Pharmacological analysis of the heterogeneous discriminative stimulus effects of ethanol in rats using a three-choice ethanol-dizocilpine-water discrimination

The present study used a three-choice operant drug discrimination procedure to determine if NMDA-mediated discriminative stimulus effects could be separated from other stimulus effects of 2.0 g/kg ethanol. Adult male Long-Evans rats (n = 7) were trained to discriminate dizocilpine (0.17 mg/kg; i.g.) from ethanol (2.0 g/kg; i.g.) from water (4.7 ml; i.g.) using food reinforcement. Substitution tests were conducted following administration of the GABA(A) positive modulators allopregnanolone (5.6-30.0 mg/kg; i.p.), diazepam (0.3-10.0 mg/kg; i.p.) and pentobarbital (1.0-21.0 mg/kg; i.p.), the non-competitive NMDA antagonist phencyclidine (0.3-10.0 mg/kg; i.p.), the 5-HT1 agonists TFMPP (0.3-5.6 mg/kg; i.p.) and RU 24969 (0.3-3.0 mg/kg; i.p.), and isopropanol (0.10-1.25 g/kg; i.p.). Allopregnanolone, diazepam and pentobarbital substituted completely (>80%) for ethanol. Isopropanol partially (77%) substituted for ethanol. Phencyclidine substituted completely for dizocilpine. RU 24969 and TFMPP did not completely substitute for either training drug, although RU 24969 partially (62%) substituted for ethanol. Successful training of this three-choice discrimination indicates that the discriminative stimulus effects of 0.17 mg/kg dizocilpine were separable from those of 2.0 g/kg ethanol. The finding that attenuation of NMDA-mediated effects of ethanol occurred without altering significantly GABA(A)- and 5-HT1-mediated effects suggests that the NMDA component may be independent of other discriminative stimulus effects of 2.0 g/kg ethanol.

Effects of moderate alcohol consumption on the central nervous system

The concept of moderate consumption of ethanol (beverage alcohol) has evolved over time from considering this level of intake to be nonintoxicating and noninjurious, to encompassing levels defined as "statistically" normal in particular populations, and the public health-driven concepts that define moderate drinking as the level corresponding to the lowest overall rate of morbidity or mortality in a population. The various approaches to defining moderate consumption of ethanol provide for a range of intakes that can result in blood ethanol concentrations ranging from 5 to 6 mg/dl, to levels of over 90 mg/dl (i.e., approximately 20 mM). This review summarizes available information regarding the effects of moderate consumption of ethanol on the adult and the developing nervous systems. The metabolism of ethanol in the human is reviewed to allow for proper appreciation of the important variables that interact to influence the level of exposure of the brain to ethanol once ethanol is orally consumed. At the neurochemical level, the moderate consumption of ethanol selectively affects the function of GABA, glutamatergic, serotonergic, dopaminergic, cholinergic, and opioid neuronal systems. Ethanol can affect these systems directly, and/or the interactions between and among these systems become important in the expression of ethanol's actions. The behavioral consequences of ethanol's actions on brain neurochemistry, and the neurochemical effects themselves, are very much dose- and time-related, and the collage of ethanol's actions can change significantly even on the rising and falling phases of the blood ethanol curve. The behavioral effects of moderate ethanol intake can encompass events that the human or other animal can perceive as reinforcing through either positive (e.g., pleasurable, activating) or negative (e.g., anxiolysis, stress reduction) reinforcement mechanisms. Genetic factors and gender play an important role in the metabolism and behavioral actions of ethanol, and doses of ethanol producing pleasurable feelings, activation, and reduction of anxiety in some humans/animals can have aversive, sedative, or no effect in others. Research on the cognitive effects of acute and chronic moderate intake of ethanol is reviewed, and although a number of studies have noted a measurable diminution in neuropsychologic parameters in habitual consumers of moderate amounts of ethanol, others have not found such changes. Recent studies have also noted some positive effects of moderate ethanol consumption on cognitive performance in the aging human. The moderate consumption of ethanol by pregnant women can have significant consequences on the developing nervous system of the fetus. Consumption of ethanol during pregnancy at levels considered to be in the moderate range can generate fetal alcohol effects (behavioral, cognitive anomalies) in the offspring. A number of factors--including gestational period, the periodicity of the mother's drinking, genetic factors, etc.--play important roles in determining the effect of ethanol on the developing central nervous system. A series of recommendations for future research endeavors, at all levels, is included with this review as part of the assessment of the effects of moderate ethanol consumption on the central nervous system.

