ISSN: 0970-938X (Print) | 0976-1683 (Electronic)

Biomedical Research

An International Journal of Medical Sciences

Abstract

Free excitatory postsynaptic densities: Morphological substrates for synapse formation and evidence of synapse elimination

Nerve cells communicate primarily through chemical synapses. Study of brain development essentially consists of study of synapse formation. The role played by prospective pre-and postsynaptic processes in synaptic development is not fully understood. The present study was aimed at understanding the role of postsynaptic component is synaptogenesis. This study has been carried out on prenatal (13 to 35 weeks) human lateral geniculate nuclei (LGN) immersion fixed in Karnovsky?s fixative and processed for transmission electron mi-croscopy. It was observed that the period between 16 to 20 weeks of gestation is marked by occurrence of numerous, pleomorphic free postsynaptic densities (PSDs). These free sites were located on different parts of differentiating neurons. Many of them had no prospective presynaptic partners in their vicinity, while others revealed variable amount of incongru-ency with their presynaptic partners and in some occasions they were associated with degenerating profiles. This period also coincided with many other events previously reported in the developing human LGN, e.g., spurt in volumetric growth, glial cell differentiation, synaptogenesis, cytoarchitectonic lamination as well as neurochemical maturation. It was concluded that the free PSDs are heterogenous in origin, being programmed/de novo and waiting to make synaptic contact for the first time; and vacated, the left out sites after pre-synaptic terminal degeneration and waiting to establish new contact for the second time and that glial cells play important roles in the whole process of synaptogenesis


Author(s): Aijaz Ahmed Khan

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