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The cAMP signaling pathway has emerged as an important modulator of the pharmacological effects of ethanol. In this respect, the cAMP-dependent protein kinase has been shown to play an important role in the modulation of several ethanol-induced behavioral actions. Cellular levels of cAMP are maintained by the activity of adenylyl cyclases and phosphodiesterases. In the present work we have focused on ascertaining the role of PDE4 in mediating the neurobehavioral effects of ethanol. For this purpose, we have used the selective PDE4 inhibitor Ro 20-1724. This compound has been proven to enhance cellular cAMP response by PDE4 blockade and can be administered systemically. Swiss mice were injected intraperitoneally (i.p.) with Ro 20-1724 (0-5 mg/kg; i.p.) at different time intervals before ethanol (0-4 g/kg; i.p.) administration. Immediately after the ethanol injection, locomotor activity, loss of righting reflex, PKA footprint and enzymatic activity were assessed. Pretreatment with Ro 20-1724 increased ethanol-induced locomotor stimulation in a dose-dependent manner. Doses that increased locomotor stimulation did not modify basal locomotion or the suppression of motor activity produced by high doses of this alcohol. Ro 20-1724 did not alter the locomotor activation produced by amphetamine or cocaine. The time of loss of righting reflex evoked by ethanol was increased after pretreatment with Ro 20-1724. This effect was selective for the narcotic effects of ethanol since Ro 20-1724 did not affect pentobarbital-induced narcotic effects. Moreover, Ro 20-1724 administration increased the PKA footprint and enzymatic activity response elicited by ethanol. These data provide further evidence of the key role of the cAMP signaling pathway in the central effects of ethanol., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

In the central nervous system ethanol (EtOH) is metabolized into acetaldehyde by different enzymes. Brain catalase accounts for 60% of the total production of EtOH-derived acetaldehyde, whereas cerebral cytochrome P450 2E1 (CYP 2E1) produces 20% of this metabolite. Acetaldehyde formed by the activity of central catalase has been implicated in some of the neurobehavioral properties of EtOH, yet the contribution of CYP 2E1 to the pharmacological actions of this drug has not been investigated. Here we assessed the possible participation of CYP 2E1 in the behavioral effects of EtOH. Thus, we induced CYP 2E1 activity and expression by exposing mice to chronic acetone intake (1% v/v for 10 days) and examined its consequences on the stimulating and uncoordinating effects of EtOH (0-3.2 g/kg) injected intraperitoneally. Our data showed that 24 h after withdrawal of acetone brain expression and activity of CYP 2E1 was induced. Furthermore, the locomotion produced by EtOH was boosted over the same interval of time. Locomotor stimulation produced by amphetamine or tert-butanol was unchanged by previous treatment with acetone. EtOH-induced motor impairment as evaluated in a Rota-Rod apparatus was unaffected by the preceding exposure to acetone. These results indicate that cerebral CYP 2E1 activity could contribute to the locomotor-stimulating effects of EtOH, and therefore we suggest that centrally produced acetaldehyde might be a possible mediator of some EtOH-induced pharmacological effects., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Many people begin to experiment with alcohol during adolescence, an important developmental period during which sex differences in the effects of ethanol appear. In the present study we evaluated the effect of ethanol (0, 0.625, 1.25 or 2.5 g/kg) on the acquisition of a conditioned place preference (CPP) in early and late adolescent male and female mice. In addition, we assessed the capacity of ethanol to induce reinstatement of the CPP after its extinction. CPP was induced in early and late adolescent females with 2.5 g/kg, and in early adolescent males with 1.25 or 2.5 g/kg of ethanol. No CPP was observed in late adolescent males. Priming with ethanol reinstated the CPP induced by the highest dose in early adolescent male and early and late adolescent female mice. Our data suggest that early adolescents of both sex and late adolescent females are particularly vulnerable to the effects of ethanol., (Copyright © 2011 Elsevier Inc. All rights reserved.)

The antioxidant enzyme catalase by reacting with H(2)O(2), forms the compound known as compound I (catalase-H(2)O(2)). This compound is able to oxidise ethanol to acetaldehyde in the CNS. It has been demonstrated that 3-nitropropionic acid (3-NPA) induces the activity of the brain catalase-H(2)O(2) system. In this study, we tested the effect of 3-NPA on both the brain catalase-H(2)O(2) system and on the acute locomotor effect of ethanol. To find the optimal interval for the 3-NPA-ethanol interaction mice were treated with 3-NPA 0, 45, 90 and 135min before an ethanol injection (2.4mg/kg). In a second study, 3-NPA (0, 15, 30 or 45mg/kg) was administered SC to animals 90min before saline or several doses of ethanol (1.6 or 2.4g/kg), and the open-field behaviour was registered. The specificity of the effect of 3-NPA (45mg/kg) was evaluated on caffeine (10mg/kg IP) and cocaine (4mg/kg)-induced locomotion. The prevention of 3-NPA effects on both ethanol-induced locomotion and brain catalase activity by L-carnitine, a potent antioxidant, was also studied. Nitropropionic acid boosted ethanol-induced locomotion and brain catalase activity after 90min. The effect of 3-NPA was prevented by l-carnitine administration. These results indicate that 3-NPA enhanced ethanol-induced locomotion by increasing the activity of the brain catalase system.