Analysis of the 5-HT2 receptor ligands dimethoxy-4-indophenyl-2-aminopropane and ketanserin in ethanol discriminations

Previous studies have suggested a modulatory role of the 5-HT2 receptor system in the behavioral effects of ethanol. The present study examined the discriminative stimulus effects of the 5-HT2A/2C agonist (-)-dimethoxy-4-indophenyl-2-aminopropane (DOI) and the 5-HT2A antagonist ketanserin in rats trained to discriminate either 1.5 g/kg of ethanol from water (intragastrically, n = 7) or 2.0 g/kg of ethanol from water (intragastrically, n = 8). In substitution tests, neither DOI (0.3 to 1.0 mg/kg, i.p.) nor ketanserin (3.0 to 17.0 mg/kg, i.p.) produced discriminative stimulus effects similar to either training dose of ethanol, although decreases in rates of responding were significant at the highest doses tested. Likewise, when given in combination with ethanol, neither 5-HT2 ligand shifted the ethanol-dose response determination in either the 1.5 or 2.0 g/kg ethanol training groups. DOI in combination with ethanol did not alter rates of responding, whereas ketanserin in combination with ethanol significantly decreased response rates. Thus, the 5-HT2A receptor ligands do not appreciably affect the discriminative stimulus effects of ethanol, in contrast to previous results with 5-HT1B ligands.

Further evaluation of the reinforcing effects of the novel cocaine analog 2beta-propanoyl-3beta-(4-tolyl)-tropane (PTT) in rhesus monkeys

2Beta-propanoyl-3beta-(4-tolyl)-tropane (PTT) is a cocaine analog which has been shown in rhesus monkeys to have cocaine-like discriminative stimulus effects and a long duration of action (>8 h), yet does not function as a reinforcer when substituted for cocaine in monkeys responding under a fixed-interval 5-min schedule (Nader et al. 1997). The purpose of the present study was to evaluate the reinforcing effects of PTT under a fixed-ratio (FR) schedule and to determine if decreasing the inter-injection interval would influence the reinforcing effects of PTT. Male rhesus monkeys (n=3) were trained to respond under a multiple FR 30 food-drug-food schedule. When responding was stable, cocaine (0.003-0.3 mg/kg per injection) or PTT (0.001-0.03 mg/kg per injection) was available during the drug component for at least five consecutive sessions and until stable responding was observed. To investigate whether the inter-injection interval would influence PTT-maintained response rates, the time-out (TO) following PTT injections was reduced from 180 or 300 s to 10 s for at least five consecutive sessions. Cocaine-maintained response rates were characterized as an inverted-U shaped function of dose, with peak rates maintained by 0.03 mg/kg per injection cocaine. PTT (0.001-0.03 mg/kg per injection) maintained response rates significantly higher than rates maintained by the PTT vehicle, but significantly lower than cocaine-maintained response rates; PTT intake increased with a dose. A reduction of the TO following PTT injections to 10 s did not alter PTT-maintained response rates or total session intake. Self-administered PTT was more potent than cocaine at decreasing food-maintained responding. These results suggest that for long-acting compounds like PTT, reinforcing effects are more likely to be observed when the drug is available under a ratio-based schedule, compared to an interval-based schedule.

Characterization of the ethanol-like discriminative stimulus effects of 5-HT receptor agonists as a function of ethanol training dose

