Histochemical study of innervation and NADPH-D activity of the thymus.

Acetylcholinesterase (ACHE)-positive nerve fibres in the thymus of the rat form perivascular plexuses as well as free ACHE-positive nerves, which do not follow the course of the vessels. A higher number of ACHE-positive nerves was observed in corticomedullary border and the medulla, a lower number in the cortex of the thymus lobuli. A gradual reduction of ACHE-positive intrathymus nerve formation was recorded and correlated with the increasing age of the rats. Nicotinamide adenine dinucleotide phosphate-diaphorase positive cells observed in the rat thymus were irregular with numerous projections and were located on the boundary of the cortex and medulla.