Rotation-induced conditioned rejection in the taste reactivity test

The taste reactivity test was used to evaluate the ability of motion sickness to produce conditioned rejection reactions, a putative measure of nausea in rats. Following three conditioning trials, rats displayed conditioned rejection reactions during an intraoral infusion of a rotation-paired saccharin solution. This is the first demonstration of conditioned rejection produced with a non-pharmacological emetic agent and provides support that the conditioned rejection reaction may serve as a rat model of nausea.

Inadequacy of computed tomography in assessing patients with esophageal carcinoma after induction chemoradiotherapy

BACKGROUND

Induction chemoradiotherapy followed by surgery may improve survival of patients with esophageal carcinoma. Computed tomography (CT) has been used to evaluate the tumor response after completing induction chemoradiotherapy. The authors examined the ability of CT to evaluate the pathologic tumor response to induction therapy and to stage the tumor correctly.

METHODS

Preinduction and postinduction chemoradiotherapy CT scans were reviewed retrospectively for 50 patients enrolled in a protocol of induction chemoradiotherapy followed by surgery. All studies were performed on third-generation or fourth-generation scanners. Radiographic response was determined using Eastern Cooperative Oncology Group solid tumor response criteria for bidimensional measurable disease. This was compared with the pathologic tumor response. CT-tumor (T) classification using the modified Tio scale was compared with the pathologic T classification.

RESULTS

CT-T classification did not correlate with the pathologic stage (P = 0.09) or the pathologic tumor response (P = 0.22). The postinduction chemoradiotherapy CT accurately staged the T classification in 42% of patients but overstaged 36% of patients and understaged 20% of patients. CT had a sensitivity of 65%, a specificity of 33%, a positive predictive value of 58%, and a negative predictive value of 41% in evaluating the pathologic tumor response.

CONCLUSIONS

CT is a poor diagnostic study tool for determining the pathologic tumor response or the pathologic disease stage after induction chemoradiotherapy in patients with esophageal carcinoma.

Naloxone-precipitated morphine withdrawal induced place aversions: effect of naloxone at 24 hours postmorphine

The aversive properties of naloxone-precipitated withdrawal from acutely administered morphine were assessed using the place-conditioning paradigm. The conditioned place aversion produced by naloxone (0.5-1.0 mg/kg, s.c.) after two conditioning trials was enhanced by pretreatment with morphine (20 mg/kg, s.c.) 24 h prior to the conditioning trial. Naloxone precipitated withdrawal from acutely administered morphine produces an aversive motivational state that becomes associated with place cues.

Ambiguous genitalia: etiology, treatment, and nursing implications

The infant presenting with ambiguous genitalia is a challenge to both the medical and nursing staff. The birth of any infant with ambiguous genitalia is considered a physical and psychologic emergency requiring prompt recognition and treatment for a positive outcome. A review of the etiology, presentation, diagnosis, and treatment of ambiguous genitalia is presented. The important aspects of family care also are discussed.

Chlordiazepoxide-induced conditioned place and taste aversion learning in rats

The hedonic properties of chlordiazepoxide (CDP) were examined using the place conditioning and the taste conditioning paradigms. Following four conditioning trials, CDP (5-20 mg/kg) produced a conditioned place aversion in an "unbiased" paradigm in which the chamber paired with CDP was counterbalanced among two equally preferred chambers. In a "biased" place-conditioning paradigm, CDP (5 and 20 mg/ kg) prevented the dissipation of the natural aversion to the nonpreferred chamber. Finally, although CDP unconditionally potentiated sucrose consumption, it produced a sucrose aversion in the taste reactivity test and sucrose avoidance in the taste avoidance test when the taste conditionally preceded injections of CDP. The pattern of findings suggest that, when novel to rats, CDP is hedonically aversive.

Conditioned sucrose aversions produced by naloxone-precipitated withdrawal from acutely administered morphine

The aversive properties of acute naloxone-precipitated morphine withdrawal were examined in the taste reactivity paradigm. Acute naloxone-precipitated withdrawal paired with sucrose solution established conditioned active rejection of the sucrose solution. Active rejection of sucrose was observed when naloxone was administered both 1 h and 22 h after morphine. When the stimulus properties of morphine were present during the conditioning trial, the conditioned sucrose aversion was only expressed when the rats were tested in the same drug state in which they had learned the aversion. However, when the stimulus properties of morphine were not present during conditioning, the aversion was expressed in the absence of the morphine state. The results suggest that palatability shifts can be conditioned to sucrose paired with acute morphine withdrawal.

