Genetic analysis of the corticosterone response to ethanol in BXD recombinant inbred mice

The genetic control over the corticosterone response to ethanol (EtOH) and its possible relationship to other EtOH-related traits was examined using BXD recombinant inbred (RI) strains derived from an F2 cross of C57BL/6J (B6) and DBA/2J (D2) progenitor strains. Quantitative trait locus (QTL) analysis of corticosterone levels 1 hr following EtOH suggested the influence of a single major gene on this trait. Two loci were predicted to account for 47% of the genetic variance in plasma corticosterone levels 6 hr following EtOH, whereas 3 loci were predicted to account for 78% of the genetic variance in corticosterone levels 7 hr following EtOH. Markers associated with corticosterone levels 7 hr following EtOH and corrected corticosterone levels 6 hr post-EtOH overlapped with ones found to influence acute and chronic EtOH withdrawal severity, suggesting some degree of common genetic determination between these traits. Overall these results indicate that gene action significantly influences stress responsiveness and suggest possible chromosomal locations of these genes.

A randomized controlled trial of hydrocolloid dressing in the treatment of hypertrophic scars and keloids

BACKGROUND

Silicone gel sheeting has been investigated for use in the treatments of keloids and hypertrophic scars. Its mechanism of action may be related to scar hydration.

OBJECTIVE

The purpose of the present study was to evaluate a hydrocolloid occlusive dressing that also acts by promoting a moist environment.

METHODS

In a randomized controlled prospective study, patients were allocated to receive hydrocolloid dressing or moisturizer to keloids or hypertrophic scars. Scar size and volume, color, patient symptoms, and transcutaneous oxygen measurements were taken.

RESULTS

There was significantly reduced itching (P < 0.03), somewhat reduced pain (P < 0.08) and increased pliability (10%) for both treatments over 2 months.

CONCLUSION

Hydration of the scar for 2 months resulted in symptomatic improvement, but no change in physical parameters.

Elevated alcohol consumption in null mutant mice lacking 5-HT1B serotonin receptors

Substantial evidence links alcohol drinking and serotonin (5-HT) functioning in animals. Lowered central 5-HT neurotransmission has been found in a subgroup of alcoholics, possibly those with more aggressive, assaultive tendencies. Several rodent studies have also suggested that intact 5-HT systems are important determinants of sensitivity and/or tolerance to ethanol-induced ataxia and hypothermia. Null mutant mice lacking the 5-HT1B receptor gene (5-HT1B-/-) have been developed that display enhanced aggression and altered 5-HT release in slice preparations from some, but not all, brain areas. We characterized these mice for sensitivity to several effects of ethanol. Mutant mice drank twice as much ethanol as wild-type mice, and voluntarily ingested solutions containing up to 20% ethanol in water. Their intake of food and water, and of sucrose, saccharin and quinine solutions, was normal. Mutants were less sensitive than wild-types on a test of ethanol-induced ataxia and, with repeated drug administration, tended to develop tolerance more slowly. In tests of ethanol withdrawal and metabolism, mutants and wild-type mice showed equivalent responses. Our results suggest that the 5-HT1B receptor participates in the regulation of ethanol drinking, and demonstrate that serotonergic manipulations lead to reduced responsiveness to certain ataxic effects of ethanol without affecting dependence.

Correlated responses to selection in FAST and SLOW mice: effects of ethanol on ataxia, temperature, sedation, and withdrawal

