Pituitary-adrenal and dopaminergic modulation of schedule-induced polydipsia: Behavioral and neurochemical evidence.

Five experiments investigated in rats the effects of increasing or decreasing plasma corticosterone levels on schedule-induced polydipsia (SIP) and dopamine efflux in the nucleus accumbens. The results indicate that the acquisition of SIP could be decreased by adrenalectomy, blockade of corticosterone synthesis, or administration of corticosterone. Performance of established SIP was also decreased by adrenalectomy. The effects of corticosterone administration on established SIP depended on the level of performance. High levels of drinking were enhanced by a high dose of corticosterone, whereas low rates of drinking were increased by a low dose. Similar injections of corticosterone also significantly increased dopamine efflux. The relative involvement of pituitary–adrenal activity and dopamine neurotransmission to the nucleus accumbens in the acquisition and performance of SIP is discussed and related to contemporary hypotheses of schedule-induced behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Water-intake volume regulation in the rat: Schedule-induced drinking compared with water-deprivation-induced drinking.

Hungry rats drink extremely large amounts of water when they are intermittently fed small amounts of food (schedule-induced polydipsia). The present 5 experiments examined whether such animals are motivated to drink for long durations, to ingest large amounts of fluid, or to do both. When drinking-tube apertures were decreased to slow the rate of water ingestion, each of 8 female Sprague-Dawley rats spent more time drinking than when larger apertures were used (averages of 11.5 vs 7.8 min, respectively). The mean volumes ingested were not different. These equal volumes were generated by adjustment of each drink duration in accordance with ingestion rate even during the first few drinks of the sessions and when the drinking tubes were frequently switched (every 1–3 min) during the sessions. During drinking induced by water deprivation when food was concurrently available, restriction of the tube apertures reduced intake volumes by 18–29%. However, when food was not concurrently available during water-deprivation-induced drinking, regulation of intake volumes was comparable with that found during schedule-induced polydipsia. Data pose difficulties for theories that ascribe a crucial role to the motor aspects of schedule-induced drinking. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioning decreases in plasma corticosterone level in rats by pairing stimuli with daily feedings.

Examined the nature of a stimulus-induced decrease in the plasma corticosterone levels of male hooded Long-Evans rats in 3 experiments. Ss maintained on a 23-hr food and water deprivation regimen were fed each morning immediately upon entrance of the experimenter into the otherwise isolated animal quarters. After only 14 feeding trials, Ss showed a marked decrease in corticosterone levels within 10 min of the experimenter's entrance whether fed and watered or not. The acquisition of this decrease was then examined over training trials and by comparing the conditioned animals (Group CD) with a group designed to control for pseudoconditioning, sensitization, and habituation (Group PC) during the use of the more distinctive conditioning stimulus of placing the rat's cage in a sound-attenuating chamber. During training, Group CD was fed .5–6 min after placement in the chamber, and Group PC was fed 1.5–2.5 hrs before or after placement. After 1 training trial, the CD and PC groups showed an increase in corticosterone levels in response to chamber placement when not fed or watered. However, after 14 training trials the CD group exhibited a significant decline, whereas the PC group exhibited a rise in corticosterone levels. Results indicate that external stimuli can cause a decrease in corticosterone level by virtue of prior association with feeding and drinking. This strongly suggests an acquired inhibition of the pituitary-adrenal system. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adrenocortical response to hypertonic saline in rats with lateral hypothalamic lesions.

Used plasma corticosterone levels to assess the response to stress induced by ip injections of hypertonic saline in 27 male albino Harlan-Sprague rats with lateral hypothalamic (LH) or sham lesions. Ss with LH lesions displayed a corticosterone response equal to that of normal Ss under basal conditions, after control injections of isotonic saline, and 20 min after injection of hypertonic saline (1.5 M, 1.0 ml/100 g of body weight). The corticosterone response of Ss with LH lesions, however, was significantly less than that of normal Ss 90 min after injection of hypertonic saline when no water was available. With access to water, normal Ss displayed substantial drinking (14.5 ml/90 min), which resulted in a reduction in plasma corticosterone concentrations to a level observed after a control injection of isotonic saline, but the little water ingested by Ss with LH lesions (2.5 ml) had no effect on the pituitary-adrenal system. It is concluded that the failure of Ss with LH lesions to drink following a hydrational challenge is not the result of an exaggerated response to stress. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The generation and maintenance of schedule-induced polydipsia in normal male rats without weight reduction

