Disposition and metabolism of [3H] cocaine in acutely and chronically treated monkeys

Quantification of 108 illicit drugs and metabolites in bile matrix by LC-MS/MS for the toxicological testing of sudden death cases

Sudden death could occur after assumption of illicit drugs for recreational purposes in adults or after intoxication in children, and toxicological testing would help identify the cause of the death. Analytical methods sensitive and specific for the quantification of a great number of drugs and metabolites in at least 2 matrices should be used. Bile, collected postmortem, may be considered a specimen alternative to blood and urine to perform toxicological testing because of its extended detection window. The present study proposed a LC-MS/MS method to quantify 108 drugs and metabolites in bile. Compounds belonging to the drugs of abuse classes of amphetamines, benzodiazepines, cocaine derivatives, barbiturates, opioids, z-drugs, and psychedelics were analyzed. The sample preparation is simple and does not require solid-phase extraction. The proposed method showed an appropriate selectivity, specificity, accuracy, and precision of the calibrators and quality controls tested (precision < 15%; accuracy < 100 ± 15%). The sensitivity allowed to identify low amounts of drugs (e.g., morphine limit of detection = 0.2 µg/L; limit of quantification = 1.1 µg/L). There is no significant matrix effect, except for buprenorphine and 11-Nor-9-carboxy-Δ9-tetrahydrocannabinol. Carry-over was not present. Analytes were stable at least for 1 month at - 20 °C. Analyzing 13 postmortem specimens, methadone (50%), and cocaine (37.5%) resulted to be the most prevalent consumed substances; the concentrations quantified in bile resulted to be higher than the ones in blood suggesting bile as a potential new matrix for identifying illicit drugs and their metabolites.

Gene expression in the striatum of cynomolgus monkeys after chronic administration of cocaine and heroin

Cocaine and heroin cause impairment of neural plasticity in the brain including striatum. This study aimed to identify genes differentially expressed in the striatum of cynomolgus monkeys in response to cocaine and heroin. After chronic administration of cocaine and heroin in the monkeys, we performed large-scale transcriptome profiling in the striatum using RNA-Seq technology and analysed functional annotation. We found that 547 and 1238 transcripts were more than 1.5-fold up- or down-regulated in cocaine- and heroin-treated groups, respectively, compared to the control group, and 3432 transcripts exhibited differential expression between cocaine- and heroin-treated groups. Functional annotation analysis indicated that genes associated with nervous system development (NAGLU, MOBP and TTL7) and stress granule disassembly (KIF5B and KLC1) were differentially expressed in the cocaine-treated group compared to the control group, whereas gene associated with neuron apoptotic process (ERBB3) was differentially expressed in the heroin-treated group. In addition, IPA network analysis indicated that genes (TRAF6 and TRAF3IP2) associated with inflammation were increased by the chronic administration of cocaine and heroin. These results provide insight into the correlated molecular mechanisms as well as the upregulation and down-regulation of genes in the striatum after chronic exposure to cocaine and heroin.

Who's your daddy? Behavioral and epigenetic consequences of paternal drug exposure

Substance use disorders (SUDs) reflect genetic and environmental factors. While identifying reliable genetic variants that predispose individuals to developing SUDs has been challenging, epigenetic factors may also contribute to the heritability of SUDs. Familial drug use associates with a wide range of problems in children, including an increased risk for developing a SUD. The implications of maternal drug use on offspring development are a well-studied area; however, paternal drug use prior to conception has received relatively little attention. Paternal exposure to several environmental stimuli (i.e. stress or diet manipulations) results in behavioral and epigenetic changes in offspring. The purpose of this review is to determine the state of the preclinical literature on the behavioral and epigenetic consequences of paternal drug exposure. Drug-sired offspring show several developmental and physiological abnormalities. These offspring also show deficits in cognitive and emotional domains. Examining sensitivity to drugs in offspring is a growing area of research. Drug-sired offspring are resistant to the rewarding and reinforcing properties of drugs. However, greater paternal motivation for the drug, combined with high drug intake, can result in addiction-like behaviors in offspring. Drug-sired offspring also show altered histone modifications and DNA methylation levels of imprinted genes and microRNAs; epigenetic-mediated changes were also noted in genes related to glutamatergic and neurotrophic factor signaling. In some instances, drug use resulted in aberrant epigenetic modifications in sire sperm, and these changes were maintained in the brains of offspring. Thus, paternal drug exposure has long-lasting consequences that include altered drug sensitivity in subsequent generations. We discuss factors (i.e. maternal behaviors) that may moderate these paternal drug-induced effects as well as ideas for future directions.

Psychostimulant-Induced Testicular Toxicity in Mice: Evidence of Cocaine and Caffeine Effects on the Local Dopaminergic System

Several organ systems can be affected by psychostimulant toxicity. However, there is not sufficient evidence about the impact of psychostimulant intake on testicular physiology and catecholaminergic systems. The aim of the present study was to further explore potential toxic consequences of chronic exposure to cocaine, caffeine, and their combination on testicular physiology. Mice were injected with a 13-day chronic binge regimen of caffeine (3x5mg/kg), cocaine (3×10mg/kg), or combined administration. Mice treated with cocaine alone or combined with caffeine showed reduced volume of the seminiferous tubule associated to a reduction in the number of spermatogonia. Cocaine-only and combined treatments induced increased lipid peroxidation evaluated by TBARS assay and decreased glutathione peroxidase mRNA expression. Importantly, caffeine-cocaine combination potentiated the cocaine-induced germ cell loss, and induced pro-apoptotic BAX protein expression and diminished adenosine receptor A1 mRNA levels. We analyzed markers of dopaminergic function in the testis and detected the presence of tyrosine hydroxylase (TH) in the cytoplasm of androgen-producing Leydig cells, but also in meiotic germs cells within seminiferous tubules. Moreover, using transgenic BAC-Drd1a-tdTomato and D2R-eGFP mice, we report for the first time the presence of dopamine receptors (DRs) D1 and D2 in testicular mouse Leydig cells. Interestingly, the presence of DRD1 was also detected in the spermatogonia nearest the basal lamina of the seminiferous tubules, which did not show TH staining. We observed that psychostimulants induced downregulation of DRs mRNA expression and upregulation of TH protein expression in the testis. These findings suggest a potential role of the local dopaminergic system in psychostimulant-induced testicular pathology.