A replicated bidirectional selective breeding program has produced lines of mice that differ in locomotor response to ethanol (EtOH). FAST mice were bred for high locomotor activation, whereas SLOW mice were bred for low or depressed locomotor activity in response to 2.0 g/kg of EtOH. We tested FAST and SLOW mice for differences in sensitivity to the incoordinating (1.5 to 2.5 g/kg), hypothermic (3.0 g/kg), and sedative (4.0 g/kg) effects of EtOH, and for differences in sensitivity to withdrawal after acute and chronic EtOH exposure. SLOW mice were more ataxic in a grid test and developed greater tolerance than FAST mice at 2.0 g/kg of EtOH, were more hypothermic than FAST mice, and were more sensitive to the sedative effects of EtOH than FAST mice, as measured by latency to and duration of loss of righting reflex, and by blood ethanol concentrations at regain of the righting reflex. FAST mice had more severe withdrawal seizures after chronic exposure, but did not differ from SLOW mice in withdrawal severity after an acute injection of EtOH. These data suggest that FAST mice are generally more sensitive to central nervous system excitation, and SLOW mice are generally more sensitive to central nervous system sedation by EtOH, and further suggest genetic overlap with respect to genes that mediate locomotor responses to EtOH and genes determining sensitivity to EtOH-induced ataxia, hypothermia, sedation, and withdrawal severity after chronic exposure. Our current observations are in contrast to observations made earlier in selection, in which few line differences in sensitivity to EtOH effects other than locomotor activity were found. Thus, it seems that continued selection for differences in locomotor response to EtOH has produced genetically correlated differences in other EtOH responses.

Evaluation of potential genetic associations between ethanol tolerance and sensitization in BXD/Ty recombinant inbred mice

Ethanol (EtOH) has both locomotor stimulant and locomotor ataxic effects. Repeated EtOH treatment can result in the development of behavioral sensitization (increased sensitivity) similar to that seen with the classical stimulant drugs amphetamine and cocaine. However, it has been suggested for EtOH that sensitization may be a by-product of the development of tolerance to the sedative/ataxic effects of EtOH. It is also possible that the converse is true: that tolerance develops as the result of sensitization development. We examined this notion by measuring EtOH sensitization and tolerance in the BXD/Ty recombinant inbred strains. Changes in locomotor activation and grid test ataxia were used as the measures of sensitization and tolerance, respectively. If a genetic relationship exists between sensitization and tolerance, then those strains most susceptible to sensitization should also develop the most robust tolerance. Genetic correlations did not support the presence of this relationship. In addition, the use of the BXD/Ty recombinant inbred strains enabled us to perform gene mapping by quantitative trait locus analysis for activity and ataxia measures. We found that 28% to 79% of the genetic variation in the various activity and ataxia responses could be explained by the identified quantitative trait loci associations. However, when associations of gene markers with behavioral phenotypes were compared, we obtained no strong evidence for common genes determining magnitude of sensitization and tolerance. Thus the results of this study do not support the hypothesis that sensitization results from development of tolerance to the sedative/ataxic effects of EtOH or, conversely, that tolerance is a by-product of sensitization.

Common genetic determinants of the ataxic and hypothermic effects of ethanol in BXD/Ty recombinant inbred mice: genetic correlations and quantitative trait loci

Sensitivity and tolerance to ethanol-induced ataxia and hypothermia are determined in part by genetic factors; some genes that affect one of these traits may affect others as well. To test this general hypothesis, we examined hypothermia and two tests of ataxia in the C57BL/6J and DBA/2J inbred mouse stains and in 18 to 25 of their recombinant inbred strains. Genetic correlations among strain mean responses revealed strong positive associations of genetic origin between sensitivity and tolerance for each of the three responses. Furthermore, tolerance to grid test ataxia and tolerance to hypothermia were positively associated. Sensitivity scores across the three responses were uncorrelated. The second method employed to assess genetic correlation was to examine the pattern of genetic locations of quantitative trait loci (QTLs) provisionally identified using genetic mapping procedures. This method identified 3 to 14 QTLs associated with each trait. Within each response, a number of these associations were in common for measures of sensitivity and tolerance; this suggests the existence of several specific genes that exert pleiotropic effects on sensitivity and tolerance. In a result consistent with the analyses of genetic correlations, there was modest evidence for QTLs associated across measures. Some QTLs associated with multiple traits mapped to chromosomal regions where candidate genes (e.g., genes for neurotransmitter receptors) have been mapped. In summary, the analyses presented suggest modest commonality of genetic influence on tolerance to some measures of ataxia and hypothermia, and they strongly support previous data indicating that sensitivity and tolerance to specific effects of ethanol share common genetic determinants.

