Mechanisms of synaptic plasticity

Abstract

We have shown that the synapse maturation phase of synaptogenesis is a model for synaptic plasticity that can be particularly well-studied in chicken forebrain because for most forebrain synapses, the maturation changes occur slowly and are temporally well-separated from the synapse formation phase. We have used the synapse maturation phase of neuronal development in chicken forebrain to investigate the possible link between changes in the morphology and biochemical composition of the postsynaptic density (PSD) and the functional properties of glutamate receptors overlying the PSD. Morphometric studies of PSDs in forebrains and superior cervical ganglia of chickens and rats have shown that the morphological features of synapse maturation are characteristic of a synaptic type, but that the rate at which these changes occur can vary between types of synapses within one animal and between synapses of the same type in different species. We have investigated, during maturation in the chicken forebrain, the properties of the N-methyl-D-aspartate (NMDA) subtype of the glutamate receptors, which are concentrated in the junctional membranes overlying thick PSDs in the adult. There was no change in the number of NMDA receptors during maturation, but there was an increase in the rate of NMDA-stimulated uptake of 45Ca2+ into brain prisms. This functional change was not seen with the other ionotropic subtypes of the glutamate receptor and was NMDA receptor-mediated. The functional change also correlated with the increase in thickness of the PSD during maturation that has previously been shown to be due to an increase in the amount of PSD associated Ca(2+)-calmodulin stimulated protein kinase II (CaM-PK II). Our results provide strong circumstantial evidence for the regulation of NMDA receptors by the PSD and implicate changing local concentrations of CaM-PK II in this process. The results also indicate some of the ways in which properties of existing synapses can be modified by changes at the molecular level.

Study of EEG Brain Maturation Signals with Multifractal Detrended Fluctuation Analysis

“…Then, sketching the function F q {s) versus s in a graph with logarithmic scales, the functions h(q) and x{q) were obtained following Eqs. (6) and (8). Figure 1 shows the variation of h(q) for Bird #1 at the electrode LF for the six week posthatch recording.…”

“…Synapse formation in the chicken brain occurs most rapidly around the time of hatching and is complete by 10 to 14 days posthatch [6]. Subsequently, the immature synapses and neurons gradually attain adult ultrastructural and biochemical properties.…”

“…Following Eqs. (4) and(6) and assume that the length N of the series is an integer multiple of the scale s,N/s X \Y(vs) -Y((v-l)s)\ q ~ j? W-1(7)Stanley and co-workers show this multifractal formalism corresponding with the standard box counting theory, and they related both formalisms.…”

Entropy-Complexity Characterization of Brain Development in Chickens

“…In the subsequent maturation phase, during which the tissue environment is broadly stable, except for an increase in myelination, there is little change in synapse number in the brain overall, but immature, yet functional, synapses are altered to become like those found in the adult, brain with synaptic circuits being fine-tuned [21,22]. Synapse formation in the chicken brain occurs most rapidly around the time of hatching, and it is complete by 10 to 14 days posthatch [49]. Subsequently, the immature synapses and neurons gradually attain adult ultrastructural and biochemical properties.…”

Association of Shank 1A Scaffolding Protein with Cone Photoreceptor Terminals in the Mammalian Retina

“…The PSD is thought to be the prime target for postsynaptic plasticity, and the entry of Ca 2+ ions into the postsynaptic compartment [21], [49], [50], [51]. Ca 2+ entry through Ca 2+ -permeable glutamate receptors is considered to be the key signal for the induction and regulation of plastic changes at postsynaptic sites [52], [53], [54]. However, Shank proteins target multiple types of proteins, including Ca 2+ channels [4], [22], [23].…”