A drug discrimination procedure was used to characterize the ethanol-like effects of a variety of 5-HT1 agonists. Previous studies found that the degree of substitution of the 5-HT1B/2C agonist TFMPP (m-trifluoromethylphenylpiperazine) depended on the training dose of ethanol. The present studies extend this initial finding to four additional 5-HT agonists with different selectivity for 5-HT1A, 5-HT1B, or 5-HT2C receptors: CGS 12066B (7-trifluoromethyl-4(4-methyl-1-piperazinyl)-pyrrolo[1,2a]quinoxaline maleate), mCPP [1-(3-chlorophenyl)piperazine diHCl], RU 24969 [5-methoxy-3(1,2,3,4-tetrahydro-4-pyridinyl]-1H-indole succinate and 8-OH DPAT [(+/-)-8-hydroxy-2-(di-n-propylamino)tetralin HBr]. Separate groups of rats were trained to discriminate 1.0 g/kg (n = 7), 1.5 g/kg (n = 6) or 2.0 g/kg (n = 8) ethanol from water. Following training, three to five doses of each 5-HT agonist were tested twice in each rat. The most selective 5-HT1B agonist tested, CGS 12066B (3-17 mg/kg; IP), completely substituted for the 1.0 g/kg ethanol, but not for 1.5 or 2.0 g/kg ethanol. Likewise, the 5-HT1B/2C agonist mCPP (0.56-1.7 mg/kg; IP) completely substituted only in the 1.0 g/kg ethanol training group. The 5-HT1A/1B agonist RU 24969 (0.1-3.0 mg/kg; IP) substituted for all training doses of ethanol, although in a lower proportion of the rats tested in the 2.0 g/kg ethanol training group. Finally, the 5-HT1A agonist 8-OH DPAT (0.1-1.0 mg/kg, IP) did not substitute completely for any ethanol training dose. The results consistently show that agonists with 5-HT1B activity produce discriminative stimulus effects similar to low and intermediate, but not high, ethanol training doses.

Assessment of the multiple discriminative stimulus effects of ethanol using an ethanol-pentobarbital-water discrimination in rats

Previous drug discrimination studies have elucidated the importance of gamma-aminobutyric acidA (GABAA), N-methyl-D-aspartate (NMDA) glutamate, and serotonin (5-HT) receptor systems in mediating the discriminative stimulus effects of ethanol. The present study used a three-choice operant drug discrimination procedure in an attempt to determine if salient GABAergic effects could be separated from other stimulus effects of 2.0 g/kg ethanol. Adult male Long-Evans rats (n = 7) were trained to discriminate pentobarbital (10.0 mg/kg; intragastrically (i.g.) from ethanol (2.0 g/kg; i.g.) from water (4.7 ml; i.g.) using food reinforcement. Stimulus substitution tests were conducted following the administration of allopregnanolone (1.0-17.0 mg/kg; intraperitoneally (i.p.)), diazepam (0.1-7.3 mg/kg; i.p.), midazolam (0.0056-17.0 mg/kg; i.p.), dizocilpine (0.01-0.56 mg/kg; i.p.), phencyclidine (1.0-5.6 mg/kg; i.p.), CGS 12066B (3-30 mg/kg; i.p.), RU 24969 (0.1-5.6 mg/kg; i.p.) and morphine (1 or 3.0 mg/kg; i.p.). Within the group, allopregnanolone and midazolam completely substituted (> 80%), and diazepam partly substituted (67%) for the discriminative stimulus effects of pentobarbital. Dizocilpine and phencyclidine partly substituted (58 and 57%, respectively) for ethanol without substantial pentobarbital-appropriate responding. RU 24969, CGS 12066B and morphine did not result in complete substitution for either ethanol or pentobarbital, although RU 24969 resulted in partial (68%) pentobarbital substitution. The ability to train the present three-choice discrimination in rats indicates that the discriminative stimulus effects of 10.0 mg/kg pentobarbital were separable from those of 2.0 g/kg ethanol. The results suggest that the pharmacological effects of ethanol, which can control behavior, may seemingly be modified by training conditions (two-versus three-choice discrimination procedures), to the extent that a receptor system prominently linked to the behavioral activity of ethanol (i.e. GABAA) appears no longer to be involved in the interoceptive effects of the drug.

Attenuation of the discriminative stimulus effects of ethanol by the benzodiazepine partial inverse agonist Ro 15-4513

The aim of the present study was to investigate whether ethanol training affects the ability of Ro 15-4513 to block the discriminative stimulus effects of ethanol dose differentially. Three different groups of rats were trained to discriminate 1.0 g/kg ethanol (n = 8), 1.5 g/kg ethanol (n = 7) or 2.0 g/kg ethanol (n = 8) from water in a two-lever, food-reinforced procedure. Ethanol and water were administered by gavage 20 min before the onset of the session. When the discrimination performance was stable, rats were pretreated with Ro 15-4513 (1-17 mg/kg; i.p.) 5 min before the administration of ethanol. Ro 15-4513 attenuated the discriminative stimulus effects of 1.0 and 1.5 g/kg ethanol but not 2.0 g/kg ethanol in each of the ethanol training groups. Overall, blockade of the discriminative stimulus effects of 1.0 and 1.5 g/kg ethanol by 5.6 mg/kg Ro 15-4513 occurred without significantly altering response rates or blood ethanol concentrations. A decrease in blood ethanol concentration was, however, found with 17 mg/kg Ro 15-4513 in combination with 2.0 g/kg ethanol. These results suggest that the benzodiazepine partial inverse agonist, Ro 15-4513, can attenuate the discriminative stimulus effects associated with low to moderate doses of ethanol (1.0-1.5 g/kg).

