Discriminative stimulus properties of 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane [(+/-)DOI] in C57BL/6J mice

RATIONALE

The drug discrimination procedure has proven to be a valuable tool for studying the mechanism of action of psychoactive drugs. Recently, mice with targeted gene mutations have been developed that may also prove useful in evaluating the role of specific receptors in mediating the actions of drugs. We were interested in studying the effects of hallucinogens in genetically modified mice using the drug discrimination procedure.

OBJECTIVE

To establish the training procedures and characterize the stimulus properties of 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane [(+/-)DOI] versus saline in wild-type mice.

METHODS

Using a two-lever drug discrimination procedure, C57BL/6J mice were trained to discriminate (+/-)DOI (2.5 mg/kg) from saline on a VI 30-s schedule of reinforcement.

RESULTS

The acquisition function was orderly and similar to that found previously with rats, although the training dose required for the mice was four times higher (2.5 versus 0.75 mg/kg). The dose-response relationship indicated that percent drug lever responding was dose-dependent. Two other hallucinogens, LSD and (-)DOB, substituted fully for (+/-)DOI. Mice were tested for their ability to discriminate (+/-)DOI following pretreatment with the 5-HT(2A) receptor antagonist MDL 100,907, or with 5-HT(2C) selective antagonists, SB 206,553 or SB 242,084. A dose of 0.25 mg/kg MDL 100,907 essentially completely blocked the discriminative stimulus effects of 2.5 mg/kg (+/-)DOI. Surprisingly, both SB 206,553 and SB 242,084 also attenuated the effect of 2.5 mg/kg (+/-)DOI. The effect of SB 206,553 was surmountable at 5.0 mg/kg (+/-)DOI.

CONCLUSIONS

These data agree with the results from studies with rats indicating a prominent role for the 5-HT(2A) receptors in mediating the discriminative stimulus effects of (+/-)DOI but in addition, suggest a small but significant role for the 5-HT(2C) receptor in mice.

Stimulus generalization by fenfluramine in a quipazine-ketanserin drug discrimination is not dependent on indirect serotonin release

The purpose of this study was to determine if animals trained to discriminate a serotonin2A (5-HT2A) receptor agonist from a 5-HT2A receptor antagonist would also be sensitive to alterations in serotonin neurotransmission brought about by 5-HT reuptake inhibitors and releasers. Previous work from our laboratory has shown that the quipazine-ketanserin discrimination is mediated solely by the 5-HT2A receptor, thus providing a behavioral continuum of 5-HT2A receptor function. Rats were trained to discriminate quipazine (0.35 mg/kg) from ketanserin (1.0 mg/kg) on a variable interval-30 schedule of reinforcement. Following acquisition, substitution tests were conducted with the training drug, quipazine, and agents that have been shown to alter the synaptic levels of 5-HT, including fenfluramine, norfenfluramine, 5-methoxy-6-methyl-2-aminoindan (MMAI) and fluoxetine. All compounds substituted, except fluoxetine. Antagonist tests with mianserin and MDL 100,907 indicated that fenfluramine's and MMAI's substitution for quipazine was mediated by the 5-HT2A receptor. Animals were pretreated with PCPA to determine whether 5-HT release or direct agonism mediated the discriminative stimulus effects of fenfluramine and MMAI. PCPA blocked the substitution of MMAI but not of fenfluramine for quipazine. Analysis of 3H-IP formation in cells showed that norfenfluramine dose-dependently stimulated phosphoinositide hydrolysis to levels similar to that of serotonin and quipazine. These results indicate that fenfluramine's substitution for quipazine in rats trained on a quipazine-ketanserin discrimination are due to direct agonism at the 5-HT2A receptor likely mediated by norfenfluramine, an active metabolite.

Effects of training dose on amphetamine drug discrimination: dose-response functions and generalization to cocaine

Rats were trained to discriminate one of three doses of amphetamine (AM), 0.5, 1, or 2 mg/kg, from vehicle (VEH) in a two-lever, food-reinforced, drug-discrimination task. The purpose of the study was to investigate the nature of the shift of the dose-response curve and generalization to cocaine (COC) as a function of training dose. In order to preclude potential differences among the groups in stimulus control, the three training-dose groups were required to perform the discrimination at high and equivalent levels of accuracy. The shift of the dose-response functions to the right as a function of increasing training dose was not parallel. The slope decreased as training dose increased. There was a dose-dependent increase in AM lever responding to test doses of COC that tended to be affected by training dose. The results suggest that proper evaluation of training-dose effects requires that groups be trained to equivalent levels of stimulus control.

