Physiology.& Behavior, Vol. 16, pp. 121-124. Pergamon Press and
Brain Research Publ., 1976. Printed in the U.S.A.
Separation of Water and Ambient Temperature Effects o n P o l y d i p s i a I H. J. CARLISLE AND M. L. L A U D E N S L A G E R2
Department o f Psychology, University o f California Santa Barbara CA 93106 USA (Received 2 0 May 1975) CARLISLE, H. J. AND M. L. LAUDENSLAGER. Separation of water and ambient temperature effects on polydipsia. PHYSIOL. BEHAV. 16(2) 121-124, 1976.- The separate contributions to schedule-induced polydipsia in rats of water temperature and ambient temperature were examined by varying each while the other was held constant. Water intake varied directly with water temperature between 5° and 30°C, and decreased at 35°C and 40°C relative to 30°C. Ambient temperature did not influence water intake when water temperature was held constant. These observations favor an orolingual locus for the effect of temperature on water intake, and rule out the participation of skin temperature receptors. Water temperature
Ambient temperature
Schedule-induced polydipsia
Waterintake
Apparatus
AMBIENT temperature and orolingual temperature have both been implicated in the control of thirst. Water intake is increased in a warm and suppressed in a cold environment [3,12]. Similarly, water intake varies directly with water temperature except when the temperature of the water approaches that of the body [6, I0, 11, 15]. In addition, thirsty rodents will lick a stream of air [14] or a cold dry tube [ 17], which suggests a short term satiation mechanism for thirst based on orolingual cooling. Schedule-induced polydipsia, the excessive consumption of water by animals on intermittent schedules of food reinforcement [7,8], is also influenced by ambient temperature and water temperature even though the polydipsia does not appear related to either cellular or extracellular thirst stimuli [4]. When ambient temperature was varied in the studies cited above [3, 4, 12], however, the independent contribution of orolingual temperature was not adequately controlled because water temperature was not held constant and was, therefore, free to vary with ambient temperature. The purpose of this study was to determine the separate contributions of ambient temperature and water temperature to scheduleinduced polydipsia by varying each while holding the other constant.
A Lehigh Valley model 1316 test apparatus was modified so that a metal drinking spout with a 3 mm aperture could be mounted with the tip of the spout 3 mm outside a 1.8 x 3.2 cm slot on the right hand side of the work panel of the animal enclosure. The center of the tube was 2.8 cm above the grid floor. A calibrated buret tube (0.1 ml divisions) was connected to the drinking tube via Tygon tubing. The lever was on the left with the food receptacle in the middle of the work panel. Recording and programming equipment were located outside the test room. Responses, reinforcements, and licks on the drinking tube were recorded on electromechanical counters, and licks and reinforcements were displayed on a cumulative recorder. The number of postreinforcement drinks was counted from the cumulative record, and 2 ratios were calculated. Dividing the number of reinforcements received by the number of drinks gave the frequency of drinking. Dividing the volume consumed per test by the number of drinks gave the average volume per drink. The actual water volume consumed per drink was sampled during some tests by reading the level of the buret tube for each of a series of 1 0 - 1 5 drinks at different times during a test. The mean of the directly measured volumes agreed quite well with the average values calculated from test totals. Water temperature was controlled by circulating water from a constant temperature bath through copper tubing that was wrapped around the drinking tube. Water temperature was measured by a thermistor positioned inside the drinking tube within 1 - 2 mm of the aperture. Water bath temperature was adjusted so that the water temperature at the tip of the drinking tube remained constant, the maximal variation being ± I°C. When ambient tem-
METHOD
Animals Six adult female rats of the Sprague-Dawley strain with body weights of 2 1 0 - 3 4 8 g were housed in individual cages at a room temperature of 24°C with a relative humidity of 50%. The animals were maintained at 80% of free feeding body weight by posttest supplements of Purina Chow pellets, as necessary. Water was available ad lib.
