Mario Sansone

Effects of repeated administration of chlordiazepoxide on spontaneous locomotor activity in mice

Spontaneous locomotor activity has been studied in mice treated with single or repeated doses (five daily injections) of chlordiazepoxide. The repeated administration enhanced the stimulatory action of the lower doses of the drug, while the depressant effect of the higher doses was reduced.

Effects of oxiracetam-nicotine combinations on active and passive avoidance learning in mice

Tested alone, in CD-1 mice, the nootropic drug oxiracetam (50 mg/kg) improved learning in a multitrial active avoidance task (shuttle-box), but did not affect one-trial passive avoidance acquisition. Nicotine, which was ineffective at the dose of 0.25 mg/kg, improved both active and passive avoidance at the dose of 0.5 mg/kg; 1 mg/kg nicotine still exerted facilitating effects on passive avoidance, but slightly depressed shuttle-box performance. Combinations of oxiracetam and nicotine improved passive avoidance more than either drug given separately. In the active avoidance task, a combination of oxiracetam with the lower dose of nicotine exerted improving effects never observed with nicotine alone, even at higher doses. The nootropic drug also prevented the slight depressant action exerted by 1 mg/kg nicotine. Thus, contrary to what was previously supposed, at least in mice subjected to shuttle-box avoidance training, nicotinic activation does not appear as the main neurochemical mechanism involved in the action of oxiracetam. Perhaps, oxiracetam and nicotine activate different types of cholinergic mechanisms, but it cannot be excluded that other neurotransmitters, particularly catecholamines, may be involved in the avoidance facilitating effects produced by nicotine and by combinations of the two drugs.

Different effects of apomorphine on locomotor activity in C57BL/6 and DBA/2 mice

Abstract The effects of apomorphine on spontaneous locomotor activity have been studied in two inbred strains of mice, the C57BL/6 and the DBA/2. In C57 mice low doses of apomorphine reduced motor activity, while higher doses produced hypermotility. In DBA mice the drug always depressed locomotor activity. The results have also been discussed in relation to the different sensitivities to morphine exhibited by the same two strains of mice.

A possible physiological role for cerebral tetrahydroisoquinolines.

Tetrahydroisoquinolines present in the mammalian brain, 1,2,3,4-tetrahydroisoquinoline (TIQ) and salsolinol, suspected to cause neurodegeneration leading to Parkinsons disease, were investigated to find their possible physiological role. To this aim their behavioral and receptor effects induced after a single dose were tested in mice and rats. Both compounds do not affect significantly the basal locomotor activity, very effectively block hyperactivity induced by apomorphine (rats) and amphetamine (mice), only partially block hyperactivity induced by scopolamine, do not affect locomotor stimulation induced by cocaine, and strongly augment the running fit induced by morphine (mice). They do not produce extrapyramidal symptoms and do not potentiate haloperidol-induced catalepsy (rats). TIQ and salsolinol do not displace antagonists of several receptors (including D1 and D2) from their binding sites, but displace the agonists of α2-adrenoreceptors, [3H] clonidine and of dopamine receptors, [3H] apomorphine. The results indicate that salsolinol and TIQ act as specific antagonists of agonistic conformation of dopamine receptors, and owing to that may play a role of endogenous feed-back regulators of the dopaminergic system. Those properties make tetrahydroisoquinolines potential antidopaminergic drugs devoid of extrapyramidal effects, with possible application in substance addiction disorder as anti-craving agents.

Analysis of the difference in the behavioral effects of apomorphine in C57BL/6 and DBA/2 mice

The influence of pimozide on the effects of apomorphine on locomotor activity and stereotypy was studied in two inbred strains of mice. In C57BL/6 mice, in which apomorphine did not produce stereotypy of gnawing, the biphasic effect of apomorphine on locomotor activity (hypomotility followed by hypermotility) was unaffected by pimozide. In DBA/2 mice, in which high doses of apomorphine produce hypomotility and compulsive gnawing, both these effects (but not hypomotility produced by low doses of apomorphine) were counteracted by pimozide. The results are consistent with the assumption that both strains of mice have separate inhibitory and stimulatory dopamine receptors mediating locomotor activity. In addition, DBA/2 but not C57BL/6 mice have dopamine receptors which mediate stereotypy and are sensitive to pimozide.

