Adrenergic Mechanisms and Amphetamine Induced Abnormal Behaviour

An open field study of stereotyped locomotor activity in amphetamine-treated rats

It is said that amphetamine induces stereotypy and locomotion in rats; however, the present paper shows amphetamine-induced stereotyped locomotion by analyzing the route of locomotion in an open field. Details of the analysis are given, normal as well as stereotypic features are discerned, and the results are discussed in relation to contemporary views on locomotion and exploration and on the mechanisms of amphetamine effect.

Atypical antidopaminergic properties of CI-686: a potential antipsychotic agent

The effects of the antipsychotic/antidepressant drug CI-686 on apomorphine- and amphetamine-induced stereotypies, dopamine metabolism, neuroleptic binding, and serum prolactin levels were determined. CI-686 displayed profiles of activity in each of these systems that differs markedly from those of other antipsychotics. CI-686's unique preclinical profile suggests a mechanism of action other than dopamine antagonism which could have implications regarding current thinking on the pathophysiology of schizophrenia.

Locomotor stimulation by L-dopa: relative importance of noradrenaline receptor activation

The importance of brain noradrenaline synthesis and receptor activation for the hyperkinesia induced by carbidopa plus L-Dopa in reserpine-treated or normal mice was analyzed in four different models. After pretreatment with reserpine and the monoamine oxidase inhibitor nialamide, the hyperkinesia induced by L-Dopa (25 mg/kg i.p.) was partly mediated via stimulation of noradrenaline receptors since it was significantly antagonized by the noradrenaline receptor-blocking agent phenoxybenzamine. Treatment with reserpine plus L-Dopa (125 mg/kg i.p.) produced an increase in motor activity probably due to stimulation of dopamine receptors since it was not accompanied by an accumulation of noradrenaline and it was not inhibited by phenoxybenzamine. The hyperkinesia following treatment with reserpine and a higher dose of L-Dopa (250 mg/kg i.p.) was probably due to stimulation of both dopamine and noradrenaline receptors since the dopamine-beta-hydroxylase inhibitor FLA-63 partly reduced the effect of L-Dopa. Phenoxybenzamine potentiated the motor stimulation by L-Dopa (125 mg/kg i.p.) in mice not pretreated with reserpine, perhaps depending on a slight enhancement of the net accumulation of brain dopamine. Thus, noradrenaline receptor activation is of importance for the L-Dopa-induced hyperkinesia, at least after high doses or after monoamine oxidase inhibition.

Evidence for a noradrenergic mechanism in the grooming produced by (+)-amphetamine and 4, alpha-dimethyl-m-tyramine (H 77/77) in rats

Rats were kept on a 12-h light-dark cycle. One hour after the light was switched on, physiological saline, (+)-amphetamine 1 mg/kg, and H 77/77 5 mg/kg were injected s.c.; the number of groomings was counted 1-2 h after the treatments. (+)-Amphetamine and H 77/77 produced increased grooming which was antagonized by the tyrosine hydroxylase inhibitor H 44/68 (250 mg/kg), the dopamine-beta-hydroxylase inhibitor FLA 63 (40), the neuroleptics haloperidol (0.1 and 0.5), and clozapine (1 and 5). The (+)-amphetamine-induced grooming was also antagonized by the NA-receptor blocker aceperone (10) but not by the sedative phenothiazines mepazine (10) and diphenhydramine (20) nor diazepam (1). These results indicate that NA-release is involved in the mediation of (+)-amphetamine- and H 77/77-induced grooming. The inhibition of haloperidol and clozapine is presumably due to NA-receptor blockade.

Schizophrenia and tardive dyskinesia: is schizophrenia also a "denervation hypersensitivity"?

In human beings, amphetamine can induce both schizophreniform psychosis and oral-facial dyskinesia resembling tardive dyskinesia, while neuroleptic agents reduce the manifestations of both conditions. This suggests that such psychosis and movement disorder may occur by the same or very similar mechanisms. It is thought that tardive dyskinesia may result from neuroleptic-induced denervation hypersensitivity to dopamine. The author cites evidence suggesting that amphetamine may act on dopaminergic pathways in the CNS to produce a denervation hypersensitivity like that caused by neuroleptic agents. Clinical evidence compatible with a denervation hypersensitivity hypothesis of schizophrenia is then discussed.

