Hormonal axes in Drosophila: regulation of hormone release and multiplicity of actions

Hormones regulate development, as well as many vital processes in the daily life of an animal. Many of these hormones are peptides that act at a higher hierarchical level in the animal with roles as organizers that globally orchestrate metabolism, physiology and behavior. Peptide hormones can act on multiple peripheral targets and simultaneously convey basal states, such as metabolic status and sleep-awake or arousal across many central neuronal circuits. Thereby, they coordinate responses to changing internal and external environments. The activity of neurosecretory cells is controlled either by (1) cell autonomous sensors, or (2) by other neurons that relay signals from sensors in peripheral tissues and (3) by feedback from target cells. Thus, a hormonal signaling axis commonly comprises several components. In mammals and other vertebrates, several hormonal axes are known, such as the hypothalamic-pituitary-gonad axis or the hypothalamic-pituitary-thyroid axis that regulate reproduction and metabolism, respectively. It has been proposed that the basic organization of such hormonal axes is evolutionarily old and that cellular homologs of the hypothalamic-pituitary system can be found for instance in insects. To obtain an appreciation of the similarities between insect and vertebrate neurosecretory axes, we review the organization of neurosecretory cell systems in Drosophila. Our review outlines the major peptidergic hormonal pathways known in Drosophila and presents a set of schemes of hormonal axes and orchestrating peptidergic systems. The detailed organization of the larval and adult Drosophila neurosecretory systems displays only very basic similarities to those in other arthropods and vertebrates.

Relationship Between Gonad Condition and Neurosecretory Cell Activity in the Green-Lipped Mussel, Perna canaliculus

The relationship between the activity of neurosecretory cells and gonad development of Perna canaliculus was investigated. The variation in staining intensity of the neurosecretory cells in different ganglia was evaluated. Changes in staining intensity of neurosecretory cells (NSC) were correlated with gonad development. The variation in colour intensity (CI) resulted from differences in the amount of secretory materials within the NSCs. The neurosecretory cell types A and B showed a similar pattern of staining intensity, and showed correlation with gametogenesis and spawning. At the beginning of gonad development, these cells possessed very few granules and the number of granules in the cells increased with gonad maturation. The staining intensity decreased in A and B- cells just after spawning. Cell types C and D did not show any substantial changes in colour intensity with gonad changes.DOI: http://dx.doi.org/10.3329/pa.v18i2.18169 Progress. Agric. 18(2): 135 - 148, 2007