Prior repeated exposure to a 5-HT3 receptor agonist does not alter the ethanol-induced conditioned taste aversion in rats

Asymmetric serial interactions between ethanol and cocaine in taste aversion learning

Although the interaction between ethanol and cocaine is well documented, it has generally been limited to situations in which the two drugs are given concurrently. Little exists on the interaction between ethanol and cocaine when one drug is given prior to the other. In Experiment 1, female Long-Evans rats were given five exposures to ethanol (2 g/kg ip) or vehicle prior to taste aversion conditioning with cocaine (32 mg/kg sc) for a total of five conditioning trials. In Experiment 2, rats were given five exposures to cocaine (32 mg/kg sc) or vehicle prior to taste aversion conditioning with ethanol (2 g/kg ip) for a total of five conditioning trials. Ethanol-preexposed, cocaine-conditioned animals (Experiment 1) displayed attenuated aversions to the cocaine-associated solution, drinking significantly greater amounts of saccharin than vehicle-preexposed, conditioned subjects. Conversely, cocaine-preexposed, ethanol-conditioned animals (Experiment 2) displayed robust aversions to the ethanol-associated solution, drinking levels comparable to those consumed by vehicle-preexposed, conditioned subjects and drinking significantly less than controls. Although the basis for these asymmetric effects is not known, they may have implications for abuse vulnerability in that drug history may impact subsequent drug toxicity that, in turn, may alter drug acceptability.

Ethanol preexposure attenuates the interaction of ethanol and cocaine in taste aversion learning

Although the potentiating effects of ethanol and cocaine have been well documented, little has been reported regarding the effects of ethanol or cocaine history on this interaction. In the present study, female Long-Evans rats received five exposures to ethanol (3.5 g/kg ip) or vehicle prior to taste aversion conditioning in which a novel saccharin solution was paired with either ethanol (0.56 g/kg ip), cocaine (25 mg/kg sc) or the combination (or the drugs' vehicle) for a total of five conditioning trials. Nonpreexposed subjects conditioned with the ethanol/cocaine combination displayed aversions, drinking levels significantly less than nonpreexposed subjects conditioned with either drug alone. Further, the aversions produced by the combination were greater than the sum of the aversions produced by ethanol and cocaine, alone. Ethanol-preexposed animals conditioned with the combination displayed an attenuated aversion, drinking significantly greater amounts of saccharin than nonpreexposed conditioned subjects and not differing from controls. Although the basis for the attenuation by ethanol of the aversions induced by the drug combination is not known, the present findings may have implications for the use and abuse of the combination in that alcohol history may reduce the subsequent toxicity of the combination that in turn may affect its acceptability.

5-HT(3) receptor antagonists and anxiety; a preclinical and clinical review

The present paper reviews the evidence for anxiolytic activity of 5-HT(3) receptor antagonists in animal models of anxiety and in clinical trials in humans. Compared to the established anxiolytics (benzodiazepine receptor agonists and, to a lesser extent, 5-HT(1A) receptor agonists) 5-HT(3) receptor antagonists display a different anxiolytic profile. They are anxiolytic in a limited number of animal anxiety models. If active, they often are very potent and display bell-shaped dose response curves, whereas the ratio between therapeutic activity and side effects appears remarkably large. 5-HT(3) receptor antagonists remain active after chronic dosing and no indications for tolerance, dependence or rebound effects were found, which seems to make these drugs an attractive alternative to the benzodiazepines. However, the large body of animal data indicating a complete lack of psychotropic activity of 5-HT(3) receptor antagonists weakens the prediction of anxiolytic activity in these drugs. Human data are also controversial; some investigators have reported positive effects in anxiety disorders (panic disorder, GAD), others did not. It can be concluded that 5-HT(3) receptor antagonists do not represent a breakthrough in the treatment of various anxiety disorders, as initially suggested.