initial impressions to mixtures o f G and sucrose do not provide an appropriate situation for studying possible competition between G and sucrose, although the studying of changes over time resulting from such a mixture might provide a profitable approach. Whether the delay is related to the relatively large size [16] and hence potentially smaller mobility of the G or to other factors, is unclear at this time.
REFERENCES
1. Andersson, B., S. Landgren, L. Olsson and Y. Zotterman. The sweet taste fibres of the dog. Acta physiol, scand. 21: 105-119, 1950. 2. Bartoshuk, L. M., G. P. Dateo, D. J. Vandenbelt, R. L. Buttrick and L. Long, Jr. Effects of Gymnema sylvestre and Synsepalum dulcificum on taste in man. In: Olfaction and Taste I11, edited by C. Pfaffmann. New York: Rockefeller Press, 1970, in press. 3. Bujas, Z. Le temps de reaction aux excitations gustatives d'intensit6 diff6rente. C. r. Soc. Biol. 119: 1360-1362, 1935. 4. Diamant, H., B. Oakley, L. Strom, C. Wells and Y. Zotterman. A comparison of neural and psychophysical responses to taste stimuli in man. Actaphysiol. seand. 64: 67-74, 1965.
5. Dzendolet, E. Theory for the mechanism of action of "miracle fruit". Percept. Psychophys. 6: 187-188, 1969. 6. Faull, J. R., P. D. Reilly and B. P. Halpern. The mechanism of action of gymnemic acid. Paper presented at Eastern Psychological Association, Atlantic City, 1970. 7. Hagstrom, E. C. Nature of taste stimulation by sugar. Unpublished Ph.D. Dissertation, Brown University, 1954. 8. Halpern, B. P. Some relationships between electrophysiology and behavior in taste. In: The Chemical Senses and Nutrition, edited by M. Kare and O. Mailer. Baltimore: Johns Hopkins, 1967, pp. 213-241. 9. Hara, S. Interrelationship among stimulus intensity, stimulated area and reaction time in the human gustatory sensation. Bull. Tokyo Med. Dent. Univ. 2: 147-158, 1955.
948 10. Hooper, D. Gymnemic acid. Chem. News 59: 159-160, 1889. 11. Kiesow, F. Ueber die Wirkung des Cocain under der Gymnesaure auf die Schleimhaut der Zunge und des Mundraums. Phil. Stud. 9: 510-527, 1894. 12. Kurihara, Y. Antisweet activity of gynmemic acid At and its derivatives. Life Sci. 8: 537-543, 1969. 13. Meiselman, H. L. Magnitude estimations of the course of gustatory adaptation. Percept. Psychophys. 4: 193-196, 1968. 14. Meiselman, H. L. and E. Dzendolet. Variability in gustatory quality identification. Percept. Psychophys. 2: 496-498, 1967.
MEISI~LMAN AND I tALPEt(N 15. Shore, L. E. A contribution to our knowlcdge o1' laste sensations. Ji Physiol. 13: 191-217, 1892. 16. Stocklin, W., E. Weiss and T. Reichstein. Gymnesaurc, das antisaccharin Prinzip yon Gymnema sylvestre. Helv. Chim. Acta 50: 474-490, 1967. 17. Warren, R. M. and C. Pfaffmann. Suppression of sweet sensitivity by potassium gymnemate. J. appl. Physiol. 14: 40-42, 1959. 18. Warren, R. P., R. M. Warren and M. G. Weninger. Inhibition of the sweet taste by Gyumema sylvestrc. Nature 223: 94-95, 1969.