Current treatment options in psoriasis

Physicians often do not appreciate the impact of the disease. A variety of topical and systemic treatments are available that--either alone or in rotation--may ameliorate psoriatic manifestations and attendant disability.

Cost effectiveness in wound care

Universal, objective definitions or formulas have not been available for calculating the costs of wounds and measuring cost/benefits of different care methods. Therefore, it is difficult to compare cost effectiveness of different treatments. A literature review revealed confusion concerning the differences between "cost" and "cost effectiveness". The costs of wound care are divided into direct costs (i.e., costs of supplies, surgical interventions, medications, inpatient care) and indirect costs (i.e., assistance with activities of daily living, days lost from work, litigation). Studies of cost effectiveness should measure cost per unit outcome. In wound care studies, outcomes are usually measured according to the goals of treatment. Common problems with published cost effectiveness studies are that cost is often confused with cost effectiveness; there is no standard method of calculating wound care costs; few studies have measured costs to achieve measured treatment outcomes; and outcomes are often measured or reported differently from study to study. In view of this, it is impossible to clarify cost effectiveness of healing, debridement, pain relief, etc. Until universal, objective scales to measure cost effectiveness are available, the clinician must read published studies critically to determine if treatment measures are indeed cost effective.

Neurochemical bases of locomotion and ethanol stimulant effects

The locomotor stimulant effect produced by alcohol (ethanol) is one of a large number of measurable ethanol effects. Ethanol-induced euphoria in humans and locomotor stimulation in rodents, a potential animal model of human euphoria, have long been recognized and the latter has been extensively characterized. Since the euphoria produced by ethanol may influence the development of uncontrolled or excessive alcohol use, a solid understanding of the neurochemical substrates underlying such effects is important. Such an understanding for spontaneous locomotion and for ethanol's stimulant effects is beginning to emerge. Herein we review what is known about three neurochemical substrates of locomotion and of ethanol's locomotor stimulant effects. Several lines of research have implicated dopaminergic, GABAergic, and glutamatergic neurotransmitter systems in determining these behaviors. A large collection of work is cited, which strongly implicates the above-mentioned neurotransmitter substances in the control of spontaneous locomotion. A smaller, but persuasive, body of evidence suggests that central nervous system processes utilizing these transmitters are involved in determining the effects of ethanol on locomotion. Particular emphasis has been placed on the mesolimbic ventral tegmental area to nucleus accumbens dopaminergic pathway, and on the ventral pallidum/substantia innominata, where GABA and glutamate have been found to play a role in altering the activity of this dopaminergic pathway. Research on ethanol and drug locomotor sensitization, increased responsiveness to the substance with repeated administration, is also reviewed as a process that may be important in the development of drug addiction.

Genetic analysis of the corticosterone response to ethanol in BXD recombinant inbred mice

The genetic control over the corticosterone response to ethanol (EtOH) and its possible relationship to other EtOH-related traits was examined using BXD recombinant inbred (RI) strains derived from an F2 cross of C57BL/6J (B6) and DBA/2J (D2) progenitor strains. Quantitative trait locus (QTL) analysis of corticosterone levels 1 hr following EtOH suggested the influence of a single major gene on this trait. Two loci were predicted to account for 47% of the genetic variance in plasma corticosterone levels 6 hr following EtOH, whereas 3 loci were predicted to account for 78% of the genetic variance in corticosterone levels 7 hr following EtOH. Markers associated with corticosterone levels 7 hr following EtOH and corrected corticosterone levels 6 hr post-EtOH overlapped with ones found to influence acute and chronic EtOH withdrawal severity, suggesting some degree of common genetic determination between these traits. Overall these results indicate that gene action significantly influences stress responsiveness and suggest possible chromosomal locations of these genes.