Epigenetic inheritance of a cocaine-resistance phenotype

A heritable phenotype resulting from the self-administration of cocaine in rats was delineated. We observed delayed acquisition and reduced maintenance of cocaine self-administration in male, but not female, offspring of sires that self-administered cocaine. Brain-derived neurotrophic factor (BDNF) mRNA and protein were increased in the medial prefrontal cortex (mPFC) and there was an increased association of acetylated histone H3 with BDNF promoters only in the male offspring of cocaine-experienced sires. Administration of a BDNF receptor antagonist (the TrkB receptor antagonist ANA-12) reversed the diminished cocaine self-administration in male cocaine-sired rats. In addition, the association of acetylated histone H3 with BDNF promoters was increased in the sperm of sires that self-administered cocaine. Collectively, these findings indicate that voluntary paternal ingestion of cocaine results in epigenetic reprograming of the germline resulting in profound effects on mPFC gene expression and resistance to cocaine reinforcement in male offspring.

Interception of cocaine by enzyme or antibody delivered with viral gene transfer: a novel strategy for preventing relapse in recovering drug users

Recent progress in enzyme engineering has led to versions of human butyrylcholinesterase (BChE) that hydrolyze cocaine efficiently in plasma, reduce concentrations reaching reward neurocircuity in the brain, and weaken behavioral responses to this drug. Along with enzyme advances, increasingly avid anti-cocaine antibodies and potent anti-cocaine vaccines have also been developed. Here we review these developments and consider the potential advantages along with the risks of delivering drug-intercepting proteins via gene transfer approaches to treat cocaine addiction.

Competitive dopamine receptor antagonists increase the equiactive cocaine concentration during self-administration

Competitive dopamine receptor antagonists increase the rate of cocaine self-administration. As the rate of self-administration at a particular unit dose is determined by the satiety threshold and the elimination half-life (t(½)) of cocaine, we investigated whether dopamine receptor antagonists altered these parameters in rats. The plasma cocaine concentration at the time of each self-administration was constant during a session demonstrating that this satiety threshold concentration represents an equiactive cocaine concentration. The plasma cocaine concentration at the time of self-administration was increased by SCH23390, consistent with pharmacological theory. In rats trained to reliably self-administer cocaine, SCH23390 had no effect on the plasma steady-state cocaine concentration produced by constant infusions of cocaine. Therefore, this antagonist had no effect on cocaine t(½) at a dose that accelerated cocaine self-administration. A constant cocaine infusion at a rate that maintained steady state concentrations above the satiety threshold stopped self-administration. SCH23390, or the D₂ dopamine receptor antagonist (-)eticlopride, reinstated self-administration in the presence of the constant cocaine infusion. This is consistent with SCH23390 and eticlopride raising the satiety threshold above the steady state level produced by the constant cocaine infusion. It is concluded that the antagonist-induced acceleration of cocaine self-administration is the result of a pharmacokinetic/pharmacodynamic interaction whereby the rate of cocaine elimination is faster at the higher concentrations, as dictated by first-order kinetics, so that cocaine levels decline more rapidly to the elevated satiety threshold. This results in the decreased interinjection intervals.

The concept of pharmacologic cocaine interception as a treatment for drug abuse

Cocaine access to brain tissue and associated cocaine-induced behaviors are substantially reduced in rats and mice by significant plasma levels of an enzyme that rapidly metabolizes the drug. Similar results have been obtained in rodents and humans with therapeutic anti-cocaine antibodies, which sequester the drug and prevent its entry into the brain. We show that an efficient cocaine hydrolase can lead to rapid unloading of anti-cocaine antibodies saturated with cocaine, and we provide a theoretical basis for the hypothesis that dual therapy with antibody and hydrolase enzyme may be especially effective.

A chimeric human/murine anticocaine monoclonal antibody inhibits the distribution of cocaine to the brain in mice

The predominantly human sequence, high-affinity anticocaine monoclonal antibody (mAb) 2E2 was cleared slowly from mouse blood by a first-order process with an elimination t(1/2) of 8.1 days. Infused 2E2 also produced a dramatic dose-dependent increase in plasma cocaine concentrations and a concomitant decrease in the brain cocaine concentrations produced by an i.v. injection of cocaine HCl (0.56 mg/kg). At the highest dose of 2E2 tested (3:1, mAb/drug), cocaine was not detectable in the brain. Pharmacokinetic studies showed that the normal disappearance of cocaine from plasma was described by a two-compartment pharmacokinetic model with distribution t(1/2alpha) and terminal elimination t(1/2beta) values of 1.9 and 26.1 min, respectively. In the presence of an equimolar dose of mAb 2E2, there was a 26-fold increase in the area under the plasma cocaine concentration-time curve (AUC) relative to the AUC in the absence of 2E2. Consequently, 2E2 decreased the volume of distribution of cocaine from 6.0 to 0.20 l/kg, which approximated that of 2E2 (0.28 l/kg). However, cocaine was still rapidly cleared from plasma, and its elimination was now described by a single-compartment model with an elimination t(1/2) of 17 min. Importantly, 2E2 also produced a 4.5-fold (78%) decrease in the cocaine AUC in the brain. Therefore, the effect of 2E2 on plasma and brain cocaine concentrations was predominantly caused by a change in the distribution of cocaine with negligible effects on its rate of clearance. These data support the concept of immunotherapy for drug abuse.

