Dopamine and serotonin in the larval CNS of a drosophilid fly, Chymomyza costata: Are they involved in the regulation of diapause?
✍ Scribed by Vladimir Kostal; Hirofumi Noguchi; Kimio Shimada; Yoichi Hayakawa
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 232 KB
- Volume
- 42
- Category
- Article
- ISSN
- 0739-4462
No coin nor oath required. For personal study only.
✦ Synopsis
Developmental profiles of dopamine (DA) and serotonin (5-hydroxytryptamine, 5-HT) in the larval CNS of Chymomyza costata were measured by HPLC using electrochemical detection. Larvae of two strains, wild-type (W) and nondiapause mutant (M), were maintained either under long-day (LD, inducing pupariation) or short-day (SD, inducing diapause in W-strain) photoperiods. The levels of DA ranged from 10 fmol/CNS (early 3rd instar larvae) to 60 fmol/CNS (150-day-old diapausing larvae); the range for 5-HT was from 10 fmol/CNS to 75 fmol/CNS in the same larvae. During the 3rd larval instar, which is the decisive stage for photoperiodic induction of diapause, no differences were found in DA developmental profiles between different strains or conditions. Some differences were found in 5-HT developmental profiles, but only after the end of sensitive stage, and were therefore regarded as insignificant for regulation of developmental mode. Similarly, no clear correlations between the developmental profiles of DA and 5-HT and the course of developmental changes during the maintenance and termination of a few-month-long larval diapause were observed. Furthermore, the DA and 5-HT levels in the CNS were pharmacologically manipulated by feeding the larvae with either precursors or enzyme inhibitors of DA and 5-HT biosynthesis. Although retardations of growth and development were observed, the treated larvae retained full capacity for the photoperiodic response, irrespective of the level of DA or 5-HT in their CNS. Larvae with their 5-HT depleted to trace levels survived and were capable of diapause induction, maintenance, and termination. Depletion of DA to trace levels resulted in 100% mortality. Collectively, the present study indicates that Abbreviations used: CNS = central nervous system; DA = dopamine; DD = continuous darkness; DOPA = L-3,4dihydroxyphenylalanine; EPI = epinephrine; HPLC-ECD = high pressure liquid chromatography-electrochemical detection; 5-HT = serotonin (5-hydroxytryptamine); 5-HTP = 5hydroxy-L-tryptophan; 3-IT = 3-iodo-L-tyrosine; JH = juvenile hormone; LD = long-day; LD20 = lethal dose 20%; M = mutant-strain;