Higher sensitivity to ethanol's aversive properties in WLP (Warsaw Low Preferring) vs. WHP (Warsaw High Preferring) rats.

Ethanol can have both an aversive and rewarding effect, which may have a significant relationship to its individual preference. So far, the reasons for the high and low ethanol preference in the WHP (Warsaw High Preferring) and WLP (Warsaw Low Preferring) lines have not been found. WHP rats spontaneously drink over 5 g/kg/day of ethanol, while WLP rats drink under 2 g/kg/day. The purpose of the work was to study the sensitivity of WHP and WLP rats to the aversive effects of ethanol at doses of 1.5 g/kg and 2.0 g/kg in the conditioned taste aversion (CTA) procedure. Lower doses (0.5 and 1.0 g/kg, i.p. [intraperitoneally]) were tested earlier and only 1.0 g/kg produced a slight aversion in WLP rats. The secondary aim was to check the additional potential factors (blood ethanol concentration, pain sensitivity, anxiety-related behavior, learning, and memory) that may constitute an important differentiating feature of the WHP and WLP lines. For this purpose, the following tests were conducted: blood ethanol concentration, novel object recognition (NOR), flinch-jump, hot-plate, and elevated plus maze (EPM). The 1.5 g/kg i.p. dose of ethanol caused the development of an aversion only in WLP rats and the aversion extinguished in the post-conditioning phase. The 2.0 g/kg i.p. dose of ethanol resulted in the development of an aversion in both the tested groups, with the aversion being maintained throughout the whole post-conditioning period only in the WLP rats. There were no differences between the lines in terms of the blood ethanol concentration and the EPM tests. WHP rats had a higher pain sensitivity compared to WLP rats in flinch-jump and hot-plate tests. WLP rats showed a shorter exploration time for both objects compared to WHP in the NOR test. In conclusion, WHP and WLP rats differ in sensitivity to the aversive effects of ethanol. This difference may partially explain their opposite ethanol preference.

Intergenerational implications of alcohol intake: metabolic disorders in alcohol-naïve rat offspring.

Alcohol drinking may be associated with an increased risk of various metabolic diseases. Rat lines selectively bred for alcohol preference and alcohol avoidance constitute an interesting model to study inherited factors related to alcohol drinking and metabolic disorders. The aim of the present study was to compare the levels of selected laboratory biomarkers of metabolic disorders in blood samples from naïve offspring of Warsaw alcohol high-preferring (WHP), Warsaw alcohol low-preferring (WLP), and wild Wistar rats. Blood samples were collected from 3-month old (300-350 g) alcohol-naïve, male offspring of WHP (n = 8) and WLP rats (n = 8), as well as alcohol-naïve, male, wild Wistar rats. Markers of metabolic, hepatic, and pancreatic disorders were analysed (levels of homocysteine, glucose, total cholesterol, triglycerides and γ-glutamyl transferase (GGT), aspartate (AST), alanine aminotransferase (ALT), and amylase serum activities). Alcohol-naïve offspring of WHP, WLP, and wild Wistar rats differed significantly in the levels of triglycerides, total cholesterol, homocysteine, as well as in the activity of GGT, ALT, AST, and amylase enzymes. Most markers in the alcohol-naïve offspring of WHP rats were altered even thought they were never exposed to alcohol pre- or postnatally. This may suggest that parental alcohol abuse can have a detrimental influence on offspring vulnerability to metabolic disorders.

Levetiracetam concentration in hair is associated with the time schedule of administration: Study on rats.

Measurement of hair drug content may be a reliable biomarker of the history of drug exposure, allowing to assess patient long-term compliance. Studies on correlations between antiepileptic drugs intake and their hair contents are limited. The aim of the study was to determine the association between the history of levetiracetam administration and its content in rat hair in controlled laboratory conditions. Additionally, the effects of levetiracetam on hair growth rate and body-weights were examined. Three groups of 12 rats each were exposed to different schedules of levetiracetam administration (10 mg/kg i.p.: every 24, 48 and 72 hours) for 30 days. The control group received daily saline injection. Levetiracetam concentrations in hair were assessed by validated LC-MS/MS method. The mean hair concentrations were as follows: 300 (±100), 170 (±60) and 130 (±80) ng/mg for rats receiving levetiracetam every 24, 48 and 72 hours, respectively. The levetiracetam accumulation in the hair was correlated with the total number of doses received (r = .699, P < .001). Levetiracetam did not affect the hair growth rate and rat body-weight. The concentration of levetiracetam measured in rat hair represents a reliable marker. It may reflect the adherence to levetiracetam treatment; however, further studies on human beings are needed.

