SYNAPTOPHYSIN-LIKE IMMUNOREACTIVITY IN THE RAT OLFACTORY-BULB DURING POSTNATAL-DEVELOPMENT AND AFTER RESTRICTED EARLY OLFACTORY EXPERIENCE

Synaptophysin is a synaptic vesicle protein that provides a marker of synaptic distribution in the brain. We used synaptophysin immunohistoc hemistry to detect changes in synaptic distribution in the main olfact ory bulb during normal early postnatal development and following early olfactory restriction. Synaptophysin-like immunoreactivity appears ea rly in the postnatal development of most bulbar laminae. In the first postnatal week, the entire glomerular neuropil is stained intensely, b ut by PND 19, the glomerular perimeter becomes more intensely stained than its core. This immunoreactivity is especially dense along that as pect of the perimeter facing the olfactory nerve layer. To determine i f this developmental pattern could be affected by early olfactory expe rience, unilateral naris closure was performed on PND 1. In deprived b ulbs at PND 19, the difference in staining between the glomerular bord er and the glomerular core is significantly less than in either contra lateral glomeruli or glomeruli from unoperated animals. The difference between the glomerular border and the glomerular core is greater in b ulbs contralateral to a closed naris than in bulbs from unoperated ani mals. Staining intensity measured over entire glomeruli is not altered by naris closure, nor is staining of other laminae; The changes detec ted after naris closure indicate that the glomerular distribution of s ynaptophysin may be particularly sensitive to early olfactory experien ce.