Long-lasting rebound cue effects following single doses of nicotine and amphetamine: implications for understanding tolerance

RATIONALE

Previous drug-discrimination studies have, with the exception of nicotine (NIC), demonstrated tolerance to the cue effects of a broad range of drugs of abuse. Barrett et al. have shown that tolerance to a drug's cue properties reflects drug-induced rebound shifts in the discrimination baseline and not a weakened or less salient cue.

OBJECTIVES

The objective of the present study was to use a discrimination task sensitive to bidirectional cue changes to characterize the interoceptive cues associated with both the primary and rebound cues produced by nicotine in an attempt to understand why a recent study by Shoaib et al. failed to observe tolerance to the nicotine cue.

METHODS

Since dopamine (DA) has been implicated in mediating the NIC cue, rats were trained to discriminate between 0.25 mg/kg amphetamine (AMPH), an indirect DA agonist, and 0.033 mg/kg haloperidol (HAL), a DA antagonist at the D2 receptor site. Training doses were chosen so that rats responded about equally on both levers when tested on saline (SAL) following acquisition. This procedure provided a behavioral baseline to assess NIC-related changes along a presumed continuum of DA-mediated cues. Following acquisition of the discrimination: (i) NIC substitution tests were conducted, (ii) rats were tested for lever choice at intervals from 2 h to 48 h following treatment with single doses of 0.25 mg/kg and 0.50 mg/kg NIC, and (iii) rats were challenged with test doses of NIC during a period of NIC rebound.

RESULTS

(i) NIC substituted for AMPH in a dose- dependent manner. (ii) At short intervals after treatment with 0.25 mg/kg and 0.50 mg/kg NIC, rats responded primarily on the AMPH lever followed by a shift to predominant responding on the HAL lever 16-24 h post-treatment, before returning to predrug levels. (iii) No evidence was observed for acute tolerance to NIC.

CONCLUSIONS

The robust and long-lasting rebound cues associated with training level doses of NIC suggest that maximal tolerance would likely develop to the NIC cue during the acquisition phase of the conventional NIC-saline discrimination study.

Inconsistent reconstitution of cytomegalovirus-specific cell-mediated immunity in human immunodeficiency virus-infected patients receiving highly active antiretroviral therapy

Cytomegalovirus (CMV)-immune recovery was characterized in human immunodeficiency virus (HIV)-infected patients receiving highly active antiretroviral therapy. CMV lymphocyte proliferation (LP), responder-cell frequency (RCF), and interferon (IFN)-gamma and interleukin (IL)-2 secretion were studied in CMV-seropositive HIV-infected patients and in CMV-seropositive HIV-uninfected control subjects. HIV-infected patients and control subjects had similar proportions of IL-2 and IFN-gamma, but levels were lower in HIV-infected patients. LP and RCF were significantly less frequent and of lower magnitude in HIV-infected patients. The measures of CMV cell-mediated immunity were correlated in HIV-uninfected but not in HIV-infected subjects. To investigate this, IL-2, IL-12, anti-CD28 plus anti-CD49d, or anti-IL-10 was added in vitro, with no effect on LP. However, CD8 cell depletion of mononuclear cells from HIV-infected patients increased LP responses to levels similar to those of uninfected control subjects; before depletion, only RCF correlated with CD4 cell counts, but after depletion, LP also correlated with CD4 cell counts.

Tubal sterilization and risk of cancer of the endometrium

OBJECTIVE

Surgical sterilization is a common method of contraception among U.S. women. Most surgical sterilizations are tubal ligations, but few studies have investigated their potential impact on endometrial cancer risk.

METHODS

A case-control study included 405 women diagnosed with endometrial cancer at 5 U.S. medical centers between 1987 and 1990 and 297 age-, race-, and location-matched controls who were identified by random-digit-dialing. Questionnaires ascertained information on tubal sterilization, and logistic regression models generated odds ratios (ORs) to estimate relative risk.