Pharmacokinetics of repeated doses of intravenous cocaine across the menstrual cycle in rhesus monkeys

Numerous studies in rodents suggest that there are sex differences in response to cocaine that are related to fluctuations in the ovarian hormones of females. Given that female rhesus monkeys have menstrual cycles that are remarkably similar to those of humans, they provide an ideal laboratory animal model for assessing the effects of cocaine across the menstrual cycle. The present study assessed the effects of 4 injections of intravenous (i.v.) cocaine (0.00, 0.25 or 0.50 mg/kg), spaced 15 min apart, in 4 female rhesus monkeys. Each monkey was tested with each dose during 4 phases of the menstrual cycle: menses, midfollicular, periovulatory and midluteal. Estradiol and progesterone levels were measured each session before cocaine administration to verify phase of the menstrual cycle. Cocaine and cocaine metabolite levels were measured 5 min after each cocaine dose and 5, 15, 30, 45, 60 and 120 min after the last cocaine dose. Similarly, levels of luteinizing hormone (LH) and prolactin levels were measured before, 5, 15, 30, 45, 60 and 120 min after the last cocaine dose. Cocaine and metabolite levels increased as a function of dose, but there were minimal differences across the menstrual cycle following repeated injections of cocaine. With a few exceptions, LH levels decreased as a function of time within the session, with no differences as a function of cocaine dose. Cocaine produced transient increases in LH levels during the luteal phase, with maximal levels occurring after the second cocaine injection. Lastly, cocaine substantially decreased prolactin levels across all menstrual cycle phases. Taken together, these data indicate that any behavioral differences observed either across the menstrual cycle or between males and females, are probably not related to alterations in the pharmacokinetics of cocaine across the menstrual cycle.

Pharmacokinetics of intravenous cocaine across the menstrual cycle in rhesus monkeys

Several studies in rodents suggest that there are sex differences in response to cocaine that are related to fluctuations in the ovarian hormones of females. Female rhesus monkeys have menstrual cycles that are remarkably similar to human menstrual cycles in both duration and hormonal variations. Therefore, data obtained in monkeys should be an ideal model for assessing the effects of cocaine across the menstrual cycle in humans. The present study assessed the acute effects of intravenous cocaine (0, 0.25, 0.50, and 1.00 mg/kg) in five female rhesus monkeys during four phases of the menstrual cycle: menses, midfollicular, periovulatory, and midluteal. To reduce the effects of stress that can occur from sedation, all animals were trained to enter primate chairs so that repeated blood samples could be obtained in awake animals. Hormone levels for estradiol and progesterone were measured each session before cocaine administration. Cocaine and cocaine metabolite plasma levels were measured at 5, 15, 30, 45, 60, and 90 min after cocaine administration. Similarly, levels of luteinizing hormone (LH) were measured before, 15, 30, 45, 60, and 90 min after cocaine administration. Within 5 min of cocaine administration, cocaine plasma levels peaked and dose-dependent behavioral changes (ie increased motor activity, mydriasis, and refusal of treats) were observed. These effects typically resolved in 15-30 min. There were few differences in the pharmacokinetic profile of cocaine across the menstrual cycle. However, the cocaine metabolites, BZE and EME, did vary across the menstrual cycle, with both being increased in the luteal phase, particularly following the highest dose of cocaine. In addition, unlike previous studies, cocaine did not produce consistent increases in LH levels. Rather, the change in LH levels depended on menstrual cycle phase and cocaine dose. In summary, there is little evidence that the pharmacokinetics of cocaine vary as a function of menstrual cycle phase.

Ovarian steroid hormone modulation of the acute effects of cocaine on luteinizing hormone and prolactin levels in ovariectomized rhesus monkeys

Cocaine stimulates significant increases in luteinizing hormone (LH) and decreases prolactin levels in gonadally intact rhesus monkeys, but cocaine did not alter plasma levels of these anterior pituitary hormones in ovariectomized females. These findings suggested that ovarian steroid hormones may contribute to the endocrine effects of acute cocaine administration. To test this hypothesis, the acute effects of cocaine and placebo-cocaine on plasma LH and prolactin levels were examined in five ovariectomized rhesus females during three chronic hormone replacement conditions: 1) estradiol (E2beta) treatment (0.0015-0.006 mg/kg/day i.m.), 2) progesterone treatment (0.32 mg/kg/day i.m.), and 3) combinations of progesterone (0.32 mg/kg/day i.m.) and E2beta (0.002 and 0.004 mg/kg/day i.m.). Cocaine (0.8 mg/kg i.v.) did not alter prolactin or LH in ovariectomized monkeys without ovarian steroid replacement. During chronic estradiol treatment, cocaine produced an estradiol dose-dependent decrease in prolactin. Cocaine also decreased prolactin during treatment with progesterone alone and progesterone + E2beta (0.004 mg/kg/day i.m.). Cocaine stimulated a significant increase in LH during treatment with progesterone alone, but not during treatment with progesterone + E2beta, or three of four estradiol treatment doses. Cocaine pharmacokinetics did not differ as a function of hormone replacement conditions. Together, these data suggest that both E2beta and progesterone modulate cocaine's effects on prolactin, whereas E2beta alone and in combination with progesterone, do not facilitate LH release in response to cocaine in ovariectomized rhesus females.

