Repeated administration of subconvulsant doses of GABA antagonist drugs. II. Effect on monoamine-mediated behaviour

Effects of desipramine and alprazolam in the forced swim test in rats after long-lasting termination of chronic exposure to picrotoxin and pentylenetetrazol

Rats were treated for 5 weeks with three subconvulsant doses of picrotoxin (PTX) and pentylenetetrazol (PTZ) per week to induce a persistent reduction of the GABAA receptor function which results in chemical kindling. Fifteen days after termination of this treatment schedule, the effect of desipramine (DMI) and alprazolam (ALP) on immobility time in the forced swim test (FST) was evaluated. Chronic PTX and PTZ did not alter the immobility time. Acute PTX and PTZ reduced the immobility of rats chronically treated with vehicle but not of those exposed chronically to PTX and PTZ. Chronic PTX did not influence the anti-immobility effect of DMI, but blocked that of ALP. Chronic PTZ markedly potentiated the anti-immobility effect of DMI but blocked that of ALP. Concomitant administration of chlordiazepoxide prevented the effects of chronic PTX and PTZ. These findings suggest that a long-lasting reduction in GABAA receptor function, unlike acute reduction, does not play an important role in the mobility of rats in the FST and in the anti-immobility effect of DMI while it blocks that of ALP.

The pharmacology of human anxiety

The human pharmacology of anxiety disorders, including panic disorder, is detailed. The major theories center around the role of benzodiazepine receptor, noradrenergic and serotonergic dysfunction. The contribution that challenge tests with lactate, hyper- and hypocapnia, beta- and alpha-2-adrenoceptor agonists, peptides, pentylenetetrazol, and caffeine make to our understanding of the biological basis of anxiety and these major theories are described and discussed.

Further evidence for a relationship between changes in GABA concentration in rat brain and enhanced monoamine-mediated behavioural responses following repeated electroconvulsive shock

Administration of bicuculline (3.5 mg/kg i.p.) or pentylenetetrazol (30 mg/kg i.p.) 3 min before each of a series of 5 electroconvulsive shocks (ECS), given over 10 days (1, 3, 5, 8 and 10), prevented the enhanced behavioural responses to the dopamine agonist apomorphine and the 5-hydroxytryptamine agonist quipazine 24 hr after the last application of ECS. Pretreatment with these antagonists of gamma-aminobutyric acid (GABA) also abolished the rise in the concentration of GABA in the corpus striatum, normally seen after repeated ECS. Taken with data showing that the change in GABA concentration occurred at times when enhanced monoamine-mediated behavioural responses were seen, these results suggest that the enhanced behavioural responses following repeated ECS might be associated with changes in GABA function. Daily injection for 8 days with pentylenetetrazol (30 mg/kg) resulted in enhanced apomorphine-mediated behaviour. However, there was no change in the concentration of striatal GABA at this time.