title: Anatomical evidence for inputs to ventrolateral medullary catecholaminergic neurons from the midbrain periaqueductal gray of the rat.
abstract: Previous studies have shown that the midbrain periaqueductal gray (PAG) projects to the ventrolateral medulla (VLM). Here, we studied PAG projections to the area of A1/C1 neurons in the VLM in the rat using phaseolus vulgaris leucoagglutinin (PHA-L) anterograde tracing combined with immunocytochemistry for tyrosine hydroxylase (TH) or phenylethanolamine N-methyl transferase (PNMT). Following PAG injections, PHA-L labeled fibers and terminals were intermingled among TH-immunoreactive (TH-ir) neurons in the VLM. High-power light microscopic examination revealed that some of the PHA-L labeled varicose fibers and boutons were in close contiguity with TH-ir elements. Such apparent appositions appeared more frequently on TH-ir elements in the A1 area than on TH-ir or PNMT-ir neurons in the C1 area. These results indicate that some PAG inputs to the VLM may directly innervate A1/C1 neurons.
mesh_terms: D000818:Animals; D002395:Catecholamines / Q000502:physiology; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology*; D009434:Neural Pathways; D009474:Neurons / Q000166:cytology; D010487:Periaqueductal Gray / Q000166:cytology*; D010835:Phytohemagglutinins; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002395:Catecholamines; D010835:Phytohemagglutinins; C100156:leukoagglutinins, plants