Radiometric solvent-partitioning assay for screening cocaine hydrolases and measuring cocaine levels in milligram tissue samples

To permit rapid screening and characterization of novel cocaine hydrolases, as well as accurate measurement of cocaine levels in small samples of tissue, a radiometric assay was developed. The assay is based on selective, organic solvent partition of [3H]benzene-labeled cocaine or of [3H]benzoic acid liberated during enzymatic hydrolysis. With dilute samples the assay can be conducted entirely in scintillation vials and quantitated by addition of appropriate aqueous buffer and toluene-based fluor, making phase separation unnecessary. In this way, several hundred samples can be assayed in an afternoon, nanogram quantities of enzyme can be characterized without prior purification, and cocaine concentrations can be accurately measured in milligram samples of tissue after administration of [3H]cocaine in vivo.

Cocaine metabolism accelerated by a re-engineered human butyrylcholinesterase

Plasma butyrylcholinesterase (BChE) is important in the metabolism of cocaine, but natural human BChE has limited therapeutic potential for detoxication because of low catalytic efficiency with cocaine. Here we report pharmacokinetics of cocaine in rats treated with A328W/Y332A BChE, an excellent cocaine hydrolase designed with the aid of molecular modeling. Compared with wild-type BChE, this enzyme hydrolyzes cocaine with 40-fold improved k(cat) (154 min(-1) versus 4.1 min(-1)) and only slightly increased K(M) (18 microM versus 4.5 microM). In rats given this hydrolase (3 mg/kg i.v.) 10 min before cocaine challenge (6.8 mg/kg i.v.), cocaine half-life was reduced from 52 min to 18 min. Mirroring the reductions of plasma cocaine were large increases in benzoic acid, a product of BChE-mediated cocaine hydrolysis. All other pharmacokinetic parameters confirmed a large, dose-dependent acceleration of cocaine removal by the injected cocaine hydrolase. These results show that A328W/Y332A, an efficient cocaine hydrolase in vivo as well as in vitro, might promote cocaine detoxication in a clinical setting.

Cocaine administration induces human splenic constriction and altered hematologic parameters

Cocaine is a potent vasoconstrictor that has been shown to alter hemoglobin, hematocrit, and red blood cell counts in both animals and humans. The present study evaluated whether cocaine administration induces splenic constriction in men and whether spleen-volume changes temporally correlate with altered hematologic parameters. Spleen volume was assessed at baseline and after cocaine administration (0.4 mg/kg) by using magnetic resonance imaging. A group of five healthy men, aged 31 +/- 2 (SE) yr and reporting occasional cocaine use (13 +/- 5 lifetime exposures), participated. Cocaine reduced spleen volume by 20 +/- 4% (P < 0.03) 10 min after drug administration. Spleen volume returned to normal (101 +/- 3% baseline) within 35 min after cocaine administration, indicating that the reduction is a transient phenomenon. In subjects administered cocaine from whom blood samples were obtained (n = 3), cocaine increased hemoglobin levels, hematocrit, and red blood cell count to 104.5 +/- 0.9, 105.6 +/- 1.2, and 106.5 +/- 1.0% of baseline levels, respectively (P < 0.03), but it did not alter white blood cell and platelet counts. Placebo administration (n = 5) did not alter hematologic parameters. These results suggest that cocaine induces splenic constriction in humans, and this may contribute to temporally concordant hematologic parameter changes. These events may help to preserve or increase tissue oxygenation in periods of high oxygen demand and/or increased vascular resistance.

Effects of follicular-phase cocaine administration on menstrual and ovarian cyclicity in rhesus monkeys

OBJECTIVE

The purpose of this study was to evaluate the effects of daily follicular-phase cocaine administration on menstrual cyclicity, gonadotropin and ovarian steroid levels, ovulation rates, and corpus luteum function in cycling rhesus monkeys.

STUDY DESIGN

Thirteen normally cycling, drug-naive adult rhesus monkeys were randomized to receive daily intravenous injections of either 4 mg/kg cocaine or an equal volume of saline solution. Treated animals were yoked to pair-fed controls to minimize differences in caloric intake. Daily blood samples were obtained through indwelling catheters for measurement of serum gonadotropin and ovarian steroid levels. Daily vaginal swabs were obtained to determine the onset of menses. Laparoscopy was performed 2 days after the midcycle estrogen peak to check for ovulation. Daily caloric intakes and pretreatment and posttreatment weights were recorded.

RESULTS

All six of the control monkeys had laparoscopically confirmed ovulation compared with one of seven in the cocaine-treated group (p < 0.004). Cycle length was normal in five of six controls versus one of seven cocaine-treated monkeys. Estradiol levels were significantly higher in the controls versus the cocaine-treated monkeys (p = 0.01) during the first 14 days of the treatment cycle. There were no differences in basal plasma gonadotropin levels between groups. Luteal-phase lengths and luteal-phase plasma progesterone levels were similar in the controls and the single ovulatory cocaine-treated monkey. There were no significant differences in weight change or caloric intake between the two groups.

CONCLUSIONS

Daily follicular-phase cocaine administration disrupts menstrual cyclicity and folliculogenesis independent of weight loss, caloric intake, and basal gonadotropin levels.

Cocaine's effects on neuroendocrine systems: clinical and preclinical studies

This review examines the effects of cocaine on the neuroendocrine system and summarizes findings from clinical studies of cocaine abusers and preclinical studies in rodents and rhesus monkeys. The effects of acute and chronic cocaine administration on anterior pituitary, gonadal, and adrenal hormones are described, and the functional consequences of chronic cocaine exposure are discussed. Many of cocaine's acute effects on the endocrine system are consistent with its actions as a monoamine reuptake inhibitor. Acute cocaine administration stimulates release of gonadotropins, ACTH, and cortisol or corticosterone and suppresses prolactin levels. It has been difficult to detect changes in basal levels of most hormones or alterations in hormone responsiveness to a challenge dose of cocaine or other agents after chronic cocaine treatment. Interpretation of clinical data is often complicated by polydrug abuse involving opiates and alcohol as well as cocaine. However, preclinical studies of the effects of chronic cocaine exposure on integrated neuroendocrine function have revealed disruptions of the estrous cycle in rats and the menstrual cycle in rhesus monkeys. Furthermore, the menstrual cycle disorders observed in rhesus monkeys parallel those reported in women who abuse cocaine. Much remains to be learned about cocaine's interactions with the endocrine system and the consequences of cocaine abuse for reproductive function.

