Pavlovian conditioning with ethanol and lithium: Effects on heart rate and taste aversion in rats.

20 female albino Simonsen rats received paired injections of either ethanol or saline as the CS and LiCl as the UCS in a Pavlovian differential conditioning paradigm. LiCl evoked a large deceleration in heart rate (80–200 beats/min) as a UCR. As a result of 10 conditioning trials, the substance paired with LiCl elicited a lower average heart rate than that elicited by the unpaired substance. Moreover, Ss that received ethanol–LiCl injections subsequently were more averse to the taste of ethanol than Ss receiving saline–LiCl pairings. However, there were no differences in ethanol's ability to serve as the UCS to induce an aversion to a novel flavor solution (i.e., the Avfail phenomenon was not observed). The overall pattern of results underscores the value of using multiple indexes of learning in drug–drug conditioning paradigms. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anticipatory hyperexcitability and tolerance to the narcotizing effect of morphine in the rat.

Examined the role of Pavlovian conditioning in tolerance to the narcotizing effect of a high dose of morphine in 32 male albino Sprague-Dawley rats. Initially, 2 groups received 9 injections of morphine (40 mg/kg), and 2 groups received 9 injections of saline. One group administered each substance was injected in 1 of 2 distinctive environments: the animal colony or a distinctive room. Subsequently, Ss in all groups received 5 morphine injections in the distinctive room. Analyses of videotape records of postinjection behavior indicated that Ss tested in the presence of the usual predrug cues were more tolerant to the narcotizing effect of morphine than Ss tested with cues different from those previously associated with morphine. In addition, Ss tested with the usual predrug cues exhibited more anticipatory "hyperexcitable" behavior than Ss tested in the absence of the usual predrug cues. Results provide further evidence that compensatory pharmacological conditional responses partially mediate tolerance and suggest that these drug-anticipatory responses contribute to so-called "withdrawal symptoms." (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behaviorally functional opioid systems in infant rats: I. Evidence for olfactory and gustatory classical conditioning.

Conducted 2 series of experiments to characterize the behavioral function of opioid systems in neonatal rats. In the 1st series, the reinforcing properties of exogenous opioids were investigated in 112 5-day-old pups. Ss' ability to associate the novel taste of saccharin, received while suckling, with intraperitoneal morphine injections was assessed. Results show that Ss that received 0.5 ml of saccharin prior to morphine administration ingested considerably more saccharin on Day 10 than did control rats. The 2nd set of experiments was conducted to determine whether 144 rat pups could associate a novel odor with morphine administration. Five days after conditioning, that stimulus was highly preferred by morphine-treated Ss compared with saline control Ss. Thus positive associations were formed with either a novel taste stimulus experienced while suckling or with an odor experienced during social isolation. Conditioning was cue specific and was retained for at least 5 days. The formation of these associations was blocked with opioid antagonists given prior to conditioning. Data suggest behaviorally functional opioid receptors and raise the possibility of a functional role of the endogenous opioids in motivational processes in infant rats. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned increases in locomotor activity produced with morphine as an unconditioned stimulus, and the relation of conditioning to acute morphine effect and tolerance.

In 5 experiments with 164 male Wistar rats, Ss administered morphine (5 mg/kg, sc) during each of several daily sessions in an open field showed an increase in locomotor activity. Since increases were not observed in Ss given morphine in a different environment (home cage) and saline in the open field, it is concluded that they were due to conditioning. Increases in activity were retained over a 7-day rest period; they were also produced when a 2nd opiate (5 μg/kg etorphine) was substituted for morphine, were not seen when 2 mg/kg naloxone (ip) was administered during treatment, and were present in Ss showing tolerance to opiate-produced hypoactivity. Morphine's direct effect on activity is believed to have a biphasic dose–response curve; therefore, the relation of dose to conditioning was also studied. Increases in activity were the only conditioned behaviors observed; they were present only at the higher doses (16, 4, and 1 vs .25, .065, and 0 mg/kg), and they occurred whether or not the dose was associated with unconditioned hypoactivity. Discussion deals with the relation of conditioning and morphine tolerance, the question of whether the UCS of morphine conditioning is a compensatory or a direct effect of morphine, and the similarity of conditioned increases in activity produced by morphine and by other reinforcing stimuli. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exposure to uncontrollable stress alters withdrawal from morphine.

