Metamorphosis of identified neurons innervating thoracic neurohemal organs in the blowfly: Transformation of cholecystokininlike immunoreactive neurons

Abstract

With antisera to gastrin/cholecystokinin, we studied the postembryonic development of neurons in the thoracic ganglia of the blowfly Calliphora erythrocephala. There are some changes in the population of thoracico-abdominal neurons displaying gastrin/CCK-like immunoreactivity (CCKLI): some CCKLI neurons cannot be found after pupariation; other neurons become immunoreactive during metamorphosis. Six large thoracic CCKLI neurons could, however, be followed through metamorphosis. These CCKLI neurons innervate neuropil in thoracic ganglia and segmental neurohemal organs in the larva. In the adult insect the same neurons innervate many regions of thoracic neuropil and extensive neurohemal areas dorsally in the fused thoracico-abdominal ganglia. The immunoreactive terminals are located in the neural sheath, and electron microscopy shows that only an extracellular basal lamina separates them from the circulating hemolymph. On the basis of the location of their terminals, it can be suggested that the six CCKLI neurons have functions as neurosecretory cells both in the larva and in the adult. In both developmental stages the neurons can interact with large portions of the thoracic nervous system and release bioactive substance into the circulation. A CCK-like substance may be used both as a transmitter/neuromodulator and as a neurohormone by the same neuron. The larval neurohemal organs are described here for the first time. They show characteristics of thoracic perisympathetic organs known to exist in more primitive insects. The adult neurohemal regions on the other hand are typical of higher insects. Since the neurohemal areas are continuously (during development) innervated by the six large CCKLI neurons, we conclude that the larval neurohemal organs metamorphose into the adult neurohemal area in the neural sheath.

Independent roles of thedachshundandeyes absentgenes in BMP signaling, axon pathfinding and neuronal specification

“…1) (Lundgren et al, 1995). The Tv neurons are unique among the ap-neurons by virtue of their expression of Fmrf and their axonal trajectory; the majority of ap cells extend their axons within an ipsilateral longitudinal fascicle, whereas the Tv axons project to the midline, exit the VNC dorsally and innervate the endocrine dorsal neurohemal organs (DNH) (Gorczyca et al, 1994;Nassel et al, 1988). The restricted Fmrf expression and unique axonal trajectory of the Tv cell together provide highly specific terminal differentiation markers with which to ask basic questions concerning cell specification in the central nervous system (Fig.…”

Distribution of synapses on two local auditory interneurones, ON1 and ON2, in the prothoracic ganglion of the cricket: relationships with GABA-immunoreactive neurones

“…Large granular vesicles have been observed in neurones containing neuropeptides (e.g. Nässel et al 1988;Ude and Eckert 1988;Elekes and Ude 1993) and/or biogenic amines (Nässel et al 1985;Elekes et al 1987;Salecker and Distler 1990;Sun et al 1993), which have been shown to play an important role in neuromodulation (Bicker and Menzel 1989). It is possible that the input from neurones containing this type of vesicle may play a role in central modulatory effects seen in ON1.…”

Fine-tuning of secondary arbor development: the effects of the ecdysone receptor on the adult neuronal lineages of theDrosophilathoracic CNS

“…The lineage arbors exist within a complex neuropil in the vicinity of future synaptic partners, making dependence on local cues likely. By contrast, the Tv neuron axon arbors are embedded within the basal lamina on the dorsal surface of the CNS, away from other neurons (Nassel et al, 1988), thereby increasing their reliance on hormonal signals rather…”