Biochemical differentiation of amphetamine vs methylphenidate and nomifensine in rats

Amphetamine-like stimulants were divided into two groups, one in which the stereotyped behaviour was not antagonized by reserpine [(+)-amphetamine, (-)-amphetamine, methamphetamine, phenmetrazine and phenethylamine] and another group in which the behavioural effects were blocked by reserpine (methylphenidate, nomifensine, pipradrol and amfonelic acid (NCA; Win 25978)). Both groups increased homovanillic acid (HVA) in whole brain 2 h after administration. The 'methylphenidate group' also increased brain 3,4-dihydroxyphenylacetic acid (DOPAC) in naive rats; whereas the '(+)-amphetamine group' decreased DOPAC in naive rats, as well as in reserpinized rats, alpha-methyl-p-tyrosine-treated rats and after acute hemisection. The reserpine antagonism of the 'methylphenidate group'-induced stereotyped behaviour was partially reversed by type A monoamine oxidase inhibition. The '(+)-amphetamine group'-induced stereotyped behaviour was not blocked by short time pretreatment with alpha-methyltyrosine, only by longer pretreatment intervals. The mechanisms by which the two groups are differentiated biochemically is discussed with special attention to possible intra-neuronal inhibition of dopamine oxidation by the '(+)-amphetamine group'.

Dopamine receptor blocking activity of sulpiride in the central nervous system

Effects of sulpiride on the central nervous system were studied in catalepsy induction (I) and antagonism to gnawing behaviour (II) induced by apomorphine and methamphetamine in normal rats, and in antagonism to rotational behaviour (III) induced by apomorphine and methamphetamine in rats with substantia nigra unilaterally lesioned chronically by microinjection of 6-hydroxydopamine. Sulpiride was administered orally and intraventricularly, and the effects of sulpiride were compared to those of haloperidol and chlorpromazine administered through the same routes. In oral administration, sulpiride was almost inactive in (I), and was several hundreds to a thousand times less potent than haloperidol in (II) and (III), while chlorpromazine was 20 to 150 times stronger than sulpiride. In intraventricular administration, sulpiride was almost equipotent to haloperidol in (I), and was equally effective to or 2 to 3 times more effective than halopridol in (III), although several times less in all respects. These findings suggest that sulpiride is essentially a potent inhibitory substance on dopamine receptors in the central nervous system and the rather weak central effects of peripherally given sulpiride are due to poor penetration through the blood brain barrier.

Changes in drug-induced stereotyped behavior after 6-OHDA lesions in noradrenaline neurons

Drug-induced stereotyped behaviors are often assessed by rating scales where the eventual appearance of sniffing, licking, and biting are rated as increasing intensity of dopaminergic stimulation. A 6-OHDA induced bilateral lesion (4 X 3-8 mug/4 mul 6-OHDA) in the ascending noradrenaline neurons, lateral to the medial raphe nucleus, of 180 g Wistar rats, affecting selectively noradrenaline and not dopamine or 5-hydroxytryptamine neurons, caused a change in the d-amphetamine sulphate (5-3 mg/kg s.c.) and phenethylamine hydrochloride (40 mg/kg) induced stereotyped sniffing behavior to the performance of discontinuous or continuous licking behavior; biting/gnawing was rarely induced. The site of the lesion and the partial antagonism of 6-OHDA by the uptake inhibitor protriptyline indicate a noradrenergic influence on the behavioral expression of the dopaminergically mediated stereotyped behavior.

Susceptibility to amphetamine-elicited dyskinesias following chronic methadone treatment in monkeys

Eight rhesus monkeys that had drunk subdependence-producing doses of methadone daily for 10-22 months, and had subsequently been drug-free for 2-17 months, were injected with low doses of methamphetamine (MA). They immediately exhibited oral dyskinesias resembling the symptoms of tardive dyskinesia in humans, a condition resulting from chronic blockade of striatal dopamine receptors by neuroleptics. Eleven control monkeys failed to develop dyskinesias during prolonged MA administration. Control monkeys then received parenteral methadone, chlorpromazine, haloperidol, or saline for 45 days. Upon subsequent retest with MA, the methadone and chlorpromazine monkeys immediately displayed oral dyskinesias. Dopaminergic antagonists blocked MA-elicited dyskinesis, whereas neither a noradrenergic blocker nor sedative doses of phenobarbital and diazepam had any effect on dyskinesias. We suggest that receptor supersensitivity is produced by chronic treatment with methadone or other dopamine receptor blockers. Following treatment, stimulation of hypersensitive striatal receptors by the dopamine released by MA results in oral dyskinesias. The clinical implications for methadone maintenance treatment program patients are discussed.

