Journal of Neuroscience, Vol 15, 7916-7928, Copyright © 1995 by Society for Neuroscience
Transiently selective activation of phosphoinositide turnover in layer V pyramidal neurons after specific mGluRs stimulation in rat somatosensory cortex during early postnatal development
JA Bevilacqua, CP Downes and PR Lowenstein
Laboratory of Cellular and Molecular Neurobiology, School of Molecular and Medical Biosciences, University of Wales College of Cardiff, United Kingdom.
Biochemical analysis of muscarinic- and metabotropic-glutamate receptor
stimulated phosphoinositide (PI) turnover in rat cortical preparations
during the first three weeks of postnatal development indicates the
existence of a transiently increased accumulation of labeled inositol
polyphosphates during the first postnatal week (Gonzales and Crews, 1985;
Dudek et al., 1989). We now report for first time the visualization of
those neurons responding with increased PI turnover to glutamatergic or
cholinergic-receptor stimulation in rat somatosensory cortex during early
postnatal development utilizing a recently described method (Bevilacqua et
al, 1994). Three, 7, 10, 14, and 21 d old rats were studied. Carbachol in
the presence of lithium stimulates 3H-CMP-PA accumulation throughout the
cortex at all ages studied. In comparison labeled neurons responding to
t-ACPD in the presence of lithium were located exclusively in layer V at P3
and P7, but were found labeled throughout the cortex at P10. Given that
glutamate and cholinergic agonist stimulation are both necessary but not
sufficient for cortical plasticity to occur, and that muscarinic and mGluRs
stimulation both induce a peak in PI turnover response during the same
period of experience-dependent neocortical plasticity, PI derived second
messengers signals might be involved in the regulation of the molecular
mechanisms of neuronal plasticity. Furthermore, our results show the
anatomical correlate of receptor-specific PI turnover activation, and
indicate that specific agonist induced PI responses are age, and layer
specific.