Chronic stress differentially regulates cannabinoid CB1 receptor binding in distinct hippocampal subfields

Exposure to chronic stress has been found to decrease cannabinoid CB1 receptor expression in the hippocampus; however, the specificity of this phenomenon to specific subfields of the hippocampus has not been characterized. To this extent, male Sprague-Dawley rats were exposed to 21 days of restraint stress (6 h/day), after which autoradiographical analysis of cannabinoid CB1 receptor binding site densities were examined in the CA1, CA3 and dentate gyrus subfields of the hippocampus. Chronic stress was found to produce a significant reduction in cannabinoid CB1 receptor binding in the dentate gyrus, while increasing cannabinoid CB1 receptor binding in the CA3. There was no effect of chronic stress on cannabinoid CB1 receptor binding in the CA1, or two other proximal regions, the retrosplenial cortical gyrus and the laterodorsal thalamus. Given the role of hippocampal cannabinoid CB1 receptor activity in the maintenance of synaptic integrity and neuroplasticity in the hippocampus, these data suggest that changes in cannabinoid CB1 receptor activity following stress may contribute to stress-induced modulation of these processes.