Glutamate receptor blockade alters the development of intracortical connections in rat barrel cortex.
We tested the hypothesis that glutamate receptor mediated activity is required for the postnatal development of intracortical connections in layers II/III of rodent barrel cortex. To block glutamate receptors, a slow release polymer (elvax) loaded with a glutamate receptor antagonist (D-AP5) was targeted subdurally over the future rat barrel cortex on P0 (day of birth). On P14-16 biotinylated dextran amine (BDA) was injected under the elvax into all layers to label neurons retrogradely. A BDA injection was made stereotactically at the mirror site of the untreated hemisphere of each animal. The animals survived to P22-24. Injection sites and retrogradely labeled cell bodies were identified in tangential sections in relation to the barrel map. D-AP5 treated and untreated hemispheres were matched according to the location of the injection site in the barrel map. Glutamate receptor blockade did not prevent the growth of intrinsic projections, but altered their organization. The normal row-like asymmetry of connections in untreated hemispheres was lacking in the D-AP5 treated cortex (ANOVA, p=0.02). Cortical activity mediated through glutamate receptors contributes to the correct development of connections between barrel columns in layers II/III.
James L. O'Leary Division of Experimental Neurology and Neurological Surgery, Department of Neurology and Neurological Surgery, Washington University School of Medicine, St Louis, MO 63110, USA. woolseyt@medicine.wustl.edu
Elias
E
Dagnew
Kalyan
K
Latchamsetty
Joseph P
JP
Erinjeri
Brad
B
Miller
Kevin
K
Fox
Thomas A
TA
Woolsey
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D001931:Brain Mapping; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D007839:Functional Laterality / Q000502:physiology; D009434:Neural Pathways / Q000187:drug effects*; D051381:Rats; D020318:Rats, Long-Evans; D017470:Receptors, Glutamate / Q000187:drug effects*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D013003:Somatosensory Cortex / Q000502:physiology*
D018691:Excitatory Amino Acid Antagonists; D017470:Receptors, Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D015763:2-Amino-5-phosphonovalerate