Abstract
Abstract The Timm sulfide silver method normally stains the hippocampus and the fascia dentata of the rat in a laminar fashion, and the laminae correspond remarkably well to the terminal fields of the various afferent systems. Surgical removal of a major afferent system with origin in the entorhinal area — the perforant path — was performed in animals from 5 to 30 days old, and the effects on the Timm staining pattern analysed. The perforant path, distinguished in a lateral and a medial part, normally terminates in non-overlapping laminae in stratum moleculare (lacunosum-moleculare) of CA3 and the outer parts of the dentate molecular layer. In the deentorhinated animals these layers had only achieved between one-half and two-thirds of their normal width. Also, the staining characteristics of the perforant path zones were absent. Depending on the age of the animals at the time of the deentorhination other staining types resembling those of the unaltered neighboring fields had replaced the normal staining in the deafferented zones, either totally or in part. According to type and predominant localization the extended staining was classified as either CA3 or CA1-subiculum associated. A special staining type resembling that of the intense black mossy fibers of the hilus of fascia dentata was regularly found above the granule cell bodies in the deentorhinated animals. The replacement of the normal staining of the deafferented layers of fascia dentata and CA3 by staining types resembling those found in adjacent fields is discussed in relation to earlier observations of aberrant growth of axons terminating in these fields. A failure of decommissuration to cause any changes in the Timm staining pattern was also observed. The ipsilateral association systems which normally share terminal fields with the commissural fibers probably preserve the integrity of these common zones.
Published Version
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