DISTRIBUTION AND SYNAPTOLOGY OF DOPAMINERGIC FIBERS IN THE MATURE ANDDEVELOPING LATERAL SEPTUM OF THE RAT

The dopamine innervation of the adult and developing lateral septum of the rat was investigated with light and electron microscope immunocyt ochemistry using anti-dopamine antibodies. Light microscopic analysis showed that the pattern of innervation of the lateral septum exhibited a marked reorganization during the first 2 postnatal weeks, when it a cquired features comparable to the adult. Ultrastructural analysis sug gested that there may be two different dopamine inputs in the lateral septum. The first develops earlier in life and, through symmetrical ax odendritic synapses, affects remote parts of neurons and may cause inh ibition. The second develops later and, through asymmetrical axosomati c synapses, affects neuronal somata and may cause excitation. These fi ndings may explain the reported contradictory results concerning the p hysiological role of dopamine in neurons of the lateral septum. (C) 19 97 Elsevier Science B.V.