Glutamate and benzodiazepine receptor autoradiography in rat brain after repetition of alcohol dependence.

Abstract

During repeated alcohol withdrawal, convulsive withdrawal behavior has been shown to be increased in a kindling-like manner in both clinical and experimental studies. In the present experiment, quantitative autoradiography was used to investigate binding of tritiated ligands to glutamate receptor subtypes and the benzodiazepine/GABA (BZ/GABA) receptor complex in rats exposed to 14 episodes of alcohol withdrawal. Seizures were detected in 25% of the animals during withdrawal episode 10-13. Repeated alcohol withdrawal resulted in a decrease in the number of [3H]-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid ([3H]-AMPA) binding sites in striatum and sub-regions of the entorhinal cortex, the cerebellum and the hippocampus, while the [3H]-flunitrazepam binding was down-regulated in the frontal cortex. There was no differences between the controls and the multiple withdrawal animals regarding the [3H]-dizocilpine ([3H]-MK801) binding and the [3H]-kainic acid binding. However, within the latter group, those animals in which withdrawal seizures were observed had increased [3H]-MK801 binding sites in focal regions of entorhinal cortex and hippocampus, compared to those in which seizures were not observed. The decreased AMPA binding suggested impaired glutamate neurotransmission. As such, this receptor probably did not contribute to alcohol withdrawal kindling, but rather was involved in seizure protective mechanisms during this process.