The three-dimensional structure of neurons in the guinea pig inferior mesenteric and pelvic hypogastric ganglia

The three-dimensional (3-D) morphology of sympathetic inferior mesenteric g anglion (IMG) neurons and sympathetic-parasympathetic pelvic hypogastric ga nglion (PHG) neurons was studied using confocal laser scanning microscopy. Cell bodies of IMG neurons were disc-shaped and were arranged orderly in la yers. The dendritic arbor of individual neurons was confined to a plane wit h a thickness that did not exceed the thickness of the parent cell body. Th e actual dendritic surface area (71,400 mu m(2)) and volume (81,500 mu m(3) ) of the IMG neurons were up to 100-fold larger than previously reported fo r similar sympathetic neurons using data of 2-D measurements and estimation s of the third dimension. PHG neurons had a much smaller dendritic surface area (4100 mu m(2)) and volume (2400 mu m(3)) compared to IMG neurons. The ratio dendritic/somal surface area for individual IMG and PHG neurons range d from 5:1 to 14:1 and from 0.1:1 to 6:1, respectively. The total dendritic path-length was 8-42 times greater for IMG than for PHG neurons. Neurons i n the IMG were either stellate with radiating dendrites or bipolar-shaped w ith dendrites emerging from the two poles of the cell body. Neurons in the PHG were of two morphological types. One type (nearly 2/3 of ail the imaged PHG neurons) had two to seven relatively long dendrites and an axon; the o ther type had only one to three short unbranched dendrites and an Neon. The spatial organization of neurons within the ganglia and the structural feat ures of individual neurons are likely to have important implications regard ing connectivity patterns between neurons within the ganglion as well as on how information is processed by the ganglion. (C) 2000 Elsevier Science B. V. All rights reserved.