Lawrence Lumeng

Phenotypic and genotypic characterization of the Indiana university rat lines selectively bred for high and low alcohol preference

The Indiana lines of selected rats, the HAD and LAD replicates and the P and NP lines, were bred for high and low alcohol preference. The P and HAD lines have met criteria for an animal model of alcoholism in that they voluntarily consume sufficient ethanol to achieve significant blood alcohol concentrations, and their alcohol-seeking behavior is reinforced by the pharmacological effects of ethanol rather than its taste, caloric content, or other properties. These lines have been characterized extensively for associated behavioral and physiological phenotypes. The P and HAD rats show an enhanced responsiveness to the stimulatory effects of ethanol and reduced sensitivity to the aversive sedative effects of ethanol. Consistent findings with the selected lines include differences in the mesolimbic dopamine reward system, as well as differences in serotonin, GABA, endogenous opioid, and neuropeptide Y systems. Genetic mapping studies have identified quantitative trait loci influencing alcohol preference on chromosomes 3, 4, and 8 in the inbred P/NP rats and on chromosomes 5, 10, 12, and 16 in the noninbred HAD1/LAD1 rats. The elucidation of the genotypes and phenotypes that result in excessive alcohol intake may lead to a better understanding of alcohol abuse and alcoholism and could guide strategies for potential treatment and prevention.

Ethanol self-infusion into the ventral tegmental area by alcohol-preferring rats

The ventral tegmental area (VTA) and its projections have been implicated in the reinforcing effects of drugs of abuse. Selectively bred alcohol-preferring (P) and alcohol-nonpreferring (NP) lines of rats were used to evaluate the reinforcing actions of ethanol in the VTA using intracranial self-administration (ICSA) operant procedures. P rats self-administered nanoliter quantities of 50-200 mg% ethanol in artificial CSF directly into the VTA whereas NP rats had low levels of responding at these ethanol concentrations. Responses on the active lever were 50-fold higher for the P compared with the NP rats for the self-infusion of 150 mg% ethanol. NP rats responded at the same level on the active and inactive levers at all ethanol concentrations and had low responses/session (3 to 15 total responses) at all concentrations. Further, operant responding on the active lever was reduced when artificial CSF alone was substituted for 100 mg% ethanol, and responding on the active lever was reinstated when ethanol was returned. For one group of rats, an illuminated house light served as a discriminative stimulus, which signalled the availability of ICSA, while a cue light was paired with the onset of ethanol infusion. Extinction in the presence of these stimuli required 6-7 sessions. However, only 2-3 extinction sessions were necessary for another group trained without stimulus cues, suggesting that cues paired with the ICSA of ethanol can acquire conditioned reinforcing properties. The findings indicate that ethanol can act as a reinforcer when administered directly into the VTA.(ABSTRACT TRUNCATED AT 250 WORDS)

Corticotropin releasing factor (CRF): studies in alcohol preferring and non-preferring rats*

Electroencephalographic (EEG) responses to corticotropin releasing factor (CRF) as well as CRF concentrations in several brain regions were measured in two lines of rats which have been genetically selected for alcohol preferring (P) or non-preferring (NP) behaviors. Fifteen rats were implanted with chronic electrodes and EEG spectra were evaluated following intracerebroventricular (ICV) administration of CRF (0.15 nmol) or saline. P rats demonstrated a significantly increased EEG response to CRF in the theta frequency range (ANOVA: PREF × DRUG 4–6 Hz,P<0.03; 6–8 Hz,P<0.05) in frontal cortex. A significantly lower concentration of CRF was found in the P rats in hypothalamus (P<0.02), amygdala (P<0.003), prefrontal cortex (P<0.01), and cingulate cortex (P<0.02). The finding that P rats had an increased response to exogenously administered CRF, taken together with decreased CRF concentrations, suggests that CRF receptors may be up-regulated in these animals. Differences in the regulation of CRF neurons may contribute to the expression of behavioral preference for ethanol consumption in these rat lines.

