Changes in brain monoamine contents in diapause pupae of Antheraea pernyi when activated under long-day and by chilling

Abstract

The contents of biogenic monoamines in the brain–subesophageal ganglion complex were measured in both bivoltine and univoltine strains of the Chinese oak silkmoth, Antheraea pernyi using HPLC-ECD. The contents in the bivoltine strain were monitored every five days under LD 12:12 and 16:8, photoperiods maintaining and terminating diapause, respectively at 25°C. The univoltine strain was chilled at 2°C and the monoamine contents were measured at 10-day intervals. Dopamine, norepinephrine and epinephrine-like peaks were detected from the crude homogenate and the eluate from the alumina oxide column. The contents of both dopamine and epinephrine-like compounds dropped significantly before the ecdysteroid surge at LD 16:8 and steadily decreased during cold storage. In contrast, 5-HT increased sharply in parallel with the surge of ecdysteroid. Cold storage also strongly affected indolamine metabolism. After cold storage, 5-HT was more predominantly metabolized by N-acetyltransferase than by monoamine oxidase, since 5-HIAA dropped significantly, while N-acetylserotonin increased during cold storage. A dual regulatory system consisting of the ecdysiotropin inhibitory pathway by catecholamaine metabolism and the ecdysiotropin stimulatory pathway by indolamine metabolism is proposed for the regulation of pupal diapause in this species.