Prenatal cocaine exposure induces deficits in Pavlovian conditioning and sensory preconditioning among infant rat pups.

Offspring derived from Sprague-Dawley dams that received daily sc injection of 40 mg/kg 3 cc–2 cocaine hydrochloride (C40) or saline (LC) from Gestational Days 8–20 were tested for first-order Pavlovian conditioning and sensory preconditioning at Postnatal Days 8 (P8), P12, and P21. Although C40 dams gained significantly less weight than LC dams, pup body weights did not differ between the 2 groups. Significant sensory preconditioning was obtained at P8 and P12 (but not at P21) in LC offspring, confirming previous reports (e.g., L. P. Spear et al; see record 1989-35900-001) of decline in performance in this task during ontogeny. In contrast, C40 offspring failed to exhibit sensory preconditioning at any test age. In addition, C40 pups tested at P8 did not display significant first-order conditioning. Taken together these results suggest a more general deficit in cognitive functioning rather than a delay in cognitive development in prenatally cocaine-exposed offspring. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differences in the liability to self-administer intravenous cocaine between C57BL/6 x SJL and BALB/cByJ mice

Application of animal models of psychostimulant abuse for experimentation in mice is becoming increasingly important for studying the contribution of genetic differences, as well as the roles of selected (targeted) genes, in specific behaviors. The purpose of this study was to investigate strain differences in cocaine self-administration behavior between C57BL/6 x SJL hybrid mice and BALB/cByJ mice. These two strains were chosen because BALB/cByJ mice have a well-developed behavioral pharmacological profile, and hybrid strains on a C57BL/6 background are commonly used for generating transgenic expressing and knockout mutant mice. C57BL/6 x SJL mice dose-dependently acquired cocaine self-administration (1.0 mg/kg/injection but not 0.25 mg/kg/injection) by responding selectively in the active nose-poke hole and maintaining stable levels of daily drug intake; they also exhibited a characteristic inverted-U-shaped cocaine dose-effect function. BALB/cByJ mice failed to acquire cocaine self-administration at either dose under the same test conditions. The strain differences observed in self-administration did not seem to be attributed to other behavioral differences because the two strains exhibited similar amounts of spontaneous nose-poking in the absence of reinforcers, and BALB/cByJ mice responded more than C57BL/6 x SJL mice in a food-reinforced nose-poke operant task. Importantly, the dose-effect function for the motor stimulating effects of cocaine (3.8-30 mg/kg intraperitoneally) suggests enhanced sensitivity but reduced efficacy of cocaine in stimulating motor activity in BALB/cByJ mice relative to the C57BL/6 x SJL hybrid mice. These results indicate that the decreased liability of BALB/cByJ mice to acquire cocaine self-administration is not the result of differences in spontaneous activity or performance, but may reflect different sensitivities to the reinforcing, or rate-disrupting, properties of cocaine. The data support an influence of genetic background in the liability to self-administer cocaine. Thus, a hypothesis is proposed that the decreased liability of BALB/cByJ mice to acquire cocaine self-administration is related to differences in brain monoamine systems linked to the high "emotionality" profile of BALB/c mice in novel or fearful situations, including perhaps cocaine administration.     

Chronic variable stress or chronic morphine facilitates immobility in a forced swim test: reversal by naloxone

The behaviors displayed in a forced swim test were investigated in rats previously exposed to a chronic variable stress treatment or chronic administration of morphine. In addition, to further explore the participation of an endogenous opiate mechanism in these behavioral effects, naloxone was either administered during the chronic treatment (prior to each stress or morphine exposure) or immediately prior to the forced swim test. Animals were submitted daily to a different stressor for 1 week or injected with morphine (10 mg/kg, IP) for 6 days, whereas controls were unmanipulated except for the injection process. On the day following the last stressor, control and stressed animals were administered saline or naloxone (2 mg/kg, IP) 15 min prior to the forced swim test. Morphine treated animals were similarly tested on the third day following the last morphine injection. In a separate group of rats, naloxone (2 mg/kg, IP) was administered daily 10 min prior to each stressor of the chronic stress regime or each daily morphine injection. A significant increase in the time spent in immobility was observed in stressed animals as well as in rats chronically treated with morphine. In both groups, this potentiated immobility was attenuated by naloxone pretreatment prior to the forced swim test or when given before each daily stressor or morphine injection. In addition, the concurrent exposure to stress or morphine along with naloxone administration enhanced struggling in the first 5 min of the forced swim test.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of prenatal exposure to cocaine on Morris water maze performance in adult rats.

