Involvement of monoaminergic targets in the antidepressant- and anxiolytic-like effects of the synthetic alkamide riparin IV: Elucidation of further mechanisms through pharmacological, neurochemistry and computational approaches.

Despite recent advances, current antidepressants have considerable limitations: late onset of action and the high profile of refractoriness. Biomedical research with natural products has gained growing interest in the last years, and had provide useful candidates for new antidepressants. Riparins are a group of natural alkamides obtained from Aniba riparia, which had marked neuroactive effects, mainly as antidepressant and antinociceptive agents. We made modifications of the basic structure of riparins, originating a synthetic alkamide, also known as riparin IV (RipIV). RipIV demonstrated a superior analgesic effect than its congeners and a marked antidepressant-like effect. However, the basic mechanism for the central effects of RipIV remains unknown. Here, we aimed to investigate the participation of monoaminergic neurotransmission targets in the antidepressant-like effects of RipIV. To do this, we applied a combined approach of experimental (classical pharmacology and neurochemistry) and computer-aided techniques. Our results demonstrated that RipIV presented antidepressant- and anxiolytic-like effects without modifying locomotion and motor coordination of mice. Also, RipIV increased brain monoamines and their metabolite levels. At the higher dose (100 mg/kg), RipIV increased serotonin concentrations in all studied brain areas, while at the lower one (50 mg/kg), it increased mainly dopamine and noradrenaline levels. When tested with selective receptor antagonists, RipIV antidepressant effect showed dependence of the activation of multiple targets, including D1 and D2 dopamine receptors, 5-HT2A/2, 5-HT3 receptors and α2 adrenergic receptors. Molecular docking demonstrated favorable binding conformation and affinity of RipIV to monoamine oxidase B (MAO-B), serotonin transporter (SERT), α1 receptor, D2 receptor, dopamine transporter (DAT) and at some extent GABA-A receptor. RipIV also presented a computationally predicted favorable pharmacokinetic profile. Therefore, this study demonstrated the involvement of monoaminergic targets in the mechanism of RipIV antidepressant-like action, and provide evidence of it as a promising new antidepressant.

Anxiolytic-like effects of standardized extract of Justicia pectoralis (SEJP) in mice: Involvement of GABA/benzodiazepine in receptor.

Justicia pectoralis (Acanthaceae) is used as an antiinflammatory, antimicrobial and bronchodilator, and its extract exerts an anxiolytic-like effect profile in animal models. This work presents the behavioral effects of an aqueous standardized extract of Justicia pectoralis (SEJP) in animal models, such as the elevated plus maze (EPM), light/dark, open field, rota rod and pentobarbital sleep time. The extract was administered intragastrically to male mice at single doses of 50, 100 and 200 mg/kg, while diazepam 1 or 2 mg/kg was used as a standard drug and flumazenil 2.5 mg/kg was used to evaluate the participation of benzodiazepinic receptors. The results showed that, similar to diazepam (1 mg/kg), SEJP significantly modified all the observed parameters in the EPM test, without altering the general motor activity in the open field, rota rod and pentobarbital sleep time tests. Flumazenil reversed not only the diazepam effect but also the SEJP effect. In the same way, all doses of SEJP increased the time of permanence in the light box in the light/dark test. The results showed that SEJP presented an anxiolytic-like effect, disproving sedative effects.

Implications of efavirenz for neuropsychiatry: a review.

Antiretroviral therapy has revolutionized the treatment of the human immunodeficiency virus because it has improved the clinical outcomes of patients. It is essential that these drugs cross the blood-brain barrier, since the virus is present in the central nervous system (CNS). Efavirenz passes through this barrier satisfactorily and can reduce the deleterious central effects of the human immunodeficiency virus. However, patients treated with efavirenz have been observed to experience psychiatric symptoms such as mania, depression, suicidal thoughts, psychosis, and hallucinations. The aim of this review is to describe the pharmacokinetic and pharmacodynamic properties of efavirenz and its major neuropsychiatric symptoms and the neurochemical pathways associated with these changes in the CNS. The databases Medline and Lilacs were used to search for review articles and preclinical and clinical research articles published from January 1996 to 2010. The search terms used were efavirenz, central nervous system, neuropsychiatry, neurotransmitters, adverse effects, and neurochemistry. Subject categories considered included effects on viral replication, pharmacokinetic and pharmacodynamic properties of efavirenz, and neuropsychiatric adverse effects including time course, duration, and probable mechanisms involved. The mechanisms involved in these changes include interference with cytochrome P450 enzymes, cytokines, tryptophan-2-3-dioxygenase, and brain creatine kinase.