Critical role for glucocorticoid receptors in stress- and ethanol-induced locomotor sensitization

Locomotor sensitization, the augmentation of the locomotor-activating effects of stimuli with repeated exposure, is being evaluated as a partial model for several phenomena including drug addiction. Alteration of dopaminergic systems has been found in sensitized animals and dopamine neurotransmission appears to be crucial for the expression of sensitized behaviors. However, stress hormones, which are released after exposure to many of the stimuli that produce sensitization, may also be involved in the development of this phenomenon. Corticosterone appears to be important in the development of amphetamine sensitization and glucocorticoid receptors (GR) have been hypothesized to mediate this effect. The purpose of these experiments was first, to determine whether repeated restraint stress sensitizes DBA/2J mice to the activating effect of ethanol (EtOH), and second, to explore the role of GR in stress- and EtOH-induced sensitization with the GR antagonist, RU 38486. This antagonist was administered before restraint or i.p. EtOH (1.5 g/kg) on each of 10 consecutive days of pretreatment. In addition, plasma corticosterone levels were determined at various points throughout the pretreatment period and on test days. The results demonstrated that 10 consecutive days of 2-hr restraint sensitized mice to EtOH's locomotor-stimulating effect. Both stress- and EtOH-induced sensitization were attenuated by administration of RU 38486 during the pretreatment phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Bidirectional selective breeding for ethanol effects on locomotor activity: characterization of FAST and SLOW mice through selection generation 35

Increased recognition of the advantages of genetic animal models has led to heightened interest in their use and development. A replicated bidirectional selective breeding project has produced lines of mice that differ in their locomotor responses to 2.0 g/kg ethanol. FAST-1 and FAST-2 mice are highly stimulated by ethanol (EtOH), whereas SLOW-1 and SLOW-2 mice are either not affected or respond with locomotor depression. Current heritability estimates indicate that approximately 6-8% of the response variance in the FAST lines and 2-10% of the response variance in the SLOW lines is of additive genetic origin. Little systematic response to selection has occurred in recent generations, which implies that the limits of selection have been reached. Analysis of saline activity over 35 generations of selection indicates that baseline activities have not changed during the course of selection in three of the lines, whereas baseline activity of FAST-1 mice has increased slightly. In EtOH dose-response studies (0.5-3.0 g/kg), FAST mice had biphasic dose-response curves, whereas the locomotor activity of SLOW mice was either unaffected or depressed by all doses of EtOH. In addition, FAST mice spent more time in motion, traveled farther per movement, traversed greater distances in the center of the test chamber, and ambulated more quickly than SLOW mice when given EtOH. FAST and SLOW mice differed in EtOH clearance rates; however, the differences were slight relative to the large difference in locomotor response. We encourage the use of FAST and SLOW mice to investigate neurophysiological factors underlying sensitivity to the behavioral effects of EtOH, with a view to further testing of the postulated homology between locomotor stimulant effects and addiction potential of drugs of abuse.

Intravenous cocaine self-administration in the C57BL/6J mouse

Freely behaving C57BL/6J mice with intrajugular catheters were trained to nose-poke for cocaine (0.75 mg/kg per 5-microliters infusion) under a fixed-ratio-10 schedule of reinforcement. Mice were given a choice between two nose-poke holes on opposite sides of the apparatus. Nose-pokes by experimental (O) subjects (operant group) were reinforced on only one side and reinforcer delivery coincided with the onset of a 10-s time-out light stimulus. Drug delivery to control subjects (yoked group) was determined by the behavior of O mice. Nose-poke rate increased in O subjects, whereas yoked subjects did not acquire the nose-poking response. Moreover, nose-poking was selective for the cocaine-paired side in O subjects. When saline infusions were substituted for cocaine (i.e., extinction), nose-poking in O subjects decreased, whereas yoked controls were unaffected. O subjects developed a preference for the drug-associated side of the apparatus during extinction. Overall, these data offer strong evidence of cocaine-directed behavior in the C57BL/6 inbred mouse strain. More generally, these findings support the feasibility of using intravenous self-administration to assess reinforcement in genetically well-defined populations.

