Sequence of ultrastructural changes induced by activation in the posterior neurosecretory cells in the brain of Rhodnius prolixus with special reference to the role of lysosomes.

The posterior neurosecretory cell (PNC) group in the brain of Rhodnius prolixus is composed of five ultrastructurally identical cells. The PNC were examined in the unfed fifth instar and at seven stages (from 15 min to 14 days) after activation was initiated by feeding. Each stage examined revealed successive changes in morphology which can be related to the synthesis, maturation, storage and transport of neurosecretory material. It is suggested, in particular, that the lysosomal system (dense bodies and multivesicular bodies) may play a role in the maturation of the secretory granules.