Effects of exposure regimen on changes in sensitivity to the effects of cocaine on schedule-controlled behavior in rhesus monkeys

It has been reported that conditions of drug exposure can influence changes in sensitivity to cocaine upon repeated administration. In the present experiment, the behavioral effects of prolonged exposure to continuous or intermittent infusion of cocaine were compared in rhesus monkeys responding under a multiple component fixed-ratio (FR) schedule of food presentation. In order to quantify changes in sensitivity to cocaine, cumulative dose-response functions for acute cocaine were determined using a multiple schedule comprised of six 10-minute components separated by time-out periods of 3 minutes. Initially, cocaine decreased responding in a dose-related manner. Continuous infusion of cocaine (4 mg/kg per day) for a period of 4 weeks resulted in a 2- to 4-fold shift to the right in the cocaine dose-response function, i.e., tolerance developed. In contrast, when the same daily dose of cocaine was injected intermittently (1.0 mg/kg per injection) four times/day to different monkeys, there was no change in the effects of cocaine on responding. The present results support the notion that the dosing regimen is an important determinant of changes in sensitivity to the behavioral effects of cocaine. Additionally, since sensitization failed to develop upon intermittent administration of cocaine, behavioral baseline may play a role in changes in sensitivity to cocaine.

Relationship between the discriminative stimulus effects and plasma concentrations of intramuscular cocaine in rhesus monkeys

The relationship between the discriminative stimulus effects and plasma pharmacokinetics of cocaine was evaluated in six rhesus monkeys trained to discriminate cocaine (0.4 mg/kg, IM) from saline under a FR30 schedule of food presentation. The same monkeys were tested in two procedures. In a cumulative dosing procedure, five cumulative doses of cocaine (0.013-1.3 mg/kg) were administered and discriminative stimulus effects were evaluated 10 min after the administration of each dose. Cocaine plasma concentrations were measured in separate sessions using the same doses and interdose intervals. In a single dosing procedure, the time-courses of the discriminative stimulus effects and plasma concentrations of cocaine were assessed after the administration of cocaine (0.4 mg/kg). A close correspondence between cocaine's discriminative stimulus effects and plasma concentrations was obtained in both procedures. Cocaine was virtually undetectable in plasma at doses that produced saline-appropriate responding (0.013 and 0.04 mg/kg), whereas increasing plasma concentrations were measured at doses that produced primarily cocaine-appropriate responding (0.13 mg/kg or higher). The time-course of the discriminative stimulus effects of cocaine was characterized by a rapid onset (within 1-3 min post-cocaine) and offset (within 20-60 min post-cocaine). Peak plasma levels were obtained at 10 min post-cocaine. No differences in plasma concentrations were found 10 min after the administration of a cumulative versus a single dose of cocaine 0.4 mg/kg (mean, 75.8 and 74.0 ng/ml, respectively). Cocaine plasma concentrations lasted longer than its discriminative stimulus effects. The results of the present study confirm that the cumulative dosing procedure used yields plasma concentrations of cocaine that are similar to the concentrations obtained after single cocaine dosing.

Cocaine accumulates in dopamine-rich regions of primate brain after i.v. administration: comparison with mazindol distribution

Pharmacological and neurochemical evidence suggest that brain dopamine systems, and the dopamine transporter in particular, contribute significantly to the behavioral effects and reinforcing properties of cocaine. The first objective of this study was to determine whether the brain distribution of cocaine supports these conclusions. A high resolution neuroanatomical map of cocaine disposition in brain after i.v. administration was developed. [3H]Cocaine ([3H](-)-cocaine) was administered to squirrel monkeys (Saimiri sciureus) at a trace dose (0.001 mg/kg) and at doses at or above the threshold for producing behavioral effects (0.1 mg/kg, 0.3 mg/kg). After 15 min, ex vivo autoradiography revealed the highest accumulation of [3H]cocaine in dopamine-rich brain regions, including the caudate nucleus, putamen, and nucleus accumbens/olfactory tubercle. The norepinephrine-rich locus coeruleus, the hippocampus, and amygdala also accumulated large quantities of [3H]cocaine. Moderately high levels were found in the stria terminalis, medial septum, substantia nigra, and other regions. Lowest levels were found in the cerebellum. A high and positive correlation was established for the brain distribution of [3H]cocaine administered at trace or at behaviorally relevant doses (r: 0.94; P < 0.001). To determine whether radioactivity represented [3H]cocaine or its metabolic products, tissue extracts from brain regions with high levels of cocaine were subjected to thin layer chromatography using two solvent systems. In caudate-putamen, nucleus accumbens, cortex, and hippocampus, radioactivity comigrated with standard [3H]cocaine. In substantia nigra, less than 70% of the radioactivity comigrated with [3H]cocaine, suggesting that cocaine metabolites are generated more rapidly in the substantia nigra than in other brain regions. The second objective was to determine the brain distribution of mazindol, a potent norepinephrine and dopamine transport inhibitor with low abuse liability in humans. The disposition of intravenously administered [3H]mazindol in brain (0.001 mg/kg, 0.007 mg/kg) was surveyed by ex vivo autoradiography. In sharp contrast to [3H]cocaine distribution, the highest accumulation of [3H]mazindol was localized in the norepinephrine-rich pineal gland, discrete regions of the hypothalamus (paraventricular nucleus, supraoptic nucleus), and the locus coeruleus. Moderately high levels were detected in the caudate-putamen, nucleus accumbens, and other regions. The following conclusions were drawn: (1) Although dopamine-rich brain regions are principal targets of cocaine after i.v. administration to the nonhuman primate, other prominent targets of cocaine (locus coeruleus, hippocampus, and amygdala) may contribute to the acute and chronic effects of cocaine.(ABSTRACT TRUNCATED AT 400 WORDS)