Effects of acute and repeated ethanol exposures on the locomotor activity of BXD recombinant inbred mice

Investigations of ethanol's (EtOH's) complex response profile, including locomotor and other effects, are likely to lead to a more in-depth understanding of the constituents of alcohol addiction. Locomotor activity responses to acute and repeated EtOH (2 g/kg, ip) exposures were measured in BXD recombinant inbred (RI) mice and their C57BL/6J (B6) and DBA/2J (D2) progenitors. Both the acute response and the change in initial EtOH response with repeated treatments were strain-dependent. The coefficient of genetic determination was 0.38-0.49 for initial locomotor response to EtOH, and 0.29 for change in response. Changes in response were largely attributable to sensitization of locomotor stimulation. Quantitative trait loci (QTL) analyses identified significant marker associations with basal activity, acute locomotor response, and change in response. Markers were for QTL on several chromosomes, and there was only one case of overlap in marker associations among phenotypes. Acute locomotor response and locomotor sensitization were negatively correlated with 3% EtOH preference drinking data collected in BXD RI strains. Overall, these results demonstrate locomotor sensitization induced by EtOH, suggest independence of genetic determination of locomotor responses to acute and repeated EtOH exposure, and partially support a relationship between reduced sensitivity to the locomotor stimulant/sensitizing effects of EtOH and EtOH consumption.

Dopamine antagonist effects on locomotor activity in naive and ethanol-treated FAST and SLOW selected lines of mice

The FAST and SLOW lines of mice are being selectively bred in replicate for differential sensitivities to the locomotor activating effects of ethanol. Whereas FAST-1 and FAST-2 mice are stimulated by 2.0 g/kg ethanol, SLOW-1 and SLOW-2 mice are not stimulated, and are often depressed, by this dose. The dopamine antagonists, SCH-23390 (D1) and raclopride (D2), produced dose-dependent decreases in the locomotor activity of EtOH-naive mice of both lines and replicates; however, FAST and SLOW mice were not differentially sensitive to these effects. The absence of a line difference in activity response to the dopamine antagonists suggests that dopamine receptor function has not been altered by selective breeding for differences in sensitivity to the stimulant effects of ethanol. The ethanol-stimulated activity of FAST-1 and FAST-2 mice was decreased by administration of the dopamine antagonists, haloperidol and raclopride, at doses that had no effect on basal locomotor activity. SCH-23390 decreased ethanol-stimulated activity of FAST-1, but not FAST-2 mice. The ethanol-induced activity changes of SLOW mice were generally unaffected by antagonist administration. These results suggest a role for dopaminergic systems in mediating ethanol-stimulated activity in selectively bred FAST mice. Coadministration of SCH-23390 and raclopride decreased ethanol-induced activation to a greater degree than either drug alone, further suggesting that both D1 and D2 receptor systems contribute to the full expression of the ethanol stimulant response.

Behavioral sensitization to drug stimulant effects in C57BL/6J and DBA/2J inbred mice

Common features shared by addictive drugs have been difficult to identify. One ubiquitous effect of these drugs is psychomotor stimulation. Further, repeated exposure commonly results in sensitization to drug stimulant effects. This study evaluates sensitization to drugs from several drug classes in C57BL/6J and DBA/2J inbred strain mice. DBA/2J mice showed sensitized responses to ethanol and methamphetamine, whereas C57BL/6J mice developed sensitization to morphine and methamphetamine. Strain susceptibilities to ethanol- and morphine-induced sensitization closely paralleled their sensitivities to the acute stimulant effects of these drugs; this was not the case for methamphetamine. The relative sensitivities of DBA/2J and C57BL/6J mice were not consistent across drugs, suggesting that the stimulant and sensitized responses to these drugs may be mediated by at least partially divergent neural mechanisms.

