The development of neurons in the cat perigeniculate nucleus and reticular nucleus of the thalamus

The postnatal development of soma size and cytochrome oxidase activity was examined in the perigeniculate nucleus (PGN) and reticular nucleus of the thalamus (RNT). Neurons in the PGN and RNT exhibited a rapid increase in soma size between 2 and 4 weeks of age. During this period of cell growth there is an increase in the intensity of cytochrome oxidase staining within the cell body. Cells in both the PGN and RNT decrease in size after 4 weeks of age, and become very fusiform in shape. During this postnatal period, there is also a shift in cytochrome oxidase staining from the cell body to the dendrites.     

Stress-induced changes in cholecystokinin and substance P concentrations in discrete regions of the rat hypothalamus

The effects of acute stress exposure upon cholecystokinin (CCK) and substance P (SP) concentrations in discrete hypothalamic regions of the adult male rat brain were studied. Animals were exposed to foot shock stress for periods of 2, 4, 10, 30 or 60 min duration; immediately afterwards they were decapitated; brains were frozen and subsequently microdissected. CCK and SP concentrations were assayed by a specific RIA, as were serum levels of ACTH, corticosterone, PRL, GH, LH and testosterone. Stress had no effect upon SP concentrations in the anterior or posterior parts of the arcuate nucleus (ARC), but led to elevated CCK levels in the posterior ARC following 60 min of exposure. In both the ventromedial and dorsomedial hypothalamic areas, stress induced depletions of both neuropeptides. In the anterior (but not the posterior) portions of the lateral hypothalamic area, CCK and SP concentrations were reduced by stress exposure. These studies demonstrate that discrete hypothalamic CCK and SP neuronal systems are responsive to stress. This suggests that endogenous hypothalamic CCK and SP participate, along with other neurotransmitters/neuromodulators, in the integrated hypothalamic stress response, and mediate stress-neuroendocrine interactions.     

The histopathology of freezing injury to the rat spinal cord. A light microscope study. I. Early degenerative changes

In an effort to develop a method of tissue injury which would provide a model for the study of axonal regrowth in adult mammalian central nervous system (CNS), we have analyzed the effects of freezing in the dorsal columns of more than 200 rat spinal cords. The effects of temperature and time of exposure upon the size, shape, distribution and histologic characteristics of the lesion have been assessed during the first seven days following the injury. The upper threshold for injury occurs at -3 degrees C for 15 minutes. Between -3 degrees C and -12 degrees C the tissue changes vary in extent and characteristics. Selective damage to axons and myelin occurs with sparing of the supportive cells followed by proliferation of a cellular matrix. At seven days, the lesions produced by -8 degrees C for 15 to 60 minutes have neither axons nor myelin sheaths and consist of a dense cellular matrix of macrophages and presumed glial cells. With these tissue characteristics, and the preservation of tissue continuity without obstructive barriers, this model would appear to be potentially suitable for the study of axonal regrowth potential in mammalian CNS.