The effect of various antidepressant drugs upon the tetrabenazine-suppressed conditioned avoidance response in rats

Reversal of guanethidine- and diethyldithiocarbamate-induced amnesia by peripherally-administered catecholamines

The effect of peripherally-administered catecholamines on guanethidine- and diethyldithiocarbamate-induced amnesia of a PA training in mice was investigated. The amnesic effect of guanethidine could be blocked with 50 mg/kg DA, or 0.75 mg/kg NE when given either before, immediately, or 10 min after but not 90 min following PA. Epinephrine or a lower dose of DA could be attenuate the guanethidine-induced amnesia. The amnesic effect of diethyldithiocarbamate could be blocked with 50 mg/kg DA, 0.75 mg/kg NE or 0.5 mg/kg E when given either before, immediately or 10 ming after but not 90 min following PA. The amnesic effects of these compounds were interpreted in terms of their peripheral antiadrenergic actions.

Comparisons of the effects of guanethidine, 6-hydroxydopamine and diethyldithiocarbamate on retention of passive avoidance

Depending on the dose levels, guanethidine and diethyldithiocarbamate produced time dependent amnesia for a one-trial passive avoidance task. 6-Hydroxydopamine given at any dose level or at any time interval before or after training did not result in retention deficits. The results were discussed in terms of the effects of these agents on peripheral biogenic amines and the possible role of these amines in memory formation.

Some aspects of the psychopharmacological activity of maprotiline (Ludiomil): effects of single and repeated treatments

Three different aspects of the psychopharmacological activity of the antidepressant maprotiline were investigated:

its influence on serotoninergic functions the effects produced by chronic treatment its central nervous depressant and anxiolytic properties.

Study of the effects of maprotiline on 5-HTP-induced head-twitch in mice pre-treated with pargyline or on hyperpyrexia in rats provided no evidence that the drug interferes with serotonin-mediated functions in the central nervous system even after quite high doses. These findings corroborate the results of extensive neurobiochemical investigations, which failed to demonstrate any influence of maprotiline on the metabolism of serotonin.

Chronic studies showed that classical effects of maprotiline such as antagonism against reserpine-induced ptosis or tetrabenazine-induced catalepsy do not change in their intensity after daily administration of the drugs in a dose of 30 mg/kg p.o.for 11 days. A new component of the action of the compound, not detectable after one single dose, seems to appear, however, after repeated treatment (8 days). This effect is manifested in the restoration of conditioned avoidance behaviour after its suppression by pre-treatment with reserpine. The same effect is produced by imipramine. It is suggested that this restorative effect may be due to an additional activation of the dopaminergic nervous system and may have a bearing on the appearance of clinical antidepressant effects.

Maprotiline was found to potentiate central nervous depressant effects of drugs like chlorpromazine, phenobarbitone and propranolol. This affords further confirmation that, in addition to its antidepressant qualities, it possesses sedative actions. An anxiolytic component was also demonstrated in rats in which maprotiline suppressed the conditioned, fear-induced rise in body-temperature.

A reappraisal of the interaction between tricyclic antidepressants and reserpine-like drugs

The administration of trycyclic antidepressants followed by reserpine-like drugs elicits a pattern of stereotyped locomotor activity. Using desmethylimipramine (DMI) followed by tetrabenazine (TBZ), activity could be reliably elicited only in young rats, and only by using very high doses of TBZ. The latency of onset of activity was up to 5 h. Animals rendered active by DMI-TBZ failed to perform a well-established operant task. The activity syndrome was apparently unaffected by pre- or posttreatment with the dopamine antagonists spiroperidol or primozide, but partial antagonism was obtained with the noradrenaline antagonists phentolamine and phenoxybenzamine. The findings are discussed in relation to the mechanism of action of the effect and its relevance to the clinical action of tricyclic antidepressants.

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.