Supported in part by NIMH grant MH-12414 awarded to the first author. 2Pr'esent address: Physiological Research Lab, Scripps Institute of Oceanography, LaJolla, California 92037. 121
122
CARLISLE AND LAUDENSLAGER
perature was varied, the test apparatus was placed in a 3 x 2.5 x 2.5 m temperature controlled chamber, the accuracy of regulation of which was +- I°C. Pre- and posttest rectal temperatures were measured with a Yellow Springs Model 46 Telethermometer and thermistor probe inserted 6 cm.
60
m
40
--
Procedure The animals were first trained to press the lever for 45 mg Noyes pellets on a continuous reinforcement schedule. When performance was stable, they were shifted to a 30 sec variable interval schedule and then to the 1 min variable interval schedule used during the remainder of the tests. The values of the intervals were 100, 5, 56, 50, 68, 12, 109, 80, 20, 120, 40, 90, and 30 sec. Two weeks of daily tests of 2 hr duration were given to assure stable water intake with neutral (25 ° C) water and ambient temperatures. Water temperature was varied between 5 ° and 40°C in 5°C steps, while ambient temperature was varied between 5° and 35°C, also in 5°C steps. Water temperature was maintained at 25°C when ambient temperature was varied, and ambient temperature was 25°C when water temperature was varied. One combination of water and ambient temperatures was in effect throughout each daily 2 hr test. Preliminary work with different animals showed that water intake became variable following sessions at high water or ambient temperatures. Therefore, a descending series of temperatures was presented starting first at a neutral (25 ° C) temperature. Three animals were tested with water temperature varied initially, and 3 were presented with variable ambient temperatures first. The conditions were then reversed for each group. Thus, each animal was tested twice at each combination of water and ambient temperature. The sequence of water temperatures was 25, 20, 15, 10, 5, 5, 10, 15, 20, 25, 30, 35, 40, 40, 35, and 30°C. The sequence of ambient temperatures was the same except that 40°C was omitted. RESULTS
Water intake varied directly with water temperature between 5 ° and 30°C, and decreased at the highest water temperatures. Variations in ambient temperature had little effect on water intake when the temperature of the water was maintained at 25°C (Fig. 1). There was considerable variability in water intake between animals, as can be seen by the standard deviations in Fig. 1. For example, when both water temperature and ambient temperature were 25°C, the range of water intakes was 2 8 - 6 2 ml. In spite of this variability between animals, the pattern shown in Fig. 1 was representative of individual animals except that peak water intake occurred at a water temperature of 35°C for one animal and at 40°C for a second animal, with the remaining 4 animals showing a peak intake at 30°C as indicated by the mean value in the figure. The animal with the lowest water intake overall showed the highest intake of 40 ° C water. The volume of water intake noted in Fig. 1 could be a function of several factors. First, drinking could be frequent (i.e., after each food reinforcement) with variability in water intake being attributable to variations in the volume consumed during each drink. Secondly, the volume consumed at each drink might remain constant with variability in intake being accounted for by a change in the frequency of drinking. The first alternative is the correct one, as seen in Fig. 2. Drinking occurred after appro-
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TEMPERATURE ( ° C ) FIG. 1. Mean w a t e r i n t a k e w h e n w a t e r or a m b i e n t t e m p e r a t u r e w a s varied. T h e vertical lines i n d i c a t e 1 S . D .