Examined the influence of the controllability/uncontrollability of shock as a stressor on the severity of subsequent morphine withdrawal in 2 experiments with 84 male Holtzman rats. In Exp I (36 Ss), Ss that received 2 daily sessions of 80 yoked-inescapable shocks, in contrast to those given 80 escapable shocks or restrained without shock, showed an enhanced series of correlated withdrawal behaviors (i.e., mouthing, teeth chattering, head/body shakes) 24 hrs later when injected with morphine sulfate (5 mg/kg) followed by a naloxone HCl (5 mg/kg) challenge. In Exp II (48 Ss), this finding was replicated with escape-yoked-restrained Ss given saline injections during the pretreatment phase, but the impact that inescapable shock had on later precipitated withdrawal was completely blocked when Ss were administered naltrexone HCl (14 mg/kg) before each shock session. Findings are discussed in terms of the capability of inescapable shock to activate an endogenous opiate system, thereby leading to a sensitization of release or receptor processes that could protentiate later morphine withdrawal. (56 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The retention and generalization of operant conditioning effects in an interview situation.

In a study of the conditioning of complex verbal habits, each of 30 female Ss had her established verbal habits assessed in 2 sessions by being asked to talk about herself. In subsequent sessions, the Ss in the experimental groups were positively reinforced (by a head nod and an "mm-hm") for either independence or affection statements, whereas control groups Ss were reinforced every 30 sec. regardless of the content of their speech. The results showed that: conditioning occurred, i.e., the experimental Ss increased in their use of the reinforced category; retention also occurred, i.e., the conditioning effects were stable over a 24-hr. period; and generalization did not occur. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Epinephrine-induced learning under anesthesia: Retention performance at several training–testing intervals.

While under deep barbiturate anesthesia, 58 male Sprague-Dawley rats received a series of 10 classical conditioning trials in which white noise was paired with intramuscular shock. The anesthetized Ss received subcutaneous injections of saline or epinephrine bitartrate (.1 mg/kg) prior to the training trials. Independent sets of Ss were tested for retention performance 2, 7, or 15 days after training. In these test trials, a conditioned suppression measure was used in which the white noise was turned on while the Ss were drinking. Results indicate that the Ss that had received saline while trained under anesthesia exhibited no evidence of later retention. Ss that had received epinephrine injections prior to training under anesthesia suppressed their drinking in the presence of the white noise when tested 2 or 7, but not 15, days later. Findings demonstrate that epinephrine can enable learning under anesthesia and that forgetting occurs within 15 days. (7 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Verapamil suppresses d-amphetamine-induced place preference conditioning

The effect of pretreatment with (+/-)-verapamil (5, 10 or 15 mg/kg, i.p.) on place preference induced with d-amphetamine (1 mg/kg, i.p. 40 min after verapamil) was studied in male rats. Place preference conditioning was performed using two-compartment shuttle boxes and 8 alternating stimulant/saline sessions. Verapamil dose-dependently suppressed amphetamine-induced place preference. No significant changes in place preference were observed following 8 alternating verapamil (no stimulant)/saline sessions, irrespective of whether verapamil injections were paired with the originally less or the originally more preferred compartment. It appears that verapamil effectively suppresses the reinforcing properties of d-amphetamine in the paradigm used.     

Changes in physiological and verbal responses of child molesters during aversion therapy.

10 19-33 yr old child molesters were each given 20 classical conditioning type aversion therapy sessions and 3 assessment (generalization) test sessions (before, after 10, and after 20 treatment sessions). Shock was the UCS. Larger skin conductance responses were made to child slides than to adult slides in all sessions. Penile circumference responses indicated a small positive shift in sexual preference in the assessment tests when averaged over Ss. Pre- and posttreatment semantic differential and slide-ranking sexual preference measures also showed increases in sexual preferences for adults relative to sexual preferences for children. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adrenal responses to reinforcement and extinction: Role of expectancy versus instrumental responding.