Cocaine metabolites in the neonate: potential for toxicity

Recent reports indicate that cocaine metabolites have biologic activity and could be toxic. To explore this possibility, two studies were initiated. The first study aimed to define the distribution of cocaine species by quantifying levels of cocaine and its metabolites norcocaine, benzoylecgonine, and benzoylnorecgonine in newborn cord blood and meconium. The second study sought to determine whether they produced a clinical effect. Compared to cord blood, meconium had a greater number of metabolites and a higher concentration of cocaine metabolites, including the previously undetectable norcocaine and benzoylnorecgonine derivatives. Benzoylecgonine was the most common species found in both sources and was usually lower in concentration in blood. An inverse relation existed between meconium benzoylecgonine levels and the serum catabolic enzyme pseudocholinesterase, implying genetic variability in cocaine metabolism. To determine whether cocaine and/or its metabolites could be linked to a distinct clinical state, a second study focusing on newborn behavior was performed with an independent large cohort of cocaine-exposed infants. Neonates with increased signs of "neuroexcitation" had benzoylecgonine and no cocaine in urine, whereas lethargic neonates had detectable urinary cocaine. These findings support the hypothesis that cocaine metabolites, especially benzoylecgonine, may play a role in altering newborn behavior and produce a clinical syndrome distinct from that related to the parent compound.

Evaluation of the monoamine uptake site ligand [123I]methyl 3 beta-(4-iodophenyl)-tropane-2 beta-carboxylate ([123I]beta-CIT) in non-human primates: pharmacokinetics, biodistribution and SPECT brain imaging coregistered with MRI

The in vivo properties of a new radioiodinated probe of the dopamine and serotonin transporter, [123I]methyl 3 beta-(4-iodophenyl)tropane-2 beta-carboxylate ([123I]beta-CIT) were evaluated in baboons and vervet monkeys. The labeled product was prepared in 65.2 +/- 2.8% yield (mean +/- SEM; n = 18) by reaction of the tributylstannyl precursor with [123I]NaI in the presence of peracetic acid followed by high pressure liquid chromatography (HPLC) purification to give a product with radiochemical purity of 97.5 +/- 0.5% and specific activity of 500-1200 Ci/mmol. After intravenous administration, whole brain activity peaked at 6-10% injected dose within 1 h post injection (p.i.) and washed out in a biphasic manner with clearance half-lives of 1-2 and 7-35 h for the rapid and slow components, respectively. Excretion occurred primarily through the hepatobiliary route, with about 30% of the injected dose appearing in the GI tract after 5 h. Estimates of radiation absorbed dose gave 0.01, 0.1, 0.2 and 0.03 mGy/MBq to the brain, gall bladder wall, lower large intestine wall and urinary bladder wall, respectively. High resolution SPECT imaging in a baboon demonstrated high uptake of tracer in the region of the striatum (striatum:cerebellum ratio 4.0), in the hypothalamus (ratio 2.6) and in a midbrain region comprising raphe, substantia nigra and superior colliculus (ratio 2.0), with regional brain uptakes measured at 210 min p.i. of [123I]beta-CIT. The anatomical locations of the regions on the SPECT image were confirmed by coregistration with MRI. Plasma metabolites and pharmacokinetics were analyzed in baboons and vervets by ethyl acetate extraction and HPLC. The major metabolite was a polar, non-extractable fraction, which increased to > 50% of the plasma activity by 30-45 min p.i. A minor lipophilic (extractable) metabolite was also observed, increasing to about 4% at 2-3 h p.i. The plasma protein bound fraction, determined by ultrafiltration, was 74.8 +/- 1.4% (n = 6). The arterial input function was characterized by the sum of three exponential terms with half-lives of 0.3-1.7, 9.7-24.9 and 77-166 min, respectively, for the concentration of free parent compound. [123I]beta-CIT promises to be a useful marker for SPECT study of the monoamine uptake system in primate brain.

SPECT imaging of dopamine and serotonin transporters with [123I]beta-CIT: pharmacological characterization of brain uptake in nonhuman primates

Single photon emission computed tomography (SPECT) studies of regional kinetic uptake and pharmacological specificity of [123I]methyl 3 beta-(4-iodophenyl) tropane-2 beta-carboxylate ([123I]beta-CIT) were performed in nonhuman primates (n = 41). In control experiments, activity was concentrated in striatum and in hypothalamic/midbrain regions. Striatal uptake increased for 140-180 min and displayed stable levels thereafter. Striatal to cerebellar activity ratios were 7.3 +/- 0.9 (mean +/- SEM) at 300 min. About 75% of striatal uptake was displaceable by injection of nonradioactive beta-CIT. Hypothalamic/midbrain activity reached maximal levels at approximately 45 min. A slow washout phase followed this peak activity. Activities in frontal, occipital, and cerebellar regions were characterized by an early peak (20-30 min), followed by rapid washout. Displacement studies demonstrated that striatal uptake was associated with dopamine (DA) transporters, as it was displaced by GBR 12909, a selective DA uptake inhibitor, but not by citalopram, a selective serotonin (5-HT) uptake inhibitor. The inverse was true in the hypothalamic/midbrain area, suggesting that the uptake in this area was associated primarily with 5-HT transporters. Maprotiline, a selective norepinephrine uptake inhibitor, did not affect [123I]beta-CIT uptake. In vivo site occupancy ED50 values of cocaine, 2 beta-carbomethoxy-3 beta-(4-fluorophenyl)tropane (CFT), and beta-CIT were measured in the striatum with a stepwise displacement paradigm. In vivo ED50 values correlated strongly with in vitro IC50 values for binding to DA transporters. Infusion of high dose of L-DOPA (250 mumol/kg) failed to displace striatal [123I]beta-CIT binding, suggesting that the binding would not be affected by L-DOPA administration in Parkinsonian patients. However, studies performed with injection of d-amphetamine indirectly suggested that high synaptic levels of DA may compete with [123I]beta-CIT binding. These studies suggest that [123I]beta-CIT will be a useful SPECT tracer of DA and 5-HT transporters in living human brain.

