Temperature-induced stress response in Lymantria dispar neurosecretory neurons

Abstract

The release of neurosecretory material from A2 neurosecretory neurons (NSNs) was stimulated in Lymantria dispar fourth instar caterpillars exposed to a temperature of 35 degrees C for 1, 12, and 24 h, as well as those allowed recover after exposure (12 h at 35 degrees C, then 12 h at 23 degrees C). The levels of 2 protein forms with the same molecular mass as bombyxin (3-4 and 4-5 kDa) increased with prolonged exposure to 35 degrees C. The second band was present only in the groups exposed to this stressor. There was intensified synthetic activity and a low level of secretion in L2' NSNs after exposure to 35 degrees C. We previously found these NSNs to be immunopositive for prothoracicotropic neurohormone. After this stress, densitometric analysis revealed a decreased amount of the 11-12 kDa isoform (present in the control group). The new isoform (13-15 kDa), expressed after exposure of the insects to a high temperature, increased in amount with prolonged exposure and after recovery at 23 degrees C. Short-term exposure of caterpillars to high temperatures (35 degrees C) is a stressor and activates carbohydrate metabolism, while PTTH immunopositive NSNs are secretory-inactive during acute thermal stress regimes.