ximately 95% of the reinforcements at all ambient temperatures, and at all water temperatures except 40°C when the frequency of drinking decreased to 83%. Th e volume of water consumed per drink varied directly with water temperature between 5° and 30°C, and decreased at 40°C. Thus, the variations in water intake noted in Fig. 1 can be accounted for entirely by variations in the volume consumed per drink except at a water temperature of 40°C when both a diminished frequency of drinking as well as a low volume per drink account for the low intake. Mean response rate varied inversely with ambient temperature, as noted previously [4], while there was no systematic variation in response rate as a function of water temperature. In spite of the variation in response rate with ambient temperature, the number of reinforcements received did not vary appreciably. The mean number of reinforcements was 115.7 when ambient temperature was varied, and 115.3 when water temperature was varied. Posttest rectal temperature averaged 38.8°C when water temperature was varied, with no significant variation across temperatures. Posttest rectal temperature varied slightly with ambient temperature, with a low of 38.7°C at 5°C and 39.05°C at 35°C. The overall mean posttest rectal temperature was 38.86°C. DISCUSSION
The main outcome of this study is that water intake varies systematically and substantially when water temperature is varied but not when ambient temperature is varied. These results conflict with a previous report [4], which emphasized the influence of ambient temperature in schedule-induced polydipsia. Although there are a number of procedural differences between that study and the present one, it would seem that when water temperature is
POLYDIPSIA AND T E M P E R A T U R E
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FIG. 2. Mean volume consumed per drink (top) and mean frequency of post pellet drinks (bottom) when water or ambient temperature was varied. held constant, amibient temperature contributes little to the variation in water intake. This outcome suggests that skin temperature receptors contribute little information to the diminished intake of cold water or the increased intake
of warm water. A number of receptor sites remain as viable contenders. Lingual temperature receptors may be important. However, bilateral denervation of the lingual, chorda tympani, and one branch of the glossopharyngeal nerves has no influence on airlicking [18], a phenomenon related to thirst. Extralingual oral temperature receptors, such as the cold receptors in the upper lip of the cat [16], may be a second possibility although these have not been described in the rat. Temperature receptors within the basal forebrain constitute a third set of potential receptors. Cooling of the preoptic area and anterior hypothalamus reduces water intake [1,2], schedule-induced polydipsia [4], and airlicking [5]. The modulation of water intake as a function of water temperature could also be secondary to some factor such as stomach distention or water diuresis. Deaux [6] has suggested that less cold water is consumed than warm water because cold water empties from the stomach at a slower rate, and therefore stomach distention would be greater for cold than for warm water. Stomach distention would not seem to be a significant factor in schedule-induced polydipsia because excessive drinking occurs throughout prolonged tests of 2 to 3 or more hr. In addition, water preloads do not reduce water intake [8]. A cool ambient temperature [9] and cooling of the hypothalamus [13] induce water diuresis, which might be expected to influence schedule-induced polydipsia. However, an increase in intake of cold water, rather than a decrease, would be expected if intake was secondary to cold induced diuresis. A cold ambient temperature did not affect water intake in the present study when water temperature was held constant. Several aspects of the hypothesis of a short term satiation mechanism for thirst based on orolingual cooling deserve comment. First, since polydipsic animals are overhydrated [19], the modulation of water intake by water temperature occurs in the absence of either cellular or extracellular thirst stimuli. Orolingual temperature thus modifies water intake under both homeostatic and nonhomeostatic conditions. Secondly, schedule-induced polydipsia is a function of 2 factors: a large volume intake per drink and a high frequency of drinking. Only the former is affected by water temperature, and thus the modulation of water intake by water temperature occurs within each brief postpellet drink.
REFERENCES 1. Andersson, B. and S. Larsson. Influence of local temperature changes in the preoptic area and rostral hypothalamus on the regulation of food and water intake. Acta physiol, scand. 52: 75-89, 1961. 2. Banet, M. and J. J. Seguin. Effects of preoptic cooling in rats acclimated to 21 and 4°C. J. appl. Physiol. 29: 385-388, 1970. 3. Budgell, P. The effect of changes in ambient temperature on water intake and evaporative water loss. Psychon. ScL 20: 275-276, 1970. 4. Carlisle, H. J. Schedule-induced polydipsia: effect of water temperature, ambient temperature, and hypothalamic cooling. J. comp. physiol. Psychol. 83: 208-220, 1973. 5. Carlisle, H. J. and M. L. Laudenslager. Inhibition of airlicking in thirsty rats by cooling preoptic area. Nature 255: 72-73, 1975. 6. Deaux, E. Thirst satiation and the temperature of ingested water. Science 181 : 1166-1167, 1973.