Experiment One demonstrated that two normal male Sprague-Dawley rats (approximately 60 days old) with free access to food and two control rats whose weights were held constant by dietary restriction acquired schedule-induced polydipsia (SIP) in daily 33-35 min sessions of fixed-time 60-s food delivery. Three of the rats showed rapid acquisition of SIP; the fourth acquired SIP more slowly and consumed less per session the other three rats. After a 36-40 day period without sessions, the constant-weight rats showed a 37% decrease in overall consumption due to reduced drinking bout length. The SIP of the free-feeding rats was not affected by the interruption. After 90-100 periodic food delivery sessions, all subjects consumed an average of 11.2-12.2 mL per session compared with 1.8-4.8 mL per session in baseline sessions with massed food presentations. Experiment Two replicated the acquisition phase of Experiment One using two non-weight-reduced rats of the age and size of those typically used in SIP studies (approximately 30 weeks old). Both acquired SIP, although one showed only a small average increase in consumption per session over baseline (2.8 mL/session under periodic food vs. 0.8 mL following massed-food presentations). Before weight reduction, the stronger drinker consumed approximately 8.8 mL per session compared with an average of 0.6 mL per session in baseline. After weight reduction, both exhibited strong SIP (18-19 mL per session in the final five sessions). This study demonstrates that weight reduction is not a necessary condition for the generation and maintenance of SIP in rats.     

Schedule-induced polydipsia in rats: Adrenocortical and hippocampal modulation.

Onset of schedule-induced polydipsia (SIP) is related to adrenal gland weight. In 4 experiments with 43 Sprague-Dawley rats, adrenalectomy, but not demedullation, hastened the emergence of SIP, and exogenous corticosterone administration tended to reverse this effect. Hippocampal lesions were followed by a rapid and uniform release of SIP. None of the above manipulations influenced normal (home-cage) drinking. A synthesis of present findings with the literature suggests that the hippocampus and the adrenal cortex interact and that the equilibrium established within this system is reflected, for any particular rat, in its adjunctive behavior. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of drinking history on food-deprived drinking in the rat.

Investigated the role of drinking during development in 40 male hooded Long-Evans rats. Experimental Ss were deprived of water during rearing; ingestion of lettuce provided for sufficient fluids. Body weight, feeding, drinking, and urine volume over successive food deprivation periods were compared with normally reared controls. The lettuce-reared Ss drank less water and ate less lettuce when food deprived, but did not differ from normal Ss in drinking or in lettuce intake when food was available ad lib. It is suggested that lettuce-reared animals drink water principally in response to fluid deficits. Other research indicates that the drinking of normally reared rats anticipates fluid deficits and is not initiated by events related to the need for water. The present results suggest that this anticipatory drinking is acquired. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Schedule induction conditions not only exaggerate intake but also enhance drug solution choice

In previous research, rats exposed to daily, 3 h sessions of schedule-induced polydipsia (SIP) self-administered high doses of cocaine orally. However, a strong and durable preference for cocaine solution to water requires training in addition to mere oral self-administration exposure. If cocaine is dissolved in a preferred vehicle solution, and the vehicle is subsequently faded to water, then a strong preference for cocaine remains. A similar preference can be instituted for lidocaine solution. Such preferences may develop because the gustatory property of a drug becomes associated with the preferred vehicle and remains to function as a durable conditioned reinforcer after vehicle fading. To determine if drug preference is solely a function of this posited conditioning mechanism, or whether it also depends upon the SIP condition, rats were exposed to daily, 3 h sessions of single-ration feeding, rather than the SIP condition. A preferred vehicle (glucose/saccharin solution) was slowly faded from a 0.19 mg/ml lidocaine solution, which was presented concurrently with a choice for water. Although a preference for lidocaine solution to water could be generated, it occurred for only 5 out of 9 rats, and the preference was relatively unstable. By contrast, in two previous studies using SIP, 26 out of 27 rats maintained a preference for lidocaine solution. Thus, SIP not only exaggerates the amount of drug solution ingested but also contributes to the fixation of the associative drug solution choice.     

Acoustic startle reflexes in the rat during consummatory behavior.

Conducted 4 experiments, using a total of 18 male albino Holtzman rats. Auditory startle reflexes were elicited in thirsty Ss when they were drinking water or were between drinking bouts. The reaction was greater during drinking, this enhancement developing over the 1st few seconds after drinking onset. The startle reaction was lowest immediately after the termination of drinking. Reflex enhancement was reduced when thirsty Ss drank milk rather than the more preferred water. The reflex was smaller with increased water deprivation, but enhancement produced by drinking was apparent at all levels of deprivation studied-satiety to 4-days deprivation. The inhibitory effect of a preliminary stimulus was not affected by consummatory behavior. Attention is drawn to suggestive parallels between these behavioral effects and other consequences of consummatory activity, primarily having to do with electrophysiological events and arousal processes. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of water temperature in the regulation of water intake.