Severe congenital neutropenia: a case study

Severe congenital neutropenia, or Kostmann syndrome, describes a rare autosomal recessive disorder in which the neutrophils fail to reach a mature and functional state. The infant with SCN often presents with severe infections beginning in the first month of life. Recently, treatment with recombinant granulocyte colony-stimulating factor has been found to be effective in reducing the mortality and morbidity of this often fatal disorder.

Pimozide does not shift palatability: separation of anhedonia from sensorimotor suppression by taste reactivity

Several "taste reactivity" studies of dopamine and reward have concluded that pimozide suppresses the hedonic reaction patterns normally elicited by sucrose but enhances aversive reaction patterns elicited by quinine. However, other taste reactivity studies have failed to find hedonic/aversive shifts in reaction patterns after dopamine antagonists or dopamine lesions. The divergent conclusions have come from two different laboratories. To resolve the controversy regarding dopamine blockade and palatability, the present study joined the two laboratories to investigate the effect of pimozide on taste reactivity patterns elicited by sucrose and quinine. The results replicated many (but not all) of the earlier findings and identified procedural factors responsible for different outcomes. Overall, the results provide evidence for sensorimotor effects of pimozide on taste reactivity but not for a hedonic shift in palatability. Pimozide suppressed both hedonic and aversive reaction patterns in a gradual sensorimotor fashion when the eliciting taste stimulus was repeated or continued for several minutes. The general suppression typically did not alter the initial reaction to a taste but emerged only after an oral infusion of sucrose or quinine continued for several minutes or trials. Aversive reactions were never enhanced. The balance between hedonic and aversive reaction patterns was not shifted by pimozide. We conclude that pimozide produces a sensorimotor impairment of taste reactivity patterns but does not shift taste palatability toward anhedonia or aversion.

Ibogaine interferes with the establishment of amphetamine place preference learning

The ability of ibogaine, injected 24 hr before amphetamine, to modify the establishment of amphetamine-induced place preference learning was assessed. A single injection of ibogaine blocked the establishment of amphetamine place preference after 1 or 2 conditioning trials, but it was less effective after 4 trials. The reduced effectiveness of ibogaine across multiple conditioning trials appears to be the result of the development of tolerance to ibogaine.

Induction chemoradiotherapy followed by esophagectomy in patients with carcinoma of the esophagus

BACKGROUND

Induction chemoradiotherapy followed by esophagectomy may provide results superior to those of single-modality treatment in patients with esophageal cancer. The purpose of this study was to review our experience with this approach for esophageal cancer.

METHODS

From 1988 to 1996, 166 consecutive patients with esophageal cancer were evaluated; 66 entered a protocol of chemotherapy (5-fluorouracil, cisplatin) concurrent with radiation (45 Gy) followed by esophagectomy. Fifty-four patients completed the protocol.

RESULTS

Toxicity associated with induction chemoradiotherapy was minimal. The actuarial survival at 12, 24, and 36 months was 59%, 42%, and 32%, respectively. The pathologic complete response (pCR) rate was 41%, with 12-, 24-, and 36-month survivals of 77%, 50%, and 45%, whereas non-pCR patients had survivals of 46%, 35%, and 23%. The difference in survival between pCR and non-pCR patients was not significant (p = 0.13), but the difference in recurrence-free survival was significant (p = 0.007).

CONCLUSIONS

This well-tolerated protocol resulted in a high pCR. Trimodality treatment for esophageal cancer may provide long-term survival in some patients regardless of their pCR status.

Recurrent alveolar proteinosis following double lung transplantation

We present a case of recurrent alveolar proteinosis following double lung transplantation.

Ibogaine interferes with the establishment of amphetamine place preference learning

The ability of ibogaine, injected 24 hr before amphetamine, to modify the establishment of amphetamine-induced place preference learning was assessed. A single injection of ibogaine blocked the establishment of amphetamine place preference after 1 or 2 conditioning trials, but it was less effective after 4 trials. The reduced effectiveness of ibogaine across multiple conditioning trials appears to be the result of the development of tolerance to ibogaine.

