THE CONTROL OF NEUROSECRETION AND DIAPAUSE BY PHYSIOLOGICAL CHANGES IN THE BRAIN OF THE CECROPIA SILKWORM

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Abstract
At pupation, the neuro-secretory cells in the brain of Platysamia cecropia lose endocrine activity. Consequently, the pupa enters diapause. Endocrine activity is restored following prolonged exposure to low temperatures. At pupation, the brain as a whole loses electrical activity and cholinesterase becomes undetectable. However, the return of endocrine activity is prefaced by the return of enzymatic and electrical activities. The same factors which influence the return of endocrine activity favor the return of activity to the brain as a whole. During diapause there is an accumulation of a cholinergic material in the brain; this accumulation is hastened by low temperatures. The accumulation is not due to an increase in the brain''s cholineacetylase. These changes are peculiar to the brain, throughout diapause the ventral nerve cord retains electrical activity and a constant level of cholinesterase and cholinergic material. The evidence suggests that the pupal diapause of Cecropia results from a failure of the entire brain.