RESULTS

The OR and 95% confidence interval for tubal sterilization, which was reported by 47 cases and 40 controls, was 0.9 (0.6-1.4) before adjustment and 1. 4 (0.8-2.4) after adjustment for age, parity, and oral contraceptive use. Age at surgery, years since surgery, or calendar years of surgery were not associated with endometrial cancer, and associations did not vary according to parity or stage of disease at diagnosis.

CONCLUSIONS

Tubal sterilization is not substantially associated with endometrial cancer.

Concurrent chemotherapy and pelvic radiation therapy compared with pelvic radiation therapy alone as adjuvant therapy after radical surgery in high-risk early-stage cancer of the cervix

PURPOSE

To determine whether the addition of cisplatin-based chemotherapy (CT) to pelvic radiation therapy (RT) will improve the survival of early-stage, high-risk patients with cervical carcinoma.

PATIENTS AND METHODS

Patients with clinical stage IA(2), IB, and IIA carcinoma of the cervix, initially treated with radical hysterectomy and pelvic lymphadenectomy, and who had positive pelvic lymph nodes and/or positive margins and/or microscopic involvement of the parametrium were eligible for this study. Patients were randomized to receive RT or RT + CT. Patients in each group received 49.3 GY RT in 29 fractions to a standard pelvic field. Chemotherapy consisted of bolus cisplatin 70 mg/m(2) and a 96-hour infusion of fluorouracil 1,000 mg/m(2)/d every 3 weeks for four cycles, with the first and second cycles given concurrent to RT.

RESULTS

Between 1991 and 1996, 268 patients were entered onto the study. Two hundred forty-three patients were assessable (127 RT + CT patients and 116 RT patients). Progression-free and overall survival are significantly improved in the patients receiving CT. The hazard ratios for progression-free survival and overall survival in the RT only arm versus the RT + CT arm are 2.01 (P =.003) and 1.96 (P =. 007), respectively. The projected progression-free survivals at 4 years is 63% with RT and 80% with RT + CT. The projected overall survival rate at 4 years is 71% with RT and 81% with RT + CT. Grades 3 and 4 hematologic and gastrointestinal toxicity were more frequent in the RT + CT group.

CONCLUSION

The addition of concurrent cisplatin-based CT to RT significantly improves progression-free and overall survival for high-risk, early-stage patients who undergo radical hysterectomy and pelvic lymphadenectomy for carcinoma of the cervix.

Mechanism of tolerance development to 2,5-dimethoxy-4-iodoamphetamine in rats: down-regulation of the 5-HT2A, but not 5-HT2C, receptor

RATIONALE

Defining the mechanism of tolerance development to hallucinogenic drugs will help to explain their mechanism of action.

OBJECTIVES

The present study was conducted to determine first, if tolerance develops to the discriminative stimulus (DS) properties of the hallucinogen, 2,5 dimethoxy-4-iodo-amphetamine (DOI) and second, the mechanism mediating tolerance.

METHODS

Rats were trained to discriminate 0.75 mg/kg DOI from saline on a concurrent VI-30-min schedule of reinforcement with a 15-min time-out for incorrect responses. To evaluate tolerance development, rats were assigned to one of four groups and treated with either chronic saline or chronic DOI. Prior to chronic treatment, two groups were tested for choice behavior following vehicle administration while the remaining two groups were tested following the administration of 0.375 mg/kg DOI. One group from each pre-test condition was injected with either saline or DOI (1 mg/kg) for 8 days. Twenty-four hours after the last chronic injection the pre-test treatments were replicated. Using receptor autoradiography, the density of 5-HT2A and 5-HT2C receptors was measured in independent groups of rats that had received identical treatment conditions.

RESULTS

Animals receiving chronic DOI showed a 60% decrease in DOI lever responding (from 100% to 40%) when tested on 0.375 mg/kg DOI, while animals receiving chronic saline showed no change in percent choice (100%) on the DOI lever. Significant changes in binding were observed in 5-HT2A receptors but not 5-HT2C receptors. The results of tests with antagonists were consistent with the changes in binding.

CONCLUSIONS

These results suggest that behavioral tolerance to DOI reflects neuroadaptive changes in 5-HT2A receptors.