LSD produces place preference and flavor avoidance but does not produce flavor aversion in rats

The hedonic properties of lysergic acid diethylamide (LSD) were assessed using the place conditioning, taste reactivity, and taste avoidance tests. LSD produced a conditioned place preference, but only at the highest dose tested (0.2 mg/kg). A single preexposure to the conditioning chamber (latent inhibition) prevented the establishment of a place preference. When paired with sucrose, doses of 0.05 to 0.2 mg/kg of LSD produced taste avoidance, but no dose of LSD produced an aversion to the taste as assessed by the taste reactivity test. These results suggest that LSD, like other rewarding drugs, produces taste avoidance by a mechanism other than that produced by emetic drugs.

Primary pulmonary chondrosarcoma mimicking bronchogenic cyst on CT and MRI

Pulmonary chondrosarcoma is a rarely encountered primary tumor of the lung. We present a case with computed tomography and magnetic resonance imaging features mimicking a bronchogenic cyst.

Ibogaine fails to interrupt the expression of a previously established one-trial morphine place preference

1. Ibogaine, a proposed anti-addictive agent, has been found to interfere with the acquisition of a weak morphine-induced place preference. The present series of experiments determined if ibogaine would interfere with the expression of a previously established morphine (5 mg/kg) place preference. 2. A single injection of 40 mg/kg of ibogaine 24 h, 12 h or 4 h prior to the preference test (Experiment 1) or 80 mg/kg of ibogaine 24 hr prior to the preference test (Experiment 3) did not interfere with the expression of a morphine conditioned place preference. 3. Furthermore, two injections of 40 mg/kg of ibogaine 48 h and 24 h or 24 h and 4 h prior to testing (Experiment 2) did not interfere with the expression of a morphine place preference. 4. Ibogaine appears to be incapable of attenuating the expression of a previously established one-trial morphine place preference.

LSD produces place preference and flavor avoidance but does not produce flavor aversion in rats

The hedonic properties of lysergic acid diethylamide (LSD) were assessed using the place conditioning, taste reactivity, and taste avoidance tests. LSD produced a conditioned place preference, but only at the highest dose tested (0.2 mg/kg). A single preexposure to the conditioning chamber (latent inhibition) prevented the establishment of a place preference. When paired with sucrose, doses of 0.05 to 0.2 mg/kg of LSD produced taste avoidance, but no dose of LSD produced an aversion to the taste as assessed by the taste reactivity test. These results suggest that LSD, like other rewarding drugs, produces taste avoidance by a mechanism other than that produced by emetic drugs.

Individual differences in reactivity to the rewarding/aversive properties of drugs: assessment by taste and place conditioning

The ability of individual differences in the strength of conditioned taste avoidance (CTA) to predict strength of place conditioning produced by the same drug was assessed. In Phase 1, rats were assigned to High CTA and Low CTA groups on the basis of their intake of saccharin solution previously paired with morphine, amphetamine, lithium, or fenfluramine. In Phase 2, the rats received place conditioning training with the same drug used during Phase 1. The rats that displayed the strongest amphetamine-induced CTA also displayed the strongest amphetamine-induced place preference, suggesting that a common mechanism mediates both effects. On the other hand, the strength of the CTA was unrelated to the strength of the place preference or place aversion produced by morphine, lithium, or fenfluramine.

Morphine enhancement of sucrose palatability: analysis by the taste reactivity test

The ability of morphine to modify sucrose palatability was assessed by the taste reactivity test. In Experiment 1, rats were injected with morphine (0.0, 0.5, 2.0, and 10.0 mg/kg, subcutaneously), 30 min before receiving a 10-min intraoral infusion of 2% or 20% sucrose solution. A dose of 2.0 mg/kg morphine enhanced ingestive reactions elicited by both concentrations of sucrose solution. In Experiment 2, the interval between morphine pretreatment and the taste reactivity test was manipulated. Rats given 2.0 mg/kg morphine 30 or 120 min before testing displayed enhanced ingestive reactions elicited by 20% sucrose solution during the first 5 min of a 10-min test. The results support the hypothesis that morphine enhances the hedonic assessment of sucrose solution.

