ISSN:
1432-0878
Keywords:
Neurosecretory cells
;
Leptinotarsa decemlineata
;
Innervation
;
Ultrastructure
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary The pathways of axonal transport of secretions from neurosecretory cells (NSC) in the medial group (viz. A-, A1, B-, and C-type NSC) and the lateral group (L-type NSC) are described. Individual axons can be recognized in the electron microscope by the kind of neurosecretory particles they contain. In general, the secretions from the medial NSC are carried to the contralateral nervi corporis cardiaci (NCC), those from the lateral NSC to the ipsilateral NCC. Some axons from the A-type NSC, in addition, may run to ipsilateral NCC. All A-type axons have collaterals which run to the ipsilateral NCC. The medial and lateral bundles of “mixed” axons run through one paired NCC but remain separated spatially. Release of secretion from the C-type NSC can take place before the corpus cardiacum is reached. A- and A1-type NSC have additional collaterals that branch from the proximal part of the axons and penetrate deeply into the neuropile of the protocerebral lobes. Local swellings appear to be closely associated with fibers from non-neurosecretory neurons. The sites of contact are characterized by the accumulation of microvesicles (400 Å) near an electron-dense cleft of 150–200 Å width, and resemble regular chemical synapses. The microvesicles prove to be present within the neurosecretory fiber in most of the specimens studied, and within the non-neurosecretory fiber in only a few cases. It seems most likely that the collaterals in some phases convey afferent signals to the NSC which inhibit the release of an efferent neurochemical “messenger” of unknown nature into the neuropile.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00223727
