A microgram dose of diazepam produces specific inhibition of ambulation in the rat

Anxiolytic potential of a microgram dose of chlordiazepoxide in the open-field test

Diazepam, when administered in very low doses (100 micrograms/kg), can induce a specific inhibition of coarse and ambulation activities in the rat, suggesting a novel mechanism of action occurring in the microgram dose range. This study fails to reproduce the same effects with chlordiazepoxide. On the contrary, greater stimulant and anxiolytic effects were measured with the lowest dose tested (0.1 mg/kg). These results demonstrate that the familiar effects of benzodiazepines should not be extrapolated uncritically to lower dose ranges without empirical testing.

Anxiolytic potential of sulpiride, clozapine and derivatives in the open-field test

Recently acquired data question the sharp dichotomy between anxiolytics and neuroleptics, since disinhibitory effects have been measured in the rat with very low doses of haloperidol and higher doses of atypical neuroleptics in FI and DRL schedules, but also in the open-field test. That the DA transmission in certain brain regions is involved in some aspects of anxiety has recently been suggested. The present study confirms this hypothesis particularly with high doses of sulpiride (80 mg/kg) and clozapine (24 mg/kg) when tested in the open-field test. Moreover, the results show how a slight chemical modification of clozapine can give a direction to pharmacological activity with one derivative still resembling clozapine and the second one resembling haloperidol. As neuroleptics do not seem to influence the synthesis and utilization of GABA, the higher entry score observed with them would seem to depend above all on DA antagonism in the mesolimbic system.

Effect of diazepam on behaviour and associated changes in ascorbate concentration in rat brain areas: striatum, n. accumbens and hippocampus

The effect of diazepam on spontaneous and tail-pinch-induced behaviour was monitored together with the measurement of extracellular ascorbate using constant potential voltammetry with carbon paste electrodes. Diazepam (3 mg/kg) was followed by eating during the 1st hour after administration in non-food-deprived rats and a reduction in the behaviour triggered by a mild tail-pinch 90 min after drug administration. There was no change in ascorbate concentration in parallel with the spontaneous eating; however, the brisk increase in ascorbate concentration in striatum, nucleus accumbens and hippocampus, which accompanies the tail-pinch, was decreased in size and duration after diazepam. This effect was blocked by the central benzodiazepine receptor antagonist Ro15 1788 (5 mg/kg).

Effects of diazepam, FG 7142, and RO 15-1788 on schedule-induced polydipsia and the temporal control of behavior

Although benzodiazepine agonists and inverse agonists have opposite effects on drinking elicited by water deprivation, there is much less information about the effects of these drugs on nonhomeostatic drinking. In this experiment the effects of diazepam (0.3-5.0 mg/kg), a benzodiazepine receptor agonist, and FG 7142 (1.0-9.0 mg/kg), an inverse agonist, were determined on drinking elicited by a FT-60 schedule of food delivery (SIP). Both diazepam and FG 7142 dose-dependently reduced SIP, measured as either licking or volume consumed. In addition, diazepam reduced panel pressing for food, decreased locomotor activity, and changed the time course of each behavior. In contrast, FG 7142 reduced schedule-induced drinking without significantly altering other behaviors. The antagonist RO 15-1788, when given in combination with these drugs, only partially restored the reductions in licking produced by diazepam, but was much more effective in reversing the effects of FG 7142 at doses of the antagonist that failed by themselves to affect responding. The opposite pattern of effects was seen on the volume of water consumed. These effects are discussed in terms of the behavioral and pharmacological specificity of these drugs.

Microgram doses of diazepam do not induce proconvulsant or proconflict effects in rodents

Cooper (1983, 1985) observed an inhibition of ambulation and fluid intake in rats following diazepam in the microgram dose range. The present study aimed at investigating the effects of microgram doses of this benzodiazepine on i) the threshold doses of either pentylenetetrazole, picrotoxin or bicuculline required to induce seizures in mice and ii) the suppression of lever pressing for food induced by the delivery of one electric footshock every ten presses in rats pretreated or not with isoniazid (64 mg/kg IP). Diazepam 4-32 micrograms/kg IP) neither reduced seizure threshold doses of either convulsant studied nor did this drug (16-128 micrograms/kg IP) reliably decrease the number of lever presses under the punishment schedule. The present study provides no further evidence for a dose-related biphasic effect of diazepam which could give new insight into the functioning of benzodiazepine-coupled brain processes.

The anorectic effect of FG 7142, a partial inverse agonist at benzodiazepine recognition sites, is reversed by CGS 8216 and clonazepam but not food deprivation

The benzodiazepine partial inverse agonist N'-methyl-beta-carboline-3-carboxamide (FG 7142; 5.0 and 10.0 mg/kg, i.p.) produced a dose-dependent reduction in the consumption of a familiar, highly palatable diet by non-food-deprived male rats. At dose levels which exhibited no significant intrinsic effects, the benzodiazepine receptor antagonist 2-phenylpyrazolo-[4,3-c]-quinoline-3(5H)-one (CGS 8216; 1.25-5.0 mg/kg, i.p.) reversed the anorectic effect of FG 7142. When clonazepam and FG 7142 were given in combination, mutual cancelling of their opposite effects occurred. These results are consistent with an action of FG 7142 at benzodiazepine recognition sites to reduce the level of palatable food consumption, and imply that a bidirectional control of food intake via benzodiazepine recognition sites can be achieved. The anorectic effect of FG 7142 was not reversed by 24-h food deprivation, indicating a possible separation from the effects of hunger mechanisms.

Clonazepam-induced hyperphagia in nondeprived rats: tests of pharmacological specificity with Ro5-4864, Ro5-3663, Ro15-1788 and CGS 9896

Nondeprived male rats were familiarised with daily 60 min access to a highly palatable diet, consisting of powdered rat diet, sweetened condensed milk and water. Clonazepam (0.625-5.0 mg/kg, IP) produced a substantial increase in food consumption within the first 30 min of access. The increase was similar across all dose conditions, suggesting that a maximal effect may have been achieved with a dose as small as 0.625 mg/kg. The hyperphagia induced by clonazepam was reversed by the benzodiazepine receptor antagonist, Ro15-1788 (5.0-20.0 mg/kg), indicating that the effect was benzodiazepine receptor-mediated. Treatments with the peripheral-type benzodiazepine agonist, Ro5-4864, did not induce a hyperphagic response. Instead, food consumption was significantly depressed following the administration of Ro5-4864 at 20 and 40 mg/kg, IP. A comparison of the clonazepam and Ro5-4864 data suggests that benzodiazepine-induced hyperphagia is mediated by central-type benzodiazepine binding sites. The pyrazoloquinoline, CGS 9896, binds with high affinity to benzodiazepine sites and has recently been described as a nonsedating anxiolytic. CGS 9896 (2.5-20.0 mg/kg, administered either IP or PO) did not affect consumption of the highly palatable diet. In consequence, anxiolytic and hyperphagic effects of drug actions at benzodiazepine receptors may be dissociated in the case of this compound. The atypical 1,4-benzodiazepine, Ro5-3663, a GABA antagonist which may act at the picrotoxinin site, produced a dose-related reduction in food consumption. Comparison with the results for Ro5-4864 rules out an interpretation for the anorexia in terms of anxiogenic effects.(ABSTRACT TRUNCATED AT 250 WORDS)