Using anticipatory and drug-evoked appetitive ultrasonic vocalization for monitoring the rewarding effect of amphetamine in a rat model of drug self-administration.

Measuring ultrasonic vocalizations (USVs) allows studying psychoactive drug use-related affective states in laboratory rats and may help understand changes underlying the progress of addictions. We aimed at finding an effective scheme for amphetamine self-administration training in rats, identifying factors affecting their anticipatory and drug-evoked, frequency-modulated 50-kHz USV responses, and verifying whether the rewarding action of amphetamine promotes current drug intake during the training. Therefore, we monitored amphetamine intake and anticipatory and drug-evoked USVs in two rat cohorts trained using two different training schemes. Then we retrospectively divided these cohorts into low-amphetamine and high-amphetamine intake subsets and analyzed their frequency-modulated 50-kHz USV responses accordingly. Anticipatory (i.e., drug-context-related) USVs as well as USVs induced by self-administration training-related non-pharmacological manipulations (tested in an additional rat group) showed surprisingly high call rates but faded spontaneously relatively quickly. Only the scheme employing short cycles of training sessions (two instead of six) and intermittent instead of continuous intra-session drug availability yielded long-lasting escalation of amphetamine intake in a sizable subset. This subset showed high initial amphetamine-evoked USV call rate, which suggests that a strong rewarding action of the drug early in the SA training favors intake escalation. A major decrease in the drug-evoked USVs during advanced training indicated the emergence of tolerance to the rewarding action in these rats, a phenomenon that is characteristic of addiction. Frequency-modulated 50-kHz rat USVs are a good index of the rewarding action of amphetamine at the absence of USVs induced by drug context and other training-related factors.

Poor sensitization of 50-kHz vocalization response to amphetamine predicts rat susceptibility to self-administration of the drug.

RATIONALE: Our previous studies showed promise for using sensitization of the frequency-modulated 50-kHz vocalization response to amphetamine (AMPH) as an index of rat vulnerability to AMPH addiction. OBJECTIVE: This study aimed to test the utility of sensitizing frequency-modulated (FM) 50-kHz vocalization in the AMPH self-administration paradigm as well as the ability of N-acetylcysteine to prevent self-administration relapse. METHODS: Rats were subjected to the so-called two-injection protocol of sensitization (TIPS) using AMPH and were categorized as low-sensitized callers (LCTIPS) or high-sensitized callers (HCTIPS) based on the individual outcomes. Then, they were given 44 sessions of AMPH self-administration followed by a 17-session N-acetylcysteine-aided extinction course and a single session of AMPH-primed self-administration reinstatement. RESULTS: LCTIPS compared to HCTIPS rats showed no considerable difference in the FM 50-kHz vocalization rate during the self-administration training or extinction course, but they were considerably more likely to acquire AMPH self-administration and experience drug-induced reinstatement of this trait. Moreover, the LCTIPS rats were more likely than HCTIPS rats to have a markedly higher FM 50-kHz vocalization rate after AMPH reinstatement. N-acetylcysteine did not affect the course of self-administration extinction or the instrumental or FM 50-kHz vocalization responses to AMPH reinstatement. CONCLUSIONS: There is no link between the FM 50-kHz vocalization and key characteristics of AMPH self-administration. Additionally, N-acetylcysteine does not help prevent AMPH self-administration relapse. However, there is a high predictive value for poor sensitization of the FM 50-kHz vocalization response to AMPH with respect to the acquisition and maintenance of self-administration of this psychostimulant.

Ethanol-induced conditioned taste aversion in Warsaw Alcohol High-Preferring (WHP) and Warsaw Alcohol Low-Preferring (WLP) rats.

The aversive action of the pharmacological properties of ethanol was studied in selectively bred Warsaw Alcohol High-Preferring (WHP) and Warsaw Alcohol Low-Preferring (WLP) rats. For this study, a conditioned-taste aversion test was used. Male WHP and WLP rats were submitted to daily 20-min sessions for 5 days, in which a saccharin solution (1.0 g/L) was available (pre-conditioning phase). Next, this drinking was paired with the injection of ethanol (0, 0.5, 1.0 g/kg), intraperitoneally [i.p.] immediately after removal of the saccharin bottle (conditioning phase). Afterward, the choice between the saccharin solution and water was extended for 18 subsequent days for 20-min daily sessions (post-conditioning phase). Both doses of ethanol did not produce an aversion to saccharin in WLP and WHP rats in the conditioning phase. However, injection of the 1.0 g/kg dose of ethanol produced an aversion in WLP rats that was detected by a decrease in saccharin intake at days 1, 3, 7, and 10 of the post-conditioning phase, with a decrease in saccharin preference for 16 days of the post-conditioning phase. Conditioned taste aversion, measured as a decrease in saccharin intake and saccharin preference, was only visible in WHP rats at day 1 and day 3 of the post-conditioning phase. This difference between WLP and WHP rats was apparent despite similar blood ethanol levels in both rat lines following injection of 0.5 and 1.0 g/kg of ethanol. These results may suggest differing levels of aversion to the post-ingestional effects of ethanol between WLP and WHP rats. These differing levels of aversion may contribute to the selected line difference in ethanol preference in WHP and WLP rats.