The effects of the catalase inhibitor, 3-amino-1,2,4-triazole (AT), on maintenance of voluntary consumption of ethanol was tested in male Long-Evans rats. AT produced a dose-dependent reduction in ethanol intake but did not affect total fluid consumption. AT also produced a dose-dependent inhibition of brain catalase lasting throughout the drinking period. These results suggest a role for brain catalase in determining the level of ethanol intake in rats.

Stress effects vary with different environmental situations or stress intensities. The effects of restraint stress on locomotion and or corticosterone were examined. Rats were restrained for 0, 15, 30, 60, 90 or 120 min, subsequent locomotion was measured for 10 min. Rats were also sacrificed for corticosterone determinations. Restraint stress affects both variables. Locomotion was recorded in rats pretreated with naltrexone or vehicle prior to restraint of 15 or 60 min. Naltrexone influenced the effects of stress differentially. It did not affect the results following 15 min of restraint but suppressed locomotion after 60-min restraint to a level comparable to that found after 15 min. Treatment with ethanol (1.0, 1.5, 2.0 g/kg) prior to 15 or 60 min of restraint resulted in the prevention of hypomotility induced by 15-min stress. It also interacted nonadditively with 15-min stress on corticosterone release. No such interaction occurred with 60 min stress. Also, naltrexone made it possible to block the effect of ethanol on restraint-induced hypomotility. Results describe stress as a nonunitary concept. Its effects tend to vary with its duration. The differential interaction of stress with naltrexone and ethanol depending on its duration supports the above notion. Results further suggest recruitment of opioid systems in long duration stress (60 min).

The role of brain aldehyde dehydrogenase (ALDH) and acetaldehyde in mediating ethanol-induced locomotor activity was investigated using several enzyme inhibitors. Cyanamide, an ALDH inhibitor elevates blood acetaldehyde levels in the presence of ethanol. Concurrent administration with 4-methylpyrazole, an alcohol dehydrogenase inhibitor, prevents peripheral accumulation of acetaldehyde by cyanamide. Two hr prior to testing locomotor activity in open field boxes, 111 male Long Evans rats were pretreated with i.p. injections of saline (S+S), 4-methylpyrazole (4MP+S), cyanamide (S+C) or 4-methylpyrazole + cyanamide (4MP+C). Subjects then received i.p. injections of one of three doses of ethanol (0.4, 0.8 or 1.2 gm/kg) or saline vehicle one minute prior to testing in the open field and locomotor activity was recorded for a 10 min period. Locomotor activity of animals pretreated with cyanamide (S+C and 4MP+C) was significantly depressed compared to groups S+S and 4MP+S particularly at the two lower doses tested. These effects cannot be attributed to elevated blood acetaldehyde levels since pretreatment with 4MP+C prevented peripheral accumulation of acetaldehyde. A characteristic common to both cyanamide-treated groups was the inhibition of brain ALDH. It is therefore suggested that brain ALDH may play a role in the mediation of locomotor effects produced by ethanol. It is conceivable that ALDH plays this role by regulating the levels of acetaldehyde in brain.

Groups of water-deprived rats were exposed to acetaldehyde, ethanol or vehicle control. On the conditioning day, the animals were first presented with a solution of saccharin after which the animals that were exposed to acetaldehyde received ethanol and those exposed to ethanol received acetaldehyde. Saccharin was again presented on three more occasions (testing days) without injection of drug. Using the percentage change in saccharin consumed from the first presentation as a measure of aversion, it was found that exposure to acetaldehyde blocked the taste aversion conditioned by ethanol. Animals exposed to ethanol showed no aversion to the saccharin which was paired with a small dose of acetaldehyde, indicating a symmetrical relationship between ethanol and acetaldehyde at this dose. However, exposure with ethanol did not block the aversion produced by conditioning with larger doses of acetaldehyde. These results suggest that the mechanism underlying the smaller dose of the taste aversion conditioned with acetaldehyde may be central while the mechanism underlying the larger dose is probably peripheral.