Individual and combined effects of ethanol and cocaine on intracellular signals and gene expression

Prenatal cocaine exposure differentially causes vascular dysfunction in adult offspring

Epidemiological studies have shown a clear association of adverse intrauterine environment and an increased risk of cardiovascular diseases and hypertension in adult life. The present study tested the hypothesis that prenatal cocaine exposure causes reprogramming of vascular reactivity, leading to an increased risk of hypertension in adult offspring. Pregnant rats received cocaine (30 mg kg(-1) day(-1)) or saline from days 15 to 21 of gestational age, and experiments were conducted in 3-month-old offspring. Cocaine had no effect on the baseline blood pressure but significantly increased norepinephrine-stimulated blood pressure and decreased the baroreflex sensitivity in male but not female offspring. The cocaine treatment significantly increased norepinephrine-induced contractions in pressurized resistance-sized mesenteric arteries but not in aortas, which was primarily because of a loss of endothelial NO synthase-mediated inhibition and an enhanced Ca(2+) sensitivity in mesenteric arteries. In addition, the cocaine treatment significantly attenuated the endothelium-dependent relaxation in mesenteric arteries in male but not female offspring. Endothelial NO synthase protein levels in aortas but not mesenteric arteries were significantly increased in the cocaine-treated animals. However, cocaine significantly decreased phosphorylation levels of endothelial NO synthase in both aortas and mesenteric arteries. The results suggest that prenatal cocaine exposure programs vascular contractility via changes in endothelial NO synthase-regulated Ca(2+) sensitivity of myofilaments in the sex- and tissue-dependent manners in resistance arteries leading to an increased risk of hypertension in male offspring.

Ethanol-responsive genes: identification of transcription factors and their role in metabolomics

Transcription factors (TFs) and their combinatorial control on cis-regulatory elements play critical role in the co-expression of genes. This affects the interaction of genes in the transcriptome and thus may affect signals that cascade through cellular pathways. Using a combination of bioinformatic approaches, we sought to identify such common combinations of TFs in a set of ethanol-responsive (ER) genes and assess the role of ethanol in affecting multiple pathways through their co-regulation. Our results show that the metallothionein genes are regulated by TF motifs cAMP responsive element binding protein (CREB) and metal-activated transcription factor 1 and primarily involved in zinc ion homeostasis. We have also identified new target genes, Synaptojanin 1 and tryptophan hydroxylase 1, potentially regulated by this module. Altered arrangement of TF-binding sites in the module may direct the action of these and other target genes in intracellular signaling cascades, cell growth and/or maintenance. In addition to CREB, other key TFs identified are ecotropic viral integration site-1 and SP1. These modulate the contribution of the target ER genes in cell cycle regulation and apoptosis or programmed cell death. Multiple lines of evidence confirm the above findings and indicate that different groups of ER genes are involved in different biological processes and their co-regulation most likely results from different sets of regulatory modules. These findings associate the role of the ER genes studied and their potential TF modules with alcohol response pathways and phenotypes.

cis-Regulatory sequences of the genes involved in apoptosis, cell growth, and proliferation may provide a target for some of the effects of acute ethanol exposure

The physiological effects of alcohol are known to include drunkenness, toxicity, and addiction leading to alcohol-related health and societal problems. Some of these effects are mediated by regulation of expression of many genes involved in alcohol response pathways. Analysis of the regulatory elements and biological interaction of the genes that show coexpression in response to alcohol may give an insight into how they are regulated. Fifty-two ethanol-responsive (ER) genes displaying differential expression in mouse brain in response to acute ethanol exposure were subjected to bioinformatics analysis to identify known or putative transcription factor binding sites and cis-regulatory modules in the promoter regions that may be involved in their responsiveness to alcohol. Functional interactions of these genes were also examined to assess their cumulative contribution to metabolomic pathways. Clustering and promoter sequence analysis of the ER genes revealed the DNA binding site for nuclear transcription factor Y (NFY) as the most significant. NFY also take part in the proposed biological association network of a number of ER genes, where these genes interact with themselves and other cellular components, and may generate a major cumulative effect on apoptosis, cell survival, and proliferation in response to alcohol. NFY has the potential to play a critical role in mediating the expression of a set of ER genes whose interactions contribute to apoptosis, cell survival, and proliferation, which in turn may affect alcohol-related behaviors.