Study pharmacologic of the GABAergic and glutamatergic drugs on seizures and status epilepticus induced by pilocarpine in adult Wistar rats.

This work was designed to study the influence of drugs during seizures and status epilepticus (SE) induced by pilocarpine and mortality in adult rats. Glutamate (10 and 20 mg/kg), N-methyl-d-aspartate (NMDA, 5 and 10 mg/kg), ketamine (1.5 and 2.0 mg/kg), gabapentin (200 and 250 mg/kg), phenobarbital (50 and 100 mg/kg) and vigabatrin (250 and 500 mg/kg) were administered intraperitoneally, 30 min prior to pilocarpine (400 mg/kg, i.p.). The animals were observed (24 h) to determine: number of peripheral cholinergic signs, tremors, stereotyped movements, seizures, SE, latency to first seizure and number of deaths after pilocarpine treatment. NMDA and glutamate had pro-convulsive effects in both doses tested. Smaller and higher doses of these drugs no protected and increased pilocarpine-induced seizures and/or mortality. Gabapentin, vigabatrin, phenobarbital and ketamine protected against seizures and increased the latency to first seizure. Thus, these results suggest that caution should be taken in the selection of pharmacotherapy and dosages for patients with seizures and SE because of the possibility of facility the convulsive process toxicity, SE and the mortality of adult animals in this seizures model that is similar temporal lobo epilepsy in humans.

Effects of levetiracetam in lipid peroxidation level, nitrite-nitrate formation and antioxidant enzymatic activity in mice brain after pilocarpine-induced seizures.

: Oxidative stress has been implicated in a large number of human degenerative diseases, including epilepsy. Levetiracetam (LEV) is a new antiepileptic agent with broad-spectrum effects on seizures and animal models of epilepsy. Recently, it was demonstrated that the mechanism of LEV differs from that of conventional antiepileptic drugs. Objectifying to investigate if LEV mechanism of action involves antioxidant properties, lipid peroxidation levels, nitrite-nitrate formation, catalase activity, and glutathione (GSH) content were measured in adult mice brain. The neurochemical analyses were carried out in hippocampus of animals pretreated with LEV (200 mg/kg, i.p.) 60 min before pilocarpine-induced seizures (400 mg/kg, s.c.). The administration of alone pilocarpine, 400 mg/kg, s.c. (P400) produced a significant increase of lipid peroxidation level in hippocampus. LEV pretreatment was able to counteract this increase, preserving the lipid peroxidation level in normal value. P400 administration also produced increase in the nitrite-nitrate formation and catalase activity in hippocampus, beyond a decrease in GSH levels. LEV administration before P400 prevented the P400-induced alteration in nitrite-nitrate levels and preserved normal values of catalase activity in hippocampus. Moreover, LEV administration prevented the P400-induced loss of GSH in this cerebral area. The present data suggest that the protective effects of LEV against pilocarpine-induced seizures can be mediated, at least in part, by reduction of lipid peroxidation and hippocampal oxidative stress.

Effect of gabaergic, glutamatergic, antipsychotic and antidepressant drugs on pilocarpine-induced seizures and status epilepticus.

This work was designed to study the influence of drugs during seizures and status epilepticus (SE) induced by pilocarpine and mortality in adult rats. Fluoxetine (10 and 20 mg/kg), NMDA (N-methyl-D-aspartate, 10 and 20 mg/kg), amitriptyline (25 and 50 mg/kg), ketamine (0.5 and 1.0 mg/kg), gabapentin (100 and 150 mg/kg) and pimozide (10 and 20 mg/kg) were administered intraperitoneally, 30 min prior to pilocarpine (400mg/kg, s.c.). The animals were observed (24h) to determine: number of peripheral cholinergic signs, tremors, stereotyped movements, seizures, SE, latency to first seizure and number of deaths after pilocarpine treatment. Fluoxetine, amitriptyline, NMDA, and pimozide had proconvulsant effects in both doses tested. Smaller and higher doses of these drugs no protected and increased pilocarpine-induced seizures and/or mortality. Gabapentin and ketamine protected against seizures and reduced the latency to first seizure. Thus, these results suggest that caution should be taken in the selection of pharmacotherapy and dosages for patients with epilepsy because of the possibility of potentiating convulsive process toxicity.