Characterizing withdrawal in rats following repeated drug administration using an amphetamine-vehicle-haloperidol drug discrimination

RATIONALE

Previous research using an amphetamine (AM)-haloperidol (HA) drug- drug discrimination task has shown that predominant responding on the HA-appropriate lever occurs 24 h after a single or multiple administrations of 10 mg/kg AM. Conversely, rebound responding on the AM-appropriate lever occurs following single or multiple administrations of 1 mg/kg HA. HA-appropriate responding was also observed 24 h following a single injection of AM using a three-lever, AM-vehicle-HA discrimination task. However, a single administration of HA did not produce robust rebound responding on the AM-appropriate lever. The present studies seek to clarify the discrepancy between responding following HA in the two- and three-choice tasks.

OBJECTIVE

Experiment 1 examined the extent of rebound responding that could be achieved following ten daily administrations of either 10 mg/kg AM or 1 mg/kg HA. Experiment 2 explored potential differences between the two- and three-choice tasks in characterizing the post-HA cue.

METHODS

Animals were trained to discriminate 0.35 mg/kg AM, vehicle, and 0.033 mg/kg HA. In experiment 1, animals received ten daily injections of 10 mg/kg AM, vehicle, or 1 mg/kg HA, and were tested 24 h after the final injection, and again 8, 15, and 22 days post-treatment. In experiment 2, animals were retrained and then treated daily with either vehicle or 1.0 mg/kg HA for 10 days, and then tested 24 h after the final injection, and again 5 and 11 days post-treatment, with either all three levers or with only the AM- and HA-appropriate levers available.

RESULTS

In experiment 1, multiple injections of AM produced robust HA lever responding, which is consistent with results from previous studies that used the two-choice, AM-HA discrimination task. However, multiple injections of HA did not produce predominant responding on the AM-appropriate lever. In experiment 2, animals treated with either vehicle or HA responded predominantly on the vehicle-appropriate lever when tested with all three levers present. When tested with the vehicle lever removed, however, animals treated with vehicle responded predominantly on the HA-appropriate lever, whereas those treated with HA responded predominantly on the AM-appropriate lever.

CONCLUSIONS

These results suggest that the two-choice and three-choice task used here differ in how the post-HA withdrawal cue is characterized. This finding emphasizes the importance of knowing the relative locations of the agonist-, vehicle-, and antagonist-produced cues on the interoceptive stimulus continuum established by discrimination training.

Agonist properties of N,N-dimethyltryptamine at serotonin 5-HT2A and 5-HT2C receptors

Extensive behavioral and biochemical evidence suggests an agonist role at the 5-HT2A receptor, and perhaps the 5-HT2C receptor, in the mechanism of action of hallucinogenic drugs. However the published in vitro pharmacological properties of N,N-dimethyltryptamine (DMT), an hallucinogenic tryptamine analog, are not consistent with this hypothesis. We, therefore, undertook an extensive investigation into the properties of DMT at 5-HT2A and 5-HT2C receptors. In fibroblasts transfected with the 5-HT2A receptor or the 5-HT2C receptor, DMT activated the major intracellular signaling pathway (phosphoinositide hydrolysis) to an extent comparable to that produced by serotonin. Because drug efficacy changes with receptor density and cellular microenvironment, we also examined the properties of DMT in native preparations using a behavioral and biochemical approach. Rats were trained to discriminate an antagonist ketanserin from an agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) in a two-lever choice paradigm. Pharmacological studies showed that responding on the DOI and ketanserin lever reflected agonist and antagonist activity at 5-HT2A receptors, and hence, was a suitable model for evaluating the in vivo functional properties of DMT. Like other 5-HT2A receptor agonists, DMT substituted fully for DOI. Intact choroid plexus was used to evaluate the agonist properties at endogenous 5-HT2C receptors; DMT was a partial agonist at 5-HT2C receptors in this native preparation. Thus, we conclude that DMT behaves as an agonist at both 5-HT2A and 5-HT2A receptors. One difference was evident in that the 5-HT2C, but not the 5-HT2A, receptor showed a profound desensitization to DMT over time. This difference is interesting in light of the recent report that the hallucinogenic activity of DMT does not tolerate in humans and suggests the 5-HT2C receptor plays a less prominent role in the action of DMT.

Conceptual foundations of schizophrenia: I. Degeneration

OBJECTIVE

This is the first of two papers that aim to identify some of the institutional processes of 19th century European psychiatry, and some prevailing cultural themes of that era that played a role in shaping the development of schizophrenia as a disease concept.