Experimental observations on the effect of amphepramone on the behavior, locomotion, pentretrazol seizures and electroencephalogram

Amphepramone, an anorectic agent, has been found to possess stimulant properties on the C.N.S. in animals, producing hypermotility and stereotyped movements which can be antagonized with neuroleptics. The stimulant activity of amphepramone observed in animals can be correlated with the amphetamine like psychosis observed in humans.

Dyskinesias in monkeys: interaction of methamphetamine with prior methadone treatment

Rhesus monkeys with a history of drinking methadone, but presently drug-free, were injected with low doses of methamphetamine (MA). They immediately developed oral dyskinesias resembling the symptoms of tardive dyskinesia in humans, a condition resulting from chronic blockade of striatal dopamine receptors by neuroleptics. Nine of 11 control monkeys failed to develop dyskinesias during prolonged MA administration. A stressful stimulus intensified the MA-elicited oral dyskinesias, an effect analogous to exacerbation of tardive dyskinesias by emotional stress. Control monkeys were then injected with methadone, chlorpromazine, haloperidol, or saline for 45 days. Ten days following this chronic treatment, MA immediately elicted oral dyskinesias in the methadone and chlorpromazine monkeys. Acute administration of the dopaminergic blocking agents chlorpromazine, spiroperidol, and clozapine eliminated MA-elicited dyskinesias, whereas the alpha-adrenergic blocker phentolamine was ineffective. Physostigmine blocked the dyskinesias in 1 of 2 cases. Sedative doses of phenobarbital and diazepam had no effect on oral dyskinesias. These data indicate that chronic treatment with methadone or other dopamine receptor blocking agents leads to receptor supersensitivity to the actions of MA.

Spontaneous and amphetamine induced head-shaking in infant rats

A variable proportion of albino rats 6-11 days old exhibit spontaneous and infrequent rotatory head-shaking episodes. This motor pattern is slightly anticipated and significantly increased in occurrence and duration by the administration of D-amphetamine (5 mg/Kg), with a maximal effect of the drug on the 9th day. The rate of amphetamine induced rhythmic head oscillations increases with age from below 5 cps on the 5th day to about 9 cps on the 10th day. The results are discussed in relation to maturation of both the underlying catecholaminergic pathways, activated by D-amphetamine, and the stretch reflex systems of the head and neck muscles participating in the rhythmic activity. Emphasis is placed on the difference between head-shaking and stereotyped activity.

Effect of cortisone, aldosterone and nialamide on "amphetamine stereotypies" and brain methamphetamine levels of adrenalectomized rats

Cortisone, aldosterone or nialamide was administered to adrenalectomized or sham-operated rats for 7 days, and methamphetamine was injected 24 hrs after the last injection of these compounds. Stereotyped head movement and licking activity were scored 5 min, 30 min and 60 min after methamphetamine injection and, in parallel brain methamphetamine levels in similarly treated rats were measured 5 min, 30 min and 60 min after the methamphetamine injection. Adrenalectomy depressed stereotyped head movements but enhanced the brain amphetamine accumulation. Nialamide but not the hormones further increased the amphetamine accumulation in adrenalectomized rats. No drugs had any effect on the amphetamine-induced head movement suppressed by adrenalectomy.

Influence of methamphetamine on nigral and striatal tyrosine hydroxylase activity and on striatal dopamine levels

In previous reports, methamphetamine was shown to depress tyrosine hydroxylase (TH) activity in the rat corpus striatum. To evaluate further the mechanism of this decrease in TH activity, enzyme activity was measured in the rat corpus striatum and substantia nigra after repetitive and single-dose methamphetamine administration. Following repeated doses of methamphetamine, nigral TH activity decreased and reached 45% of controls at 12 hr and returned to normal at 60 hr. Striatal TH activity decreased to 40% of control at 36 hr and returned toward normal at 60 hr. When methamphetamine was administered every 6 hr for 30 hr and then discontinued, nigral TH activity returned toward control levels 4 days prior to recovery of striatal TH activity. Methamphetamine initially increased striatal dopamine levels at 6 hr (170% of control). Dopamine levels then decreased in parallel with striatal TH activity but failed to increase as the enzyme recovered. Concurrent administration of chlorpromazine with methamphetamine prevented the methamphetamine-induced decrease in nigral and striatal TH activity and striatal dopamine levels. The results indicate that the methamphetamine-induced depression of striatal and nigral TH activity may be related to increased stimulation of dopamine receptors in the striatum.

