No abstract

The rhesus monkey is widely used as an experimental animal model in the study of brain function and disease. While previous quantitative studies have provided knowledge of regional numbers, little is known of the total neocortical neuron and glial cell numbers in this species. The aim of this study is to establish quantitative norms. We use the optical fractionator and Cavalieri principle to examine the right hemisphere of eight young rhesus monkeys taken from the control group of an ongoing study. Applying these methods to agar-embedded and vibratome-sectioned tissue, we generate estimates of cell numbers and regional volumes of neocortical and hippocampal regions with coefficients of variance (CV) around 10%. The mean unilateral neocortical neuron number is 1.35 3 10 9 (CV 6 0.10) and the mean unilateral neocortical glial cell number is 0.78 3 10 9 (CV 6 0.17). Mean unilateral neocortical volume is found to be 8.5 (CV 6 0.10) cm 3 after processing, or 19 cm 3 when correcting for shrinkage. The neuron/glia ratio is 1.77. The neurons are distributed with 18% in the frontal cortex, 57% in the temporal and parietal cortices, and 25% in the occipital cortex. In the hippocampal subregions, we found unilateral neuron number of 1.72 3 10 6 (CV 6 0.13) and glial number of 2.25 3 10 6 (CV 6 0.17) in CA1, and 0.80 3 10 6 (CV 6 0.27) neurons and 1.05 3 10 6 (CV 6 0.26) glial cells in CA2-3. Comparisons with related studies show quantitative variation, but also variations in methods and applications. The results are phylogenetically consistent, apart from the neuron/glia ratio, which is remarkably higher than what is found in other species.

No abstract

Background Anatomical evidence of brain damage from electroconvulsive therapy (ECT) is lacking, but there are no modern stereological studies in primates documenting its safety. Magnetic seizure therapy (MST) is under development as a less invasive form of convulsive therapy, and there is only one prior report on its anatomical effects. We discerned no histological lesions in the brains of higher mammals subjected to electroconvulsive shock (ECS) or MST, under conditions that model closely those used in humans. We sought to extend these findings by determining whether these interventions affected the number of neurons or glia in the frontal cortex or hippocampus. Methods Twenty-four animals received 6 weeks of ECS, MST, or anesthesia alone, 4 days per week. After perfusion fixation, numbers of neurons and glia in frontal cortex and hippocampus were determined by unbiased stereological methods. Results We found no effect of either intervention on volumes or total number or numerical density of neurons or glia in hippocampus, frontal cortex, or subregions of these structures. Conclusions Induction of seizures in a rigorous model of human ECT and MST therapy does not cause a change in the number of neurons or glia in potentially vulnerable regions of brain. This study, while limited to young, healthy, adult subjects, provides further evidence that ECT and MST, when appropriately applied, do not cause structural damage to the brain.