METHOD

Three areas of psychiatric history are examined: the first is concerned with the key figures who coined the concept of dementia praecox; the second with the rise of the asylum; and the third is to do with the ideology of 19th century psychiatric science and its relationship to a broader intellectual milieu. These three literatures are examined for common themes.

RESULTS

The theme of degeneration is evident in all three literatures, and denotes both a biological process (neuro-degeneration) and a moral state (degeneracy).

CONCLUSIONS

The idea of degeneration, a pervasive cultural theme of the 19th century, dominated psychiatric thinking long before schizophrenia was developed as a diagnostic category. It contributed to the ideational form-work that gave foundation, structure and shape to the concept of schizophrenia.

Conceptual foundations of schizophrenia: II. Disintegration and division

OBJECTIVE

This is the second of two papers that aim to identify some cultural themes and institutional processes that shaped the development of schizophrenia as a disease concept.

METHOD

A number of domains within 19th century European history are explored for evidence of the concept of the divided or disintegrated person. These include German academic psychiatry, Mesmerism and hypnosis, neurology and neurophysiology, psychoanalysis and German Romantic literature, and its descendants within a wider European literature.

RESULTS

Representations of division or disintegration are evident in all these domains, enjoying widespread currency and penetration throughout the 19th century.

CONCLUSIONS

These culturally based ideas, combined with the idea of degeneration, were important elements in the foundation of the schizophrenia concept.

Evidence for a common etiology for endometrial carcinomas and malignant mixed mullerian tumors

OBJECTIVE

To elucidate factors linked to the development of malignant mixed mullerian tumors (MMMT) and determine whether the risk factor profile for these tumors corresponds with that for the more common endometrial carcinomas.

METHODS

A multicenter case-control study of 424 women diagnosed with endometrial carcinoma, 29 women diagnosed with MMMT, and 320 community controls was conducted. Review of pathological reports and slides was performed to classify cases by histological type. All participants were asked to respond to a questionnaire which ascertained information on exposure to factors postulated to be linked to the development of uterine tumors.

RESULTS

Women with endometrial carcinomas and MMMTs were similar with respect to age and educational attainment. Women diagnosed with MMMTs were more likely than those diagnosed with carcinomas to be of African-American descent (28% vs 4%; P = 0.001). Weight, exogenous estrogen use, and nulliparity were related to risk of both tumor types. Marked obesity was associated with a 4.8-fold (95% CI = 3.0,7.6) increase in risk of carcinoma and a 3.2-fold (95% CI = 1.1,9.1) increase in risk of MMMT development. Use of exogenous estrogens increased the odds of developing carcinomas by 2-fold (95% CI = 1.3,3.2) and that of developing MMMTs by 1.8-fold (95% CI = 0.57,5.5). Nulliparity was associated with a 2.9-fold (95% CI = 1.9,4.8) increase in risk of carcinomas and a 1.7-fold (95% CI = 0.53,5.6) increase in risk of MMMTs. Oral contraceptive use protected against the development of both carcinomas (OR = 0.39; 95% CI = 0.26,0.58) and MMMTs (OR = 0.76; 95% CI = 0.25,2.3). Current smokers were at a reduced risk of developing endometrial carcinomas (OR = 0.34; 95% CI = 0.21,0.55) and MMMTs (OR = 0.57; 95% CI = 0.15,2.3), while former smokers were at an increased risk of MMMT (OR = 2.7; 95% CI = 1.1,6.8) but not carcinoma development (OR = 0.81; 95% CI = 0.56,1.2).

CONCLUSION

Results from this study suggest that MMMTs and carcinomas have a similar risk factor profile. This observation is compatible with the hypothesis that the pathogenesis of these two histological types of uterine tumors is similar.

Analysis of histopathological features of endometrioid uterine carcinomas and epidemiologic risk factors

A large case-control study was performed to determine whether risk factors for endometrioid carcinoma, the most common type of endometrial cancer, vary according to the histological features of the tumor. Study subjects consisted of 328 women with newly diagnosed endometrioid adenocarcinoma and 320 population-based control subjects. Variables studied included age at menarche, menopausal estrogen use, weight, parity, cigarette smoking, and oral contraceptive use. The risk factor profile for endometrioid carcinomas with and without squamous differentiation was very similar. No striking differences in risk factors were observed between endometrioid cancers with and without adjacent endometrial hyperplasia. Finally, none of the risk factors varied substantially between early-stage and late-stage tumors or low-grade and high-grade tumors. In summary, this study indicates that risk factors for endometrioid carcinomas are not related to the morphological features of the tumor.

