1056 



HANDBOOK OF PII^•SInLOOV 



NEUROPHYSIOLOGY II 



extracts required to produce ACITH release. The 

 activity of this partially purified substance can be 

 demonstrated both in vitro and in vivo. A synthetic 

 lysine-vasopressor substance has been reported to 

 produce increased adrenocortical hormone secretion 

 (210). 



The morphological, chemical and experimental 

 results obtained from these different laboratories 

 agree to the extent that a specific substance is con- 

 cerned in stimulating ACTH release. Its close rela- 

 tionship with the posterior lobe hormones, their sites 

 of .synthesis and storage, make it seem likely that the 

 neurosecretory system plays a role in the formation 

 and deli\'ery of this hypothalamic substance. 



Central Nervous System Neurosecretory Systems 

 not Demonstrated ivith Chrom/iemato.xylin 



ANTERIOR HYPOTHALAMUS. In this area of the hypo- 

 thalamus exist a large number of cells which contain 

 granular and colloid inclusions not staining with 

 chromhematoxylin or paraldehyde fuchsin (37, 38). 

 The functional significance of this material is not 

 clear. 



TUBER ciNEREUM. In many species of fish, specific 

 indication of neurosecretory activity is found in the 

 lateral tuberal nuclei (38, 240, 280, 282, 302, 308) 

 although with isolated exceptions (191, 302) the 

 secretory material in these cells is not stained with 

 chromhematoxylin (30, 128, 131, 163, 232, 307, 317). 

 In lower forms, an evident participation of the nuclei 

 in secretory activity as well as seasonal variations of 

 activity is particularly characteristic for the cells in 

 the.se tuberal nuclei (44, 105, 131, 163, 281, 282). In 

 man, cytoplasmic colloid and granular inclusions as 

 well as unusual nuclear shapes have been described 

 for the cells in the tuberal nuclei (128, 255, 345); how- 

 ever, no evidence of axonal transport of secretory 

 material is present. In mammals, axons from the 

 tuberal nuclei, especially the nucleus infundibularis 

 tuberis (arcuate nucleus), nucleus principalis (Cajal) 

 and the posterior periventricular tuberal region, 

 form the tuberohypophyseal tract, and in the region 

 of the median eminence assume a close relationship 

 to the primary plexus of the portal vessels. The termi- 

 nations of these fibers lie superficial to the area 

 traversed by the supraopticohypophyseal tract. 



The question of whether these axons of the tuberal 

 nuclei release a neurosecretory substance into the 

 portal vessels cannot be answered with certainty at 

 this time (44, 346). A colloid material which does not 



stain with chromhematoxylin has been observed in the 

 median eminence {149, 339) as well as within the 

 portal vessels. This may be an indication of a second 

 form of neurosecretion, released into the blood stream 

 in this area and traversing the portal vessels to the 

 anterior lobe of the pituitary (157). Through measure- 

 ment of nuclear volume as an index of cellular ac- 

 tivity, the periventricular, ventromedial and pre- 

 mammillary hypothalamic nuclei have been identified 

 as regions which undergo characteristic changes 

 paralleling the phases of the reproductive cycle of the 

 mouse (160, 161). It has been suggested that their 

 function may be similar to that of the anterior hypo- 

 thalamic areas (174). A notable array of experimental 

 and clinical evidence indicates that considerable hypo- 

 thalamic control exists over the gonadotropic activity 

 of the anterior lobe (20, 43, 44, 122); this is discussed 

 in the chapter in this work by Sawyer on reproductive 

 behavior. 



SPINAL CORD. The discovery of gland-like cells in the 

 spinal cord of fish by Dahlgren (75) and Speidel 

 {305, 306) forms the first description of neurosecretion 

 but paradoxically has remained unexplained from a 

 functional standpoint. Speidel has described these 

 peculiar variations of the anterior horn cells only in 

 the caudal segments of the spinal cord in 26 out of 30 

 species of fish in the elasmobranchs, teleosts and 

 ganoids. The cells may be unusually large (200 x 200 

 x I 76 yu) and contain nuclei which are lobular or even 

 distorted in shape. The cytoplasm of these cells con- 

 tains a variable accumulation of proteinaceous gran- 

 ules or colloid droplets which are Millon-positive 

 (305) but which do not stain with chromhematoxylin 

 (289). Similar observations have been presented 

 recently for cells in the lumbosacral segments of the 

 cord of various species of birds (271, 321). See also 

 Sano (272). 



Neurosecretion in Peripheral Nervous System 



Lenette & Scharrer (201) have described cytoplas- 

 mic inclusions in autonomic ganglion cells of the 

 monkey and have interpreted these findings as evi- 

 dence of neurosecretory activity. Similar observations 

 were subsequently presented for the cells of a variety 

 of mammalian species including ganglion cells of the 

 sympathetic chain (95, 219, 291, 295), uterine cervix 

 (200, 311, 312) and adrenal medulla (94, 251, 252). 

 Vacuoles and colloid droplets may accumulate in 

 these cells to such a degree as to produce visible 

 swelling of the cell without producing any evidence 

 of nuclear or cytoplasmic damage or degeneration. 