The nitric oxide synthase inhibitor L-NAME (N omega-nitro-L-arginine methyl ester) does not produce discriminative stimulus effects similar to ethanol

N-methyl-D-aspartate (NMDA) antagonists substitute for the discriminative stimulus effects of ethanol, indicating that a component of ethanol's behavioral activity is produced via blockade of NMDA receptor/channel function. Recently, it has been reported that ethanol inhibits NMDA-stimulated nitric oxide synthase (NOS) activity in cortical neurons, thereby decreasing the formation of nitric oxide (NO) in the brain. These findings suggest that some of the behavioral effects of ethanol may be mediated by inactivation of NOS. The present study examined the role of NO formation in mediating the discriminative stimulus effects of ethanol. To address this hypothesis, an NOS inhibitor, N omega-nitro-L-arginine methyl ester (L-NAME) and an NMDA competitive antagonist, (D)-4-(3-phosphonoprop-2-enyl) piperazine-2-carboxylic acid (CPPene), were administered to two groups of rats trained to discriminate 1.5 g/kg of ethanol (n = 6) or 2.0 g/kg (n = 7) of ethanol from water. After training, dose ranges of CPPene (3 to 17 mg/kg, ip) and L-NAME (100 to 780 mg/kg, ip) were tested for ethanol-like effects. L-NAME was also tested under a range of pretreatment times (20, 60, 90, and 120 min). An additional group of rats trained to discriminate 2.0 g/kg (n = 7) of ethanol from water was also tested with CPPene (10 mg/kg, ip) and L-NAME (100 and 300 mg/kg, ip) to verify data gathered from the original 2.0 g/kg of ethanol group tested with L-NAME after a 20-minute pretreatment. Although overall, 17 of 20 animals trained to discriminate ethanol from water exhibited complete substitution of CPPene for ethanol, L-NAME, without affecting response rates, did not consistently substitute for either 1.5 g/kg or 2.0 g/kg of ethanol. These results indicate that inhibition of NO formation is less effective than direct NMDA receptor antagonism in producing ethanol-like discriminative stimulus effects.

Are reconstructed self-reports of drinking reliable?

When follow-up interviews are missed, researchers sometimes try to reconstruct the data that would have been obtained by asking clients to recall the missed interval when they are interviewed at a later point. Are such data reliable? The reliability of remote reconstruction was estimated by asking 57 participants in a clinical trial to recall their drinking for the 12-month follow-up interval when interviewed, on average, 33 weeks later. These reports were obtained after delays averaging 231 days. These reconstructed reports were compared with the same clients' self-reports obtained during the 12-month interview. Reconstructed data were found to be reasonably accurate estimates of clients' reports at the time of original interview on global alcohol use variables including percentage of drinking days and total volume of consumption. No systematic bias was found for over-reporting or under-reporting at the point of reconstruction. However, on some variables (e.g. total drinks consumed), clients on average reported more drinking at the reconstruction period than during the initial interview. Discrepancies between initial and reconstructed reports were found to be unrelated to the length of delay in the second interview or to client characteristics.

Molecular characterization of pldA, the structural gene for a phospholipase A from Campylobacter coli, and its contribution to cell-associated hemolysis

A gene (pldA) encoding a 35.0-kDa protein with significant homology to the Escherichia coli outer membrane phospholipase was identified upstream of an operon encoding an enterochelin transport system in Campylobacter coli. The results of this study suggest that this gene encodes an outer membrane phospholipase A in C. coli. First, expression of the pldA gene product in a PldA-deficient mutant of E. coli led to the restoration of phospholipase A activity. The recombinant product also partitioned to the outer membrane, suggesting that it may be similarly located in C. coli. Second, heterologous overexpression in E. coli, followed by in vitro folding and purification of C. coli PldA, resulted in pure protein which displayed calcium-dependent lysophospholipase and phospholipase A activities in vitro. Finally, mutants of C. coli in which the pldA gene had been inactivated by allelic exchange were deficient in phospholipase A activity. Phospholipases are associated with lysis of erythrocytes by a number of bacterial pathogens. The pldA mutant was shown to have a reduced hemolytic activity compared to the wild-type strain, suggesting a role for the phospholipase A in the lysis of erythrocytes by C. coli. Since hemolysins are intimately associated with the disease-causing potential of a number of bacterial pathogens, it is likely that the phospholipase A plays some role in Campylobacter virulence.