c-fos and cleaved caspase-3 expression after perinatal exposure to ethanol, cocaine, or the combination of both drugs

Poly-drug abuse during pregnancy is a major public health concern. The combined effects of cocaine and ethanol may be more injurious to the fetal nervous system than either drug alone. In order to identify areas of the brain vulnerable to concurrent exposure, we examined the expression of the immediate-early gene (IEG), c-fos, and cleaved caspase-3, the 'executioner' caspase in apoptosis. Pregnant rats were treated with either ethanol diet, cocaine binge, or both. At birth, the brains of fetuses exposed to cocaine exhibited an increase in Fos immunoreactivity in many brain regions. Prenatal exposure to ethanol did not increase Fos expression above that observed in control rats at early points after birth. However, Fos expression at 24 h after birth was higher after ethanol diet treatment in several brain regions, such as the amygdala, ventromedial hypothalamus, and medial thalamus. Only in the striatum did the combination of ethanol and cocaine cause greater Fos expression than either prenatal cocaine or ethanol alone. Increased cleaved caspase-3 expression was observed at the 24-h time point for both ethanol- and cocaine-exposed brains, most notably in the septum, retrosplenial cortex, and the hippocampus. Concurrent ethanol and cocaine exposure did not elevate cleaved caspase-3 expression beyond that of either drug alone. Analysis of the extent of c-fos and caspase-3 induction did not indicate a consistent relationship of expression in any of the drug treatment groups nor in any brain region. These results indicate that both prenatal cocaine and prenatal ethanol exposure increase Fos and cleaved caspase-3 expression in the developing brain in a time- and region-dependent manner, but that the combination of low-dose, chronic ethanol, and binge cocaine does not cause greater apoptosis.

Effects of single and dual administration of cocaine and ethanol on opioid and ORL1 receptor expression in rat CNS: an autoradiographic study

The co-abuse of cocaine and ethanol is common among human addicts and has been reported to produce a stronger increase of euphoria as compared to either drug given alone. Both cocaine and ethanol increase the extracellular dopamine concentration in the nucleus accumbens, a terminal region in the mesolimbic dopamine pathway. In addition, both cocaine and ethanol affect the endogenous opioid system, which in turn alters the activity of the mesolimbic dopamine pathway. We have carried out quantitative autoradiography mapping of the opioid receptors as well as the opioid receptor-like 1 receptor in the brains of rats treated with both single and dual cocaine and ethanol. Rats received acute cocaine, ethanol or both drugs in combination. Ethanol alone or in combination with cocaine modulated the receptor densities in rat central nervous system. The kappa receptor densities were generally decreased, while both the mu and the opioid receptor-like 1 receptors were up-regulated. The mu opioid receptor levels were mainly increased in non-cortical regions, whereas the opioid receptor-like 1 receptors were increased in cortical structures. No changes in delta opioid receptors were observed. Cocaine alone did not influence the receptor levels in any of the treatment groups.

HIV-1 infection in peripheral blood lymphocytes (PBLs) exposed to alcohol

Epidemiological and in vitro studies have implied that heavy alcohol consumption may increase an individual's risk of HIV-1 infection. To examine the role of alcohol in direct infection of T-cells, viral reverse transcripts and HIV-1 receptor expression were examined in infected peripheral blood lymphocytes (PBLs) pretreated with alcohol. PCR results showed that alcohol increased HIV-1 DNA in PBLs by at least 10-fold. Alcohol enhanced the expression of the CXCR4 chemokine co-receptor but not the major HIV-1 CD4 receptor. Pretreatment with alcohol was also associated with increased intracellular cAMP. Thus, alcohol may facilitate enhanced viral infection by increasing the availability of HIV-1 co-receptor. This effect is associated with increases in intracellular cAMP.