Pharmacological studies of the opioids, mood stabilizer and dopaminergic drugs on pilocarpine-induced seizures and status epilepticus.

This work was designed to study the influence of drugs during seizures and status epilepticus (SE) induced by pilocarpine and mortality in adult rats. Morphine (0.1 and 0.2 mg/kg), SCH 23390 (0.1 and 0.2 mg/kg), haloperidol (5 and 10mg/kg) and lithium (30 and 60 mg/kg) were administered intraperitoneally (i.p.), 30 min before to pilocarpine (400 mg/kg, s.c.). The animals were observed (24 h) to determine: number of peripheral cholinergic signs, tremors, stereotyped movements, seizures, SE, latency to first seizure and number of deaths after pilocarpine treatment. Morphine and haloperidol had proconvulsant effects in both doses tested. Smaller and higher doses of these drugs no protected and increased pilocarpine-induced seizures, SE and/or mortality. SCH 23390 protected against seizures, increased the latency to first seizure and reduced the mortality of the animals treated with pilocarpine Theses results suggest that dopamine receptor system receptor subtypes exert opposite functions on the regulation of convulsive activity. The morphine is proconvulsant in lower doses. The opioids in high doses tested exert an action proconvulsant during the establishment of epileptic activity induce by pilocarpine. The lithium no protected the animals against seizures induced by pilocarpine and is used which a model of epilepsy associated with lower doses of pilocarpine in several studies, suggesting absence of the effect anticonvulsants in rodents.

Acetylcholinesterase activities in hippocampus, frontal cortex and striatum of Wistar rats after pilocarpine-induced status epilepticus.

Experimental manipulations suggest that in vivo administration of cholinergic agonists or inhibitors of acetylcholinesterase (AChE) increases the concentration of acetylcholine. Biochemical studies have proposed a role for AChE in brain mechanisms responsible by development to status epilepticus (SE) induced by pilocarpine. The present study was aimed at investigating the changes in AChE activities in hippocampus, striatum and frontal cortex of adult rats after pilocarpine-induced SE. The control group was treated with 0.9% saline (s.c., control group) and another group received pilocarpine (400 mg/kg, s.c.). Both groups were sacrificed 1 h after treatment. The results have shown that pilocarpine administration and resulting SE produced a significant decrease in the AChE activity in the hippocampus (63%), striatum (35%) and frontal cortex (27%) of adult rats. Our results demonstrated a direct evidence of a decrease in the activity of the AChE in rat brain regions during seizure activity that could be responsible by regulation of acetylcholine levels during the establishment of SE induced by pilocarpine.

Evaluation of levetiracetam effects on pilocarpine-induced seizures: cholinergic muscarinic system involvement.

Levetiracetam (LEV) is a new antiepileptic drug effective as adjunctive therapy for partial seizures. It displays a unique pharmacological profile against experimental models of seizures, including pilocarpine-induced seizures in rodents. Aiming to clarify if anticonvulsant activity of LEV occurs due to cholinergic alterations, adult male mice received LEV injections before cholinergic agonists' administration. Pretreatment with LEV (30-200 mg/kg, i.p.) increased the latencies of seizures, but decreased status epilepticus and death on the seizure model induced by pilocarpine, 400 mg/kg, s.c. (P400). LEV (LEV200, 200 mg/kg, i.p.) pretreatment also reduced the intensity of tremors induced by oxotremorine (0.5 mg/kg, i.p). [3H]-N-methylscopolamine-binding assays in mice hippocampus showed that LEV200 pretreatment reverts the downregulation on muscarinic acetylcholine receptors (mAChR), induced by P400 administration, bringing back these density values to control ones (0.9% NaCl, i.p.). However, subtype-specific-binding assays revealed that P400- and LEV-alone treatments result in M1 and M2 subtypes decrease, respectively. The agonist-like behavior of LEV on the inhibitory M2 mAChR subtype, observed in this work, could contribute to explain the reduction on oxotremorine-induced tremors and the delay on pilocarpine-induced seizures, by an increase in the attenuation of neuronal activity mediated by the M1 receptors.

Pilocarpine-induced status epilepticus: monoamine level, muscarinic and dopaminergic receptors alterations in striatum of young rats.