The effects of nicotine and nicotine withdrawal on taste reactivity

The effect of nicotine pretreatment on the palatability of flavored solutions was assessed using the taste reactivity test. In Experiment 1, low doses of nicotine [0.2-0.4 mg/kg, subcutaneously (s.c.)] suppressed the aversive taste properties of quinine and quinine-sucrose mixture and enhanced the hedonic taste properties of sucrose (0.4 mg/kg, s.c.) in rats that were nicotine naive. In Experiment 2, rats were chronically preexposed to nicotine or saline over a period of 21 pretreatment days. Tolerance developed to the ability of nicotine to enhance the palatability of sucrose. Furthermore, rats that were chronically preexposed to nicotine displayed enhanced hedonic evaluation of sucrose 24 h after nicotine was withdrawn. These results confirm human self-reports that withdrawal from nicotine dependency enhances the palatability of sweet-tasting foods.

Necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a disease characterized by ischemia and necrosis of the gastrointestinal tract frequently leading to perforation of the intestine. It occurs primarily in the premature infant and is a major cause of mortality and morbidity in the low birth weight infant. Careful nursing and medical care can greatly reduce the incidence and severity of this disease, thus decreasing both the associated morbidity and mortality. This article reviews the pathophysiology, diagnosis, and treatment of NEC; presents a case study; and provides a nursing care plan for treatment of this disease.

Morphine-induced modification of quinine palatability: effects of multiple morphine-quinine trials

Morphine pretreatment attenuates aversive taste reactions elicited by quinine solution when assessed by the taste reactivity test. To determine whether this effect changes across trials, rats were administered morphine (2 mg/kg, subcutaneously) 30 min before a 5-min intraoral infusion of quinine solution (0.05%) on each of eight trials. Neither tolerance nor sensitization developed to morphine-induced attenuation of quinine aversiveness; morphine suppressed quinine-elicited aversive reactions on each trial. In addition, when tested in the absence of morphine, rats displayed a reduced aversion to quinine, suggesting that quinine became conditionally less aversive following previous pairings with morphine.

Chlordiazepoxide enhances the palatability of lithium-, amphetamine-, and saline-paired saccharin solution

The ability of chlordiazepoxide to modify taste reactions elicited by a saccharin solution that was paired on three occasions with amphetamine (1 or 3 mg/kg), lithium (0.3 or 1.2 mEq/kg), or saline solution was assessed using the taste reactivity test. Chlordiazepoxide enhanced positive ingestive reactions regardless of the conditional properties of the tastant and had no effect on aversive reactions. These results support previous reports that chlordiazepoxide directly modifies the palatability of tastants.

Rewarding drugs produce taste avoidance, but not taste aversion

Paradoxically, drugs that animals will self-administer also produce conditioned taste avoidance at similar dosage levels. The present review presents evidence that the taste avoidance produced by these rewarding drugs differs qualitatively from the taste avoidance produced by the nonrewarding, emetic drug, lithium chloride. An analysis of data pooled across 6 experiments compares the nature of flavor-drug associations produced by various rewarding drugs (amphetamine, cocaine, methamphetamine, methylphenidate, morphine, nicotine and phencyclidine) with that produced by lithium. The data from the groups conditioned with the rewarding drugs and with lithium were combined into the two categories of low/moderate and high doses. When assessed by the CTA test, the rewarding drugs did not differ from lithium in the strength of the CTA at low/moderate or at high doses. However, when assessed by the TR test, lithium produced more prominent aversive taste reactions than did the rewarding drugs. These findings suggest that the flavor-drug association produced by lithium and rewarding drugs differs qualitatively. With the large pooled data set we also assessed the relationship among the various TR categories, resulting in two factors of "Ingestion" and "Aversion" accounting for 55% of the total variability within the data.

THC-induced place and taste aversions in Lewis and Sprague-Dawley rats

The hedonic properties of delta-9-tetrahydrocannabinol (THC) were assessed in place and taste conditioning paradigms in both Lewis and Sprague-Dawley rat strains. THC produced place avoidance, taste avoidance, and aversive taste reactivity responses in both strains. The Lewis strain displayed more aversive taste reactions and a stronger taste avoidance when conditioned with lower doses of THC than did the Sprague-Dawley strain of rats. THC is an anomalous drug of abuse that appears to be aversive to rats when assessed by these measures.