Flexible sigmoidoscopy plus air contrast barium enema versus colonoscopy for suspected lower gastrointestinal bleeding.

A randomized, controlled trial was performed to compare the diagnostic yields and cost-effectiveness of two strategies for the evaluation of nonemergent lower gastrointestinal bleeding. Three hundred eighty patients aged greater than or equal to 40 yr were randomized to undergo initial flexible sigmoidoscopy plus air contrast barium enema or colonoscopy; 332 completed the initial studies. Initial colonoscopy detected more cases of polyps less than 9 mm in size, adenomas, and arteriovenous malformations but fewer cases of diverticulosis. No significant difference was found between strategies in the number of patients detected with cancers or polyps greater than or equal to 9 mm in size. In both strategies, cancers were more common in subjects aged greater than or equal to 55 yr (8% overall) than in those aged less than 55 yr (1%). Among patients aged less than 55 yr with suspected lower gastrointestinal bleeding, initial flexible sigmoidoscopy plus air contrast barium enema is a more cost-effective strategy for the detection of colonic neoplasms than initial colonoscopy. However, initial colonoscopy is more cost effective for those aged greater than or equal to 55 yr.

Comparison of Three Nonsurgical Treatments for Bleeding Esophageal Varices

Ninety-seven patients with recent or active variceal bleeding were randomly assigned to oral propranolol, endoscopic sclerotherapy plus oral propranolol, or transhepatic sclerotherapy plus oral propranolol. The effects of treatment on the number of units transfused, rebleeding of any magnitude, major rebleeding, and death were assessed in these patients, 82% of whom were alcoholic and 81% Childs Class C. After a minimum follow-up interval of 2 yr (range, 27-65 mo), major rebleeding rates were 65% for propranolol alone, 45% for endoscopic sclerotherapy plus propranolol, and 60% for transhepatic sclerotherapy plus propranolol. The corresponding death rates were 81% for propranolol alone, 55% for endoscopic sclerotherapy plus propranolol, and 66% for transhepatic sclerotherapy plus propranolol (p = 0.03). Thirty-three patients (34%) never received propranolol; 8 due to medical contraindications and 25 because they died or bled enough to meet the definition of treatment failure within 3 or 4 days of randomizations (no significant differences among treatment groups). Patients assigned to propranolol alone bled sooner, bled more units, and had a higher mortality rate than patients treated by endoscopic sclerotherapy plus propranolol. Patients treated with transhepatic sclerotherapy plus propranolol had intermediate results. Propranolol alone is inadequate treatment for esophageal variceal bleeding in patients with advanced liver disease.

Biphasic stimulation of amino acid uptake by glucagon in hepatocytes.

Abstract Glucagon, 1.4 μM, increased the steady-state distribution ratios of alanine and α-aminoisobutyric acid in rat hepatocytes. As a function of time, glucagon stimulated the one-min rates of uptake of alanine and α-aminoisobutyric acid in two distinct phases. In the first phase both valinomycin and glucagon rapidly increased the rate of alanine uptake in a medium containing 6 mEq/l K + but not in one containing 12 mEq/l K + . Cycloheximide did not alter the first but completely abolished the second phase of stimulation. These results indicate that the biphasic stimulation of alanine uptake in liver produced by glucagon depends upon cell membrane hyperpolarization in the first phase and on protein synthesis in the second.