Inhibition of 4,alpha-dimethyl-m-tyramine (H 77/77)-induced hypermotility in rats by single and repeated administration of chloropromazine, haloperidol, clozapine and thioridazine

The effect of H 77/77 (5 mg/kg s.c.) on motility of rats kept in a familiar cage was investigated. H 77/77 produced hypermotility, which was reduced by oral pretreatment with chlorpromazine, haloperidol, clozapine and thioridazine. The 4 neuroleptics were administered acutely and for a 14 day period. H 77/77 was given 30 min after the single or last dose of neuroleptc (chronic treatment) condition. After both single and repeated administration the neuroleptics showed H 77/77-antagonism in doses ranging from 0.1-2.0 mg/kg. The effect on H 77/77 activity did not change significantly after repeated treatment. Clozapine and thioridazine, which clinically produce only minor extrapyramidal side effects, exert a weak effect or none at all in tests commonly used for neuroleptic activity. These 2 neuroleptics were potent H 77/77-antagonists. Inhibition of H 77/77-hypermotility may possibly be used as a test for neuroleptics.

The behavioral pharmacology of butaclamol hydrochloride (AY-23,028), a new potent neuroleptic drug

Butaclamol hydrochloride (AY-23,028) is a member of a new chemical class for which antipsychotic activity in humans has recently been demonstrated. The compound antagonized amphetamine-induced stereotyped behavior in rats, amphetamine toxicity in aggregated mice and apomorphine-induced emesis in dogs. It depressed both discriminated avoidance and continuous lever-pressing behavior in rats and inhibited ambulation and rearing in the open field. At higher doses, AY-23,028 induced catalepsy. Adrenergic blocking activity, measured by the antagonism of epinephrine-induced mortality, was weak. These pharmacological actions are characteristic of neuroleptic drugs. In the dose range where the aforementioned effects were observed AY-23,028 did not antagonize either the tetrabenazine-induced ptosis or the tremorine syndrome and did not cause either hypothermia or ataxia. The potency and onset of action of AY-23,028 were comparable to those of fluphenazine but AY-23,028 was of longer duration. The results are discussed in relation to current concepts of neuroleptic mechanisms.

The effect of the chronic administration of D-amphetamine upon circadian changes in amino acids in the pineal and pituitary glands of the rat

The formation of dansyl derivatives of amino acids, 5-hydroxyindoleacetic acid and histamine, and their separation on polyamide plates provided a reliable and sensitive method for studying circadian changes in single pineal and pituitary glands of the rat. There appears to be no correlation between the circadian changes in concentrations of these substances in the pineal and pituitary glands. Chronically administered D-amphetamine altered the circadian rhythms of five amino acids in the pituitary, including the putative transmitters taurine, glycine, and glutamate; in the pineal gland only the rhythmical changes of lysine and 5-hydroxyindoleacetic acid were affected.

A neuronal basis for the alerting action of (+)-amphetamine

1. (+)-Amphetamine mimicked the excitatory and inhibitory actions of (-)-noradrenaline on single neurones in the brain stem of acute halothaneanaesthetized rats when these compounds were applied by iontophoresis. (+)-Amphetamine had no actions on neurones unaffected by (-)-noradrenaline.2. These mimicking actions of (+)-amphetamine could not be observed 20 h after treatment of the animals with reserpine 5 mg/kg.3. The enzyme inhibitors alpha-methyl-p-tyrosine and FLA 63 also greatly reduced the number of (-)-noradrenaline-mimicking responses to (+)-amphetamine.4. In animals pretreated with alpha-methyl-p-tyrosine, but not in those pretreated with FLA 63, excitatory actions of (+)-amphetamine on neurones excited by (-)-noradrenaline could be elicited 45-90 min after systemic injection of L-DOPA.5. These results indicate that (+)-amphetamine can release noradrenaline from presynaptic sites in the brain stem, which may be a basis for its alerting actions.