Drinking of flavored solutions by high preferring (WHP) and low preferring (WLP) alcohol-drinking rats.

BACKGROUND: Selective breeding alcohol-preferring (P) and alcohol-nonpreferring (NP) rats showed a strong preference for the sucrose solutions, whereas P rats intake greater amounts than NP rats. The aim of this study was the estimation of selectively bred ethanol-preferring (WHP - Warsaw High Preferring) and ethanol-nonpreferring (WLP - Warsaw Low Preferring) rats for their preference for various tastes. METHODS: The oral drinking of the following substances was studied at a range of concentrations: sucrose (0.5-64.0 g/100 ml), NaCl (0.025-3.2 g/100 ml), citric acid (0.008-2.048 g/l), and sucrose octaacetate (0.002-0.512 g/l) solutions. Separate groups of 7-8 rats from each line were investigated of each of the four tastes. The investigated solutions were presented continuously keeping water and food always available. Concentrations of the various flavors were doubled every 48 h. RESULTS: Rats from WHP and WLP lines clearly revealed the preference for the sucrose solution and the highest preference was at the 4.0 and 8.0 g/100ml sucrose concentration. Similar to sucrose, both lines exposed strong preference for the NaCl solution and this preference enhanced together with the increase of the NaCl concentration. Nevertheless their preference for the NaCl solutions decreased when the concentration of NaCl reached 1.600 g/100 ml. Both lines of rats did not differ in citric acid or sucrose octaacetate intake at any of the concentrations studied. CONCLUSION: Selective breeding of rats (WHP) for high and rats (WLP) for low ethanol drinking is favorably correlated with the drinking of sweet and salty solutions and negatively correlated with the consumption of sour and bitter tastes.

Neonatal serotonin (5-HT) depletion does not affect spatial learning and memory in rats.

BACKGROUND: Extensive previous research has suggested a role for serotonin (5-HT) in learning and memory processes, both in healthy individuals and pathological disorders including depression, autism and schizophrenia, most of which have a developmental onset. Since 5-HT dysfunction in brain development may be involved in disease etiology, the present investigation assessed the effects of neonatal 5-HT depletion on spatial learning and memory in the Morris water maze (MWM). METHODS: Three days old Sprague-Dawley rats were pretreated with desipramine (20 mg/kg) followed by an intraventricular injection of the selective 5-HT neurotoxin 5,7-dihydroxytryptamine (5,7-DHT, 70 µg). Three months later rats were tested in the MWM. RESULTS: Despite a severe and permanent decrease (80-98%) in hippocampal, prefrontal and striatal 5-HT levels, treatment with 5,7-DHT caused no spatial learning and memory impairment. CONCLUSIONS: Limited involvement of chronic 5-HT depletion on learning and memory does not exclude the possibility that this neurotransmitter has an important neuromodulatory role in these functions. Future studies will be needed to identify the nature of the compensatory processes that are able to allow normal proficiency of spatial learning and memory in 5-HT-depleted rats.

Cocaine self-administration in Warsaw alcohol high-preferring (WHP) and Warsaw alcohol low-preferring (WLP) rats.

Individuals prone to drug self-administration may be vulnerable not only to a single drug reinforcer but to a variety of drug reinforcers. It has been shown that two thirds of alcoholics regularly use drugs other than ethanol (alcohol). Up to 30% of alcohol-dependent patients report concurrent misuse of cocaine. The aim of the present study was to investigate intravenous cocaine self-administration in selectively bred, alcohol-preferring WHP (Warsaw high-preferring) and non-preferring WLP (Warsaw low-preferring) rats. It was hypothesized that WHPs could be more prone to cocaine self-administration in comparison to WLPs. Rats from both lines were allowed to nose-poke for cocaine infusions (0.33 mg/kg/infusion) under the FR-1, FR-2, and FR-3 schedule of reinforcement. Dose-response curves were assessed with increasing doses of cocaine (0.03, 0.1, 0.33, 1.0mg/kg/infusion). The WHP and WLP rats did not differ in cocaine self-administration. Both groups quickly acquired nose-poke responding for cocaine, presented a similar response profile when the schedule of reinforcement was increased from FR-1 to FR-3, and similar sensitivity to cocaine in the dose-response test. The present results may indicate that the selective breeding of alcohol-preferring WHP and alcohol non-preferring WLP rats did not lead to differences in cocaine's rewarding effects as assessed in the self-administration procedure.