An electromyographic study of strength and upper extremity muscle activity in simulated meat cutting tasks

Meat cutting has long been associated with a high incidence rate of upper extremity musculoskeletal disorders. This study examined upper extremity muscle activities and force exertion capabilities to identify postures which have potential for causing overexertion injuries. Fifteen subjects exerted force against a handle in postures similar to those observed in the meatpacking industry. Exertion level, direction of exertion, handle height, reach distance and grip type were varied. Activity in the posterior deltoid, biceps brachii, triceps brachii, extensor digitorum and flexor digitorum superficialis was monitored via surface electromyography (EMG). The ratio of normalized EMG activity to force produced during the exertion was computed for each muscle under each condition. The results showed that handle position had a significant effect on force exertion capability and the EMG/force ratio in all muscles. Force exertion capability was maximized, and the EMG/force ratio was generally minimized when participants pulled downward on a handle positioned at full arm's reach above the shoulder. For vertical cuts, force decreased and muscle activity generally increased as the handle height was lowered. For horizontal cuts, the full reach distance tended to allow greater force exertion with lower EMG/force ratios. The stab grip also tended to be associated with higher forces and lower EMG/force ratios than the slice grip. This study supports the premise that musculoskeletal stresses in meatpacking tasks can be altered through tool and workstation redesign. The data provided herein may be useful in selecting design modifications that reduce biomechanical stress on the upper extremities.

Discriminative stimulus effects of ethanol and 3 alpha-hydroxy-5 alpha-pregnan-20-one in relation to menstrual cycle phase in cynomolgus monkeys (Macaca fascicularis)

The present study was designed to characterize the discriminative stimulus effects of ethanol and the neurosteroid 3 alpha-hydroxy-5 alpha-pregnan-20-one (allopregnanolone) in nonhuman primates as a function of menstrual cycle phase. Female cynomolgus monkeys (Macaca fascicularis) were trained in a two-lever procedure to discriminate 1.0 g/kg ethanol (IG, 30 min pretreatment) from water using food reinforcement. A cumulative dosing procedure was used to assess changes in the potency of ethanol and an endogenous anxiolytic steroid in the follicular versus the luteal phase of the menstrual cycle. Plasma progesterone and allopregnanolone levels were determined within 24 h of testing to verify phase of menstrual cycle. The monkeys were more sensitive to the discriminative stimulus effects of ethanol and the ethanol-like effects of the endogenous neuroactive steroid allopregnanolone during the luteal phase of the menstrual cycle. These findings suggest that changes in the endogenous levels of ovarian-derived progesterone and allopregnanolone alter sensitivity to the discriminative stimulus effects of ethanol.

Specific identification of the enteropathogens Campylobacter jejuni and Campylobacter coli by using a PCR test based on the ceuE gene encoding a putative virulence determinant

A PCR method for the rapid identification and discrimination of thermophilic Campylobacter jejuni and Campylobacter coli was developed by using a gene encoding a protein involved in siderophore transport (ceuE). A nucleotide sequence divergence of approximately 13% in the ceuE genes of C. jejuni and C. coli facilitated the design of two species-specific PCR primer sets. The specificity of the PCR amplification reactions was confirmed by using two nonradioactively labelled species-specific internal oligonucleotide hybridization probes for each of these species.