Amphetamine-induced withdrawal responding: effects of repeated drug administration

The first purpose of this research was to assess withdrawal haloperidol-appropriate lever responding 24 h after a single administration of 0.35, 0.75, and 1.00 mg/kg amphetamine. Rats were trained to discriminate among 0.35 mg/kg amphetamine (AM), distilled water (DW), and 0.033 mg/kg haloperidol (HA) in a three-lever drug discrimination task. An increase in HA-appropriate lever responding occurred following the 1.00 mg/kg dose of AM but not after either of the lower doses. The second purpose was to determine the effect of repeated administration of 0.75 mg/kg AM. Two groups of animals were given five administrations of drug, one at an interdose interval (IDI) of 24 h and the other at an IDI of 48 h. Control animals were given injections of DW. Increased HA-appropriate lever responding occurred in both of the AM-treated groups. The magnitude of this effect tended to be less in the 48-h IDI group. Thus, even though HA-lever responding was not evident 24 h after a single administration of 0.75 mg/kg AM, it was produced by repeated administration of this dose, even at 48-h intervals.

Risk factors and hormone levels in patients with serous and endometrioid uterine carcinomas

We performed a multi-institutional, incident case-control study of 328 endometrioid and 26 serous carcinomas to assess whether risk factors and circulating hormone levels in women with serous carcinoma differ from the expected profile for endometrial carcinoma We also evaluated exposures potentially related to endometrial cancer risk, anthropometric measurements, and circulating levels of sex hormones and related carrier proteins. Histopathologic specimens were reviewed without knowledge of the other data. As expected, a statistically significant association was observed for high body mass index (BMI) (relative risk, 3.5) and use of menopausal estrogens (relative risk, 2.4) in the endometrioid carcinoma cases, whereas serous carcinomas were not strongly associated with these factors. Smoking and oral contraceptive use decreased risk for both tumor types. For five of six sex hormones tested, age-adjusted mean serum levels in patients with serous carcinoma were significantly lower than those in women with endometrioid carcinoma. After adjustment for BMI, these differences were narrowed, but levels of albumin-bound estradiol and estrone remained significantly lower in the serous cases. Age and BMI-adjusted levels of sex hormone-binding globulin were significantly higher in patients with serous carcinoma than in women with endometrioid carcinomas. In conclusion, risk factors and sex hormone levels in patients with uterine serous carcinoma seem to differ from those in women with endometrioid carcinoma, suggesting that there may be at least two different pathways of endometrial carcinogenesis.

Tolerance to the anticonflict effects of diazepam: importance of methodological considerations

The present study examines the effects of chronic diazepam treatment on conflict behavior in rats using the Geller-Seifter paradigm. A dose-response function for the effects of diazepam (DZ) on punished and unpunished responding was determined (0.0, 0.63, 1.25, 2.5, and 5.0 mg/kg DZ intraperitoneally) using five independent groups. The test doses of DZ produced an inverted U-shaped function where punished responding increased as a function of dose up to 2.5 mg/kg and then decreased at 5.0 mg/kg. All groups were then treated with 2 x 5 mg/kg DZ per day for 5 days. When the dose-response function was redetermined at 36 h post-chronic treatment, it was found that the function had shifted to the right, indicating tolerance. Because of the inverted U-shaped nature of the original function, tolerance was manifested as a decrease in responding on the ascending portion of the function and as an increase in responding on the dose (5 mg/kg) representing the descending side of the inverted U.

Intrauterine device use and endometrial cancer risk

BACKGROUND

Because intrauterine devices (IUD) invoke acute and chronic inflammatory responses in the endometrium, it is possible that prolonged insertion of an IUD could induce endometrial cancer.

METHODS

We examined the relation between use of an IUD and endometrial cancer risk using data from a multicentre case-control study involving 405 endometrial cancer cases and 297 population controls.

