Intracellular injection of neurobiotin or horseradish peroxidase reveals separate types of preganglionic neurons in the sacral parasympathetic nucleus of the cat.
Sacral preganglionic neurons are essential to the neural control of the excretory and sex organs. Previously employed multi-cell tracing methods have certain limitations in the precise morphological analysis of the neural pathways that control these organs. These limitations were overcome by the intracellular injection of neurobiotin or horseradish peroxidase into single preganglionic neurons in the lateral sacral parasympathetic nucleus of the cat. Following light microscopic examination, these neurons, as a group, were found to have an average of five stem dendrites, which divided into 15 dendritic end-branches that were distributed among eight dendritic terminal fields. These dendrites had a major transverse orientation and were quite long, many of them reaching well into the dorsal and ventral horns and into the dorsal gray commissure. These dendrites also exhibited a major longitudinal orientation, extending an average of 869 microns (combined length of rostral and caudal dendrites) within the nucleus. Two groups of cells emerged on the basis of different dendritic patterns. Cells classed as Type I had dendrites in lamina I and in the ventral horn but lacked a significant projection into the lateral funiculus. Cells classed as Type II had major dendritic projections into the lateral funiculus but lacked dendrites in lamina I. The diverse dendritic patterns of these two cell types indicate dissimilar afferent control mechanisms and suggest that these preganglionic neurons may innervate different target organs.
Morgan
C W
CW
Department of Anatomy and Neurobiology, Eastern Virginia Medical School, Norfolk 23501.
De Groat
W C
WC
Felkins
L A
LA
Zhang
S J
SJ
D000818:Animals; D001339:Autonomic Fibers, Preganglionic / Q000737:chemistry*; D001369:Axons / Q000648:ultrastructure; D001710:Biotin / Q000031:analogs & derivatives*; D002415:Cats / Q000378:metabolism*; D003712:Dendrites / Q000648:ultrastructure; D005260:Female; D006735:Horseradish Peroxidase; D008297:Male; D008845:Microinjections; D009474:Neurons / Q000737:chemistry* / Q000648:ultrastructure; D013116:Spinal Cord / Q000737:chemistry* / Q000166:cytology
C070614:neurobiotin; D001710:Biotin; D006735:Horseradish Peroxidase