Performed 3 experiments on small groups (n = 2-6) of thirsty Carworth female albino rats. Cool water suppressed water intake. The suppression was apparent from the 1st min of drinking. Suppression occurred for both short (20-min) and long (100-min) daily drinking sessions, and occurred whether the water was available from a sipper tube or a bowl. When cellular hydration was delayed by giving Ss isotonic saline instead of water, the suppression by cooling was enhanced. Cool-water suppression of water intake appears to be a short-latency satiety mechanism that anticipates cellular and extracellular hydration. (27 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Schedule-induced polydipsia: Effect of water temperature, ambient temperature, and hypothalamic cooling.

Conducted 3 polydipsia experiments with a total of 26 female Sprague-Dawley rats, 6 of which were implanted with thermodes and thermistors and 2 of which were implanted with thermistors alone in the medial preoptic area or posterior hypothalamus. A cold (5.C) ambient temperature reduced the amount of water consumed by food-deprived Ss tested with a VI schedule of reinforcement, while a warm (30.C) ambient increased water intake. Response rate in the cold was twice that in a neutral temperature. A hot (38.C) ambient suppressed the rate of responding and drinking. Cooling the hypothalamus substantially reduced water intake in a neutral ambient temperature. Ambient temperature affected the volume of a drink but not the frequency of drinking, while hypothalamic cooling affected both volume and frequency. Water temperature had little effect on polydipsia although less cold water was consumed than warm water. It is concluded that schedule-induced polydipsia is a temperature-dependent phenomenon. (39 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Packrats (Neotoma albigula and N. micropus) compared in an operant analogue of foraging behaviors.

Used a barpress chamber as a simplified laboratory analog to illustrate a method of establishing behavioral economics and its potential for the study of foraging patterns in 2 closely related species of packrats. There were 16 adult Ss in each species. During the 1st 40 days of captivity, drinking water was freely available; on the 41st day of captivity, Ss faced a test requiring associative learning to obtain water by barpressing. Results show that N. albigula Ss, who were trapped from a relatively moist habitat, were not prepared to survive without water; they earned moderate amounts to drink whether terms of access were easy or difficult. N. micropus Ss, who were trapped from relatively barren and rocky terrain, gorged themselves when terms were easy and were frugal in expending energy when access was made difficult, a foraging pattern consistent with the conservatism of animals that maximize fitness in desert environments. Findings confirm the potential of traditional analog research in providing incisive comparative data in a simplified laboratory apparatus for the analysis of foraging patterns. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relation of feeding and activity following septal lesions in rats.

The patterns of intake of liquid diet (Exp I) and water (Exp II) were recorded in 12 female Long-Evans diet-deprived rats with septal lesions and 13 neurologically intact controls during the 1st hr of diet access. The occurrences of grooming, resting/sleeping, and exploring were also recorded. Findings show that both groups consumed similar amounts of diet in 1 meal during the 1-hr diet access period. Controls consumed the meal in 1 prolonged bout of eating, while lesioned Ss consumed the meal in numerous small bouts of eating. Lesioned Ss were active for longer periods, exhibiting continuous alternation of brief bouts of eating, drinking, exploring, and resting throughout the meal. In tests in which water was not available during the diet access period, both groups increased their intrameal bout size, but lesioned Ss still showed much smaller bouts of ingestion than did controls. Data suggest that the small-bout pattern of ingestion may reflect a general disruption in the control of behavioral sequences, rather than processes uniquely related to the regulation of eating or drinking. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Slower acquisition of positively reinforced behavior following medial, but not dorsolateral, septal lesions in rats.

Examined the effects of medial septal lesions (MSLs) and dorsolateral septal lesions (DSLs) on acquisition of leverpressing for water established with a modified autoshaping task. 22 male Sprague-Dawley rats were randomly assigned to receive either MSLs, DSLs, or control operations. Results show that, following MSLs, leverpressing responses had long latencies and were fewer than following either DSLs or control operations. However, during later sessions, MSL Ss started to press. It is suggested that the long response latencies and low response rates shown initially by MSL Ss may have been due to delayed classical conditioning. Following MSLs, the acetylcholinesterase activities of the different subdivisions of the hippocampus correlated positively with the number of leverpress responses emitted during Session 1. DSL Ss acquired the task just as fast as the control group and showed higher response rates than the other 2 groups during the final sessions. These findings are ascribed to generally increased locomotor activity. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fragmented behavior sequences in rats with lateral hypothalamic lesions: An alternative reason for intrameal prandial drinking.

50 Sprague-Dawley and Long-Evans rats in Stages 3 or 4 after lateral hypothalamic lesions were studied in several feeding situations. As expected, Ss showed intrameal prandial drinking when dry food and water were available. Meals of liquid diet were interrupted by short bouts of activity, and saccharin drinking in Stage 3 was composed of many small drafts. It is suggested that these animals have a propensity to interrupt ongoing behaviors (fragmentation), which can account for general activity and wheel running that occurs along with intrameal prandial drinking. The probability of drinking during meals was decreased with water infusions and increased with NaCl infusion. When they were hungry, recovered laterals ate 4.5 g of dry food without pausing to drink. These new data raise questions concerning the state of the salivary-insufficiency (dry mouth) explanation of intrameal drinking; the fragmentation hypothesis can incorporate the data, and the possible neural correlates of this fragmentation are discussed. (49 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heavy drinking occasions and the occurrence of sexual activity.

