title: Developmental decline in modulation of glutamatergic synapses in layer IV of the barrel cortex by group II metabotropic glutamate receptors.
abstract: Previously, we demonstrated that group II metabotropic glutamate receptors (mGluRs) reduce glutamate release from thalamocortical synapses during early postnatal development (P7-11). To further examine the role of group II mGluRs in the modulation of somatosensory circuitry, we determined whether group II mGluRs continue to modulate thalamocortical synapses until adulthood and whether these receptors also modulate intra-cortical synapses in the barrel cortex. To address these issues, we examined the effect of the group II mGluR agonists on thalamocortical excitatory postsynaptic currents (EPSCs) and intra-barrel EPSCs in slices from animals of different ages (P7-53). We found that the depression of thalamocortical EPSCs by group II mGluRs rapidly declined after the second postnatal week. In contrast, adenosine continued to depress thalamocortical EPSCs via a presynaptic mechanism in young adult mice (P30-50). Activation of group II mGluRs also reduced intra-barrel EPSCs through a postsynaptic mechanism in young mice (P7-11). Similar to the thalamocortical synapses, the group II mGluR modulation of intra-barrel excitatory synapses declined with development. In young adult animals (P30-50), group II mGluR stimulation had little effect on intra-barrel EPSCs but did hyperpolarize the neurons. Together our results demonstrate that group II mGluRs modulate barrel cortex circuitry by presynaptic and postsynaptic mechanisms depending on the source of the synapse and that this modulation declines with development.
authors.affiliation: Department of Biology, Pontifical Catholic University of Puerto Rico, Ponce, Puerto Rico 00717.
authors.forename: Z
authors.initials: Z
authors.lastname: Mateo
authors.affiliation: Department of Physiology, Pharmacology and Toxicology, Ponce School of Medicine, Ponce, Puerto Rico 00732. Electronic address: jporter@psm.edu.
authors.forename: J T
authors.initials: JT
authors.lastname: Porter
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000033:anatomy & histology / Q000187:drug effects / Q000254:growth & development* / Q000502:physiology; D004558:Electric Stimulation; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism*; D051379:Mice; D008839:Microelectrodes; D009434:Neural Pathways / Q000033:anatomy & histology / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D018408:Patch-Clamp Techniques; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*; D018047:Receptors, Purinergic P1 / Q000378:metabolism; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D013788:Thalamus / Q000033:anatomy & histology / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D046509:Tissue Culture Techniques
chemical_list: D018094:Receptors, Metabotropic Glutamate; D018047:Receptors, Purinergic P1; D018698:Glutamic Acid
keywords: barrel cortex; development; metabotropic glutamate receptors