The reinforcing and discriminative stimulus effects of the novel cocaine analog 2beta-propanoyl-3beta-(4-tolyl)-tropane in rhesus monkeys

2beta-propanoyl-3beta-(4-tolyl)-tropane (PTT), is a cocaine analog that inhibits dopamine uptake, binding with high affinity and selectivity to the dopamine transporter. In the present study, the behavioral effects of PTT were evaluated in two models of cocaine abuse: drug self-administration and drug discrimination. In the first experiment, rhesus monkeys (n = 3) were trained to self-administer cocaine (0.03 and 0.1 mg/kg/injection, i.v.) under a fixed-interval 5-min schedule. Presession administration of PTT (0.03-0.3 mg/kg, i.v.) or cocaine (0.3-3.0 mg/kg, i.v.) were evaluated. At both self-administered doses of cocaine, PTT decreased response rates and total session intakes and was approximately 0.5 to 1.0 log units more potent than cocaine. In experiment 2, the reinforcing effects of PTT (0.003-0.1 mg/kg/injection) were evaluated in a separate group of monkeys (n = 4) responding under a fixed-interval 5-min schedule of cocaine (0.03 mg/kg/injection) presentation. When substituted for cocaine, PTT maintained response rates similar to saline-maintained rates and significantly lower than rates maintained by cocaine (0.003-0.3 mg/kg/injection). Total session PTT intake was significantly lower than cocaine intake. In experiment 3, the discriminative stimulus effects of PTT (0.003-0.1 mg/kg, i.m.) were evaluated in monkeys (n = 3) trained to discriminate cocaine (0.2 mg/kg, i.m.) from saline (0.5 ml). PTT substituted for cocaine in a dose-dependent manner and was 0.5 to 1.0 log units more potent than cocaine. At the highest PTT dose, cocaine-appropriate responding was observed 8 to 24 hr after the injection. These results demonstrated that the long-acting indirect dopamine agonist PTT was effective in decreasing cocaine self-administration and in abuse liability testing showed a unique behavioral profile, not functioning as a reinforcer when substituted for cocaine and producing discriminative stimulus effects similar to cocaine.

Social stress, depression, and brain dopamine in female cynomolgus monkeys

Socially subordinate adult female cynomolgus monkeys are hypercortisolemic, the targets of aggression, fearful, vigilant, receive little positive affiliative contact, exhibit pathological behaviors indicating anxiety, and are disengaged in the social events around them. Subordinates also have altered dopaminergic activity that may be due to decreased D2 receptor binding. Dopaminergic activity indices were more closely associated with affiliative than agonistic behaviors.

Metabolic mapping of the effects of chronic voluntary ethanol consumption in rats

The 2-[14C]deoxyglucose method was used to examine the effects of chronic, voluntary ethanol consumption on rates of local cerebral glucose utilization (LCGU). LCGU was measured in male Long-Evans rats immediately following the completion of a 60-min schedule-induced polydipsia drinking session. Three groups of animals were examined: animals with a history of ethanol consumption that received ethanol on the test day (ethanol-ethanol), animals with a similar ethanol history that were presented with water on the test day (ethanol-water), and a control group that received water throughout the experiment (water-water). Ethanol consumption on the test day resulted in a highly discrete pattern of metabolic changes, with significant decreases in glucose utilization in the hippocampal complex, habenula, anterior ventral thalamus, and mammillary bodies, whereas increases were observed in the nucleus accumbens and locus coeruleus. Rates of LCGU in the ethanol-water group were increased throughout all regions of the central nervous system examined, indicating that the long-term consumption of moderate ethanol doses that do not produce physical dependence can cause significant changes in functional brain activity.

Ethanol-like discriminative stimulus effects of the neurosteroid 3 alpha-hydroxy-5 alpha-pregnan-20-one in female Macaca fascicularis monkeys

The present study was designed to characterize the discriminative stimulus effects of ethanol and the neurosteroid 3 alpha-hydroxy-5 alpha-pregnan-20-one (allopregnanolone) in non-human primates. Female cynomolgus monkeys (Macaca fascicularis) were trained in a two-lever procedure to discriminate 1.0 g/kg ethanol (IG, 30 min pretreatment) from water using food reinforcement. Consistent with previous results in a variety of species, pentobarbital (0.56-17 mg/kg, IG) resulted in a dose-dependent substitution for the discriminative stimulus effects of ethanol, with an average ED50 value of 1.9 mg/kg. Administration of allopregnanolone (0.3-5.6 mg/kg, IV) also produced complete substitution for the discriminative stimulus effects of ethanol, with an ED50 value of 1.0 mg/kg. Plasma allopregnanolone levels 35 min following the administration of 3.0 mg/kg allopregnanolone ranged from 33 to 69 ng/ml. The ethanol-like discriminative stimulus effects of 1.0 mg/kg allopregnanolone (IV) were present for 60 min, with a return to complete water-appropriate responding at 90 min post-treatment. The results indicate that the endogenous neuroactive steroid allopregnanolone produces subjective effects in cynomolgus monkeys that are similar to ethanol. These findings suggest that changes in the endogenous levels of allopregnanolone could alter sensitivity to the subjective effects of ethanol.

