Axonal transport of [3H]fucosyl glycoproteins in noradrenergic neurons in the rat brain.

The transport of [3H]fucosyl glycoproteins has been investigated in the noradrenergic pathway from the locus coeruleus (LC) to the hypothalamus in the rat brain by use of local injection of L-[6-3H]fucose into the LC. Two discrete waves of 3H-glycoprotein pass through the hypothalamus in a caudorostral direction traveling at 4 mm/h (96 mm/day) and 2 mm/h (48 mm/day) respectively. Both waves appear to originate from the LC at approximately 2 h after the injection of [3H]fucose, a time when incorporation into glycoprotein has not yet peaked in the LC. Lesioning the LC-hypothalamic pathway with 6-OHDA, but not carrier solution, blocks both waves of 3H-glycoprotein demonstrating that transport occurs exclusively in the catecholamine axons within the pathway. DEAE-Sephadex chromatography combined with 6-OHDA lesions demonstrates clear differences in the character of 3H-glycoproteins in the two waves undergoing transport. The relative lack of labelling of hypothalamic glycoproteins in the interval before and after these waves suggests that relatively few rapidly transported glycoproteins contribute to the non-terminal axon membrane and are probably primarily transported to the nerve terminal. No evidence for slow axoplasmic transport of [3H]fucosyl glycoproteins is found.