Structural differences between optic synapses in the suprachiasmatic nucleus of hooded and albino rats

Synapses of retinal afferents (optic synapses) in the suprachiasmatic nucleus (SCN) were morphometrically compared between hooded and albino rats. Optic synapses from albino rats show larger boutons with larger mitochondria, synaptic appositions with less postsynaptic density material, relatively more symmetric (presumably inhibitory) contacts, and relatively less asymmetric (presumably excitatory) contacts, compared with hooded rats. There are no differences in the numbers of clear and dense core vesicles, the size of synaptic appositions, and their numerical density in area of micrograph. Possible differences in activity and/or metabolism between optic synapses from hooded and albino rats are discussed.