Regulation of tyrosine hydroxylase levels and activity and Fos expression during opioid withdrawal in the hypothalamic PVN and medulla oblongata catecholaminergic cell groups innervating the PVN

Morphine withdrawal increases the hypothalamic-pituitary-adrenocortical (HPA) axis activity, which is dependent on an hyperactivity of noradrenergic pathways innervating the hypothalamic paraventricular nucleus (PVN). However, the possible adaptive changes that can occur in these pathways during morphine dependence are not known. We studied the alterations in tyrosine hydroxylase (TH; the rate-limiting enzyme in catecholamines biosynthesis) immunoreactivity levels and TH enzyme activity in the rat NTS-A2/VLM-A1 noradrenergic cell groups and in the PVN during morphine withdrawal. In the same paradigm, we measured Fos expression as a marker of neuronal activation. TH and Fos immunoreactivity was determined by quantitative Western blot analysis, combined with immunostaining for TH and Fos for immunohistochemical identification of active neurons during morphine withdrawal. Dependence on morphine was induced by a 7-day s.c. implantation of morphine pellets. Morphine withdrawal was precipitated on day 8 by an injection of naloxone (5 mg/kg s.c.). Morphine withdrawal induced the expression of Fos in the PVN and NTS/VLM, which indicates an activation of neurons in these nuclei. TH immunoreactivity in the NTS/VLM was increased 90 min after morphine withdrawal, whereas there was a decrease in TH levels in the PVN at the same time point. Following withdrawal, Fos immunoreactivity was present in most of the TH-positive neurons of the A2 and A1 neurons. TH activity was measured in the PVN, a projection area of noradrenergic neurons arising from NTS-A2/VLM-A1. Morphine withdrawal was associated with an increase in the enzyme activity at different time points after naloxone-precipitated morphine withdrawal. The present results suggest that an increase in TH protein levels and TH enzyme activity might contribute to the enhanced noradrenergic activity in the PVN in response to morphine withdrawal.

Consequences of maternal cocaine on cerebral microvascular functions in piglets

Maternal cocaine abuse is associated with fetal and neonatal neurological abnormalities. Prolonged exposure to cocaine can induce blood flow disorders, growth restriction, and hypoxia in the newborn. We investigated the impact of chronic fetal cocaine exposure on cerebral microvascular reactivity and autonomic function in the piglets. Pregnant pigs received cocaine (1 mg/kg i.v.; twice weekly) or saline throughout the last trimester. Prenatal exposure to cocaine did not have any significant effect on the birth weight of the piglets as compared to the control. Following delivery, effects of recurrent prenatal cocaine exposure on cerebral microvascular functions were examined in piglets (3-6 days old). Pial arteriolar responses to applications of 5-hydroxytryptamine (5-HT), endothelin-1 (ET-1), and clonidine were examined using closed cranial windows. Functional effects of prenatal cocaine exposure on changes in mean arterial pressure (MAP) and pial arteriolar diameter induced by intracisternal injection (i.c.) of clonidine (1 microg/kg) were also determined. Topical applications of 5-HT, ET-1, and clonidine dose-dependently decreased pial arteriolar diameter in the control and these constrictions were significantly enhanced in the in utero cocaine-exposed piglets. Prenatal cocaine exposure did not have any significant effects on the resting MAP and heart rate as there were no differences between the groups. IC clonidine caused sustained decrease in MAP in both groups but the decrease was more pronounced in the cocaine than the control group. IC clonidine causes cerebral microvascular dilation coincident with the development of hypotension. Such dilation was severely attenuated in the cocaine group, even though the hypotension was much more pronounced than in the control. In conclusion, prenatal cocaine exposure resulted in attenuated autoregulatory vasodilation and potentiated responses to vasoconstrictor agents. The mechanisms behind the effects of in utero cocaine exposure on alteration of newborn cerebral functions need further investigation. Such actions may be important in development of cerebral pathologies associated with recurrent prenatal cocaine exposure.

Alcohol differentially affects c-Fos expression in the supraoptic nucleus of long-sleep and short-sleep mice

Ethanol administration in long-sleep (LS) and short-sleep (SS) mice results in a large number of Fos-IR neurons in the supraoptic nucleus (SON) in LS, and almost no Fos-IR neurons in the same nucleus in SS mice. In contrast, isotonic saline, hypertonic saline, with or without ethanol, resulted in a similar pattern of Fos-IR in both strains. These data indicate a differential effect of ethanol on c-Fos signaling specifically in the SON. Since the LS and SS mice were specifically selected for differential sensitivity to the sedative/hypnotic effects of ethanol, this differential in c-Fos activity may be causally implicated in their differential sensitivity to ethanol.