Behavioural changes, muscarinic and dopaminergic receptors density and levels of monoamines were measured in striatum of rats after pilocarpine-induced status epilepticus (SE). Wistar rats at the age of 21 days were treated with pilocarpine (400mg/kg; subcutaneously) whilst the control group was treated with 0.9% saline (s.c.). Both groups were sacrificed 1h following the treatment. SE induced a muscarinic receptor downregulation of 64% in pilocarpine group. This effect was also observed to be 57% in D(1) and 32% in D(2). In the dissociation constant (K(d)) values in muscarinic and D(1) receptor no alterations were verified. On the other hand, the K(d) value for D(2) was observed to increase 41%. High performance liquid chromatography determinations showed 63, 35, 77 and 64% decreases in dopamine, 3-methoxy-phenylacetic acid, serotonin and 5-hydroxyindoleacetic acid contents, respectively. The homovanilic acid level was verified to increase 119%. The noradrenaline content was unaltered. A direct evidence of monoamine levels alterations can be verified during seizure activity and receptor density changes appear to occur in an accentuated way in immature brain during the estabilishment of SE induced by pilocarpine.

Effects of chronic ethanol treatment on monoamine levels in rat hippocampus and striatum

We studied the effects of ethanol on concentrations of noradrenaline (NE), dopamine (DA) and serotonin (5-HT) and their metabolites in rat hippocampus and striatum. Ethanol (2 or 4 g/kg, po, from a 20 percent aqueous solution) was administered daily to male Wistar rats (4-13 per group) for 30 days and animals were sacrificed 30 min or 48 h after the last administration. Monoamines were measured by HPLC and considered significant at P < 0.05. A 47 percent increase in 5-HT levels was observed in the hippocampus with 4 g/kg ethanol in the 30-min protocol. Ethanol (2 and 4 g/kg) decreased DA (2114.5 ± 126.4 and 1785.1 ± 234.2 ng/g wet tissue, respectively) and 3,4-dihydroxyphenylacetic acid (DOPAC, 1477.6 ± 132.1 and 1218.8 ± 271.7 ng/g wet tissue, respectively) levels, while the higher dose also decreased NE (159.8 ± 13.5), 5-HT (228.0 ± 46.8) and 5-hydroxy-3-indoleacetic acid (5-HIAA, 304.4 ± 37.2 ng/g wet tissue), in the striatum after a 48-h withdrawal as compared to controls (DA: 3063.9 ± 321.3; DOPAC: 2379.6 ± 256.0; NE: 292.8 ± 50.2; 5-HT: 412.4 ± 36.2; 5-HIAA: 703.9 ± 61.4 ng/g wet tissue). In the 30-min protocol, ethanol (2 or 4 g/kg) decreased striatal NE (66 and 70 percent) and DA (50 and 36 percent) levels. On the other hand, increases were seen in 5-HIAA (146 and 153 percent) and 5-HT (59 and 86 percent) levels. Ethanol (2 g/kg, po) increased the homovanillic acid (HVA)/DA ratio (129 percent) in the striatum in the 30-min protocol, while at the higher dose it increased the HVA/DA ratio in the 48-h protocol (61 percent). These results indicate alterations in monoamines, mainly in the striatum, after chronic ethanol, which are influenced by dose and by the length of time after the last drug administration.

Effects of chronic ethanol treatment on monoamine levels in rat hippocampus and striatum.

