Abstract
Agmatine is a metabolite of L‐arginine by arginine decarboxylase. Recent evidence suggests that it exists in mammalian brain and is a novel neurotransmitter. The present study measured agmatine levels in several memory‐associated brain structures in aged (24‐month‐old), middle‐aged (12‐month‐old), and young (4‐month‐old) male Sprague Dawley rats using liquid chromatography/mass spectrometry. Agmatine levels were significantly decreased in the CA1, but increased in the CA2/3 and dentate gyrus, subregions of the hippocampus in aged and middle‐aged rats relative to the young adults. In the prefrontal cortex, a dramatic decrease in agmatine level was found in aged rats as compared with middle‐aged and young rats. There were significantly increased levels of agmatine in the entorhinal and perirhinal cortices in aged relative to middle‐aged and young rats. In the postrhinal and temporal cortices, agmatine levels were significantly increased in aged and middle‐aged rats as compared with young adults. The present findings, for the first time, demonstrate age‐related changes in agmatine levels in memory‐associated brain structures and raise a novel issue of the potential involvement of agmatine in the aging process. © 2008 Wiley‐Liss, Inc.