Nicotine is a widely used addictive drug, with an estimated 73 million Americans 12 years of age or older having used a tobacco product in the last month, despite documented risks to personal health. Nicotine alters cognitive processes, which include effects on attention and impulsivity, a mechanism that may contribute to the addictive properties of the drug. Individuals with a variety of psychological disorders ranging from attention deficit hyperactivity disorder (ADHD) to schizophrenia smoke at a higher rate than the rest of the population and show deficits in impulse control. The present studies evaluated the effects of acute, chronic, and withdrawal from chronic nicotine on an operant task that measured premature and signaled nose pokes, as well as performance efficiency in C57BL/6J mice. Results indicate that acute nicotine (0.09 mg/kg intraperitoneally) does not alter the acquisition of the task, but does significantly increase performance efficiency once the behavior has been learned. In contrast, chronic nicotine (0, 6.3, 12.6, and 36 mg/kg/day subcutaneously) and withdrawal from chronic nicotine had no effect on performance efficiency. These results suggest that initial nicotine use may have beneficial effects on inhibitory control, but these effects are not maintained with chronic nicotine consumption as tolerance develops. The findings may provide an explanation for higher rates of smoking in patients with impulse control issues, as the smoking may represent an initial attempt at self-medication.

DBA/2 mice have altered hippocampal structure and perform poorly in several hippocampus-dependent contextual/spatial learning tasks. The performance of this strain in higher cognitive tasks is less studied. Transitive inference is a hippocampus-dependent task that requires an abstraction to be made from prior rules to form a new decision matrix; performance of DBA/2 mice in this task is unknown, whereas contextual fear conditioning is a hippocampus-dependent task in which DBA/2 mice have deficits. The present study compared DBA/2J and C57BL/6J inbred mice in two different contextual fear conditioning paradigms and transitive inference to test if similar deficits are seen across these hippocampus-dependent tasks. For background fear conditioning, mice were trained with two paired presentations of an auditory conditioned stimulus (CS, 30 second, 85 dB white noise) paired with an unconditioned stimulus (US, 2 second, 0.57 mA foot shock), the context was a continuous background CS. Mice were tested for contextual learning 24 hours later. Foreground fear conditioning differed in that no auditory CS was presented. For transitive inference, separate mice were trained to acquire a series of overlapping odor discrimination problems and tested with novel odor pairings that either did or did not require the use of transitive inference. DBA/2 mice performed significantly worse than the C57BL/6 in both foreground and background fear conditioning and transitive inference. These results demonstrate that the DBA/2 mice have deficits in higher-cognitive processes and suggest that similar substrates may underlie deficits in contextual learning and transitive inference.

Background Initial sensitivity to ethanol and the capacity to develop acute functional tolerance (AFT) to its adverse effects may influence the amount of alcohol consumed and may also predict future alcohol use patterns. The current study assessed sensitivity and AFT to the ataxic and hypnotic effects of ethanol in the first replicate of mice (HDID-1) selectively bred for high blood ethanol concentrations (BECs) following limited access to ethanol in the Drinking in the Dark (DID) paradigm. Methods Naïve male and female HDID-1 and HS/Npt mice from the progenitor stock were evaluated in three separate experiments. In experiments 1 and 2, ethanol-induced ataxia was assessed using the static dowel task. In experiment 3, ethanol-induced hypnosis was assessed by the method of Ponomarev and Crabbe (2002), using modified restraint tubes to measure the loss of righting reflex (LORR). Results HDID-1 mice exhibited reduced initial sensitivity to both ethanol-induced ataxia (p < 0.001) and hypnosis (p < 0.05) relative to HS/Npt mice. AFT was calculated by subtracting the BEC at loss of function from the BEC at recovery (Experiments 1 and 3) or by subtracting BEC at an initial recovery from the BEC at a second recovery following an additional alcohol dose (Experiment 2). The dowel test yielded no line differences in AFT, but HS/Npt mice developed slightly greater AFT to ethanol-induced LORR than HDID-1 (p < 0.05). Conclusions These results suggest that HDID-1 mice exhibit aspects of blunted ataxic and hypnotic sensitivity to ethanol which may influence their high ethanol intake via DID, but do not display widely different development of AFT. These findings differ from previous findings with the high alcohol-preferring (HAP) selected mouse lines, suggesting that genetic predisposition for binge, versus other forms of excessive alcohol consumption, is associated with unique responses to ethanol-induced motor incoordination.