Individual and combined effects of ethanol and cocaine on the human dopamine transporter in neuronal cell lines

Concurrent use of cocaine and alcohol results in reinforced behavioral consequences, but the molecular mechanisms associated with the co-use of both drugs are not clear. We report here that a 24-h exposure of the human dopamine transporter (hDAT)-transfected mouse neuroblastoma N1E-115 cell line (6C6) to cocaine (1 microM), or ethanol (1%) or both, increased dopamine re-uptake by approximately 25, 29 and 44%, respectively. The same treatment also increased dopamine re-uptake by the hDAT-transfected mouse neuroblastoma Neuro2A cell line (3B7) by approximately 36, 41 and 77%, respectively. However, no increase of dopamine re-uptake was observed in the hDAT-transfected non-neuronal CHO cell line (10E9). These data support the hypothesis that the DAT may be a common neural substrate for cocaine and ethanol in dopaminergic neurons and it may be involved in the psychological effects of both addictions.

Changes in hypothalamic paraventricular nucleus catecholaminergic activity after acute and chronic morphine administration

The participation of hypothalamic noradrenaline in the expression of neuroendocrine signs of morphine withdrawal has been proposed. The present study in rats examined: (1) the relationships between corticosterone secretion and the possible modifications in noradrenaline and dopamine content and turnover in the hypothalamic paraventricular nucleus after acute and chronic morphine administration; (2) the changes in cyclic adenosine monophosphate (cAMP) levels in the paraventricular nucleus after the same treatments. The results showed that acute morphine injection in control rats increased corticosterone release, 3-methoxy-4-hydroxyphenylethylene glycol (MHPG) production, and noradrenaline turnover. Dopamine turnover in the paraventricular nucleus was decreased and the cAMP levels remained unchanged. In chronic morphine-treated rats, there was no elevation in noradrenaline turnover or in corticosterone secretion, indicating that tolerance developed to the acute effects of the opioid. Correspondingly, no alterations in dopamine turnover were observed when chronic morphine-treated rats were compared with control rats acutely injected with morphine. cAMP levels in the paraventricular nucleus were unchanged during the tolerant state. The results raise the possibility that noradrenergic afferents play a significant role in the alterations of paraventricular nucleus function and pituitary-adrenal axis activity in response to acute and chronic morphine and suggest that these modifications are not mediated through adenylate cyclase activation. The present data provide further support for the idea of adaptive changes in noradrenergic neurons projecting to the paraventricular nucleus during chronic morphine exposure.

Noradrenergic and dopaminergic activity in the hypothalamic paraventricular nucleus after naloxone-induced morphine withdrawal

Previous research has shown an increase in hypothalamo-pituitary-adrenal axis activity following naloxone administration to morphine-dependent rats. In the present study, we investigated the adaptive changes in the noradrenaline (NA) and dopamine (DA) systems in the hypothalamic paraventricular nucleus (PVN) during morphine dependence and withdrawal. Additionally, we examined the possible change in 3',5'-cyclic adenosine monophosphate (cAMP) levels in that nucleus under the same conditions. Rats were made dependent on morphine by morphine or placebo (naïve) pellet implantation for 7 days. On day 8, rat groups received an acute injection of saline or naloxone (1 mg/kg subcutaneously) and were decapitated 30 min later. NA and DA content as well as their metabolite production in the PVN were estimated by HPLC/ED. Both plasma corticosterone levels and cAMP concentration in the PVN were measured by RIA. Naloxone administration to morphine-dependent rats (withdrawal) induced a pronounced increase in the production of both the NA metabolite MHPG and the DA metabolite DOPAC and an enhanced NA and DA turnover. Furthermore, an increase in corticosterone secretion was observed in parallel to the changes in catecholamine turnover. However, no alterations in cAMP levels were seen during morphine withdrawal. These results raise the possibility that catecholaminergic afferents to the PVN could play a significant role in the alterations of PVN functions and consequently in the pituitary-adrenal response during morphine abstinence syndrome. These data provide further support for the idea of adaptive changes in catecholaminergic neurons projecting to the PVN during chronic morphine exposure.

