Ultrasonic vocalization in rats self-administering heroin and cocaine in different settings: evidence of substance-specific interactions between drug and setting

Rationale Clinical and preclinical evidence indicates that the setting of drug use affects drug reward in a substance-specific manner. Heroin and cocaine co-abusers, for example, indicated distinct settings for the two drugs: heroin being used preferentially at home and cocaine preferentially outside the home. Similar results were obtained in rats that were given the opportunity to self-administer intravenously both heroin and cocaine. Objectives The goal of the present study was to investigate the possibility that the positive affective state induced by cocaine is enhanced when the drug is taken at home relative to a non-home environment, and vice versa for heroin. Methods To test this hypothesis, we trained male rats to self-administer both heroin and cocaine on alternate days and simultaneously recorded the emission of ultrasonic vocalizations (USVs), as it has been reported that rats emit 50-kHz USVs when exposed to rewarding stimuli, suggesting that these USVs reflect positive affective states. Results We found that Non-Resident rats emitted more 50-kHz USVs when they self-administered cocaine than when self-administered heroin whereas Resident rats emitted more 50-kHz USVs when self-administering heroin than when self-administering cocaine. Differences in USVs in Non-Resident rats were more pronounced during the first self-administration (SA) session, when the SA chambers were completely novel to them. In contrast, the differences in USVs in Resident rats were more pronounced during the last SA sessions. Conclusion These findings indicate that the setting of drug taking exerts a substance-specific influence on the ability of drugs to induce positive affective states

Repeated Exposures to Heroin and/or Cadmium Alter the Rate of Formation of Morphine Glucuronides in the Rat

After absorption, heroin is transformed into mono-acetyl-morphine and then into morphine. Morphine, in turn, is metabolized to morphine-3-glucuronide (M3G), an inactive compound, and morphine-6-glucuronide (M6G), a potent opioid agonist. Thus, changes in the rate of formation of M6G may alter the pharmacological consequences of a treatment with heroin or morphine. In this study, we investigate the effect of repeated exposures (10 daily i.p. injections) to heroin, morphine, cadmium (which has been previously shown to inhibit M3G formation in vitro), or heroin + cadmium on morphine glucuronidation both in vivo and ex vivo (i.e., microsomal preparation obtained from rats treated in vivo). Repeated heroin (2.5, 5.0, and 10 mg/kg) increased plasma levels of M6G (which was undetectable in all other groups) and reduced those of M3G. Also, the microsomal preparations obtained from the liver of repeated heroin rats, when incubated with morphine, yielded significant amounts of M6G (which was undetectable in all other groups) and decreased levels of M3G relative to the control groups. These effects were reversible upon discontinuation of heroin administration. In contrast, repeated morphine (10, 20, and 40 mg/kg) only slightly reduced M3G formation at the dose of 40 mg/kg. Repeated cadmium (5, 15, and 45 microg/kg) reduced the rate of M3G formation without inducing M6G synthesis. The effects of the repeated coadministration of heroin (10 mg/kg) and cadmium (15 microg/kg) were virtually identical to those of repeated heroin alone. In summary, repeated exposure of rats to heroin can shift morphine glucuronidation toward the formation of the active metabolite M6G

Solubility of calcium deoxycholate

Gu et al.1 proposed an investigation to determine the approximate solubility products of some calcium salt of bile salts. In this comunication the solubility of calcium (II) deoxycholate is studied at 25°C. To minimize the activity coefficients change in spite of the concentration of the reagent variation, the constant ionic medium was adopted. All the investagetd solutions were 0.5 mol dm-3 NaCl or N(CH3)4Cl. The solid calcium (II) deoxycholate was prepared by adding a slight excess of calcium (II) chloride to a sodium deoxycholate solution. The obtained solid was analysed by thermogramimetry for the stochiometric composition. The solid was equilibrated with solutions in the selected ionic medium at different concentration of calcium (II), deoxycholate and in the range 7.5 –log cH 11.3. Solubility was evaluated by analysing filtrated solutions by determining calcium (II) by means of Atomic Absorption Spectrophotometry. Experimental data could be explained by assuming the presence of a complex between calcium (II) and deoxycholate (log = 5.46), beside to the solubility product (-log Ks = 9.15). 1. Gu, J-J; Hofmann, A.F.; Ton-Nu, H.-T.; Schteingart, D.; Mysels, K.J. J.Lip. Res. 1992, 33, 63

Development and validation of an analytical method based on high performance thin layer chromatography for the simultaneous determination of lamotrigine, zonisamide and levetiracetam in human plasma.

Abstract Methods based on HPLC technology are the most frequently adopted for monitoring blood levels of novel antiepileptics. Here a rapid method based on HPTLC was developed for quantitative determination of lamotrigine (LTG), zonisamide (ZNS) and levetiracetam (LVT) in human plasma and compared with HPLC and LC-MS/MS methods. Chromatographic separation was achieved on silical gel 60F(254) plates using ethylacetate:methanol:ammonia (91:10:15v/v/v) as mobile phase. Quantitative analysis was carried out by densitometry at a wavelength of 312, 240 and 210nm for LTG, ZNS and LVT, respectively. Calibration curves were linear over range of 0-200ng for LTG and ZNS and 0-400ng for and LVT. The limit of quantification of LTG, ZNS and LTV was found to be 3.69, 3.7 and 6.85μg/ml, respectively. Intra and inter-assay precision provided relative standard deviations lower than 10% for all three analytes. Correlation and Bland-Altman plot showed general agreement between HPTLC and LC-MS/MS quantification, with a mean bias of -0.25, -0.46 and 0.5μg/ml for LTG ZNS and LVT, respectively. Likewise, comparison between HPLC-UV and LC-MS/MS showed good agreement for all the three compounds analyzed. In conclusion, the proposed HPTLC method is simple, rapid, precise and accurate. It therefore is appropriate for the routine quantification of therapeutic levels of LTG, ZNS and LVT in human plasma

Induction of morphine-6-glucuronide synthesis by heroin self-administration in the rat

RATIONALE Heroin is rapidly metabolized to morphine that in turn is transformed into morphine-3-glucuronide (M3G), an inactive metabolite at mu-opioid receptor (MOR), and morphine-6-glucuronide (M6G), a potent MOR agonist. We have found that rats that had received repeated intraperitoneal injections of heroin exhibit measurable levels of M6G (which is usually undetectable in this species). OBJECTIVE The goal of the present study was to investigate whether M6G synthesis can be induced by intravenous (i.v.) heroin self-administration (SA). MATERIALS AND METHODS Rats were trained to self-administer either heroin (50 μg/kg per infusion) or saline for 20 consecutive 6-h sessions and then challenged with an intraperitoneal challenge of 10 mg/kg of heroin. Plasma levels of heroin, morphine, 6-mono-acetyl morphine, M3G, and M6G were quantified 2 h after the challenge. In vitro morphine glucuronidation was studied in microsomal preparations obtained from the liver of the same rats. RESULTS Heroin SA induced the synthesis of M6G, as indicated by detectable plasma levels of M6G (89.7 ± 37.0 ng/ml vs. 7.35 ± 7.35 ng/ml after saline SA). Most important, the in vitro V (max) for M6G synthesis was correlated with plasma levels of M6G (r (2) = 0.78). Microsomal preparations from saline SA rats produced negligible amounts of M6G. CONCLUSION Both in vivo and in vitro data indicate that i.v. heroin SA induces the synthesis of M6G. These data are discussed in the light of previous studies conducted in heroin addicts indicating that in humans heroin enhances the synthesis of the active metabolite of heroin and morphine