Conditioned place aversion to the "hangover" phase of acute ethanol administration in the rat

The purpose of this study was to examine ethanol's delayed effects (termed hangover) using conditioned place testing. Four groups of rats received a single pairing of a distinctive environment (tactile and visual) 10 h after injection with ethanol (0, 2, 3, 4 g/kg, i.p. ) or saline in a counterbalanced design. Rats receiving 3 and 4 g/kg ethanol showed a conditioned place aversion to ethanol hangover. Conditioning 10 h after 0 or 2 g/kg ethanol did not produce a significant place preference or aversion. The results suggest that the hangover following an acute injection of high doses of ethanol (3-4 g/kg) produces a significant and dose-related conditioned place aversion in the rat.

A genetic developmental model of iron deficiency: biological aspects

Numerous studies have demonstrated the negative impact of iron deficiency on growth and development. The present study expands on the published literature by exploring the role of genetics and developmental timing on the impact of iron deficiency on development in two strains of mice. Growth rates, organ weights, and hematological responses to an iron-deficient diet differed by strain and sex. The results from this study provided novel insight into iron metabolism and the impact of iron deficiency in C57 and DBA strains of mice. Future studies should continue to examine the contributions of both genetics and sex to the development of iron deficiency.

Ethanol modulates cocaine-induced behavioral change in inbred mice

We recently conducted a study of the behavioral effects of combined cocaine and ethanol in genetically defined mice. Male and female C57BL/6 (B6) and DBA/2 (D2) were tested in an automated activity monitor on 2 consecutive days. On day 1, all animals received an IP injection of sterile saline and were placed into the activity monitor for 30 min. Behaviors measured were total distance traveled, stereotypy, nosepokes, and wall-seeking. On day 2, all animals were tested again for 15 min following injection of one of the following: saline, 10% v/v ethanol at 2.0 g kg(-1) or 2.0 g kg(-1) ethanol plus 5, 15, or 30 mg kg(-1) cocaine. Cocaine alone at the same doses was injected into separate groups of animals. For the B6 strain, the overall effect of ethanol was to reduce cocaine-induced locomotor stimulation; no consistent effect of ethanol on cocaine-induced locomotion was observed in D2 mice. Cocaine-induced inhibition of nosepokes in both strains and sexes was partially reversed by ethanol. Ethanol also partially reversed cocaine-elevated stereotypy in both strains and both sexes. In B6 mice, cocaine-increased wall seeking tended to be reversed by coadministration of ethanol, whereas no consistent pattern was observed in the D2s. Results from this study suggest that the several measures affected by cocaine (locomotor activity, stereotypy, exploration, thigmotaxis) were, in turn, differentially affected by concurrent treatment with ethanol. Furthermore, our results point to genetic-based differences in ethanol's effects on cocaine-related behaviors. We address the implications for combined ethanol and cocaine use in humans.

Distribution and clearance of cocaine in brain is influenced by genetics

The purpose of this study was to examine the pharmacokinetics of cocaine in two inbred mouse strains, C57BL/6 (B6) and DBA/2 (D2). Male and female mice were administered 30 mg kg(-1) cocaine IP and killed after 5, 15, 30, or 60 minutes postinjection. Brains were removed quickly and assayed for total brain cocaine concentration. Quantification of cocaine was conducted using gas chromatography and mass spectrometry. The results of this study revealed a strain difference in total brain cocaine kinetics. Specifically, we observed that at 5 min onward, B6 mice cleared cocaine from the brain with a t1/2 estimated at 22.3 min, while distribution in D2 mice appeared to be incomplete until 15 min with a subsequent t1/2 estimated at 11.2 min. These results show that despite faster clearance by D2 mice, the prolonged time to distribution in this strain may help explain why D2 mice show initial greater locomotor activation by cocaine, compared to B6s.

Behavioral responses to low doses of cocaine are affected by genetics and experimental history

We recently conducted a set of two experiments to investigate the possible co-operation between genetics and exposure to novelty on the putative locomotor inhibiting effects of low doses of cocaine in male and female C57BL/6 and DBA/2 mice. Experiment one examined the effects of three low doses of cocaine (0.1, 0.5, and 1.0 mg/kg) on locomotion, exploration, stereotypy and wall-seeking in an automated activity monitor. Testing occurred on two consecutive days, with subjects receiving an IP injection of saline on day one, and one dose of cocaine on day 2 (S-C). Immediately following injection, subjects were placed into automated activity monitors, where four behaviors were recorded; total distance, nosepokes, stereotypy and margin time. Using this S-C injection regimen, we found significant decreases in measures of total distance and stereotypy when compared to saline in both male and female C57 mice. Experiment two was designed to determine if the observed decrease in locomotor activity was the result of low-dose cocaine or pre-exposure to the test procedure and apparatus. All conditions and procedures were identical to those in experiment one, with the exception of the injection regimen. In this experiment, we injected all subjects IP with 0.1 mg/kg cocaine on day one, followed by saline on day two (C-S). Additionally, a group of subjects receiving saline on both days (S-S) served as the control. In contrast to experiment one results, cocaine produced locomotor activation. Furthermore, significant sex and strain differences were found in both experiments. The results of our experiments suggest that the behavioral effects of low doses of cocaine are markedly influenced by both the genetic constitution of the experimental animal and by familiarity with the test apparatus.