Measured plasma corticosterone levels during operant conditioning to determine the effect of reinforced and nonreinforced responding (extinction) on adrenal activation; Ss were 44 male Long-Evans rats. The influence of instrumental responding was assessed by comparing trained Ss with yoked Ss that received a matched reward schedule in the absence of an operant task. Reinforcement sessions resulted in a significant decrease in adrenal secretion at 20 min but not at 5 min, whereas extinction caused a rapid increase in corticosterone levels at 5 min and an even greater elevation at 20 min. Comparison of the operant and yoked Ss showed that this effect of reinforcement and extinction was not dependent on instrumental responding, but rather on the receipt or withdrawal of the expected reward. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A homeostatic model of Pavlovian conditioning: Tolerance to scopolamine-induced adipsia.

In Phase 1 of Exp I, with 60 male Sprague-Dawley rats, Ss given access to water while under the influence of scopolamine developed adipsic tolerance, but Ss denied access to water in the drug state did not. In Phase 2, Ss displayed adipsic tolerance only when scopolamine was administered with cues associated with previous drug injections. In Phase 3, adipsic-tolerant Ss showed a polydipsic response to an injection of phenobarbital relative to nontolerant Ss with the same pharmacological history. In Exp II, with 48 male Sprague-Dawley rats, the effect of deprivation level on the Pavlovian extinction of adipsic tolerance was assessed. Ss satiated with water during extinction showed a loss of adipsic tolerance, but water-deprived Ss did not. The proposed model is discussed in relation to (1) tolerance in other response systems such as morphine analgesia, (2) theories of extinction for nonpharmacological Pavlovian conditioning, and (3) homeostatic regulation and incentive motivation. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Androgens and imprinting: Differential effects of testosterone on filial preference in the domestic chick.

After hatching, chicks received either a subcutaneous injection of testosterone enanthate (0.5–5 mg) in oil or oil alone (controls). Ss were then trained by exposing them to a rotating imprinting stimulus, either a red box or a stuffed jungle fowl. A preference score was then determined, providing a measure of the strength of imprinting. Plasma testosterone concentration after testing did not differ significantly between males and females and was unaffected by the type of training stimulus. In fowl-trained Ss, preference score was positively correlated with plasma testosterone concentration. The mean preference score of the fowl-trained Ss that had received exogenous testosterone was significantly higher than that of controls; no such effect was found in box-trained Ss. A previous study by D. C. Davies et al (1985) showed that imprinting with the box, but not the fowl, was profoundly impaired by a noradrenergic neurotoxin. Results suggest that some of the neural systems supporting the preference for a simple artificial object are different from some of those supporting the preference for the stuffed jungle fowl. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Overshadowing effects in the stimulus control of morphine analgesic tolerance.

Attempted to replicate previous demonstrations of classical conditioning of morphine analgesic tolerance and to determine whether stimulus overshadowing effects might explain previous conflicting findings. In Exp I, 8 groups of male Sprague-Dawley rats received a series of 10 morphine (5 mg/kg) and/or saline injections, differing only with respect to the contingency between a compound visual-auditory CS and the substance injected. When tested for analgesic responding to morphine in the presence of the compound CS, only those groups for which the CS and morphine injections were paired during the acquisition sequence evidenced tolerance. In Exp II, tolerant Ss were tested in the presence of 1 component of the compound CS. When a loud tone (85 db) was used in the compound, less analgesic tolerance was elicited later by the weaker visual stimulus alone. This differential stimulus control of the analgesic response suggests that overshadowing may contribute to failures to replicate conditioned morphine tolerance. It is possible that internal morphine-produced stimuli may overshadow external cues. (18 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)     

Emetic and electric shock alcohol aversion therapy: Assessment of conditioning.

20 male alcoholic volunteers (mean age 42 yrs) were randomly assigned to 1 of 3 groups: emetic aversion conditioning, shock aversion conditioning, or a no-treatment control group. All Ss participated in psychophysiological assessment sessions and taste-test sessions before and after conditioning. Dependent measures all indicated that only emetic Ss acquired aversions to alcohol. (53 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of brightness preferences in young chicks: Effects on brightness discrimination learning.

