Retinal afferents form Gray-type-I and type-II synapses in the suprachiasmatic nucleus (rat).
The synapses of optic nerve afferents in the suprachiasmatic nucleus (SCN) usually form Gray type I (asymmetrical) synapses, but about 13% show clear-cut Gray type II ( symmetrical) active zones. Some presynaptic elements form a Gray type I--active zone with one dendrite and a Gray type II-active zone with another postsynaptic element at the same time. It is discussed whether this variabilility is related to a simultaneous excitatory and inhibitory action, to a variable activity or efficiency of the synapses or to various stages of maturation.
D000818:Animals; D003712:Dendrites / Q000648:ultrastructure; D005260:Female; D007031:Hypothalamus / Q000033:anatomy & histology*; D008297:Male; D009433:Neural Inhibition; D051381:Rats; D012160:Retina / Q000033:anatomy & histology*; D013495:Supraoptic Nucleus / Q000033:anatomy & histology*; D013569:Synapses / Q000648:ultrastructure*; D009435:Synaptic Transmission; D013572:Synaptic Vesicles / Q000648:ultrastructure; D014795:Visual Pathways / Q000033:anatomy & histology