GABA receptor subunits and global behaviour.
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Biomedical subjects
Georges Chapouthier
Publications and source records attributed to Georges Chapouthier.
Posture and balance responses to a sensory challenge are related to anxiety in mice.
Anxiety disorders and balance disorders share common clinical features related to perception such as spatial disorientation or dizziness. The search for the mechanism underlying this core of symptoms led us to investigate impairments in multisensory integration. In mice, the 'rotating beam test' allows analysis of changes in balance control and posture in response to a multisensory challenge. We used the BALB/c and C57BL/6 inbred strains of mice, known for their contrasted anxiety-related behavior. The level of anxiety was also manipulated using anxiolytic and anxiogenic pharmacological compounds. Despite equal sensori-motor abilities, anxious mice were more prone to fall off the rotating beam and showed more imbalance than non-anxious mice. Striking inter-strain differences in posture were also observed. Diazepam and beta-CCM reversed these strain-specific responses in opposite directions. We demonstrated that balance and postural strategies developed in response to a multisensory challenge vary as a function of the level of anxiety in mice.
Animals↗
Long-lasting potentiation effects induced in rats by kindling with an inverse agonist of the benzodiazepine receptor.
The present work analyzed the changes in evoked field potentials of freely moving rats after kindling induced by a convulsant inverse agonist of the GABA(A)-benzodiazepine receptor complex, methyl beta-carboline-3-carboxylate (beta-CCM). Two doses of beta-CCM (2 mg/kg and 4 mg/kg) were used. In kindled and control animals, a stimulating electrode was implanted in the perforant pathway and a recording electrode in the dentate gyrus. Results showed that, after an acutely injected dose of 20 mg/kg pentylenetetrazol (PTZ), all kindled animals showed a decrease in population spike amplitude after 20 min. After 60 min, only fully kindled rats showed a long-lasting potentiation, also visible up to 24 h later, as compared to controls or nonkindled animals. Changes in glutamate and GABA receptor binding measured in previous experiments may explain this potentiation effect observed in fully kindled rats.
Animals↗
Mouse lines differing in sensitivity to beta-CCM differ in tasks used for testing antidepressants.
Two lines of mice, previously selected for their sensitivity (BS) or their resistance (BR) to an anxiogenic benzodiazepine (BZ) receptor inverse agonist, methyl beta-carboline-3-carboxylate (beta-CCM), have recently been shown to present several differences in anxiety. In the present study, attempt was made to extend their behavioral profile in two situations classically used for testing antidepressant drugs. Reassessment of locomotor performance of these new populations confirmed that the motor activity of BR mice was lower than that of BS mice. In both the forced-swimming and the tail suspension tests, the immobility time of BS mice was significantly higher than that of BR mice. In the tail suspension test, two administrations of imipramine (30 mg/kg i.p., 5 h and 30 min before testing) significantly reduced the immobility time of BS mice but not of BR mice. From these data, it appears that BS mice are more "depressed" than BR mice. Thus, these selectively bred lines may represent potentially useful animal models to investigate behavioral, neurochemical and neuroendocrine correlates of antidepressant action.
Animals↗
GABA-A receptor complex and memory processes.
Considerable evidence has been provided these last years for the involvement of the GABAA receptor complex in memory processes. Compounds that enhance the action of GABA, such as benzodiazepines, impair memory processing. On the contrary, compounds that reduce the action of GABA, such as -CCM, pentylenetetrazol or picrotoxin, have the opposite action, that is : enhance memory processing. All these actions seem to focus mainly on the acquisition (learning) processes. Depending on the dose, the same compounds also have effects on anxiety and on seizuring. Benzodiaze-pines are well-known anxiolytic and anticonvulsant agents whereas compounds that reduce the action of GABA have been found to produce anxiogenic and convulsant actions. The GABAA receptor complex might thus be the location of a possible link between a pathological state (epilepsy) and two normal functions (anxiety and learning). This link is likely to involve common genetic pathways. In the normal subject, these data also emphasize the idea that normal memory processing involves a moderate level of anxiety.
Animals↗