We studied the effects of ethanol on concentrations of noradrenaline (NE), dopamine (DA) and serotonin (5-HT) and their metabolites in rat hippocampus and striatum. Ethanol (2 or 4 g/kg, po, from a 20% aqueous solution) was administered daily to male Wistar rats (4-13 per group) for 30 days and animals were sacrificed 30 min or 48 h after the last administration. Monoamines were measured by HPLC and considered significant at P < 0.05. A 47% increase in 5-HT levels was observed in the hippocampus with 4 g/kg ethanol in the 30-min protocol. Ethanol (2 and 4 g/kg) decreased DA (2114.5 +/- 126.4 and 1785.1 +/- 234.2 ng/g wet tissue, respectively) and 3,4-dihydroxyphenylacetic acid (DOPAC, 1477.6 +/- 132.1 and 1218.8 +/- 271.7 ng/g wet tissue, respectively) levels, while the higher dose also decreased NE (159.8 +/- 13.5), 5-HT (228.0 +/- 46.8) and 5-hydroxy-3-indoleacetic acid (5-HIAA, 304.4 +/- 37.2 ng/g wet tissue), in the striatum after a 48-h withdrawal as compared to controls (DA: 3063.9 +/- 321.3; DOPAC: 2379.6 +/- 256.0; NE: 292.8 +/- 50.2; 5-HT: 412.4 +/- 36.2; 5-HIAA: 703.9 +/- 61.4 ng/g wet tissue). In the 30-min protocol, ethanol (2 or 4 g/kg) decreased striatal NE (66 and 70%) and DA (50 and 36%) levels. On the other hand, increases were seen in 5-HIAA (146 and 153%) and 5-HT (59 and 86%) levels. Ethanol (2 g/kg, po) increased the homovanillic acid (HVA)/DA ratio (129%) in the striatum in the 30-min protocol, while at the higher dose it increased the HVA/DA ratio in the 48-h protocol (61%). These results indicate alterations in monoamines, mainly in the striatum, after chronic ethanol, which are influenced by dose and by the length of time after the last drug administration.

Monoamine levels after pilocarpine-induced status epilepticus in hippocampus and frontal cortex of Wistar rats.

Pilocarpine-induced status epilepticus (SE) is an useful model to study the involvement of neurotransmitter systems as epileptogenesis modulators. Some researches have shown that pharmacological manipulations in dopaminergic, serotonergic, and noradrenergic systems alter the occurrence of pilocarpine-induced SE. The control group was treated with 0.9% saline (control group, s.c.). Another group of rats received pilocarpine (400mg/kg, s.c.) and both groups were sacrificed 24 h after the treatment. This work was performed to determine the alterations in monoamine levels (dopamine (DA), serotonin (5-HT) and norepinephrine (NE)) and their metabolites (3,4-hydroxyphenylacetic acid (DOPAC), homovanilic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA)) after pilocarpine-induced SE in hippocampus and frontal cortex of adult rats. The monoamines and their metabolites were determined by reverse-phase high-performance liquid chromatography with electrochemical detection. DA and 5-HIAA concentrations were not altered in the hippocampus of the pilocarpine group, but in the same group the 5-HT (160%), DOPAC (316%) and HVA (21%) levels increased, whereas, the NE (47%) content declined. For the frontal cortex determinations, there was an increase of 20 and 72% in DA and DOPAC levels, respectively, and a decrease in NE (32%), 5-HT (33%) and 5-HIAA (19%) concentrations, but HVA content remained unaltered. These results indicate that pilocarpine-induced SE can alter monoamine levels in different ways depending on the brain area studied, suggesting that different mechanisms are involved.

Catalase activity in cerebellum, hippocampus, frontal cortex and striatum after status epilepticus induced by pilocarpine in Wistar rats.

The mechanism underlying the vulnerability of the brain to status epilepticus (SE) induced by pilocarpine remains unknown. Oxidative stress has been implicated in a variety of acute and chronic neurologic conditions, including SE. The present study was aimed at was investigating the changes in catalase activity after pilocarpine-induced seizures and SE. The Control group was treated with 0.9% saline (NaCl, subcutaneously (s.c.)) and sacrificed 1h after the treatment. Another group was treated with pilocarpine (400 mg/kg, s.c., Pilocarpine group) and sacrificed 1h after treatment. The catalase activity in the cerebellum, hippocampus, frontal cortex and striatum of Wistar rats was determined. The results have shown that pilocarpine administration and resulting SE produced a significant increase in the catalase activity in the hippocampus (36%), striatum (31%) and frontal cortex (15%) of treated adult rats. Nevertheless, in the adult rat cerebellum after SE induced by pilocarpine no change was observed in the catalase activity. Our results demonstrated a direct evidence of an increase in the activity of the scavenging enzyme (catalase) in different cerebral structures during seizure activity that could be responsible for eliminating oxygen free radicals and might be one of the compensatory mechanisms to avoid the development of oxidative stress during the establishment of SE induced by pilocarpine. Our reports also indicate clear regional differences in the catalase activity caused by pilocarpine-induced seizures and SE and the hippocampus might be the principal area affected and cerebellum does not modify for this parameter studied during epileptic activity.

Pilocarpine-induced status epilepticus in rats: lipid peroxidation level, nitrite formation, GABAergic and glutamatergic receptor alterations in the hippocampus, striatum and frontal cortex.

