The Journal of Neurophysiology Vol. 84 No. 4 October 2000, pp. 1881-1887
Copyright ©2000 by the American Physiological Society

Laminar and Temporal Heterogeneity of NMDA/Metabotropic Glutamate Receptor Binding in Posterior Cingulate Cortex

Thomas G. Hedberg,^1,2,6 Ellen F. Sperber,^1,2,5 Jana Velíková,^1,2,4 and Solomon L. Moshé^1,2,3,4

 ¹Department of Neurology,  ²Department of Neuroscience, and  ³Department of Pediatrics, Albert Einstein College of Medicine; and  ⁴Center for Epilepsy Management, Montefiore Medical Center, Bronx 10461;  ⁵Mercy College, Dobbs Ferry, New York 10522; and  ⁶Novartis Pharmaceuticals, East Hanover, New Jersey 06851

Hedberg, Thomas G., Ellen F. Sperber, Jana Velíková, and Solomon L. Moshé. Laminar and Temporal Heterogeneity of NMDA/Metabotropic Glutamate Receptor Binding in Posterior Cingulate Cortex. J. Neurophysiol. 84: 1881-1887, 2000. Both N-methyl-D-aspartate (NMDA) and quisqualate/AMPA-insensitive metabotropic glutamate (mGlu) receptors mediate plasticity induction in neocortex, but their interlaminar distribution in cortical microcircuits is largely unknown. We used (+)³H-MK801 and ³H-glutamate binding plus saturating concentrations of NMDA, AMPA, and quisqualate to autoradiographically map NMDA and mGlu receptor sites by lamina in posterior cingulate cortex in adult male rats. Specific binding at NMDA receptor sites in laminae II/III and VI was significantly reduced in comparison to other laminae. Brains prepared from rats killed during dark phase of a 12h/12h light/dark cycle showed a mean 129% increase in overall (+)³H-MK801 binding versus light phase brains but retained reduced binding densities in laminae II/III and VI. In contrast to NMDA findings, specific binding at mGlu sites was consistently elevated during light phase in both laminae II/III and VI. Specific ³H-glutamate binding in dark-phase brains showed an overall 147% increase versus light phase binding but did not retain significant interlaminar heterogeneity. Interpreted in accordance with our physiologically derived models of hippocampo-cortical microcircuitry, these results suggest that spatial and temporal variations in glutamate receptor distribution may play an important role in intracingulate neural processing of afferent input from hippocampus.