Cocaine impairs gonadotropin secretion in oophorectomized monkeys

OBJECTIVE

Our objective was to determine whether cocaine alters gonadotropin secretion in oophorectomized monkeys.

STUDY DESIGN

Oophorectomized monkeys with elevated gonadotropin levels were chronically cannulated to allow blood sampling every 15 minutes. Monkeys received either saline solution or 2 or 4 mg/kg cocaine hydrochloride as an intravenous bolus. Other oophorectomized monkeys were pretreated with either saline solution or 4 mg/kg cocaine 2 hours before bolus gonadotropin-releasing hormone administration, and plasma luteinizing hormone and follicle-stimulating hormone levels were measured every 15 minutes for 3 hours. Monkeys were also given either saline solution or 4 mg/kg of cocaine with gonadotropin-releasing hormone simultaneously, and plasma gonadotropin levels were measured every 15 minutes for 3 hours. Serum luteinizing hormone and follicle-stimulating hormone levels were measured by radioimmunoassay.

RESULTS

Both doses of cocaine resulted in a significant decrease in luteinizing hormone levels compared with controls. Follicle-stimulating hormone levels were significantly decreased only with the 4 mg/kg dose of cocaine. There was no difference in luteinizing hormone and follicle-stimulating hormone responses to gonadotropin-releasing hormone in the cocaine-treated monkeys compared with saline solution-treated monkeys by using repeated-measures analysis of variance.

CONCLUSION

These findings demonstrate that acute cocaine administration to oophorectomized primates inhibits basal luteinizing hormone-follicle-stimulating hormone secretion but not gonadotropin-releasing hormone-stimulated luteinizing hormone and follicle-stimulating hormone release. In the absence of an effect on gonadotropin-releasing hormone-stimulated gonadotropin release, we conclude that the impaired luteinizing hormone-follicle-stimulating hormone secretion after cocaine administration is due in part to a direct effect of cocaine on gonadotropin-releasing hormone neurons or on hypothalamic neurotransmitter modulation of gonadotropin-releasing hormone release.

High-affinity binding of [125I]RTI-55 to dopamine and serotonin transporters in rat brain

RTI-55 (3 beta-(4-iodophenyl)tropan-2 beta-carboxylic acid methyl ester), one of the most potent inhibitors of dopamine uptake reported to date, was radioiodinated and tested as a probe for the cocaine receptor in Sprague-Dawley rat brain. Saturation and kinetic studies in the striatum revealed that [125I]RTI-55 bound to both a high- and low-affinity site. The Kd for the high-affinity site was 0.2 nM, while the Kd for the low-affinity site was 5.8 nM. The corresponding number of binding sites in the striatum was 37 and 415 pmol/g protein. The pharmacological profile of specific [125I]RTI-55 binding in the striatum was consistent with that of the dopamine transporter. Additionally, [125I]RTI-55 was found to bind with high affinity to the cerebral cortex. Scatchard analysis revealed a single high-affinity component of 0.2 nM with a density of 2.5 pmol/g protein. The pharmacological profile demonstrated by [125I]RTI-55 in the cerebral cortex matched that of the serotonin transporter. Autoradiographic analysis of sagittal brain sections with [125I]RTI-55 binding was consistent with these findings. Specific binding of [125I]RTI-55 was blocked by dopamine uptake inhibitors in areas rich in dopaminergic nerve terminals. Conversely, serotonin uptake inhibitors blocked the binding of [125I]RTI-55 in brain areas rich in serotonergic neurons. These results demonstrate that [125I]RTI-55 may be a very useful ligand for the dopamine and serotonin transporters.

Effects of cocaine on the brain-stem auditory evoked potential in the Long-Evans rat

The present study examined the effects of an acute psychoactive dose of cocaine hydrochloride (HCl) in the rat, using the brain-stem auditory evoked potential (BAEP) as an objective, quantitative measure of this substance's effects on brain and auditory electrophysiology. The animals were 8 adult Long-Evans rats (4 female, 4 male). BAEPs were recorded from skull screw electrodes during a baseline period as well as 30-90 min after cocaine HCl treatment (10 mg/kg, i.p.). Normothermia was maintained to control for possible temperature-related effects. Cocaine's effects on the BAEP were examined over a broad range of stimulus intensities (intensity profiles) and repetition rates (rate profiles). Cocaine prolonged latencies of several BAEP components at low stimulus intensities and shortened these latencies at high stimulus intensities. The average BAEP threshold was also increased by cocaine treatment. These results were not strong, but were suggestive of a recruitment type change in auditory function. Cocaine treatment had no convincing effects on the BAEP as a function of stimulus repetition rate.