Downregulation of kappa opioid receptor mRNA levels by chronic ethanol and repetitive cocaine in rat ventral tegmentum and nucleus accumbens

The combination of ethanol and cocaine is commonly abused by human addicts which has serious clinical consequences. Here, the effects of separately and concurrently administered ethanol and 'binge' cocaine on kappa opioid receptor (KOR) mRNA in the ventral tegmental area (VTA) and nucleus accumbens (NAc) of rats were studied. KOR mRNA was down-regulated in both brain regions during concurrent as well as separate treatment with these drugs. In the VTA, the most pronounced decrease was obtained following combined treatment with ethanol and 'binge' cocaine. In the NAc, the strongest decrease was observed in the 'binge' cocaine group. This profound decrease of KOR mRNA in regions important for brain reward suggests a potential role of the KOR system in the abuse of cocaine and ethanol.

Drugs of abuse and brain gene expression

Addictive drugs like cocaine, ethanol, and morphine activate signal transduction pathways that regulate brain gene expression. Such regulation is modulated by the presence of certain transcription factor proteins present in a given neuron. This article summarizes the effects of several addictive drugs on transcriptional processes contributing to the development of a drug-dependent state. The characterization of drug-induced changes in gene expression shows promise for improving our understanding of drug-addiction phenomena and cellular modes of cocaine, ethanol, and morphine action.

Cocaethylene: effects on brain systems and behavior

Cocaethylene is a psychoactive metabolite formed during the combined consumption of cocaine and ethanol. In this brief review, we discuss several well-characterized effects of this metabolite with an emphasis on the neurobiological and behavioral correlates of polydrug addiction. Included herein are the descriptions of some of the changes in trans-synaptic transmission and their relationship to pathological behaviors associated with a chronic, drug-dependent state that may be altered by the spatial or temporal dynamics of cocaethylene.

Cocaethylene synthesis in Drosophila

Cocaethylene is an active cocaine metabolite that targets mammalian neural reward pathways and thus contributes to the reinforcing and addictive properties of ethanol and cocaine. Using gas chromatography-mass spectrometry, we find that fruit flies (Drosophila melanogaster) possess a cellular mechanism through which cocaine can be converted to cocaethylene, presumably via ethanol-sensitive enzymes. These findings illustrate the striking similarity of gene products in humans and flies, which might reflect a homologous role in the metabolic inactivation of cocaine. Further, this conservation of metabolic steps suggests that Drosophila can be used to study cellular, molecular and biochemical processes leading to polydrug abuse and addiction.

Blood ethanol levels and adenylyl cyclase activity in lymphocytes of alcoholic patients

BACKGROUND

The adenylyl cyclase (AC) signal transduction pathway is a target of acute and chronic ethanol actions. This study examined whether AC activity in lymphocyte membranes of male alcoholic patients correlated with blood concentrations of ethanol.

METHODS

Patients (n = 13; mean age: 40 +/- 8 years) were studied on the day of admission (day 0) and 2 days later under detoxification. Moreover, 13 age-matched male healthy controls (mean age 40 +/- 9 years) were included. Lymphocyte membranes were prepared by differential centrifugation whereby blood ethanol was washed out. As a measure of AC activity the formation of cyclic adenosine monophosphate (cAMP) from adenosine triphosphate was determined without (basal activity) and with stimulation of the second messenger system by the guanosine triphosphate (GTP) analogue GTP gamma S (20 mumol/L) via the G-protein or by forskolin (100 mumol/L) acting directly on the AC enzyme.

RESULTS

On day 0, when ethanol blood concentrations were 38-100 mmol/L, we found a significant negative correlation between ethanol blood levels and stimulated AC activities. On day 2, the negative correlation with blood ethanol levels of day 0 had disappeared.

CONCLUSIONS

The consumption of ethanol affects the AC system in lymphocytes of alcohol-dependent patients by a persistent effect on the cAMP forming enzyme.

Behavior and drug measurements in Long-Evans and Sprague-Dawley rats after ethanol-cocaine exposure