Dizocilpine-like discriminative stimulus effects of low-affinity uncompetitive NMDA antagonists

The dizocilpine-like discriminative stimulus effects of a variety of channel blocking (uncompetitive) N-methyl-D-aspartate (NMDA) receptor antagonists were examined in rats trained to discriminate dizocilpine (0.17 mg/kg, i.p) from saline in a two-lever operant procedure. The dissociative anesthetic-type NMDA antagonists dizocilpine (ED50 0.05 mg/kg), phencyclidine (ED50 3.4 mg/kg) and ketamine (ED50 14 mg/kg) showed complete substitution without producing significant decreases in response rates, whereas dexoxadrol (ED50 4.3 mg/kg) also produced complete substitution with a concomitant decrease (35%) in response rate. Similarly, the low-affinity antagonist memantine resulted in complete substitution (ED50 9.7 mg/kg) at doses that significantly reduced (68%) the response rate. All other low-affinity antagonists resulted in either partial or no substitution for the discriminative stimulus effects of dizocilpine at doses that significantly decreased average response rates. These include (ED50 values in parentheses) remacemide (29 mg/kg), the remacemide metabolite 1,2-diphenyl-2-propylamine (ARL 12495) (14 mg/kg), phencylcyclopentylamine (25 mg/kg), dextromethorphan (46 mg/kg), (+/-)-5-aminocarbonyl-10,11-dihydro -5H-dibenzo-[a,d]cyclohepten-5,10-imine (ADCI; no substitution) and levoxadrol (no substitution). We conclude that low-affinity uncompetitive NMDA antagonists have discriminative stimulus properties distinct from dissociative anesthetic-type uncompetitive NMDA antagonists. The lowest-affinity antagonists show virtually no substitution for dizocilpine, whereas the relatively more potent low-affinity antagonists (such as memantine) exhibit greater substitution, but complete substitution is obtained only at rate-reducing doses.

Work activities and musculoskeletal complaints among preschool workers

The potential for musculoskeletal trauma among preschool workers has been largely unexplored in the United States. This case report describes an investigation conducted to identify and evaluate possible causes of back and lower extremity pain among 22 workers at a Montessori day care facility. Investigators met with and distributed a questionnaire to school employees, and made measurements of workstation and furniture dimensions. Investigators also recorded the normal work activities of school employees on videotape, and performed a work sampling study to estimate the percentage of time employees spend performing various tasks and in certain postures. Questionnaire results from 18 employees indicated that back pain/discomfort was a common musculoskeletal complaint, reported by 61% of respondents. Neck/shoulder pain, lower extremity pain and hand/wrist pain were reported by 33, 33 and 11% of respondents, respectively. Observation and analysis of work activities indicated that employees spend significant periods of time kneeling, sitting on the floor, squatting, or bending at the waist. Furthermore, staff members who work with smaller children (i.e. six weeks to 18 months of age) performed more lifts and assumed more awkward lower extremity postures than employees who work with older children (3-4 years of age). Analysis of two lifting tasks using the revised NIOSH lifting equation indicated that employees who handle small children may be at increased risk of lifting-related low back pain. Investigators concluded that day care employees at this facility are at increased risk of low back pain and lower extremity (i.e. knee) injury due to work activities that require awkward or heavy lifts, and static working postures. Recommendations for reducing or eliminating these risks by modifying the workplace and changing the organization and methods of work are presented.

An analysis of scanning postures among grocery cashiers and its relationship to checkstand design

Mounting evidence suggests that musculoskeletal disorders are prevalent among US retail food workers. Cashiers who use electronic scanners appear to be at especially high risk for upper extremity musculoskeletal disorders. Checkstand design has been implicated as a contributor to musculoskeletal injury among cashiers because workstation design can significantly impact working posture. The present study examines working posture among two groups of cashiers to determine if checkstand design is associated with substantial differences in posture and movement during scanning. The work activities of twenty grocery cashiers using one of two checkstand designs (front-facing and right-hand takeaway) were examined. Videotapes of cashiers performing scanning tasks were observed and associated postures and movements were visually coded. The right-hand takeaway design was associated with a significantly higher percentage of non-neutral trunk postures than the front-facing design. However, there were no significant differences in shoulder posture, grasp, or scanning motion associated with checkstand/scanner design. Factors that appeared to affect cashier work posture during scanning included stature, order size, and product type. Although improving the checkstand design may reduce the occurrence of certain awkward postures and static muscle loading conditions among cashiers, the success of these interventions is likely to be limited unless follow-up programmes are instituted to ensure that cashiers are able to use these designs effectively. Furthermore, fundamental changes in cashier work may be required to fully eliminate hazards for musculoskeletal disorders from this job.