7. Falk, J. L. Production of polydipsia in normal rats by an intermittent food schedule. Science 133: 195-196, 1961. 8. Falk, J. L. Conditions producing psychogenic polydipsia.Ann. N. Y. Acad. Sci. 157: 569-593, 1969. 9. Fregly, M. J. and I. W. Waters. Water intake of rats immediately after exposure to a cold environment. Can. J. Physiol. Pharrnac. 44:651-662, 1966. 10. Gold, R. M., G. Kapatos, J. Prowse, P. M. Quackenbush and T. W. Oxford. Role of water temperature in the regulation of water intake. J. cornp, physiol. Psychol. 85: 52-63, 1973. 11. Gold, R. M. and J. Prowse. Water temperature preference shifts during hydration.Physiol. Behav. 13: 291-296, 1974. 12. Hamilton, C. L. Interactions of food and temperature regulation in the rat. J. comp. physiol. Psychol. 56: 476-488, 1963. 13. Hayward, J. N. and M. A. Baker. Diuretic and thermoregulatory responses to preoptic cooling in the monkey. Am. J. Physiol. 214: 843-850, 1968.
124 14. Hendry, D. P. and R. H. Rasche. Analysis of a new nonnutritive positive reinforcer based on thirst. J. cornp, physiol. Psychol. 54: 4 7 7 - 4 8 3 , 1961. 15. Kapatos, G. and R. M. Gold. Tongue cooling during drinking: a regulator of water intake in rats. Science 176: 6 8 5 - 6 8 6 , 1972. 16. Kenshalo, D. R. and E. A. Brearly. Electrophysiological measurement of the sensitivity of cats' upper lip to warm and cool stimuli. J. comp. physiol. Psychol. 70: 5 - 1 4 , 1970.
CARLISLE AND LAUDENSLAGER 17. Mendelson, J. and D. Chillag. Tongue cooling: a new reward for thirsty rodents. Science 170: 1418-1419, 1970. 18. Mendelson, J. and R. Zec. Effects of lingual denervation and desalivation on airlicking in the rat. Physiol. Behav. 8: 7 1 1 - 7 1 4 , 1972. 19. Stricker, E. M. and E. R. Adair. Body fluid balance, taste, and postprandial factors in schedule-induced polydipsia. J. comp. physiol. Psychol. 62: 4 4 9 - 4 5 4 , 1966.
Brain Research Publ., 1976. Printed in the U.S.A.
Separation of Water and Ambient Temperature Effects o n P o l y d i p s i a I H. J. CARLISLE AND M. L. L A U D E N S L A G E R2
Department o f Psychology, University o f California Santa Barbara CA 93106 USA (Received 2 0 May 1975) CARLISLE, H. J. AND M. L. LAUDENSLAGER. Separation of water and ambient temperature effects on polydipsia. PHYSIOL. BEHAV. 16(2) 121-124, 1976.- The separate contributions to schedule-induced polydipsia in rats of water temperature and ambient temperature were examined by varying each while the other was held constant. Water intake varied directly with water temperature between 5° and 30°C, and decreased at 35°C and 40°C relative to 30°C. Ambient temperature did not influence water intake when water temperature was held constant. These observations favor an orolingual locus for the effect of temperature on water intake, and rule out the participation of skin temperature receptors. Water temperature
Ambient temperature
Schedule-induced polydipsia
Waterintake
Apparatus
AMBIENT temperature and orolingual temperature have both been implicated in the control of thirst. Water intake is increased in a warm and suppressed in a cold environment [3,12]. Similarly, water intake varies directly with water temperature except when the temperature of the water approaches that of the body [6, I0, 11, 15]. In addition, thirsty rodents will lick a stream of air [14] or a cold dry tube [ 17], which suggests a short term satiation mechanism for thirst based on orolingual cooling. Schedule-induced polydipsia, the excessive consumption of water by animals on intermittent schedules of food reinforcement [7,8], is also influenced by ambient temperature and water temperature even though the polydipsia does not appear related to either cellular or extracellular thirst stimuli [4]. When ambient temperature was varied in the studies cited above [3, 4, 12], however, the independent contribution of orolingual temperature was not adequately controlled because water temperature was not held constant and was, therefore, free to vary with ambient temperature. The purpose of this study was to determine the separate contributions of ambient temperature and water temperature to scheduleinduced polydipsia by varying each while holding the other constant.