Differences in ethanol sensitivity of brain NMDA receptors of long-sleep and short-sleep mice

Long-Sleep (LS) and Short-Sleep (SS) mice, selectively bred mice that differ in the duration of anesthesia produced by an acute dose of ethanol, were used to determine the possible association of differing ethanol sensitivity of brain NMDA receptors with differing sensitivity to the anesthetic effects of ethanol in vivo. NMDA receptor-mediated responses were determined by measurement of L-glutamate-stimulated increases in free intracellular calcium concentration (Cai) using the fluorescent indicator for Cai, Indo 1, in microsacs (a cell-free brain membrane vesicle preparation) isolated from hippocampi or cerebral cortices of the two mouse lines. In the absence of added drugs, NMDA responses did not differ between the two lines in hippocampal or cerebrocortical microsacs. However, a high concentration of ethanol (200 mM) inhibited NMDA responses in hippocampal microsacs from LS mice. In contrast, a moderate concentration of ethanol (50 mM) stimulated NMDA responses in hippocampal microsacs isolated from SS mice. In cerebrocortical microsacs, ethanol inhibited NMDA responses in the two lines to an equivalent degree. MK-801, a noncompetitive blocker of NMDA receptors, blocked NMDA responses at lower concentrations in hippocampal microsacs from LS mice than in SS mice, but produced a similar degree of inhibition of NMDA responses in cerebrocortical microsacs from the two lines. A high concentration of ethanol (200 mM) increased resting Cai in hippocampal microsacs from LS mice but not in hippocampal microsacs from SS mice, and increased resting Cai in cerebrocortical microsacs isolated from both lines of mice equally. The small change in resting Cai produced by MK-801 in cerebrocortical microsacs did not differ between the two lines.(ABSTRACT TRUNCATED AT 250 WORDS)

Ethanol sensitivity of brain NMDA receptors in mice selectively bred for differences in response to the low-dose locomotor stimulant effects of ethanol

Brain NMDA receptor responses and their sensitivity to ethanol in vitro were determined in replicate lines of FAST and SLOW mice, selectively bred for differences in sensitivity to the locomotor stimulant effects of a low dose of ethanol. L-Glutamate-stimulated increases in the intracellular free calcium concentration (Cai) were determined in microsacs, a cell-free brain membrane preparation, isolated from hippocampus or cerebral cortex. Previous work showed that L-glutamate-stimulated increases in Cai in microsacs are mediated by activation of NMDA receptors. The concentration response for L-glutamate-stimulated increases in Cai did not differ between the lines in either hippocampal or cerebrocortical microsacs. Ethanol produced a concentration-dependent decrease in L-glutamate-stimulated increases in Cai in hippocampal and cerebrocortical microsacs from SLOW mice, but this effect of ethanol was reduced or absent in microsacs isolated from FAST mice. Resting Cai and the ability of a high ethanol concentration to increase resting Cai did not differ between the lines. These results suggest that differences in the sensitivity of brain NMDA receptors to the effects of ethanol determine, at least in part, differences in the locomotor stimulant effects of low doses of ethanol in FAST and SLOW mice. These differences are not due to ethanol effects on resting Cai.

