Transient Synaptic Potentiation in the Visual Cortex. II. Developmental Regulation

• Published in: Journal of neurophysiology 1997-03, Vol.77 (3), p.1284-1293
• Main Authors: Harsanyi, Krisztina, Friedlander, Michael J
• Format: Article
• Language: English
• Subjects: Aging - physiology; Animals; Calcium - physiology; Electric Stimulation; Guinea Pigs; In Vitro Techniques; Membrane Potentials - physiology; Neuronal Plasticity - physiology; Neurons - physiology; Nitric Oxide - biosynthesis; Nitric Oxide - physiology; Patch-Clamp Techniques; Receptors, N-Methyl-D-Aspartate - antagonists & inhibitors; Synapses - physiology; Visual Cortex - cytology; Visual Cortex - growth & development; Visual Cortex - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.1997.77.3.1284

Krisztina Harsanyi and Michael J. Friedlander Department of Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama 35294 Harsanyi, Krisztina and Michael J. Friedlander. Transient synaptic potentiation in the visual cortex. II. Developmental regulation. J. Neurophysiol. 77: 1284-1293, 1997. In our previous study, pairing-induced transient synaptic potentiation in supragranular layers of the visual cortex was described in mature guinea pigs. In the present study, the development of this type of synaptic plasticity and the underlying cellular mechanisms that mediate it were evaluated in animals from postnatal day (PND) 5 to 180. Potentiation is more reliably evoked in younger animals (likelihood: 75%, PND 5-30; 51%, PND 34), and the magnitude of the effect is greater (+40 ± 3%, mean ± SE, PND 5-30; +26 ± 3%, PND 34). Similar to data obtained from the mature animals, visual cortical transient synaptic potentiation in the immature cortex occurs at excitatory synaptic sites directly activated by the stimulation, and activation by local recurrent cortical circuits is not necessary for the induction of this potentiation. This is demonstrated by 1 ) experiments in which action potential output from the paired neuron was blocked by Lidocaine, N -ethyl bromide quaternary salt applied into the neuron (5 of 5), and 2 ) experiments in which the contribution to the compound postsynaptic potential by inhibitory synapses was eliminated by selective, intracellular blockade of -aminobutyric acid-mediated inhibitory postsynaptic potentials only onto the recorded neuron (7 of 11). Thus these perturbations do not reduce the likelihood or magnitude of this synaptic potentiation. In contrast to the N -methyl- D -aspartate (NMDA) receptor dependence for induction of this synaptic potentiation in the cortex of mature animals, in the young animals' cortices (PND 11-27) potentiation is readily induced during blockade of NMDA receptors (72%, 13 of 18, not different from control: 75%, 40 of 53). Thus the NMDA receptor becomes functionally linked to a synaptic potentiation cascade during development, replacing another 2-amino-5-phosphonovaleric acid (APV)-insensitive potentiation process in the neonatal cortex. Postsynaptic intracellular calcium has a critical role in the induction of this form of synaptic potentiation in all ages studied. Synaptic potentiation was prevented (8 of 11 cases) or was replaced by synaptic depression (3 of 11 cells) in experiments in which po