BRIEF COMMUNICATION Human Judgments of Gymnema sylvestre and Sucrose Mixtures ''2 HERBERT
L. M E I S E L M A N
AND
B R U C E P. H A L P E R N
Pioneering Research Laboratory, United States Army Natick Laboratories, Natick, Massachussetts, U.S.A. and Department of Psychology, Section on Neurobiology and Behavior, Cornell University, Ithaca, New York, U.S.A. (Received 11 F e b r u a r y 1970)
MEISELMAN,H. L. ANDB. P. HALPERN. Humanjudgments ofGymnema sylvestre andsucrose mixtures. PHYSIOL.BEHAV. 5 (8), 945--948, 1970.--The effects of the sweet suppressant, Gymnema sylvestre (G), were studied in mixture with sucrose. Both an aqueous decoction and purified Gymnemic acid were studied. The initial impression of sweetness of the mixture of G and sucrose was not different from the sweetness of a suitable control. The lack of suppression was attributed to the relatively slow buildup of effect of G. This buildup and the following recovery were quantitatively examined. At least 30 sec were needed for the full effect of G to appear, and recovery was not complete 50 min later. Taste
Inhibition
Receptor mechanisms
Sweetness
THE GUSTATORYeffects on human judgments of the leaves of Gymnema sylvestre (G) have been studied with several different preparations of leaves, with different psychophysical procedures, and with various test compounds. Suppression o f sweetness has been reported in every case [10, 18]. Although no significant depression of sourness has been reported, depression of saltiness [11, 15] and bitterness [10,11 ] has been observed. Bartoshuk et al. [2] demonstrated that rinsing the mouth with distilled water after G extracts eliminated both the taste of the G and an effect on bitter judgments produced under their conditions through cross-adaptation. Similarly, the presence of salts in some early G preparations [11, 15] could account for the slight salty depression noted. This apparent specificity of G to sweet judgments is supported by human chorda tympani recordings in which G suppressed activity in response to sucrose and saccharin but not NaCI, citric acid, or quinine hydrochloride [4]. However, neural recordings from other human gustatory afferent nerves (cranial IX and X) are not available. The electrophysiological findings from the distal portion of cut peripheral gustatory nerves in man [4i and other mammals [1, 7] suggest that G works peripherally, probably at the distal end of the receptor [8]. Warren and Pfaffmann [17] suggested receptor site competition as the mode of action, and Dzendolet [5] has related a site competition effect to his
Gymnemasylvestre
general sweetness model, suggesting that the G straddles a receptor site, blocking entrance to the "stimulus". Recently, however, Warren et aL reported that prior presentation of sucrose or sodium saccharin did not affect the elevation of threshold produced by G without sweet additives [18]. The authors concluded that their findings argue against competition for receptor sites as a mechanism, and suggested that G might interfere with an intermediate step in nerve stimulation. In contrast, Faull et al. [6] report that data from several G experiments are fit by a competitive inhibition model. The above conflicting experiments questioned the site and mechanism of action of G. To test part of the Warren et al. proposal that G acts at a secondary step in gustatory receptor transduction, judgments of sucrose solutions were made before, during (as a mixture), and after the presentation of G or a suitable control. This tested the basic logic of their experiment, since if a prior presentation of sucrose is going to modify the effect of G, then the time required by G to reach the sucrose receptor sites must be comparable to the time required by sucrose itself. Thus, G should reduce sweet judgments when presented as a G-sucrose mixture. We conducted two such main experiments at different times using independent groups of subjects and different testers. Both experiments used the same psychophysical procedure and differed only in the form of G used: An aqueous decoction
1This work was supported by a United States Public Health Service Postdoctoral Fellowship to Dr. Meiselman, and Grant No. NB-06945 from the National Institute of Neurological Disease and Stroke, United States Public Health Service to Dr. Halpem. ~Dr. Linda Bartoshuk is thanked for the supply of Gymnema sylvestre leaves, and for reading the manuscript. Mr. John Faull also read the manuscript, and aided greatly in purifying the Gymnemasylvestre. Mr. Howard Fillet and Mr. Charles Schaninger tested the subjects. 945
946
M E I S E L M A N ,AND H A L P E R N
(GS) or gymnemic acid (HG). It will be shown that G has no immediate effect on sucrose. This lead to a brief third experiment on the time course of the G effect.
'~o
METHOD
Subjects were eleven nonsmoking male undergraduates at Cornell University, chosen from a larger group on the basis of their performance in a gustatory screening task [14]. Six subjects were used to test effects of the GS and five for the HG. All solutions were made with distilled water (conductivity < 6 × l0 -6 mhos/cm, refractive index = 1.3330). Solutions of reagent grade sucrose at 0.0, 0.1, 0.35 and 1.25 M were presented to subjects in disposable plastic beakers at 32°C. The GS or its control tea was prepared by adding 5 g of either Gymnema sylvestre leaves or orange pekoe leaves (Sahib Brand, S. S. Pierce, Boston, Massachusetts), respectively, to 75 ml distilled water, and heating in a water bath for 1 hr at 95°C. The decoction was filtered and refrigerated at 4°C for up to 2 days until use. When H G was used, it was prepared using a procedure based on that reported by Bartoshuk et al. [2], and a 0.05% solution was used. In this case, the control solution was 2 x 10-~ M quinine hydrochloride (U. S. P. grade). During any one session, the subject was presented with
5
E
4o~
0
0
Pre Mix Post Pre Mix Post Pre Mix Post Pre Mix Post HeO 0.10 0.35 1.25 Sucrose concentrotion, M
FIG. lb. Mean magnitude estimations of sweet, sour, bitter and salty for presentations of sucrose and water preceding the mixture (PRE), sucrose and HG or quinine control (MIX), and sucrose and water following the mixture (POST). The HG conditions are shown in striped lines and the quinine control in solid lines.