Long-Evans and Sprague-Dawley rats show differential behavioral responses to cocaethylene, a metabolite derived from the simultaneous ingestion of ethanol and cocaine. Such differences may also be manifested when these outbred strains are exposed to ethanol and cocaine. To test this hypothesis, both strains were fed an ethanol-diet (8.7% v/v) in conjunction with cocaine (15 mg/kg) injections for 15 days. The following parameters were evaluated: (a) ethanol consumption, (b) cocaine-induced behavioral activity, (c) blood ethanol levels, (d) blood, liver, or brain cocaine and cocaethylene levels, and (e) liver catalase and esterase activity. We found that Long-Evans rats drank significantly more of the ethanol diet relative to the Sprague-Dawley line during the first few days of the test session. This rat phenotype also differed significantly from the Sprague-Dawley line in terms of behavioral activity after cocaine administration. Blood ethanol levels did not differ between strains. Similarly, we failed to detect strain-dependent differences in blood, liver, or brain cocaine levels as measured by gas chromatography/mass spectrometry. Cocaethylene levels, however, were higher in blood and brain of Long-Evans relative to Sprague-Dawley cohorts. Although the ethanol-cocaine regimen produced a marked suppression of catalase and esterase activity compared with control-fed rats, this suppression was roughly equivalent in both rat phenotypes. These data are discussed in the context of genotypic background and vulnerability to polysubstance abuse.

Effects of cocaethylene on dopamine and serotonin synthesis in Long-Evans and Sprague-Dawley brains

We examined the behavioral and neurochemical effects of cocaethylene treatment in Long-Evans (LE) and Sprague-Dawley (SD) rats. Cocaethylene-induced behaviors were significantly less in LE rats. Cocaethylene caused an inhibition of dopamine synthesis in the caudate nucleus and nucleus accumbens that was equivalent in both rat lines. Serotonin synthesis was also suppressed by cocaethylene treatment, however this phenomenon was less pronounced when compared with the effects on dopamine synthesis.

Activating properties of cocaine and cocaethylene in a behavioral preparation of Drosophila melanogaster

The use of Drosophila as a model to study the behavioral consequences of stimulant drugs was analyzed in an active preparation of decapitated Drosophila. Application of cocaine and cocaethylene to discrete nerve cord cells regulating motor programs of behavior produced striking patterns of behavioral activity in a concentration-related manner. In general, intense circling behavior and significant wing buzzing activity were distinguishable behavioral markers in flies treated with mM concentrations of cocaine or cocaethylene. The significant changes in motor behavior induced by stimulant drugs in decapitated flies were not reproduced by the application of apomorphine, a direct dopamine (DA) agonist, or octopamine, a naturally occurring transmitter in arthropods. Because both cocaine and cocaethylene interfere with DA reuptake in mammals, we characterized the role of DA receptors mediating increased stereotypy and motor behavior in flies. Coadministration of SCH-23390, a specific D1 receptor antagonist, significantly attenuated the behavior-activating properties of cocaine and cocaethylene in this active experimental preparation. Therefore, the receptor protein mediating the behavioral responses to stimulant drugs in Drosophila is pharmacologically similar to the mammalian D1 subtype. In rats, cocaine- and cocaethylene-induced behavioral activity is complex, with increasing evidence that the D1 receptor interacts significantly with N-methyl-D-aspartate (NMDA) receptor pathways to produce an altered behavioral phenotype. To further characterize additional receptor subtypes targeted by the actions of cocaine and cocaethylene, we pretreated flies with MK-801 and dextromethorphan. Both of these drugs are potent, selective noncompetitive NMDA receptor antagonists. Interestingly, MK-801 and dextromethorphan profoundly reduced the behavior-activating properties of cocaine and cocaethylene in Drosophila. Therefore, as in rats, the NMDA (and D1) receptor pathways in this arthropod represent obligatory targets for the behavioral effects of stimulant drugs.

Differential behavioral responses to cocaethylene of Long-Evans and Sprague-Dawley rats: role of serotonin

