A COMPARISON OF IMIPRAMINE, CHLORPROMAZINE AND RELATED DRUGS IN VARIOUS TESTS INVOLVING AUTONOMIC FUNCTIONS AND ANTAGONISM OF RESERPINE

Common changes in rat cortical gene expression after antidepressant drug treatment: Impacts on metabolism of polyamines, mRNA splicing, regulation of RAS by GAPs, neddylation and GPCR ligand binding

OBJECTIVES

This study sought to identify pathways affected by rat cortical RNA that were changed after treatment with fluoxetine or imipramine.

METHODS

We measured levels of cortical RNA in male rats using GeneChip® Rat Exon 1.0 ST Array after treatment with vehicle (0.9% NaCl), fluoxetine (10 mg/kg/day) or imipramine (20 mg/kg/day) for 28 days. Levels of coding and non-coding RNA in vehicle treated rats were compared to those in treated rats using ANOVA in JMP Genomics 13 and the Panther Gene Ontology Classification System was used to identify pathways involving the changed RNAs.

RESULTS

18,876 transcripts were detected; there were highly correlated changes in 1010 levels of RNA after both drug treatments that would principally affect the metabolism of polyamines, mRNA splicing, regulation of RAS by GAPs, neddylation and GPCR ligand binding. Using our previously published data, we compared changes in transcripts after treatment with antipsychotic and mood stabilising drugs.

CONCLUSIONS

Our study shows there are common, correlated, changes in coding and non-coding RNA in the rat cortex after treatment with fluoxetine or imipramine; we propose the pathways affected by these changes are involved in the therapeutic mechanisms of action of antidepressant drugs.

Animal models of depression in drug discovery: a historical perspective

Over the course of the last 50 years many models of major depressive disorder have been developed on the basis of theoretical aspects of this disorder. These models and procedures have been crucial in the discovery and development of clinically-effective drugs. Notwithstanding, there is presently great concern about the discrepancy between positive outcomes of new candidate drugs in animal models and apparent lack of efficacy in humans i.e., the predictive validity of animal models. Some reasons for this concern lie in the over-reliance in the face value of behavioural models, design of clinical trials, placebo responses, genetic variations in response to drugs, species differences in bioavailability and toxicology, and not least, disinterest of pharmaceutical sponsors to continue developing certain drugs. Present model development is focusing on endophenotypic aspects of behaviours rather than trying to model whole syndromes. This essay traces the origins and theoretical bases of our animal models of depression or depressed-like behaviours in humans and indicates how they have evolved from behavioural assays used to measure the potency and efficacy of potential candidate drugs to tools by which endophenotypes of depression may be identified and verified pharmacologically. A cautionary note is included though to indicate that the true predictive validity of our models will not be fully assessed until we can determine the attrition rate of molecules discovered from new drug targets translating into clinically-effective drugs.

Behavioral differentiation between pharmacokinetic and pharmacodynamic components of the interaction of antidepressants or neuroleptics with methamphetamine

This study proposes a method capable of separating the pharmacodynamic from the pharmacokinetic component in the methamphetamine (MA) hyperactivity potentiation induced by antidepressants. Several antidepressants and neuroleptics, other centrally-acting drugs and the inhibitor of hepatic drug metabolism SKF 525-A were studied. The motility counts taken between 10 and 20 min after MA injection were considered as an index of pharmacodynamic interaction and the whole duration of the hyperactivity syndrome as an index of pharmacokinetic interaction. The duration of MA effect was prolonged by some of the drugs studied and left unchanged by the others regardless of their clinical classification. On the contrary, our evaluation of the intensity of MA effect produced a sharp differentiation between classical neuroleptics and typical antidepressants: the former antagonized and the latter potentiated MA peak intensity. Only the D-2 blocking neuroleptics sulpiride and tiapride potentiated MA intensity. Regarding the specificity of our model, none of the compounds known to be devoid of clinical antidepressant or antipsychotic activity interacted with MA in such a way as to be included in either category. As to the sensitivity of the test, two "false negatives" were obtained: the neuroleptic clozapine and the antidepressant mianserin. Such exceptions were discussed taking into account their peculiar mechanisms of action.

The validity of animal models of depression

Eighteen animal models of depression are reviewed in relation to three sets of validating criteria. Of the 18 models, five could only be assessed for predictive validity, seven could be assessed for predictive and face validity, and six could potentially have predictive, face and construct validity. Some traditional models (reserpine reversal, amphetamine potentiation) are rejected as invalid; the models with the highest overall validity are the intracranial self-stimulation, chronic stress and learned helplessness models in rats, and the primate separation model.

The effect of anti-Parkinsonian drugs on oxotremorine-induced analgesia in mice

The antagonism of oxotremorine-induced analgesia in mice can be used to obtain a quantitative and objective assessment of the central anticholinergic activity of potential anti-Parkinsonian drugs.

The effect of antidepressants and "tranquilizers" on the response of mice to ethanol

1. The techniques and apparatus used for investigation of the interaction of various psychotropic drugs with ethanol in mice are described. The parameters measured were (a) length of loss of righting reflexes; (b) continuous coma; (c) subjects remaining in coma 12 hr after dosing; (d) changes in toxicity.2. The following drugs were tested: amitriptyline, trimipramine, imipramine, nortriptyline, desipramine, thioridazine, phenelzine, methylphenidate, chlorpromazine, trifluoperazine, phenobarbitone, and diazepam. The total number of mice used was 3,140.3. Imipramine caused no significant changes in the effects of ethanol. Methylphenidate and desipramine protected the mice against ethanol induced coma. All other drugs induced statistically significant potentiation of the depressant and toxic effects of ethanol in mice.4. Late (delayed) deaths after a tricyclic antidepressant have been noted in animals and man.5. It is suggested that the potentiation of alcohol by some psychotropic drugs may add to the hazards of drug overdosage and contribute to traffic accidents. Hence it is necessary to test all psychotropic drugs for interaction with alcohol.