Neonatal serotonin (5-HT) depletion does not disrupt prepulse inhibition of the startle response in rats.

The neurodevelopmental hypothesis of many brain disorders is based on the notion that environmental factors have significant effects on brain maturation. Because serotonin (5-HT) dysfunction in development may be involved in disease etiology, the present investigation assessed the effects of neonatal 5-HT depletion on prepulse inhibition of the startle response (PPI) in rats. Three-day-old Sprague-Dawley rats were pretreated with desipramine (20 mg/kg), followed by an intraventricular injection of the selective 5-HT neurotoxin 5,7-dihydroxytryptamine (5,7-DHT, 70 µg dissolved in 2 µl of 0.1% saline solution in ascorbic acid) on each side. Three months later, the rats' PPI was tested. Despite a severe and permanent decrease (80-100%) in hippocampal, prefrontal and striatal 5-HT levels, treatment with 5,7-DHT caused no disruption of PPI. In contrast to this lack of effect, the 5,7-DHT treatment increased basal startle activity, as measured in response to a 120 dB stimulus. Thus, our results clearly indicate that neonatal 5-HT depletion does not interrupt prepulse inhibition in rats. Studies involving lesions of brain structures or chemical systems run the risk of inducing compensatory changes in brain function, resulting in an amelioration of any deficit. The development of such compensatory mechanisms seems likely in the current study, due to the severe and long-lasting effect of neonatal 5,7-DHT-induced reduction on 5-HT levels.

Diverse behavioral, monoaminergic and Fos protein responses to opioids in Warsaw high-alcohol preferring and Warsaw low-alcohol preferring rats.

Predisposition to addictions is presumably related to a dysfunction of the brain reward system, which can be 'compensated' by the intake of different psychoactive drugs. Hence, animals showing propensity for developing dependence to a specific drug class may also be useful for modeling other addictions. We compared the effects of repeated (14 daily doses) morphine (10 mg/kg) or methadone (2 mg/kg) treatment followed by a 2-week withdrawal and a morphine challenge (5 mg/kg) on locomotor activity, brain Fos expression and selected brain regional levels of dopamine, serotonin and their metabolites in the 38th generations of selectively bred Warsaw low-alcohol-preferring (WLP) and Warsaw high-alcohol-preferring (WHP) rat lines. The rats were given the opioids during the active (i.e. dark) phase of their daily cycle. Drug-naïve WHP rats compared to their WLP counterparts showed higher locomotor activity in an open field test and higher propensity for lasting behavioral sensitization to morphine. Morphine did not significantly enhance, but suppressed Fos expression in certain brain regions of drug-naïve WLP and WHP rats. Fos expression revealed considerable differences in the responses of WLP and WHP rats to morphine challenge, particularly after methadone pretreatment. These differences were associated with differences in monoamine metabolite levels that were suggestive of elevated basal ganglia and lowered frontal cortical dopamine function, and of lowered somatosensory cortex serotonin function, in the morphine-challenged WHP rats (irrespective of the pretreatment type). Hence, the WLP/WHP line pair may be useful for the search of factors that underlie the propensity for developing opiate dependence.

Active versus passive cocaine administration: differences in the neuroadaptive changes in the brain dopaminergic system.

There is considerable evidence that chronic exposure to cocaine is associated with low striatal dopamine D2 receptor availability. In the present study we wished to determine whether neuroadaptive changes in densities of D2 receptors were due to direct pharmacological actions of cocaine or they reflected motivational states that were present when cocaine injection depended on active drug-seeking behavior and whether these changes were related to the actual expression of D2 mRNA. To achieve this goal we utilized a "yoked" procedure in which rats were tested simultaneously in groups of three, with only one rat actively self-administering cocaine while the other two received yoked injections of either cocaine or saline. Only passively administered cocaine produced a decrease in dopamine D2 receptor levels in the anterior and central regions of caudate/putamen, and both the shell and core of the nucleus accumbens, as measured by in vitro quantitative autoradiography. In contrast, examination of D2 receptor gene expression using in situ hybridization analysis revealed that there was an increase in D2 receptor mRNA levels in the ventral tegmental area of rats actively self-administered cocaine. We conclude that the reductions in striatal D2 receptor densities may be related to the chronic administration of cocaine per se and not to the motivated process of reinforced responding. Our results also suggest that increases in D2 receptor mRNA levels in limbic regions do not necessarily result in increased receptor densities and these changes likely reflect motivational states that were present when cocaine injection dependent on active drug self-administration.