Targeted and random mutagenesis of the Campylobacter coli chromosome with integrational plasmid vectors

A number of integrational vectors were developed for use as genetic tools in the food-borne pathogen Campylobacter coli. Integration of the plasmids occurred following genetic recombination via a Campbell-like mechanism. For an integrative plasmid containing a DNA fragment internal to the C. coli catalase gene, the insertion was mutagenic and led to a catalase-deficient phenotype. A procedure for generating random mutations in the C. coli chromosome, with these suicide-plasmids, was developed. In addition, the construction and utility of an integrable plasmid for generating transcriptional fusions to a cat reporter gene is described.

The role of 5-HT3 receptors in drug dependence

Since the discovery of serotonin receptor subtypes in 1957, the classification of serotonin receptors now includes 5-HT1 through 5-HT7 receptors, with further subtypes of receptors in each family. Unique among this expanding group of 5-HT receptor subtypes is the 5-HT3 receptor, which is the only known 5-HT receptor that directly gates an ion channel. The channel conducts primarily Na+ and K+, resulting in rapid depolarization followed by a rapid desensitization. The immediate consequence of neuronal depolarization resulting from 5-HT3 receptor activation is the release of stored neurotransmitter. The subsequent release of stored neurotransmitter, particularly dopamine in the mesolimbic pathways, suggest a potentially important role for this receptor system in neuronal circuitry involved in drug abuse. The following review broadly covers the structure, function and distribution of the 5-HT3 receptor system in the CNS and data addressing the potential role of this receptor system in modulating the effects of a wide variety of abused drugs. Most of the evidence indicates an association between the ability of 5-HT3 antagonists to decrease mesolimbic dopamine levels and to attenuate the psychomotor stimulant effects of drugs. However 5-HT3 receptor antagonists are less robust at attenuating other drug effects that are believed to be related to their abuse liability, such as discriminative stimulus and reinforcing effects. The one exception may be ethanol, which directly potentiates the effects of 5-HT at the 5-HT3 receptor channel complex. In addition to the implications of an interaction with the mesolimbic dopaminergic system, the ability of 5-HT3 receptor antagonists to function as anxiolytics suggest they could be useful pharmacotherapies during drug withdrawal. However, further studies are needed since currently available 5-HT3 receptor antagonists do not have uniform behavioral effects, may interact with other receptor systems, and have atypical dose-response effects.

The direct application of the polymerase chain reaction to DNA extracted from foods

Two methods for the successful extraction of DNA from foods are described. The rapid lysis method uses a proteinase K buffer system to lyse cells and solubilize food samples. DNA is then precipitated using isopropanol. The second method achieves cell lysis using toluene and mutanolysin, and solubilization using guanidium thiocyanate. Following protein removal with organic solvents DNA is precipitated with isopropanol. Both methods enabled the polymerase chain reaction to be applied directly to DNA extracted from samples of cheese, coleslaw and raw chicken and allowed the direct rapid, sensitive and specific detection of Yersinia enterocolitica, Aerococcus viridans and Listeria monocytogenes in these foods.

An evaluation of a hospital-based drinking and driving prevention program

For the past four years, Victoria Hospital has provided a drinking and driving prevention program: IMPACT - Impaired Minds Produced by Alcohol Cause Trauma. The program provides information to Grade 11 students about the potential "impact" of alcohol-related trauma on themselves, their family and their future. At the end of the program, students were asked to complete a short evaluative questionnaire; 74.2% completed the questionnaire. Of those responding, 97.5% agreed that the program increased their awareness of drinking and driving, and 79.4% agreed that the program would cause them to change their own behaviour. Determining whether or not increased knowledge and changed attitude in fact results in changed behaviour is beyond the scope of this study. Further longitudinal, quantitative evaluation of program effectiveness, based on traffic safety indices, is being undertaken.