Ethanol drinking experience attenuates (-)sulpiride-induced increases in extracellular dopamine levels in the nucleus accumbens of alcohol-preferring (P) rats

BACKGROUNDnThe reinforcing properties of ethanol may be partly mediated through the mesolimbic dopamine (DA) system. This study examines the effects of local application of the DA D(2) receptor antagonist (-)sulpiride (SUL) on ethanol drinking of alcohol-preferring (P) rats, and extracellular DA levels in the nucleus accumbens (NAc) of P rats that were either ethanol-naive or had been chronically drinking ethanol.nnnMETHODSnMicrodialysis was used to sample NAc DA levels, and reverse microdialysis was used to locally administer the D(2) antagonist (-)sulpiride (SUL) into the NAc of adult female P rats that were either drinking ethanol (n = 17) or were ethanol-naive (n = 24). Stable intake of 15% (v/v) ethanol (>/=0.75 g/kg) was established for the ethanol-drinking group in daily 1-hr access periods over a minimum of 4 weeks before surgery. Naive and ethanol-drinking rats were implanted with bilateral guide cannulae aimed 4 mm above the NAc shell. After recovery from surgery, microdialysis probes (active area = 2 mm) were inserted bilaterally into the NAc. Two days later, rats in the ethanol-drinking and naive groups were each divided into two groups; one group was bilaterally perfused (1.0 microl/min) with artificial cerebrospinal fluid (aCSF) and the other group was further divided into three subgroups that were perfused with aCSF + either 50, 100, or 200 microM SUL for 240 min. During the last 60 min of perfusion, the ethanol-drinking rats were given their daily 1-hr ethanol access period. Following ethanol access, the aCSF + SUL subgroups were then given aCSF only. The entire perfusion procedure was repeated 24 hr later, but the aCSF only and aCSF + SUL group treatment conditions were transposed.nnnRESULTSnIn ethanol-drinking rats, 100 and 200 microM SUL increased extracellular NAc DA levels to approximately 200% of basal values, but did not significantly alter ethanol intake. In ethanol-naive P rats, 100 and 200 microM SUL increased extracellular NAc DA levels significantly more (450% of basal; p < 0.05) than in the ethanol-drinking group.nnnCONCLUSIONSnThe findings are consistent with the hypothesis that ethanol-drinking experience causes a desensitization or a down-regulation of D(2) autoreceptors in the NAc of P rats.

Involvement of CNS cholinergic systems in alcohol drinking of P rats.

Abstract Experiments were undertaken to determine if CNS muscarinic‐ and nicotinic‐cholinergic receptors are involved in regulating alcohol drinking of rats from the selectively‐bred alcohol‐preferring P line. Intracerebroventricular (i.c.v.) drug infusions were administered into the lateral ventricle of female P rats 15 minutes before ethanol access. The muscarinic antagonists pirenzepine and scopolamine were tested on limited access (4 hours/day) to a 10% (v/v) ethanol solution. Food and water were available ad libitum. Nicotine and the nicotinic antagonist mecamylamine were tested on limited access (4 hours/day) to 10% (v/v) ethanol and 0.0125% saccharin solutions. Food was available ad libitum and water was available during the remaining 20 hours. The baseline ethanol intakes ranged between an average of 3.0 ± 0.3 g/kg/4 hours and 3.4 ± 0.3 g/kg/4 hours. Administration of 40‐100 m g pirenzepine (M1‐selective antagonist) had no effect on ethanol, food or water consumption. However, 20‐80 m g scopolamine, a non‐selective muscarinic antagonist, dosedependently decreased ethanol intake as much as 60% (p < 0.05) without altering food or water consumption. The nicotinic antagonist mecamylamine (20‐120 m g) did not alter ethanol intake, but nicotine (40‐80 m g) dose‐dependently decreased ethanol drinking as much as 60% within the first 30 minutes (p < 0.05) without an effect on saccharin intake. The results suggest that: (a), muscarinic receptors, with the possible exception of the M1 subtype, are involved in regulating alcohol drinking and (b), activation of nicotinic receptors can reduce alcohol drinking of the P line of rats.

