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Nishijima T, Okamoto M, Matsui T, Kita I, Soya H. Hippocampal functional hyperemia mediated by NMDA receptor/NO signaling in rats during mild exercise. J Appl Physiol (1985) 2012; 112:197-203. [DOI: 10.1152/japplphysiol.00763.2011] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Current studies have demonstrated that exercise increases regional cerebral blood flow (rCBF), an index of neuronal activity. However, neuronal regulation of the increased rCBF in the brain parenchyma is poorly understood. We developed a running model with rats for monitoring hippocampal cerebral blood flow (Hip-CBF) and found that mild treadmill running increases Hip-CBF in a tetrodotoxin-dependent manner, suggesting that functional hyperemia, an increase in rCBF in response to neuronal activation, occurs in the running rat's hippocampus (Nishijima T and Soya H. Neurosci Res 54: 186–191, 2006). To further support our hypothesis, it was important to discover the neurogenic pathways behind the increase in Hip-CBF that occurred during running. Here, we examine the possible role of N-methyl-d-aspartate (NMDA) receptor/nitric oxide (NO) signaling and group I metabotropic glutamate receptors in mediating the Hip-CBF increase. Hip-CBF during running was measured by laser-Doppler flowmetry. Intrahippocampal drug administration was performed by microdialysis. Mild treadmill running (10 m/min) increased Hip-CBF, which was remarkably attenuated by either NMDA receptor antagonists (1 mM MK-801) or NO synthase inhibitors (2 mM NG-nitro-l-arginine methyl ester). However, group I metabotropic glutamate receptor antagonists {1 mM 7-(hydroxyimino)cyclopropa[ b]chromen-1a-carboxylate ethyl ester + 1 mM 2-methyl-6-(phenylethynyl)pyridine hydrochloride} augmented the running-induced Hip-CBF increase. We also found that rCBF in the olfactory bulb was unchanged with running. These results strongly suggest that Hip-CBF during mild exercise is regulated locally under hippocampal neuronal activity, mediated mainly through NMDA receptor/NO signaling. Collectively, these results, together with our previous findings, support our hypothesis that mild exercise elicits neuronal activation, which then triggers functional hyperemia in the rat hippocampus.
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Affiliation(s)
- Takeshi Nishijima
- Laboratory of Exercise Biochemistry and Neuroendocrinology, University of Tsukuba Graduate School of Comprehensive Human Sciences, Ibaraki; and
- Laboratory of Behavioral Physiology, Department of Human Health Sciences, Tokyo Metropolitan University, Tokyo, Japan
| | - Masahiro Okamoto
- Laboratory of Exercise Biochemistry and Neuroendocrinology, University of Tsukuba Graduate School of Comprehensive Human Sciences, Ibaraki; and
| | - Takashi Matsui
- Laboratory of Exercise Biochemistry and Neuroendocrinology, University of Tsukuba Graduate School of Comprehensive Human Sciences, Ibaraki; and
| | - Ichiro Kita
- Laboratory of Behavioral Physiology, Department of Human Health Sciences, Tokyo Metropolitan University, Tokyo, Japan
| | - Hideaki Soya
- Laboratory of Exercise Biochemistry and Neuroendocrinology, University of Tsukuba Graduate School of Comprehensive Human Sciences, Ibaraki; and
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