With the advent of the AIDS epidemic, research on the relationship of drinking to sexual activity takes on increased importance. Although several studies have investigated the characteristics of sexual encounters that do and do not involve alcohol, few studies have examined drinking incidents that may or may not result in sexual activity. Respondents (N?=?1,110) in 3 surveys were asked about the circumstances of a recent heavy drinking occasion. Approximately one third of the Ss reported having sex during this maximum consumption episode, and the likelihood of having sex was a significant positive linear function of the amount of alcohol consumed. Ss who drank more heavily in the episode were slightly more likely to have sex with a new or casual partner. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrical aversion conditioning with chronic alcoholics.

Previous studies suggest the utility of electrical aversion conditioning, but fail to include adequate controls. Pseudoconditioning (random shock delivery), sham conditioning (no shock), and ward controls (routine hospital treatment) were compared with 2 conditioning groups. Conditioning-only (contingent shock) and booster Ss (additional conditioning sessions after release from hospital) were shocked for drinking and reinforced by shock termination for spitting out the alcohol. Sessions were run in a simulated bar setting. 51 of 73 chronic male alcoholics completed treatment and were available for follow-up. The technique significantly increased time to relapse when compared with control groups, among which no significant differences were found. Results suggest the possible usefulness of booster sessions and the potential long-term effectiveness of the technique for some Ss. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cache recovery and spatial memory in Clark's nutcrackers (Nucifraga columbiana).

Clark's nutcrackers cache pine seeds and recover them months later. Four experiments with 5 nutcrackers tested their ability to relocate their caches when the cache sites were selected by the experimenters. During Exp I, Ss had 18 cache sites available during each of 3 caching sessions, followed 10 days later by 4 recovery sessions. Recovery performance was above chance, and there were frequent revisits to previously emptied cache sites. During Exp II, hunger level (manipulated by prefeeding) had no effect on recovery accuracy. During Exp III, Ss were released into the experimental room with no seeds present. Probing behavior was directed at the old cache sites of Exp I and especially of Exp II. During Exp IV, the number of holes available during caching sessions had no effect on the accuracy of 3 of the 4 Ss. Findings suggest that spatial memory is a primary mechanism by which nutcrackers locate their caches. (30 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Influence of experiential factors and gonadal hormones on pituitary-adrenal response of the mouse to novelty and electric shock.

Plasma corticosterone elevations have been shown to occur in response to exposure to a novel environment and to the delivery of painful stimulation, such as footshock. The present experiment investigated the effects of experience with these types of stimuli on the responsivity of the pituitary-adrenal system in 240 C57BL/KA mice. When Ss were subjected to repeated footshock, the adrenocortical response was increased. When Ss were repeatedly shocked in a specific environment, the adrenocortical-stimulating properties of the situational stimuli were also elevated. On the other hand, plasma corticosterone elevations in response to merely being placed in an experimental chamber were not affected by 10 exposures to the situation. Previous data show that Ss shocked in one environment were generally more responsive to many types of stimulus changes; this suggests that the pituitary-adrenal system is subject to sensitization processes and that the CNS substrate which controls its function is normally involved with the production of states of arousal. This configuration of results was quite pronounced in the female mouse regardless of hormonal state, and it was absent in the intact male. The results of studies with gonadectomized males suggest that testosterone inhibits sensitization. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of 6-hydroxydopamine lesions of the nucleus accumbens septi and olfactory tubercle on feeding, locomotor activity, and amphetamine anorexia in the rat.

In Exp I with 24 male albino Wistar rats, bilateral 6-hydroxydopamine lesions of the nucleus accumbens septi (NAS) and olfactory tubercle (OT) caused enhanced intake of wet mash in 23-hr-food-deprived Ss tested in photocell activity cages during restricted 30-min sessions. This mild hyperphagia was accompanied by a significant hypoactivity in the group with NAS/OT lesions. No hyperphagia was observed during a prolonged 120-min test session or in free-feeding tests conducted in the home cage. Anorexia induced by dextroamphetamine (.5 and 1.5 mg/kg) was unaltered by the lesion, although the locomotor stimulant action of the drug was attenuated. Results of Exp II, with 36 Ss, show that the NAS/OT lesion also enhanced food intake in the photocell cages during 30-min sessions with dry food pellets but that food-associated drinking was concomitantly reduced. Results are consistent with the hypothesis that the behavioral changes caused by mesolimbic neuron destruction result in part from an inability to switch from one behavioral activity to another. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)