Pharmacogenetics of cocaine: a critical review

The development of genetic models to help explain individual differences in sensitivity to and susceptibility to misuse certain CNS active substances, like ethanol and psychostimulants, spans a brief, thirty-plus years. The first animal models involved inbred strains and selected lines of mice and rats and predicted genetic-based differential sensitivity to ethanol and its misuse in humans found a few years later. With drugs like cocaine, tracking genetic differences in sensitivity and misuse liability in humans is difficult because of legal problems. Genetically-defined animals, however, have shown most if not all of cocaine-related behavioural, neurophysiological and toxicological effects to evince wide variation with most effects being influenced by several genes. Thus, we argue that animal and human studies of individual differences in drug sensitivity be studied from both quantitative and molecular genetic approaches. For the former, new techniques involving recombinant inbred strains of rodents, genetic correlational analysis and quantitative trait loci analysis are particularly useful, especially as genetic synteny between rodents and humans becomes better described. Also, because drug effects are highly labile to environmental conditions as well as genetic-based individual differences, multivariate, systems level studies should be developed to provide more complete descriptive and mechanistic views of a multifaceted problem.

Intracerebroventricular infusions of morphine, and blockade with naloxone, modify the olfactory preferences for pup odors in lactating rats

Systemic morphine exposure disrupts both maternal behavior (MB) and postpartum aggression, possibly through alterations of olfactory preferences [29]. In the current studies, adult female rats were timed mated and implanted with a unilateral cannula in the lateral ventricle. On day 5 or 6 of lactation, the females were infused with either morphine (2.0 micrograms) or saline (5 microliters) (Experiment 1); or, they were infused with 2.0 micrograms morphine and saline or morphine plus 0.5 micrograms naloxone (Experiment 2). One hour later, they were exposed to bedding soiled by pups, or to clean bedding. The amount of time spent investigating the two bedding types was compared. Morphine produced an aversion to the odor of pups, relative to the saline condition, wherein the females expressed a preference for the odor of pups. Naloxone reversed the effect of the morphine, restoring the preference for pup odors in the females. Thus, morphine disruption of MB may be due to central action on olfactory sensory mechanisms.

Detection of vent-blocking on light and ultralight cigarettes

Trained raters can reliably identify vent-blocking in ultralight cigarettes based on tar stain patterns, yet detection of this phenomenon has not been previously studied in light cigarettes. This study was conducted to extend the research on vent-blocking in ultralight cigarettes to the much more popular light cigarettes. We wanted to find out if individuals could discriminate among stain patterns on cigarette butts with unblocked (0%), partially blocked (50%), and fully blocked (100%) vents using both light and ultralight cigarettes. Subjects were able to use the stain pattern technique to detect vent-blocking in light cigarettes as well as ultralight cigarettes.

Strain and housing affect cocaine self-selection and open-field locomotor activity in mice

We recently conducted an experiment to investigate the possible cooperation between genetic makeup and differential housing on cocaine self-administration in male and female C57BL/6J and DBA/2J mice. Cocaine self-selection was measured in a two-choice test with one choice being cocaine-HCl solution of 40 mg% in tap water and the other choice being plain tap water. Housing conditions began at weaning (21-23 days of age) and consisted of group housed (GH) with 2-3 mice per cage, and isolated housed (IH) with 1 mouse per cage. The results of this study revealed overall strain, sex and housing differences, with C57BL/6Js consuming more cocaine solution than DBA/2J subjects, females consuming more cocaine solution than males, and group housed consuming more than isolate housed subjects. In a second study, the effect of differential housing on open-field locomotor activity was investigated. Testing was conducted on two consecutive days, with subjects receiving an IP injection of saline on day 1, and 15 mg/kg cocaine HCl on day 2. Four behaviors were recorded, including: total distance, nosepokes, stereotypy, and margin time. Overall, the results revealed significant strain differences for stereotypy and nosepokes, and males were found to be more activated by cocaine than females. Additionally, DBA males tended to be differentially affected by housing condition, with IH showing suppressed locomotor activity as compared to GH subjects. Last, significant strain by housing interactions occurred in nosepokes and stereotypy time.