A Lehigh Valley model 1316 test apparatus was modified so that a metal drinking spout with a 3 mm aperture could be mounted with the tip of the spout 3 mm outside a 1.8 x 3.2 cm slot on the right hand side of the work panel of the animal enclosure. The center of the tube was 2.8 cm above the grid floor. A calibrated buret tube (0.1 ml divisions) was connected to the drinking tube via Tygon tubing. The lever was on the left with the food receptacle in the middle of the work panel. Recording and programming equipment were located outside the test room. Responses, reinforcements, and licks on the drinking tube were recorded on electromechanical counters, and licks and reinforcements were displayed on a cumulative recorder. The number of postreinforcement drinks was counted from the cumulative record, and 2 ratios were calculated. Dividing the number of reinforcements received by the number of drinks gave the frequency of drinking. Dividing the volume consumed per test by the number of drinks gave the average volume per drink. The actual water volume consumed per drink was sampled during some tests by reading the level of the buret tube for each of a series of 1 0 - 1 5 drinks at different times during a test. The mean of the directly measured volumes agreed quite well with the average values calculated from test totals. Water temperature was controlled by circulating water from a constant temperature bath through copper tubing that was wrapped around the drinking tube. Water temperature was measured by a thermistor positioned inside the drinking tube within 1 - 2 mm of the aperture. Water bath temperature was adjusted so that the water temperature at the tip of the drinking tube remained constant, the maximal variation being ± I°C. When ambient tem-
METHOD
Animals Six adult female rats of the Sprague-Dawley strain with body weights of 2 1 0 - 3 4 8 g were housed in individual cages at a room temperature of 24°C with a relative humidity of 50%. The animals were maintained at 80% of free feeding body weight by posttest supplements of Purina Chow pellets, as necessary. Water was available ad lib.
Supported in part by NIMH grant MH-12414 awarded to the first author. 2Pr'esent address: Physiological Research Lab, Scripps Institute of Oceanography, LaJolla, California 92037. 121
122
CARLISLE AND LAUDENSLAGER
perature was varied, the test apparatus was placed in a 3 x 2.5 x 2.5 m temperature controlled chamber, the accuracy of regulation of which was +- I°C. Pre- and posttest rectal temperatures were measured with a Yellow Springs Model 46 Telethermometer and thermistor probe inserted 6 cm.
60
m
40
--
Procedure The animals were first trained to press the lever for 45 mg Noyes pellets on a continuous reinforcement schedule. When performance was stable, they were shifted to a 30 sec variable interval schedule and then to the 1 min variable interval schedule used during the remainder of the tests. The values of the intervals were 100, 5, 56, 50, 68, 12, 109, 80, 20, 120, 40, 90, and 30 sec. Two weeks of daily tests of 2 hr duration were given to assure stable water intake with neutral (25 ° C) water and ambient temperatures. Water temperature was varied between 5 ° and 40°C in 5°C steps, while ambient temperature was varied between 5° and 35°C, also in 5°C steps. Water temperature was maintained at 25°C when ambient temperature was varied, and ambient temperature was 25°C when water temperature was varied. One combination of water and ambient temperatures was in effect throughout each daily 2 hr test. Preliminary work with different animals showed that water intake became variable following sessions at high water or ambient temperatures. Therefore, a descending series of temperatures was presented starting first at a neutral (25 ° C) temperature. Three animals were tested with water temperature varied initially, and 3 were presented with variable ambient temperatures first. The conditions were then reversed for each group. Thus, each animal was tested twice at each combination of water and ambient temperature. The sequence of water temperatures was 25, 20, 15, 10, 5, 5, 10, 15, 20, 25, 30, 35, 40, 40, 35, and 30°C. The sequence of ambient temperatures was the same except that 40°C was omitted. RESULTS
Water intake varied directly with water temperature between 5 ° and 30°C, and decreased at the highest water temperatures. Variations in ambient temperature had little effect on water intake when the temperature of the water was maintained at 25°C (Fig. 1). There was considerable variability in water intake between animals, as can be seen by the standard deviations in Fig. 1. For example, when both water temperature and ambient temperature were 25°C, the range of water intakes was 2 8 - 6 2 ml. In spite of this variability between animals, the pattern shown in Fig. 1 was representative of individual animals except that peak water intake occurred at a water temperature of 35°C for one animal and at 40°C for a second animal, with the remaining 4 animals showing a peak intake at 30°C as indicated by the mean value in the figure. The animal with the lowest water intake overall showed the highest intake of 40 ° C water. The volume of water intake noted in Fig. 1 could be a function of several factors. First, drinking could be frequent (i.e., after each food reinforcement) with variability in water intake being attributable to variations in the volume consumed during each drink. Secondly, the volume consumed at each drink might remain constant with variability in intake being accounted for by a change in the frequency of drinking. The first alternative is the correct one, as seen in Fig. 2. Drinking occurred after appro-
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TEMPERATURE ( ° C ) FIG. 1. Mean w a t e r i n t a k e w h e n w a t e r or a m b i e n t t e m p e r a t u r e w a s varied. T h e vertical lines i n d i c a t e 1 S . D .