RESULTS

A total of 20 (4.9%) cases and 34 (11.4%) controls reported any use of an IUD. After adjustment for potential confounders, IUD use was not associated with an increased risk of endometrial cancer (RR = 0.56 for ever use; 95% CI: 0.3-1.0). Little reduction in risk was observed among women who last used an IUD within 10 years of the index date (RR = 0.84; 95% CI: 0.3-2.4) but risk was decreased among women who used an IUD in the more distant past (RR = 0.45; 95% CI: 0.2-1.0). Risk did not vary consistently with number of years of IUD use or with years since first use. Risk was not increased among women who used inert devices (RR = 0.46; 95% CI: 0.3-3.6) or those who used devices containing copper (RR = 1.08; 95% CI: 0.1-3.6).

CONCLUSION

These data are reassuring in that they do not provide any evidence of an increased risk of endometrial cancer among women who have used IUD.

Rebound responding following a single dose of drug using an amphetamine-vehicle-haloperidol drug discrimination

The purpose of this research was to characterize drug-induced rebound cue states using a three-choice, agonist-vehicle-antagonist drug-discrimination procedure. Rats were trained to discriminate among 0.50 mg/kg amphetamine (AM), distilled water (DW), and 0.03 mg/kg haloperidol (HA) in a three-lever drug discrimination task. Time-dependent changes in cue state were assessed following single doses of AM (5 and 10 mg/kg), HA (1 mg/kg), and cocaine (30 and 40 mg/kg). Consistent with expectations derived from the results of a study that used a two-lever AM-HA discrimination task, single doses of AM produced rebound responding on the HA-appropriate lever that was dose-dependent and peaked at 24 h following administration. In addition, cocaine substituted for AM at 0.5-2 h post-injection and then produced HA-like rebound responding that peaked at 24-36 h post-administration. Contrary to expectations, however, rebound AM-like responding did not occur following HA administration. Perhaps two- and three-choice discrimination tasks differ in their ability to characterize qualitative aspects of the post-haloperidol cue state. Knowledge of the time course of drug-induced adaptive processes, measured as withdrawal in the present research, is necessary for a complete description of a drug's effects and is important in understanding the effects of repeated drug administration.

Racial differences in endometrial cancer survival: the black/white cancer survival study

OBJECTIVE

To identify factors that explain a lower survival rate among black women with endometrial cancer when compared to white women.

METHODS

Data are from the National Cancer Institute's Black/White Cancer Survival Study, a population-based study of racial differences in cancer survival. Subjects included 329 white and 130 black women, ages 20-79 years, residing in the metropolitan areas of Atlanta, New Orleans, or San Francisco-Oakland, diagnosed with endometrial cancer from 1985 to 1987. Known prognostic factors were assessed as potential explanatory variables for the black-white survival difference using proportional hazards regression. Information was derived from interviews, abstracts of hospital and physicians' records, and a centralized review of biopsy and surgical specimens.

RESULTS

Adjusting for age and geographic location, risk of death among black women was 4.0 times (95% confidence interval [CI] 2.8, 5.6) that of white women. Approximately 40% of this difference could be attributed to a more advanced stage at diagnosis among black women, and 23% to tumor characteristics and treatment. Further adjustment for all remaining factors reduced the hazard ratio to 1.6 (95% CI 1.0, 2.6).

CONCLUSION

Eighty percent of the excess mortality among black women is explained by racial differences in stage at diagnosis, tumor characteristics, treatment, sociodemographic characteristics, hormonal and reproductive factors, and factors related to comorbidities and health behavior. Difference in stage at diagnosis is prominent in explaining the disparity in endometrial cancer survival rates in black and white women. Potential differences in treatment within stage merit further exploration.

Teaching colloquial Australian English to medical students from non-English speaking backgrounds

Lack of fluency in the language of instruction can form a barrier to medical education. There has been an effort within Australian universities to teach English to students from non-English speaking backgrounds (NESB), but little systematic attention has been given to the teaching of informal or colloquial English. This paper provides evidence that colloquial language is a pervasive and important aspect of doctor-patient communication. It describes a teaching project for NESB medical students which aimed to introduce them to colloquial English, and to provide them with a contextual approach to learning this form of language. Forty-four first year medical students enrolled at the University of Adelaide were required to gather examples of colloquial language by interviewing a native English speaker. Ninety-four examples of colloquial sayings were recorded. These were compiled in the form of a handbook which served as a student resource. Student evaluation of this exercise was positive. The benefits of an interactive method of teaching local and setting-specific language are discussed, and the implications of this approach for clinical teaching and for medical practice are explored.