_J_. g "6
o
mm
E -
g ~5 ~
o
5
o Pre Mix Post Pre Mix Post Pre Mix Post Pre Mix Post Hz 0 0.10 0.55 1.25 Sucrose concentrotion,
M
three 10 ml samples of solution. Each sample was separated from the next by 3 min rest intervals. Each solution was held in the mouth for 3 sec, and then expectorated. The first solution (PRE) was 5 ml of one of the 4 concentrations of sucrose mixed with 5 ml of distilled water. The four concentrations were presented in random order in separate sessions. The subject was asked to consider the first solution in each session a standard and assign it a value of ten. Further, he was asked to divide this total intensity among four taste categories: Sour, salty, bitter and sweet (profile). The subjects usually assigned the mixture of sucrose and water values close to sweet 10, salty 0, sour 0 and bitter 0, whereas the G and sucrose mixture received ratings fi'om more than one category. After assigning the standard a value often, subjects were asked to estimate the magnitude of the two later stimuli using numbers in proportion to the strength of the standard, according to the procedure of magnitude estimation. The subjects rated their initial impression of each stimulus and gave their magnitude estimates immediately after expectorating each solution. Three min after the first solution (PRE), 5 ml of the same sucrose concentration mixed with 5 ml of either G or control was presented, and the subject was asked for a four category profile (MIX). After 3 more rain, the standard of sucrose and water was presented again for profiling (POST).
F I G . la. M e a n magnitude estimations o f sweet, sour, bitter and salty for presentations of sucrose and water preceding the mixture
RESULTS AND mSCUSSIO~
(PRE), sucrose and GS or control tea (MIX), and sucrose and water following the mixture (POST). The GS conditions are shown in striped lines and the control tea conditions in solid lines.
and H G and their controls for the initial (PRE) ratings
Sweet ratings of sucrose solutions were s i ~ t a r for both GS
GYMNEMA SYLVESTRE AND SUCROSE MIXTURES
947
(t test p > 0.10) and comparable depressions of sweet ratings were obtained for the mixtures (MIX) (t test p > 0.10). However, sweetness measured three minutes after exposure to the mixture (POST) showed a depression of sweetness for the G conditions relative to the control conditions (t test p < 0.001). The sweetness of the H G control was approximately the same for PRE and POST conditions (t test p > 0.10) although a depression was noted with the GS control (t test p < 0.01). Both HG, GS and their controls were predominantly bitter as indicated by their profile when in combination with 0.0 M sucrose (distilled water) the GS and control tea being considerably more bitter than the H G and quinine control. F o r the GS and its tea control, the increased ratings of sweet and decreased ratings of bitter in the mixture parallel the three increasing concentrations of sucrose. F o r the H G mixture and its quinine control, the results were in the same direction but not as clear. The lack of any immediate differential effect between Gsucrose mixtures and suitable controls (MIX), considered together with the strong after-effect (POST), indicates that the presence in sucrose solutions of G does not interfere immediately with the receptor process. Also, the presence of sucrose does not prevent the subsequent G effect, as Warren et al. had reported [18]. In other words, the taste of the sucrose in the mixture is not immediately affected by the pharmacological action of G. The immediate effect of both H G and GS in mixtures is due to their sapid properties as shown by identical effects from control, having only sapid action. The delayed effect of G may be a gradual action on the receptor membrane, by either displacing the sucrose stimulus from its sites or by occupying sites when they are vacated by sucrose. It is suggested that the slight but significant after-effect on sweetness for control tea but not for quinine control resulted from the relatively intense and persisting taste of the former. Removing the strong taste, as in the quinine control, removed this after-effect. The lack of immediate differential effect by G suggested the possibility of a temporal advantage in favor of the sucrose. Kurihara [12] stated that the antisweet activity of H G reached its maximum after being held in the mouth for about 30 sec, but reported no specific data. We made a brief experiment to illuminate the time course of the effect of G. F o u r subjects from the H G mixture experiment were asked to give a fourcategory taste profile of a 0.35 M sucrose and H G mixture every 5 sec for 50 sec, during which the solution was held in the mouth. Then, 0.35 M sucrose was presented repeatedly at intervals over the next 50 min for profiling, to plot the recovery from HG. N o rinses were used.