ximately 95% of the reinforcements at all ambient temperatures, and at all water temperatures except 40°C when the frequency of drinking decreased to 83%. Th e volume of water consumed per drink varied directly with water temperature between 5° and 30°C, and decreased at 40°C. Thus, the variations in water intake noted in Fig. 1 can be accounted for entirely by variations in the volume consumed per drink except at a water temperature of 40°C when both a diminished frequency of drinking as well as a low volume per drink account for the low intake. Mean response rate varied inversely with ambient temperature, as noted previously [4], while there was no systematic variation in response rate as a function of water temperature. In spite of the variation in response rate with ambient temperature, the number of reinforcements received did not vary appreciably. The mean number of reinforcements was 115.7 when ambient temperature was varied, and 115.3 when water temperature was varied. Posttest rectal temperature averaged 38.8°C when water temperature was varied, with no significant variation across temperatures. Posttest rectal temperature varied slightly with ambient temperature, with a low of 38.7°C at 5°C and 39.05°C at 35°C. The overall mean posttest rectal temperature was 38.86°C. DISCUSSION
The main outcome of this study is that water intake varies systematically and substantially when water temperature is varied but not when ambient temperature is varied. These results conflict with a previous report [4], which emphasized the influence of ambient temperature in schedule-induced polydipsia. Although there are a number of procedural differences between that study and the present one, it would seem that when water temperature is
POLYDIPSIA AND T E M P E R A T U R E
.50
123
B
A.
DRINK
VOLUME
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TEMPERATURE
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FIG. 2. Mean volume consumed per drink (top) and mean frequency of post pellet drinks (bottom) when water or ambient temperature was varied. held constant, amibient temperature contributes little to the variation in water intake. This outcome suggests that skin temperature receptors contribute little information to the diminished intake of cold water or the increased intake
of warm water. A number of receptor sites remain as viable contenders. Lingual temperature receptors may be important. However, bilateral denervation of the lingual, chorda tympani, and one branch of the glossopharyngeal nerves has no influence on airlicking [18], a phenomenon related to thirst. Extralingual oral temperature receptors, such as the cold receptors in the upper lip of the cat [16], may be a second possibility although these have not been described in the rat. Temperature receptors within the basal forebrain constitute a third set of potential receptors. Cooling of the preoptic area and anterior hypothalamus reduces water intake [1,2], schedule-induced polydipsia [4], and airlicking [5]. The modulation of water intake as a function of water temperature could also be secondary to some factor such as stomach distention or water diuresis. Deaux [6] has suggested that less cold water is consumed than warm water because cold water empties from the stomach at a slower rate, and therefore stomach distention would be greater for cold than for warm water. Stomach distention would not seem to be a significant factor in schedule-induced polydipsia because excessive drinking occurs throughout prolonged tests of 2 to 3 or more hr. In addition, water preloads do not reduce water intake [8]. A cool ambient temperature [9] and cooling of the hypothalamus [13] induce water diuresis, which might be expected to influence schedule-induced polydipsia. However, an increase in intake of cold water, rather than a decrease, would be expected if intake was secondary to cold induced diuresis. A cold ambient temperature did not affect water intake in the present study when water temperature was held constant. Several aspects of the hypothesis of a short term satiation mechanism for thirst based on orolingual cooling deserve comment. First, since polydipsic animals are overhydrated [19], the modulation of water intake by water temperature occurs in the absence of either cellular or extracellular thirst stimuli. Orolingual temperature thus modifies water intake under both homeostatic and nonhomeostatic conditions. Secondly, schedule-induced polydipsia is a function of 2 factors: a large volume intake per drink and a high frequency of drinking. Only the former is affected by water temperature, and thus the modulation of water intake by water temperature occurs within each brief postpellet drink.
