Auditory sensory gating in hippocampus and reticular thalamic neurons in anesthetized rats

Auditory gating is thought to reflect sensory information processing and is absent or diminished in schizophrenic patients. Although abnormal thalamic sensory processing has been proposed in schizophrenia, sensory gating of thalamic neurons has not been demonstrated experimentally. The aim of the present study was to establish whether auditory gating is present in the rat thalamus using a well-characterized animal model of auditory gating and schizophrenia.

Hippocampal electroencephalogram and single-unit activity in the thalamic reticular nucleus (nRT) were recorded in anaesthetized rats. Evoked potentials in the hippocampus and neuronal activity in the nRT were monitored in response to bilateral auditory stimuli. The effects of the psychostimulant D-amphetamine and the antipsychotic haloperidol on auditory gating were evaluated.

Thalamic reticular nucleus neurons showed gated responses to paired-tone auditory stimuli, resembling hippocampal auditory gating. D-amphetamine disrupted auditory gating of nRT neurons and abolished their burst activity. D-amphetamine also disrupted hippocampal auditory gating and induced hippocampal theta activity. The amphetamine-induced gating deficit was reversed by haloperidol in both regions.

Our findings provide the first experimental evidence for auditory gating of nRT neurons. We demonstrated that amphetamine disrupts sensory processing of nRT neurons, indicating similarities between hippocampal and thalamic sensory gating. These findings support the presumed connection between dopamine hyperfunction and abnormal thalamic filtering in schizophrenia.