The profile clearly indicates that sweet ratings did not reach a minimum for 20--40 sec, and that bitter ratings of the H G reached a maximum within 25 see (Fig. 2). The sweet minimum was a decrease of almost 90 per cent while magnitude estimates of aqueous sucrose held in the mouth for 5 rain decreased by only 50 per cent [13]. Although no control for
ICo
o
Sweet Bitter
Z L~ o
STD
//
I I
~
I I0
t
I I00
T i m e within session,
t
I
I
~000
sec
FIG. 2. Mean magnitude estimations of sweet and bitter of the standard (STD), the sucrose--HG mixture, and the sucrose solutions presented to measure recovery from HG.
G was run in this experiment, it is doubtful whether the temporal delay to maximum magnitude is common to other compounds with a bitter taste, since the reaction time for QHCI has been reported to be well below 5 sec [3, 9]. While the bitterness quickly returns to its initial value, sweetness has not recovered completely even after 50 min. The reciprocal nature of decreased sweet and increased bitter judgments in the development period suggest that the bitter taste parallels the blocking onset. Thus, it appears that judgments of the initial impression of sweetness in mixtures of sucrose and G are not affected by the pharmacological action of the latter because of the delay of effect of the G. Therefore, judgments of initial impressions to mixtures o f G and sucrose do not provide an appropriate situation for studying possible competition between G and sucrose, although the studying of changes over time resulting from such a mixture might provide a profitable approach. Whether the delay is related to the relatively large size [16] and hence potentially smaller mobility of the G or to other factors, is unclear at this time.
REFERENCES
1. Andersson, B., S. Landgren, L. Olsson and Y. Zotterman. The sweet taste fibres of the dog. Acta physiol, scand. 21: 105-119, 1950. 2. Bartoshuk, L. M., G. P. Dateo, D. J. Vandenbelt, R. L. Buttrick and L. Long, Jr. Effects of Gymnema sylvestre and Synsepalum dulcificum on taste in man. In: Olfaction and Taste I11, edited by C. Pfaffmann. New York: Rockefeller Press, 1970, in press. 3. Bujas, Z. Le temps de reaction aux excitations gustatives d'intensit6 diff6rente. C. r. Soc. Biol. 119: 1360-1362, 1935. 4. Diamant, H., B. Oakley, L. Strom, C. Wells and Y. Zotterman. A comparison of neural and psychophysical responses to taste stimuli in man. Actaphysiol. seand. 64: 67-74, 1965.
5. Dzendolet, E. Theory for the mechanism of action of "miracle fruit". Percept. Psychophys. 6: 187-188, 1969. 6. Faull, J. R., P. D. Reilly and B. P. Halpern. The mechanism of action of gymnemic acid. Paper presented at Eastern Psychological Association, Atlantic City, 1970. 7. Hagstrom, E. C. Nature of taste stimulation by sugar. Unpublished Ph.D. Dissertation, Brown University, 1954. 8. Halpern, B. P. Some relationships between electrophysiology and behavior in taste. In: The Chemical Senses and Nutrition, edited by M. Kare and O. Mailer. Baltimore: Johns Hopkins, 1967, pp. 213-241. 9. Hara, S. Interrelationship among stimulus intensity, stimulated area and reaction time in the human gustatory sensation. Bull. Tokyo Med. Dent. Univ. 2: 147-158, 1955.
948 10. Hooper, D. Gymnemic acid. Chem. News 59: 159-160, 1889. 11. Kiesow, F. Ueber die Wirkung des Cocain under der Gymnesaure auf die Schleimhaut der Zunge und des Mundraums. Phil. Stud. 9: 510-527, 1894. 12. Kurihara, Y. Antisweet activity of gynmemic acid At and its derivatives. Life Sci. 8: 537-543, 1969. 13. Meiselman, H. L. Magnitude estimations of the course of gustatory adaptation. Percept. Psychophys. 4: 193-196, 1968. 14. Meiselman, H. L. and E. Dzendolet. Variability in gustatory quality identification. Percept. Psychophys. 2: 496-498, 1967.
MEISI~LMAN AND I tALPEt(N 15. Shore, L. E. A contribution to our knowlcdge o1' laste sensations. Ji Physiol. 13: 191-217, 1892. 16. Stocklin, W., E. Weiss and T. Reichstein. Gymnesaurc, das antisaccharin Prinzip yon Gymnema sylvestre. Helv. Chim. Acta 50: 474-490, 1967. 17. Warren, R. M. and C. Pfaffmann. Suppression of sweet sensitivity by potassium gymnemate. J. appl. Physiol. 14: 40-42, 1959. 18. Warren, R. P., R. M. Warren and M. G. Weninger. Inhibition of the sweet taste by Gyumema sylvestrc. Nature 223: 94-95, 1969.