REFERENCES 1. Andersson, B. and S. Larsson. Influence of local temperature changes in the preoptic area and rostral hypothalamus on the regulation of food and water intake. Acta physiol, scand. 52: 75-89, 1961. 2. Banet, M. and J. J. Seguin. Effects of preoptic cooling in rats acclimated to 21 and 4°C. J. appl. Physiol. 29: 385-388, 1970. 3. Budgell, P. The effect of changes in ambient temperature on water intake and evaporative water loss. Psychon. ScL 20: 275-276, 1970. 4. Carlisle, H. J. Schedule-induced polydipsia: effect of water temperature, ambient temperature, and hypothalamic cooling. J. comp. physiol. Psychol. 83: 208-220, 1973. 5. Carlisle, H. J. and M. L. Laudenslager. Inhibition of airlicking in thirsty rats by cooling preoptic area. Nature 255: 72-73, 1975. 6. Deaux, E. Thirst satiation and the temperature of ingested water. Science 181 : 1166-1167, 1973.
7. Falk, J. L. Production of polydipsia in normal rats by an intermittent food schedule. Science 133: 195-196, 1961. 8. Falk, J. L. Conditions producing psychogenic polydipsia.Ann. N. Y. Acad. Sci. 157: 569-593, 1969. 9. Fregly, M. J. and I. W. Waters. Water intake of rats immediately after exposure to a cold environment. Can. J. Physiol. Pharrnac. 44:651-662, 1966. 10. Gold, R. M., G. Kapatos, J. Prowse, P. M. Quackenbush and T. W. Oxford. Role of water temperature in the regulation of water intake. J. cornp, physiol. Psychol. 85: 52-63, 1973. 11. Gold, R. M. and J. Prowse. Water temperature preference shifts during hydration.Physiol. Behav. 13: 291-296, 1974. 12. Hamilton, C. L. Interactions of food and temperature regulation in the rat. J. comp. physiol. Psychol. 56: 476-488, 1963. 13. Hayward, J. N. and M. A. Baker. Diuretic and thermoregulatory responses to preoptic cooling in the monkey. Am. J. Physiol. 214: 843-850, 1968.
124 14. Hendry, D. P. and R. H. Rasche. Analysis of a new nonnutritive positive reinforcer based on thirst. J. cornp, physiol. Psychol. 54: 4 7 7 - 4 8 3 , 1961. 15. Kapatos, G. and R. M. Gold. Tongue cooling during drinking: a regulator of water intake in rats. Science 176: 6 8 5 - 6 8 6 , 1972. 16. Kenshalo, D. R. and E. A. Brearly. Electrophysiological measurement of the sensitivity of cats' upper lip to warm and cool stimuli. J. comp. physiol. Psychol. 70: 5 - 1 4 , 1970.
CARLISLE AND LAUDENSLAGER 17. Mendelson, J. and D. Chillag. Tongue cooling: a new reward for thirsty rodents. Science 170: 1418-1419, 1970. 18. Mendelson, J. and R. Zec. Effects of lingual denervation and desalivation on airlicking in the rat. Physiol. Behav. 8: 7 1 1 - 7 1 4 , 1972. 19. Stricker, E. M. and E. R. Adair. Body fluid balance, taste, and postprandial factors in schedule-induced polydipsia. J. comp. physiol. Psychol. 62: 4 4 9 - 4 5 4 , 1966.
