Cerebral Cortex Advance Access originally published online on December 22, 2004
Cerebral Cortex 2005 15(8):1250-1260; doi:10.1093/cercor/bhi008
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© Oxford University Press 2005; all rights reserved
Synaptic and Vascular Associations of Neurons Containing Cyclooxygenase-2 and Nitric Oxide Synthase in Rat Somatosensory Cortex
Department of Neurology and Neuroscience, Weill Medical College of Cornell University, New York, NY 10021, USA
Address correspondence to Virginia M. Pickel, Department of Neurology and Neuroscience, Cornell University Medical College, 411 E 69th Street, Room KB-410, New York, NY 10021, USA. Email: vpickel{at}mail.med.cornell.edu.
Cyclooxygenase-2 (COX-2) is a rate-limiting enzyme for prostanoid synthesis that is present in cortical pyramidal neurons and highly implicated in control of cerebral blood flow during neural activity. We examined the electron microscopic localization of COX-2 and neuronal nitric oxide synthase (nNOS), a functionally related enzyme, in the somatosensory cortex of rat brain to determine the relevant functional sites. COX-2 immunoreactivity was detected in significantly more somatodendritic than axonal profiles, while nNOS was more often seen in axon terminals. The dendritic COX-2 was localized to endomembranes near synaptic inputs from axon terminals, some of which contained nNOS. Conversely, COX-2 terminals formed asymmetric, excitatory-type synapses with dendrites containing nNOS. The dendritic and axonal profiles containing COX-2 as well as those containing nNOS were minimally separated from penetrating arterioles and capillaries by filamentous glial processes. The perivascular COX-2 labeled terminals were among those that also formed axo-dendritic synapses, suggesting that the release of prostanoids and/or excitatory transmitters from a single terminal may simultaneously affect neuronal activity and cerebral blood flow. Thus, COX-2 has a compartmental distribution in somatosensory cortical neurons consistent with the local neuronal synthesis of prostanoids that are involved in neurovascular coupling and whose actions are modulated by nitric oxide.
Key Words: cerebral blood flow • excitatory transmission • hyperemia • prostaglandins • synaptic plasticity
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