Cocaine cue in pigeons: time course studies and generalization to structurally related compounds (norcocaine, WIN 35,428 and 35,065-2) and (+)-amphetamine

1 Pigeons trained to discriminate between the presence or absence of effects induced by cocaine hydrochloride (5.6 mg/kg) were tested for generalization with norcocaine and two phenyltropane analogues (WIN 35,428 and WIN 35,065-2). Separate dose-effect curves were obtained at different intervals after the injections so that possible changes both in potency and duration of action could be evaluated.2 Results showed that all of these drugs fully generalized to cocaine. The order of potency was WIN 35,428 > norcocaine > WIN 35,065-2 > cocaine when tested either at 15 or 60 min after injection. The cocaine-like effects were strongest for all drugs when tested 15 min after injection as compared to the tests at the 60 min interval. The decay of the cocaine-like stimulus effects occurred at about the same rate.3 Apomorphine (0.3, 0.56 and 1 mg/kg), morphine (3 and 5.6 mg/kg), Delta(9)-tetrahydrocannabinôl (0.3 and 0.56 mg/kg), and lysergic acid diethylamide (LSD-25, 0.056 and 0.1 mg/kg) did not induce more than 30% cocaine appropriate responses. (+)-Amphetamine produced 73% and 85% cocaine appropriate responses depending on the injection-test interval used, 15 and 30 min respectively.4 The amphetamine homologue, para-hydroxyamphetamine (3.8 mg/kg) did not generalize to cocaine. Tests with 30 mg/kg of procaine produced 40% cocaine appropriate responses. Cocaine is effective also when administered by gavage into the opening of the proventriculus.5 The use of the drug discrimination technique for studying structure activity relationships of drugs is discussed.

Influence of acid or alkaline treatment on tissue distribution and urinary excretion of (3H)-cocaine on acutely treated rats

The effects of acid (NH4Cl, 60 mg/kg) or alkaline (NaHCO3, 400 mg/kg) pretreatment on tissue disposition and urinary excretion of (3H)-cocaine and its metabolites were assessed in rats. Animals were decapitated 4 hr after 1.9 microCi in 40 mg/kg cocaine (Cl-) in experiments on the biological disposition and the plasma, brain, and liver were assayed. In experiments on urinary excretion, 10 microCi were given and urine was assayed after 18, 24, and 48 hr. Pretreatment with NH4Cl produced a decrease of rates of cocaine + norcocaine in the brain as well as of the polar metabolites (benzoylecgonine, ecgonine benzoylnorecgonine). Forty-eight hours after injection of (3H)-cocaine, NH4Cl produced an increase of the rates of cocaine and its metabolites in the urine. Pretreatment with NaHCO3 causes a decrease of total radioactivity (cocaine + metabolites) in the plasma and in the liver, as well as a decrease of the levels of cocaine + norcocaine in the liver, as well as an increase of the rate of polar metabolites that are excreted in the urine. These data suggest that the decrease of pH after acid treatment produces ionization of basic molecules; these do not penetrate as well in the tissues for which they have no affinity. As a consequence, the urinary excretion is more important. It is possible that alkaline treatment accelerates the excretion of cocaine and its metabolites because it increases diuresis.

Metabolism of norcocaine, N-hydroxy norcocaine and cocaine-N-oxide in the rat

1. The metabolism of [3H]norcocaine, N-hydroxy[3H]norcocaine and cocaine-N-oxide has been investigated in rats after i.v. injection. 2. The biological t 1/2 of norcocaine (dose 2 mg/kg i.v.) in plasma, liver and brain were 0.4, 1.6, 0.5 h, respectively and the compound was not detectable in the central nervous system 6 h after injection. The % dose of norcocaine excreted unchanged in urine and faeces in 96 h were 0.7 and 1.0, respectively. Benzoylnorecgonine, norecgonine, norecgonine methyl ester and an unidentified compound were excreted in urine. 3. The biological t 1/2 of N-hydroxynorcocaine (5 mg/kg i.v.) in brain and plasma were 0.3, 1.6 h respectively and only 1.3 and 1.6% of dose were excreted unchanged in urine and faeces in 96 h. N-Hydroxybenzoylnorecgonine and N-hydroxynorecgonine methyl ester were the major urinary metabolites. N-hydroxynorcocaine was not metabolized to norcocaine in vitro by liver microsomes. Doses of greater than 7.5 mg/kg i.v. resulted in death of rats by cardiorespiratory arrest. 4. Cocaine-N-oxide (50 mg/kg i.v.) yielded ecgonine-N-oxide methyl ester as its major metabolite; other minor metabolites were cocaine (0.5%), norcocaine (1%), benzoylecgonine, ecgonine, ecgonine-N-oxide, along with minor amounts of unmetabolized compound. Lethality of cocaine-N-oxide (100 mg/kg i.v.) was possibly due to metabolism to norcocaine and cocaine.

Alteration in pattern of EEG activities and convulsant effect of cocaine following chronic adminsitration in the rhesus monkey

The effects of chronic administration of high doses of cocaine were studied in monkeys (Ss) with electrodes implanted in the brain. The Ss were injected daily with cocaine at a minimal convulsant dose (MCD) during polygraphic recording of EEGs, eye movement, respiratory and heart rates. The initial cocaine MCDs ranged from 3.2 to 6.5 mg/kg i.v. in ten Ss and markedly increased on each successive day following repeated daily injection (75--100% increase within 5--12 days). The elevated daily cocaine MCD was maintained for 1.5--2 months, and thereafter it gradually decreased and stabilized at levels between 20 and 30% above baseline within 2 months. During this period, the duration of daily convulsions evoked by cocaine MCD markedly decreased and stabilized at a constant level (30--35 sec) along with the latency of convulsions. The pattern of daily convulsions evoked by cocaine MCD changed from multiple episodes of intermittent tonic-clonic convulsions, which occurred during the earlier stage (1--2 months) of chronic treatment, to a single episode of sustained tonic-clonic convulsion. The Ss became extremely placid and tame or were profoundly depressed in their overall behavior most of the time. Simultaneously, the Ss continuously showed persistent rhythmic slow waves (5--6 c/sec) predominantly in the neocortex and limbic system structures. The results strongly suggested that chronic cocaine administration at high doses caused relatively permanent alteration of EEGs and behavior in the Ss, and the limbic system structures played an important role in the effect.