DARK AND LIGHT NEURONS IN THE HUMAN BRAIN, WITH SPECIAL REFERENCE TO THEIR REACTIONS TO GOLGI-SILVER-NITRATE, LUXOL-FAST-BLUE-MBS AND AZOCARMINE-G

Sections from the human somatosensory cortex were observed with a ligh t microscope, The neurons were classified into light and dark ones. Th e light neurons mere slightly stained with thionin, luxol fast blue RI BS and azocarmine G (80% of all neurons), The dark neurons were more o r less shrunken, and stained intensely with these dyes (20% of all neu rons), Double staining with luxol fast blue BIBS and azocarmine G was especially useful to demonstrate the dark neurons, since it clearly st ained even their fine processes, Neither light nor dark neurons were r eactive to nick end labeling for detection of DNA fragmentation. Tripl e staining with Golgi's silver nitrate (or Gallyas's ammoniacal silver carbonate), luxol fast blue BIBS and azocarmine G showed that the maj ority of the dark neurons were argyrophilic (argyrophilic dark neurons , 15% of all neurons), while some of them were not argyrophilic (non-a rgyrophilic dark neurons, 5% of all neurons), Triple staining also sho wed that the light neurons were only occasionally argyrophilic (argyro philic light neurons, 5% of ail neurons); usually, the light neurons m ere not argyrophilic (non-argyrophilic light neurons, 75% of all neuro ns), The results confirm that dark neurons usually represent certain p opulations of neurons in the human brain, and that they are basically identical to the argyrophilic neurons. The discussion suggests that th e argyrophilic light and dark neurons are excited cells, the non-argyr ophilic dark neurons are exhausted cells, and the non-argyrophilic lig ht neurons are resting cells. Triple staining further demonstrated tha t some glial cells were darkened and stained with Golgi's silver nitra te or Gallyas's silver carbonate, Additional Golgi's silver block stai ning showed that the argyrophilic neurons stained by the conventional block staining method usually possessed a shrunken cell body, which wa s characteristic of the dark neurons.