Exploratory Head-dipping Research Articles

Intrinsic behavioural actions of n-propyl β-carboline-3-carboxylate

The behavioural effects of n-propyl β-carboline-carboxylate (β-CCP) were assessed in the social interaction test of anxiety and in the holeboard test of exploratory behaviour. nPropyl β-carboline-3-carboxylate (2 mg/kg) significantly reduced the time spent in social interaction without affecting locomotor activity, indicating an anxiogenic action. This reduction was not significantly reversed by chlordiazepoxide (3 mg/kg). In the holeboard, β-CCP (4 mg/kg) reduced exploratory head-dipping and rearing; neither of these effects was significantly reversed by chlordiazepoxide (5 mg/kg). The actions of β-CCP in these two tests are similar to those of the structurally-related compound ethyl β-carboline-3-carboxylate.

Repeated electroconvulsive shock has no specific anxiolytic effect but reduces social interaction and exploration in rats

Administration of repeated electroconvulsive shock (ECS) to rats did not result in a specific anxiolytic profile in the social interaction test, but did significantly reduce several spontaneous behaviours: social interaction, locomotor activity, exploratory head-dipping and rearing. None of these behavioural changes was reversed by the administration of pentylenetetrazol prior to each seizure, a treatment that abolishes ECS-induced changes in GABA and 5-HT in the brain.

Behavioural effects of pentylenetetrazole reversed by chlordiazepoxide and enhanced by RO 15-1788.

The effects of low doses of pentylenetetrazole (PTZ) on exploratory behaviour and locomotor activity in the rat, were measured in the holeboard apparatus. PTZ (30 mg/kg) significantly reduced exploratory head-dipping, an effect that was significantly reversed by chlordiazepoxide (5 mg/kg) and enhanced by RO 15-1788 (20 mg/kg). RO 15-1788 (20 mg/kg) also significantly enhanced the reduction in locomotor activity produced by PTZ (30 mg/kg); although this reduction was not reversed by chlordiazepoxide (5 mg/kg) the reduction in locomotor activity with the drug combination was no greater than that with either drug alone. The results are discussed with respect to a coupling between the benzodiazepine receptors and the site at which PTZ acts.

Sedative effects of PK 9084 and PK 8165, alone and in combination with chlordiazepoxide.

1 The sedative effects in rats of two phenylquinolines, PK 9084 and PK 8165 (5-50 mg/kg), were examined in a holeboard: both when given alone and when given in conjunction with chlordiazepoxide (5 mg/kg). 2 Both phenylquinolines produced significant dose-related decreases in locomotor activity and rearing, with an ED50 about twice that for chlordiazepoxide. 3 When the phenylquinolines were combined with chlordiazepoxide the degree of sedation was equal to that seen with either drug given alone, whichever produced the greater sedation; the sedative effects of the two drugs were never additive. 4 PK 9084 (10 and 50 mg kg) significantly reduced rectal temperature, as did chlordiazepoxide (5 mg/kg), but there was no addition nor interaction of their effects. 5 Both phenylquinolines also reduced exploratory head-dipping, as did chlordiazepoxide, but in combination they antagonized each other's effects. 6 The classification of the phenylquinolines as non-sedative anxiolytics, acting as agonists at the benzodiazepine receptors needs revision.

Chlordiazepoxide-induced ataxia, muscle relaxation and sedation in the rat: effects of muscimol, picrotoxin and naloxone.

Chlordiazepoxide-induced ataxia was potentiated by muscimol (0.5 mg/kg) and antagonised by picrotoxin (2 and 4 mg/kg) and by naloxone (2 and 4 mg/kg). The muscle-relaxant effects of chlordiazepoxide were not significantly altered by any of these three drugs and nor was the chlordiazepoxide-induced decrease in exploratory head-dipping. However, the sedative effects of chlordiazepoxide, measured by a reduction in spontaneous motor activity, were antagonised by picrotoxin.

β-CCE and chlordiazepoxide reduce exploratory head-dipping and rearing: No mutual antagonism

Intravenous injection of ethyl β-carboline-3-carboxylate (β-CCE, 2 mg/kg) significantly reduced exploratory behaviour in a holeboard and 1 & 2 mg/kg markedly reduced the number of rears made. These effects were similar to those found with chlordiazepoxide (5 mg/kg). When they were given together the two drugs neither counteracted each other's effects, nor were their combined effects additive. We suggest that β-CCE and the benzodiazepines might both act at one class of benzodiazepine receptor, as agonists to produce the same behavioural effects. The results are also discussed with reference to other intrinsic actions of these compounds.

Intrinsic actions of benzodiazepine antagonists

RO 15–1788 (4–20 mg/kg), both alone and in combination with chlordiazepoxide (5 mg/kg), increased exploratory head-dipping in a holeboard above control levels. This intrinsic action of a benzodiazepine antagonist is not reversed, and is even augmented, by chlordiazepoxide. RO 15–1788 alone had no effect on locomotor activity, but antagonized the sedative effects of chlordiazepoxide. β-CCE (1 and 2 mg/kg) was without effect on locomotor activity, but the higher dose reduced head-dipping.

Naloxone reduces social and exploratory activity in the rat.

Naloxone (1,2, and 4 mg/kg) produced a dose-related decrease in exploratory head-dipping in rats placed singly in a holeboard for 10 min, without a concomitant reduction in locomotor activity. Naloxone (2 mg/kg) reduced the time spent in active social interaction by pairs of rats tested in an unfamiliar or in a familiar test arena, and also reduced the amount of motor activity shown by the pairs of rats. The results are consistent with proposed roles for opiate peptides in behavioural responses to novel environments and in mediating social contact.

Superior colliculus lesions in rat abolish exploratory head-dipping in hole-board test

Superior colliculus lesions in rat abolish exploratory head-dipping in hole-board test