The spatial memory of adult rats prenatally exposed to cocaine and that of control offspring was assessed using the Morris water maze. Offspring were derived from Sprague Dawley dams that received subcutaneous injection of 40 mg/kg/3 cc cocaine hydrochloride (C40) daily on gestational Days 8-20, pair-fed dams injected with saline, or nontreated control dams. After acquisition, the platform was moved to a new location (reversal phase). Probe trials were conducted at the end of acquisition and reversal training. On the 1st acquisition day, adult male and female offspring prenatally exposed to cocaine required significantly more time and traversed a greater distance to find the hidden platform than did control offspring. Despite these initial differences observed in C40 offspring performance, all of the rats were performing at equivalent levels at the time probe trials were conducted. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Photoelectrochemical reduction of nitrate on p-Si coated with metallic Re thin films

In this study we examined the rhenium electrodeposition process onto p-Si(100) from acidic media. The study was carried out by means of cyclic voltammetry and the potential-steps method from which the corresponding nucleation and growth mechanism were determined. Both methods were performed under illumination using a solar simulator for electron photogeneration. A 3D progressive nucleation, diffusion-controlled growth of rhenium films was found. Likewise, a morphologic analysis was completed for the deposits obtained at different potential values by means of atomic force microscopy. An energetic characterization through capacitance measurements (Mott–Schottky plots and parallel capacitance) of the p-Si/NO₃⁻ and p-Si/Re/NO₃⁻ interfaces was done.The photoelectrochemical reduction of nitrate ions, PERN, on the different p-Si/Re electrode systems synthesized was studied. An overpotential decrease of 0.3 V and a photocurrent increase for the PERN on p-Si(100)/Re electrode systems compared with p-Si(100) and metallic Re was found. Finally, the kinetic parameters of the cathodic reactions in the p-Si and p-Si/Re acidic media were estimated using intensity modulated photocurrent spectroscopy. A brief analysis from this technique was done. According to these results, the p-Si/Re electrode system could be a potential photoelectrocatalyst for the PERN.     

Strain distribution of mice in discriminated Y-maze avoidance learning: Genetic and procedural differences.

The current study was conducted to characterize discriminated avoidance learning in mice by using a Y-maze task. In Experiment 1, the task parameters were manipulated, including the amount of time spent in the start arm, the amount of time to make the avoidance response, and the intertrial interval (ITI) using C57?×?SJL F1 hybrid mice. Avoidance performance was significantly improved with longer times to avoid the shock and longer ITIs. In Experiment 2, mice from 4 inbred strains (BALB/cByJ, DBA/2J, C57BL/6J, and SJL/J), an F1 hybrid (C57?×?SJL), and 1 outbred strain (CD1) were tested with various ITIs. Strain differences were observed in avoidance learning, with BALB, DBA, C57?×?SJL and CD1 mice showing significantly better avoidance learning than C57 mice, which were better than SJL mice. These data demonstrate that Y-maze performance is significantly influenced by the genetic background of the mouse and the parameters of the task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal cell firing correlates of delayed-match-to-sample performance in the rat

Hippocampal CA1 and CA3 neurons were recorded in rats performing a delayed-match-to-sample (DMTS) task. Complex spike cells showed significant firing peaks following sample and match responses and during delivery of water reward. Individual cells were classified into 4 subtypes according to the presence or absence of firing in each of these 3 phases. There were significant differences in delay interval firing among the 4 subtypes, but firing during the delay did not predict the correct response: 34% of the cells showed a linear change in firing during the delay. Further analyses revealed significant lever position firing biases in approximately 70% of the cells tested irrespective of subtype. The complexity of firing correlates of the neurons recorded in this DMTS task suggests that the hippocampus divides specific aspects of the performance demands of the task across different cell subtypes, which together provide sufficient information to resolve the matching-to-sample problem on any given trial.     

Effects of prenatal exposure to cocaine on conditional discrimination learning in adult rats.

Adult male rats that were gestationally exposed to cocaine and control offspring were trained on an instrumental conditioning task for assessment of the acquisition and reversal of an appetitive conditional discrimination based on olfactory cues. Offspring were derived from Sprague-Dawley dams that had received subcutaneous/ly (sc) injections of 40 mg/kg/3 cc cocaine hydrochloride (C40) daily on Gestational Days 8–20, pair-fed (PF) dams that were injected with saline, nutritional control dams (NC) that received saline injections, and nontreated control dams (LC). There were no differences among the prenatal treatment groups in acquisition of the barpress response or response rate throughout all phases of training. All prenatal treatment groups required approximately the same number of sessions to criterion on the initial odor discrimination. In contrast, adult C40 offspring required more sessions to acquire the reversal of the conditional discrimination than did animals from the other treatment groups (PF, NC, and LC). In addition, even at criterion performance for acquisition of the reversal discrimination, C40 animals exhibited lower accuracy on the 1st 10 responses and made significantly more errors before the 1st reward. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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