Abstract
To the Editor:
We thank Kuge and his colleagues for pointing out the importance of Harderian gland radioactivity located just in front of the brain structures. We had previously noted the high radioactivity on the rostral slice located in front of the brain. Therefore, we carefully avoided such high activity areas in determining the regions of interest in the frontal lobes.
Our study was based on the cerebral glucose metabolic rate (CMRglc) and metabolic rate constants calculated from the radioactivity of the brain and artery, so that even if there were some influence of the Harderian gland on radioactivity of the frontal lobes, it would lead to abnormally high CMRglc value and abnormally deviated metabolic rate constants. Our calculated data were consistent with previously reported data based on the autoradiographic method; therefore, we assumed that there was no influence of the Harderian glands on frontal lobe radioactivity. Furthermore, there would be no possibility that cholinergic destruction of the basal forebrain would affect the fluorodeoxyglucose accumulation in the Harderian glands. Therefore, we do not think that the results of our experiments were affected by the activities of the Harderian glands.