NEUROSECRETION 



1057 



FIG. 25. Neurosecretion-rich cells (m-ccUs) from the subesophageal ganglion of Lumhricus. The 

 cell processes are visible in some cases. Paraldehyde-fuchsin stain. [From Hubl (lySl.j 



FIG. 26. Neurosecretory cells in the brain of Lumhricus after sectioning of the nerve cord. The 

 vacuolated appearance of the c-cells is believed to reflect heightened functional activity. Azan 

 staining. [From Hubl (176).] 



Specific staining methods for demonstrating the .secre- 

 tory products of these cells are not available. The nu- 

 clei frequently exhibit evidence of participating in the 

 secretory activity of these neurons (296, 297). In the 

 pregnant rat, neurons of the uterine cervix ganglion 

 exhibit increased vacuolation (200). Similar changes 

 have been described following treatment with estro- 

 gens and chorionic gonadotrophins (31 1 ). Pilocarpine 

 accentuates while atropine restricts the secretory 

 activity of these cells (312). In spite of many such 

 studies, the functional significance of neurosecretory 

 activity in peripheral neurons is not clear. Likewise, 

 the attempts to ascribe neurosecretory activity to 

 certain neurons of the retina (41) must be considered 

 with some reservation. 



NEUROSECRETION IN INVERTEBRATES 



General Considerations 



Although neurosecretory elements are demon- 

 strated easily in invertebrates with routine staining 

 methods (fig. 24), the application of chromhematoxy- 

 lin and paraldehyde fuchsin (fig. 25) has substantially 

 advanced our information in this domain. The use of 

 these methods has permitted differentiation of several 

 closely localized neurosecretory products. It is char- 

 acteristic of a large number of in\ertebrates that 

 neurosecretory axons terminate intercellularly in 

 glands which, in turn, are themselves secretory in 

 nature. In such complexes, the neuro.secretory ma- 

 terial is stained with chromhematoxvlin while the 





FIG. 27. Neurosecretory fibers from the crossing nervus cor- 

 poris cardiaci of Leucophaea matlerae. Chromhematoxylin- 

 phloxin. X 392. [From Scharrer & Scharrer (289).] 



.secretion of the glandular cells exhibits acidophilic 

 properties (14, 19, 108, 114, 116, 229). The neuro- 

 secretory material is finely granular and easily 

 differentiated from the mitochondria in fresh prepara- 