Oxiracetam prevents mecamylamine-induced impairment of active, but not passive, avoidance learning in mice

The nicotinic antagonist mecamylamine (2.5 and 5 mg/kg/IP) depressed both active (shuttle-box) and passive (step-through) avoidance learning in mice of the DBA/2 strain. The nootropic drug oxiracetam (50 and 100 mg/kg/IP) improved acquisition in the multitrial active avoidance test, but had no effect on one-trial passive avoidance learning. When the two drugs were combined, oxiracetam did not counteract mecamylamine-induced impairment of passive avoidance learning, even if it maintained a facilitating action on shuttle-box avoidance acquisition in mice receiving the nicotinic receptor blocker. Prevention of mecamylamine-induced shuttle-box avoidance depression by oxiracetam indicates that central nicotinic mechanisms are probably involved in the improving effects exerted by nootropic drugs on learning.

Influence of benzodiazepine tranquilizers on scopolamine-induced locomotor stimulation in mice

Four benzodiazepine tranquilizers have been tested, alone or in combination with scopolamine, on the spontaneous locomotor activity of BALB/c mice. Scopolamine-induced locomotor stimulation was enhanced by chlordiazepoxide, diazepam, and medazepam, but not by bromazepam. These effects are similar to those exerted by the four benzodiazepines on amphetamine-induced locomotor stimulation and allow the same differentiation between the four derivatives.

Shuttle-Box Avoidance Learning in Mice: Improvement by Combined Glucose and Tacrine

Glucose and the acetylcholinesterase inhibitor tacrine were tested, alone and in combination, in mice of the CD-1 strain subjected to five daily shuttle-box training sessions. Pretraining intraperitoneal administration of glucose alone (50-400 mg/kg) had no significant effect, while tacrine alone (0.5-3 mg/kg) improved avoidance acquisition at the dose of 2 mg/kg only. Significant avoidance learning improvements were instead produced by 50 or 100 mg/kg glucose combined with 0.5 or 1 mg/kg tacrine. The effects on shuttle-box avoidance acquisition produced by glucose combined with a cholinomimetic agent support the hypothesis that cholinergic mechanisms may be involved in the action of glucose on learning and memory. However, the main finding of the present study is related to the enhancement by glucose of the learning improving action of a drug clinically used as cognitive enhancer.

Facilitation of avoidance learning by chlordiazepoxide-amphetamine combinations in mice

Chlordiazepoxide and amphetamine, given separately or in combination, were tested in mice subjected to 5 100-trial avoidance sessions in the shuttle-box.Facilitation of avoidance responding was much more evident and statistically significant when the two drugs were combined. Drug mixtures produced effects which could not be obtained when the drugs were given separately.

Effect of caffeine and nicotine on avoidance learning in mice: lack of interaction

Abstract— Tested alone, nicotine (0·25 or 0·5 mg kg−1) improved shuttle‐box avoidance learning in mice of the CD‐1 strain. Caffeine had no effect at doses of 2·5 and 5 mg kg−1 and impaired performance at a dose of 10 mg kg−1. Combinations of the two drugs did not increase avoidance responses more than nicotine alone, nor was nicotine able to attenuate performance depression induced by the highest dose of caffeine. Lack of drug interaction in the avoidance test contrasts with the occurrence of interactive effects of the two drugs in a locomotor activity test. When given in combination, caffeine and nicotine increased locomotor activity at doses ineffective by themselves. The results seem to indicate no advantage in combining caffeine and nicotine to improve active avoidance learning.