Effects of the benzodiazepine inverse agonist RO19-4603 alone and in combination with the benzodiazepine receptor antagonists flumazenil, ZK 93426 and CGS 8216, on ethanol intake in alcohol-preferring (P) rats

The present study investigated dose dependence and time course effects of the benzodiazepine (BDZ) partial inverse agonist, RO19-4603 (0.005-0.30 mg/kg) alone, and in combination with the BDZ receptor antagonists flumazenil, ZK 93426, and CGS 8216 (20 mg/kg) in selectively bred alcohol-preferring (P) rats provided a two-bottle choice test between ethanol (EtOH) (10% v/v), and a palatable saccharin (0.0125% g/v) solution. A single dose of RO19-4603 as low as 0.009 mg/kg selectively reduced EtOH drinking during the initial 15 min of a 4 h access to 19-0% of control levels on day 1. The 0.08, 0.15 and 0.30 mg/kg doses of RO19-4603 significantly reduced total EtOH intake in the 4 h access period to 57-45% of controls on day 1. On day 2, no RO19-4603 injections were given; however, six of the seven doses of RO19-4603 (0.009, 0.02, 0.04, 0.08, 0.15, and 0.30 mg/kg) continued to reduce EtOH intake to 42-3% of control levels at the initial 15 min interval, while the 0.005, 0.009, 0.08, and 0.30 mg/kg doses reduced total 4 h EtOH intake to 60-42% of controls. Saccharin intake was either not altered by RO19-4603 or showed increases during the initial 15 min intervals and the total 4 h sessions on days 1 and 2. Food intake was also unaffected by RO19-4603. The CGS 8216, but neither flumazenil nor ZK 93426, reliably reversed the RO19-4603-induced suppression of EtOH intake on days 1 and 2. That certain BDZ inverse agonists can attenuate motivated behavior for EtOH reinforcement over a prolonged time course may provide a possible therapeutic approach to reducing EtOH consumption associated with alcoholism.

The benzodiazepine inverse agonist RO19-4603 exerts prolonged and selective suppression of ethanol intake in alcohol-preferring (P) rats

The time course of the benzodiazepine (BDZ) inverse agonist RO19-4603 in antagonizing ethanol (EtOH) intake was investigated in alcohol-preferring (P) rats (n=7) maintained on 24-h continuous free-choice access to EtOH (10% v/v), water, and food. After fluid intakes had stabilized over several weeks, animals were injected with Tween-80 vehicle solution or RO19-4603 (0.075, 0.150, and 0.30 mg/kg). EtOH and water intakes were determined at 8- and 24-h intervals. RO19-4603 caused a marked attenuation of EtOH drinking with each of the doses tested. EtOH intake during the 8-h following 0.075, 0.150, and 0.30 mg/kg RO19-4603 was decreased by approximately 36, 74, and 57%, respectively. Intakes during the 24-h interval were similar to the vehicle control condition. However, 32 h post-drug administration, EtOH intakes were reduced to approximately 27, 31, and 29% following the 0.075, 0.150 and 0.30 mg/kg doses, respectively. To further confirm the reliability of the RO19-4603 dose-response effect, and its selectivity for EtOH, the highest dose condition (0.30 mg/kg) was tested twice. The second 0.30 mg/kg dose condition exerted a profile of effects similar to the initial treatment; 8 h following administration, intake was decreased to 60% of the control level, and 32 h post-drug administration intake was decreased to approximately 46% of the controls. These decreases were evidently selective in comparison with water, since water drinking showed compensatory increases which paralleled the decreased EtOH consumption. Dose-response comparisons indicated that 0.150 mg/kg approaches the maximum effective dose, since the 0.30 mg/kg dose of RO19-4603 did not produce an additional decrease in EtOH intake. Furthermore, unlike the lower doses, the 0.30 mg/kg dose failed to yield reliable compensatory increases in water drinking. The results demonstrated that a single acute administration of RO19-4603 produces prolonged and selective suppression of EtOH intake in P rats maintained on 24-h continuous free access to EtOH. While it is not clear at present what properties of the ligand might explain the observed effects on EtOH intake, these findings along with our previous work, clearly suggest that RO19-4603 may modify neuronal processes that promote EtOH self-administration. Neural transmission at the GABAA-BDZ receptor complex may play an important role in mediating EtOH reinforcement.