Selective deficits in appetitive conditioning as a consequence of ethanol withdrawal.

The acquisition of a conditioned response to a cue associated with a fearful event has been shown to be impaired in animals that had been repeatedly withdrawn from ethanol, but not in animals with the same chronic ethanol treatment but only a single withdrawal episode [D. N. Stephens et al. (2001) Eur. J. Neurosci., 14, 2023-2031]. Lesion studies have shown that the amygdala plays a vital role in this type of conditioning process. Here we investigate aspects of conditioning for appetitive reinforcers in operant tasks, also shown to rely on amygdala processing, in rats following repeated withdrawal from ethanol. Rats were chronically treated with either an ethanol-containing liquid diet for 24 days continuously (single withdrawal) or interspersed with 2 x 3-day withdrawal periods (repeated withdrawal), or with a control diet (control). Two weeks after the final withdrawal, operant training began. In tasks that are impaired by lesions of the basolateral amygdala, conditioned reinforcement and reinforcer devaluation, there was no effect of chronic ethanol treatment or withdrawal on acquisition or performance. However, in a task that is dependent upon functioning of the central nucleus of the amygdala, Pavlovian-to-instrumental transfer, the single and repeated withdrawal groups were significantly impaired. Therefore, chronic ethanol treatment and withdrawal resulted in deficits in behavioural tasks that are sensitive to central but not to basolateral amygdala lesions, and may reflect different sensitivities of these areas to ethanol.

[Effect of the novel dipeptide nootropic agent noopept and its metabolite cyclo-L-prolylglycine on the transcallosal evoked potential in the rat brain]. / Vliianie novogo dipeptidnogo nootropa noopepta i ego metabolita tsiklo-L-propilglitsina na transkallozal'nyi vyzvannyi potentsial mozga krys.

The effect of new nootropic dipeptides--noopept (N-phenylacetyl-L-prolylglycine, GVS-111) and its metabolite (cyclo-L-prolylglycine)--and a standard nootrope piracetam on the transcallosal evoked potential (TEP) in rat brain was studied. In the dose range from 150 to 300 mg/kg, piracetam increased the TEP amplitude, which exhibited a maximum after 1.5-2 h and then gradually decreased. Both noopept and cyclo-L-prolylglycine also increased the TEP amplitude, which attained a plateau and retained this level over the entire observation time (above 3.5 h). All the nootropes studied increased both components of the evoked potential. Piracetam and cyclo-L-prolylglycine led to an approximately equal increase in both waves, while noopept induced a somewhat greater increase in the negative TEP wave amplitude. It is suggested that the positive effect of noopept and cyclo-L-prolylglycine upon the interhemispheric signal transfer (indicated by the improved transcallosal response) can be considered as a potential neurophysiological basis for a positive drug influence on the behavioral level.

Effect of nooglutil on benzodiazepine withdrawal syndrome and binding of 3H-spiperone with D2 receptors in rat striatum.

A new nootropic preparation nooglutil (N-(5-oxynicotinoyl)-L-glutamic acid), a positive modulator of AMPA receptors for glutamate, administered intraperitoneally in a dose of 70 mg/kg reduced anxiety of rats in the Vogel conflict test after 24-h withdrawal from chronic diazepam treatment (4 mg/kg intraperitoneally for 45 days). Nooglutil (5 nM-750 microM) had no effect on in vitro binding of (3)H-spiperone in intact rats. Systemic administration of 50 mg/kg nooglutil in vivo increased the dissociation constant and density of D(2)receptors. Increasing the dose to 100 mg/kg abolished this effect. Our findings suggest that nooglutil produces an indirect effect on the brain dopaminergic system under normal and pathological conditions and this effect is probably mediated via the glutamatergic system.

[The nootropic and anxiolytic properties of different doses of piracetam]. / Nootropnye i anksioloiticheskie svoistva raznykh doz piratsetama.

The effect of piracetam at various doses on the behavioral and electrophysiological characteristics was studied, including the development of passive and active avoidance conditional reflexes in rats, their behavior in conflict situations, and the transcallosal evoked response (TER) in rabbit brain. In the dose range from 50 to 300 mg/kg, piracetam improved the avoidance performance of both types and produced a dose-dependent increase in the TER amplitude, but did not affect the behavior of rats in conflict situations. As the drug dose was increased to 400-1000 mg/kg, the positive learning influence disappeared (sometimes the effect was even negative) and the TER increase changed to decrease. In contrast, the conflict situation tests revealed pronounced anxiolytic activity of piracetam at elevated doses. Thus, the nootropic and anxiolytic effects of piracetam (and, probably, of the other tranquilizers as well) do not coexist and are significantly shifted relative to one another on the dose scale, being probably realized via different mechanisms.

[Is "scopolamine-induced amnesia" in rats the result of state-dependent learning?]. / Iavliaetsia li "skopolaminovaia amneziia" u krys rezul'tatom oblucheniia, zavisiiashchego ot sostoianiia?

The effects of a single and repetitive administration of m-cholinoblocker scopolamine (Sc) to male rats on retention of step-through passive avoidance (PA) or active avoidance (AA) in a shuttle-box were compared. In case of PA Sc (1 mg/kg) was injected i.p. only 30 min before training, only 30 min before testing, or both before training and before testing. In case of AA Sc (0.5 mg/kg/day) was injected i.p. only 15 min before each training session or both before training and before testing (44 days after achievement of learning criterion). The PA and AA retention were impaired only in the experiments, where the drug was administered before training, but did not differ from control, when Sc was injected twice. The Sc-induced amnesia (like many other cases of memory deficits) is suggested to be a manifestation of state-dependent learning. Similarity between the brain state during memory consolidation and during the retention test is necessary for recollection.

[The effect of the new nootropic dipeptide GVS-111 in different functional disorders of the escape reaction]. / Effekt novogo nootropnogo dipeptida GVS-111 pri razlichnykh funktsional'nykh narusheniiakh reaktsii izbeganiia.

The authors studied the effect of a new nootropic agent with anxiolytic properties GVS-111 (ethyl ether N-phenylacetyl-L-prolylglycine) on formation of the avoidance reaction (AR) in rats and its functional disorders which were induced by two methods. In one case the stereotype of the relations between the stimulus, reaction and its consequence which developed during the experiment were urgently disturbed: the change of the animal to the other half of the chamber in response to a conditioned stimulus did not lead to its cutting off and prevention of the electropain stimulation for three successive combinations (AR error). In another case the spatial stereotype of the experiment was altered by changing the place of the opening through which the animal avoided the stimulus (spatial remodeling). Intraperitoneal injection of GVS-111 (0.1 mg/kg/day) improved the learning, but the effect differed from experiment to experiment. Along with this, the dipeptide prevented AR disturbance during the error and quickened restoration of the habit in spatial remodeling. It was shown earlier that AR disorders during an error are prevented by anxiolytics and nootropic agents but during spatial remodeling only by nootropic agents. It may be assumed that the positive effect of GSV-111 on AR in functional disorders is due to its nootropic effect.