The aim of the study was to investigate the lipid peroxidation levels, nitrite formation, GABAergic and glutamatergic receptor densities in the hippocampus, frontal cortex and striatum of Wistar rats after seizures and status epilepticus (SE) induced by pilocarpine. The control group was treated with 0.9% saline and sacrificed 1 h after the treatment. One group of rats was administered with pilocarpine (400 mg/kg sc) and sacrificed 1 h after treatment. The result shows that pilocarpine administration and the resulting SE produced a significant increase of lipid peroxidation level in the hippocampus (46%), striatum (25%) and frontal cortex (21%). In nitrite formation, increases of 49%, 49% and 75% in hippocampus, striatum and frontal cortex, respectively, was observed. Pilocarpine treatment induced down-regulation of GABAergic receptors in the hippocampus (38%), striatum (15%) and frontal cortex (11%). However, with regard to glutamatergic receptor densities, increases in the hippocampus (11%), striatum (17%) and frontal cortex (14%) was observed during the observation period. These results show a direct evidence of lipid peroxidation and nitrite formation during seizure activity that could be responsible for the GABAergic and glutamatergic receptor concentration changes during the establishment of SE induced by pilocarpine.

Effect of one-week ethanol treatment on monoamine levels and dopaminergic receptors in rat striatum.

We studied the effects of ethanol on the levels of norepinephrine, dopamine, serotonin (5-HT) and their metabolites as well as on D1- and D2-like receptors in the rat striatum. Ethanol (2 or 4 g/kg, po) was administered daily by gavage to male Wistar rats and on the 7th day, 30 min or 48 h after drug administration, the striatum was dissected for biochemical assays. Monoamine and metabolite concentrations were measured by HPLC and D1- and D2-like receptor densities were determined by binding assays. Scatchard analyses showed decreases of 30 and 43%, respectively, in D1- and D2-like receptor densities and no change in dissociation constants (Kd) 48 h after the withdrawal of the dose of 4 g/kg. Ethanol, 2 g/kg, was effective only on the density of D2-like receptors but not on Kd of either receptor. Thirty minutes after the last ethanol injection (4 g/kg), decreases of D2 receptor density (45%) as well as of Kd values (34%) were detected. However, there was no significant effect on D1-like receptor density and a 46% decrease was observed in Kd. An increase in dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC), a decrease in norepinephrine, and no alteration in 5-HT levels were demonstrated after 48-h withdrawal of 4 g/kg ethanol. Similar effects were observed in dopamine and DOPAC levels 30 min after drug administration. No alteration in norepinephrine concentration and a decrease in 5-HT levels were seen 30 min after ethanol (4 g/kg) administration. Our findings indicate the involvement of the monoaminergic system in the responses to ethanol.

Effect of one-week ethanol treatment on monoamine levels and dopaminergic receptors in rat striatum

We studied the effects of ethanol on the levels of norepinephrine, dopamine, serotonin (5-HT) and their metabolites as well as on D1- and D2-like receptors in the rat striatum. Ethanol (2 or 4 g/kg, po) was administered daily by gavage to male Wistar rats and on the 7th day, 30 min or 48 h after drug administration, the striatum was dissected for biochemical assays. Monoamine and metabolite concentrations were measured by HPLC and D1- and D2-like receptor densities were determined by binding assays. Scatchard analyses showed decreases of 30 and 43 percent, respectively, in D1- and D2-like receptor densities and no change in dissociation constants (Kd) 48 h after the withdrawal of the dose of 4 g/kg. Ethanol, 2 g/kg, was effective only on the density of D2-like receptors but not on Kd of either receptor. Thirty minutes after the last ethanol injection (4 g/kg), decreases of D2 receptor density (45 percent) as well as of Kd values (34 percent) were detected. However, there was no significant effect on D1-like receptor density and a 46 percent decrease was observed in Kd. An increase in dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC), a decrease in norepinephrine, and no alteration in 5-HT levels were demonstrated after 48-h withdrawal of 4 g/kg ethanol. Similar effects were observed in dopamine and DOPAC levels 30 min after drug administration. No alteration in norepinephrine concentration and a decrease in 5-HT levels were seen 30 min after ethanol (4 g/kg) administration. Our findings indicate the involvement of the monoaminergic system in the responses to ethanol