Agonist Amphetamine Research Articles

Lithium attenuates the development of lesion-induced behavioral supersensitivity to apomorphine

The unilateral nigrostriatal lesion preparation was used to examine the effect of long-term treatment with lithium on rotation in response to the dopamine agonists apomorphine and amphetamine. Rats with unilateral striatal denervation received daily injections of either lithium chloride or saline for 14 days, beginning 24 h after surgery. Rats treated with lithium showed a reversible reduction in apomorphine-induced contralateral rotation. Lithium treatment failed to substantially alter amphetamine-induced ipsilateral rotation. When treatment was initiated 14 days after surgery, rats treated with lithium showed no reduction in apomorphine-induced contralateral rotation. These findings suggest that lithium attenuates the development of lesion-induced behavioral supersensitivity but fails to alter supersensitivity which has developed previously.

Estrogen potentiates the stereotypy induced by dopamine agonists in the rat

Abstract Repeated weekly treatment with 100 μg/kg of estradiol benzoate (EB) to ovariectomized female rats intensified the stereotypy induced by the dopamine agonists amphetamine and apomorphine. A similar effect on amphetamine-stereotypy was produced 48 hours after a single injection of 10 μg/kg of EB. The fact that EB failed to increase blood or brain levels of either 3 H-amphetamine or 3 H-apomorphine suggests that these behavioral effects were not due to altered peripheral drug metabolism or uptake into the brain. The enhancement of stereotypy produced by EB is viewed as one manifestation of a more complex modulatory influence of estrogen on DA function.

Dopaminergic and non-dopaminergic circling activity of mice

Abstract Male ICR albino mice kept in a closed space tend to rotate and have a preferred direction of rotation, which is more often to the left (65%) than to the right (35%). This circling asymmetry was measured with a rotometer in a group of animals following administration of various drugs. Morphine, amphetamine, apomorphine, atropine and pentylenetetrazol caused hyperactivity which was maximal for morphine and decreased in that order. All the drugs also increased the rate of rotation and the percentage of turning in the preferred direction, the latter again being maximal for morphine and decreasing in the order morphine, atropine, amphetamine, apomorphine, pentylenetetrazol. The dopaminergic agonists amphetamine and apomorphine also increased several-fold the rate of turning in the non-preferred direction, but this effect was much less obvious for the other drugs. Our results do not support a previous suggestion that rotational asymmetry is related to dopaminergic asymmetry in the brain. While the rotational asymmetry is influenced by the degree of activity of the animals, other unidentified factors are operating.

Interaction between noradrenergic and cholinergic systems in the rat brain: Behavioural function in locomotor activity

Abstract Anticholinergic drugs such as scopolamine and atropine induce a mild locomotor stimulation when given intraperitoneally to rats. This effect is usually ascribed to interaction between dopaminergic and cholinergic transmission in the striatum or nucleus accumbens. However, an interaction of acetylcholine with noradrenergic systems is also apparent from biochemical data and the results reported here indicate that at least part of the locomotor activity induced by scopolamine or atropine involves a noradrenergic component. Depletion of forebrain noradrenaline by injection of 4 μg of the selective neurotoxin 6-hydroxydopamine into the dorsal bundle was found to potentiate the locomotor activation induced by various doses of scopolamine or atropine. This was a central effect since methylscopolamine, which does not pass the blood-brain barrier, failed to induce locomotor activity and was not affected by the noradrenergic lesion. The noradrenergic interaction was restricted to cholinergic drugs since locomotor activity induced by the indirect dopamine agonist amphetamine was not affected by noradrenaline depletion. These studies show that the interaction between noradrenergic and cholinergic transmission, which has previously been indicated by biochemical analysis, influences behaviour and they also cast some light on the functions of the central noradrenergic system itself.

Effects of opiates on the discriminative stimulus properties of dopamine agonists

Two groups of rats were trained to discriminate the dopamine agonists amphetamine (0.75 mg/kg) or apomorphine (0.38 mg/kg) from saline in a two-lever operant task. Various doses of morphine and pentazocine were tested for generalization to and interference with the discriminative stimulus complexes produced by the dopamine agonists. Low doses of morphine appeared to produce a stimulus complex which is similar to that produced by apomorphine, but which differs from the produced by amphetamine. Pentazocine showed no evidence of generalization to either the apomorphine or the amphetamine cue. Neither opiate interfered with discriminative stimuli produced by the dopamine agonists, although decreases in the number of animals responding occurred.