Conducted 7 experiments with a total of 256 1-3 day old Vantress * Arbor Acre chicks to investigate the effects of interactions between the S and its sensory environment on both emergence of brightness preferences and modification by conditioning. In a simultaneous brightness discrimination, Ss were rewarded with heat for approaching either a bright or dim stimulus. Results indicate (a) brightness preference was so stable that it could not be eliminated by incubating, hatching, and rearing in the dark; (b) light experience significantly increased this preference; and (c) modification of this preference by heat reinforcement depended on age of S, prior rearing condition, sensory stimulation between testing sessions, and the length of interval between testing sessions. (28 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The septohippocampal cholinergic system and classical conditioning of the rabbit's nictitating membrane response.

28 New Zealand albino rabbits received bilateral microinjections of scopolamine (1 μl) or saline into either the dorsal hippocampus (Exp I) or the medial septal nucleus (Exp II). Ss then underwent classical conditioning of the nictitating membrane response in which a light served as a CS and eye shock served as the UCS. Results indicate that whereas hippocampal injections of scopolamine had no effect on conditioning, scopolamine injected into the medial septum retarded acquisition of the response. A 3rd experiment indicated that this retardation of conditioning was not due to changes in sensitivity to either the CS or UCS. Results are discussed in terms of accumulating evidence that manipulations that produce certain patterns of activity in the hippocampus are detrimental to acquisition of the nictitating CR. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Failure of sodium- and calcium-deficient rats to acquire conditioned taste aversions to the object of their specific hunger.

Attempted to condition taste aversions to the objects of 2 mineral-specific hungers in 2 experiments with a total of 116 male Sprague-Dawley rats. Both the innate preference of adrenalectomized Ss for sodium and the learned preference of parathyroidectomized Ss for calcium were studied. None of the sodium-deficient Ss poisoned after drinking NaCl reached a taste-avoidance criterion, even after 9 pairings of salt ingestion with aversive lithium chloride injections. 6 of 11 calcium-deficient Ss did not meet the salt-avoidance criterion after 10 pairings. Nondeficient control Ss learned to avoid these salt solutions completely after an average of only 3 such pairings. Besides unmasking a surprising degree of similarity between the learned and innate specific hungers studied, results clearly demonstrate a powerful influence of physiological need on aversion conditioning. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pavlovian second-order conditioned analgesia.

Three experiments, with 118 Sprague-Dawley rats, assessed conditioned analgesia in a Pavlovian 2nd-order conditioning procedure by using inhibition of responding to thermal stimulation as an index of pain sensitivity. In Exp I, Ss receiving 2nd-order conditioning showed longer response latencies during a test of pain sensitivity in the presence of the 2nd-order conditioned stimulus (CS) than Ss receiving appropriate control procedures. Exp II found that extinction of the 1st-order CS had no effect on established 2nd-order conditioned analgesia. Exp III evaluated the effects of post 2nd-order conditioning pairings of subcutaneous morphine sulfate (10–20 mg/kg) and the shock unconditioned stimulus/stimuli (UCS). Ss receiving paired morphine–shock presentations showed significantly shorter response latencies during a hot-plate test of pain sensitivity in the presence of the 2nd-order CS than did Ss receiving various control procedures; 2nd-order analgesia was attenuated. Data extend the associative account of conditioned analgesia to 2nd-order conditioning situations and are discussed in terms of the mediation of both 1st- and 2nd-order analgesia by an association between the CS and a representation or expectancy of the UCS, which may directly activate endogenous pain inhibition systems. (52 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition of conditional discriminations in hippocampal lesioned and decorticated rats: Evidence for learning that is separate from both simple classical conditioning and configural learning.

This study examined whether hippocampal or neocortical lesions would impair acquisition of a discrimination task using taste aversions. Male rats were injected with a drug 15 min before a flavored solution–LiCl pairing. On alternate days, vehicle injections preceded and followed access to the same flavored solution. Ss learned to consume significantly more of the flavored solution after vehicle injections than after drug injections. Ss with hippocampal lesions or neonatal decortication performed as well as controls. Ss with hippocampal lesions also learned a similar task in which visual and textural cues predicted whether access to a flavored solution would be followed by an injection of LiCl or vehicle. However, these hippocampal lesions did impair performance in the Morris water task. Occasion setting may involve a type of learning dissociated from both simple classical conditioning and configural learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)