Observations on the anatomy and pathology of the palmar intercarpal ligaments in the middle carpal joints of thoroughbred racehorses

Ten carpi from juvenile Thoroughbred horses were dissected in detail to record the anatomy of the palmar intercarpal ligaments (PICLs). These were found not to be substantially attached to the palmar carpal ligament. The lateral PICL was sited at the convergence of the palmar aspects of the third, fourth, intermediate and ulnar carpal bones and aligned predominantly in a proximodistal direction. The medial PICL had a large origin distally on the lateral aspect of the radial carpal bone (Cr) and attached to third (C3) and second (C2) carpal bones with apparently separate fibre orientations. Fibres between Cr and C3 aligned obliquely from dorsoproximomedial to palmarodistolateral which corresponds to the direction of movement of Cr relative to C3 during carpal extension. Video recordings of arthroscopic evaluations of 67 middle carpal joints of juvenile Thoroughbred horses in race training were reviewed retrospectively and the osteochondral and ligamentous pathology visible in each recorded. Damage to the Cr-C3 part of the medial PICL was present in 47 (70%) joints and, in 6 joints, comprised complete rupture of this branch. A significant (P < 0.001) relationship was found between the presence of remodelling of the dorsodistal margin of Cr and the severity of ligament damage. It is considered that the orientation of fibres of the Cr-C3 branch of the MPICL is consistent with a putative role to alternate forces borne by Cr and C3 during axial loading of the limb and that the injuries of this structure seen in young racehorses may represent a fatigue-type pathology analogous to that seen concurrently in the related osteochondral tissues.

Women in dermatology. Challenges and recommendations

The total number of women physicians in the United States tripled between 1970 and 1990. Almost 50% of incoming residents in dermatology are women. This article discusses some of the changes, opportunities, and challenges within our profession wrought by these demographic changes. The incorporation of women into all aspects of our specialty is a subject that warrants review, consideration, and creative solutions.

Localization of genes affecting alcohol drinking in mice

The genomic map locations of specific genes controlling behaviors can be identified by studying a panel of recombinant inbred (RI) mouse strains. The progenitor C57BL/6J (B6) and DBA/2J (D2) strains, and 19 of the BXD RI strains derived from an F2 cross of these progenitors, were tested for 3% and 10% ethanol (EtOH) intake. The test sequence began with two-bottle free choice between tap water and unsweetened ethanol, and ended with free choice between water and saccharin-sweetened ethanol. Saccharin preference was also measured. Correlational analyses indicated that 59% of the genetic variance in 10% ethanol and sweetened 10% ethanol consumption was held in common, 24% of the genetic variance in saccharin and sweetened 10% ethanol consumption was held in common, and only 7% of the genetic variance in saccharin and unsweetened 10% ethanol consumption was held in common. These percentages for 3% ethanol solutions were 21%, 36%, and 14%. In addition, the severity of handling-induced convulsions during ethanol withdrawal was found to be significantly associated with the amount of ethanol consumed from the sweetened ethanol drinking tubes, suggesting that genetic differences in avidity for ethanol could lead to the development of physical dependence. Quantitative trait loci (QTL) analyses revealed that several genetic markers were associated with ethanol consumption levels, including markers for the D2 dopamine receptor. QTL analyses of saccharin and sweetened ethanol consumption identified the sac locus, thought to determine the ability to detect saccharin. In general, our results suggest that saccharin and ethanol consumption are determined by the actions of multiple genes (QTL), some in common, and suggest specific map locations of several such QTL on the mouse genome.

Behavioral sensitization to drug stimulant effects in C57BL/6J and DBA/2J inbred mice

Common features shared by addictive drugs have been difficult to identify. One ubiquitous effect of these drugs is psychomotor stimulation. Further, repeated exposure commonly results in sensitization to drug stimulant effects. This study evaluates sensitization to drugs from several drug classes in C57BL/6J and DBA/2J inbred strain mice. DBA/2J mice showed sensitized responses to ethanol and methamphetamine, whereas C57BL/6J mice developed sensitization to morphine and methamphetamine. Strain susceptibilities to ethanol- and morphine-induced sensitization closely paralleled their sensitivities to the acute stimulant effects of these drugs; this was not the case for methamphetamine. The relative sensitivities of DBA/2J and C57BL/6J mice were not consistent across drugs, suggesting that the stimulant and sensitized responses to these drugs may be mediated by at least partially divergent neural mechanisms.