Cocaethylene is a neuroactive metabolite derived from the concurrent consumption of cocaine and ethanol. The effects of cocaethylene on locomotor activity, stereotypy, and rearing in Long-Evans and Sprague-Dawley rats were compared. A single cocaine injection (molar equivalent of 60 mumol/kg cocaethylene, intraperitoneal) elicited a robust series of motor output behaviors, including locomotion, stereotypy, and rearing over a 30-minute testing period in Long-Evans rats. In contrast, cocaethylene administration, under comparable testing conditions, produced no significant changes in locomotor and investigatory behaviors. Because cocaethylene has relatively little impact on serotonin (5-HT) reuptake as opposed to reuptake of dopamine, we pretreated Long-Evans rats with fluoxetine (10 mg/kg; i.p.), a selective 5-HT reuptake inhibitor. Fluoxetine profoundly augmented cocaethylene-stimulated behaviors in this rat phenotype. To examine whether other rat strains exhibit a similar response to cocaethylene, Sprague-Dawley rats were injected (i.p.) with cocaethylene and their behavior patterns monitored over a 30-minute testing period. Cocaethylene produced marked locomotor and exploratory behaviors in this strain, suggesting therefore that Long-Evans and Sprague-Dawley rat differ in their response to cocaethylene. To relate these behavioral differences to possible structural differences in the neuronal density of dopaminergic or serotonergic neurons, Long-Evans and Sprague-Dawley brains were evaluated for tyrosine hydroxylase and 5-HT immunocytochemistry. No gross morphological differences in neuronal architecture or density were found in the ventral tegmental area or dorsal raphe nucleus of the two rat phenotypes. These results indicate that two commonly used rat strains show a differential response to cocaethylene and the neurochemical basis for this behavioral difference may be related to synaptic 5-HT bioavailability.

Dopaminergic and glutamatergic mechanisms mediate the induction of FOS-like protein by cocaethylene

Cocaethylene is a psychoactive metabolite formed during the combined consumption of cocaine and ethanol. As this metabolite has many properties in common with cocaine, it is conceivable that cocaethylene administration may induce the activity of nuclear transcription factors that regulate the expression of late-response genes. Therefore, the temporal induction of FOS-like protein in rat brain was examined following IP administration of 60 micromol/kg cocaethylene. Immunoreactivity for the protein was detectable at 1 h in striatal neurons and had virtually disappeared 6 h after drug treatment. Administration of specific dopaminergic (SCH-23390; 0.5 mg/kg) and glutamatergic (MK-801; 1 mg/kg) receptor antagonists prior to cocaethylene indicated a significant role for dopamine (D1) and N-methyl-D-aspartate receptor subtypes in mediating the nuclear induction of the aforementioned transcription factor protein. In contrast, no significant effects on FOS-like protein in discrete neurons of the caudate putamen were found when spiradoline (U-62066), a kappa opioid-receptor agonist, was administered either IP (10 mg/kg) or directly (50 nmol) into the brain parenchyma. In addition, we uncovered a differential sensitivity of Long-Evans rats to the behavioral effects of cocaethylene, with the psychoactive metabolite producing significantly less behavioral activity (e.g., locomotion, rearing, and continuous sniffing) than that produced by cocaine (molar equivalent of 60 micromol/kg cocaethylene). These findings indicate both common and disparate effects of cocaethylene and its parent compound, cocaine, on receptor pathways that regulate target alterations in gene expression and drug-induced motor behavior.

Cocaethylene stimulates the secretion of ACTH and corticosterone and the transcriptional activation of hypothalamic NGFI-B

Cocaethylene is an active cocaine metabolite formed by hepatic carboxylesterases in the presence of alcohol. The effects of cocaethylene on the hypothalamic-pituitary-adrenal (HPA) axis were investigated in vivo using adrenocorticotropic hormone (ACTH) and corticosterone secretion as indices of peripheral stimulation. To ascertain the central effects of cocaethylene on discrete neurons of the paraventricular nucleus (PVN) of the hypothalamus, a specific cRNA probe was used to follow changes in the transcriptional activation of nerve growth factor I-B (NGFI-B), a member of the family of immediate-early genes. Intravenous (i.v.) injection of cocaethylene (16 mumol/kg) to rats produced a marked but transient increase in plasma levels of ACTH and corticosterone within 10 min of drug exposure. Secretion of these hormones was accompanied by elevated levels of NGFI-B mRNA detected 30 min after i.v. or intraperitoneal (i.p., 60 mumol/kg) cocaethylene administration. The transcriptional stimulation of this immediate-early gene within parvocellular secretory neurons was relatively brief in duration, returning to basal levels by 180 min after drug exposure. As expected both routes of cocaethylene administration produced an increase in locomotor activity compared to saline-vehicle rats, with no differences between i.v. or i.p. routes with respect to duration of behavioral activation. Taken together, these findings indicate that cocaethylene has neuroendocrine properties on its own, targeting a critical region of the brain that regulates stressful events in the body. This, combined with other neurochemical properties, points to the possibility of cocaethylene augmenting the effects of a drug-dependent state.