Human enteric neurons: Morphological, electrophysiological, and neurochemical identification

Abstract

Background: Access to tissue, difficulties with dissection, and poor visibility of enteric ganglia have hampered electrophysiological recordings of human enteric neurons. Here, we report a method to combine intracellular recording with simultaneous morphological identification of neurons in the intact myenteric plexus of human colon ex vivo. Methods: Specimens of human colon were dissected into flat-sheet preparations with the myenteric plexus exposed. Myenteric neurons were impaled with conventional microelectrodes containing 5% 5,6-carboxyfluorescein in 20 mM Tris buffer and 1 M KCl. Key Results: Electrophysiological recordings identified myenteric neurons with S and AH type properties (n = 13, N = 7) which were dye filled and classified during the recording as Dogiel type I (n = 10), Dogiel type II (n = 2), or filamentous (n = 1) cells. This classification was confirmed after fixation, in combination with immunohistochemical characterization. Conclusions & Inferences: This method allows electrophysiological characterization with simultaneous identification of morphology. It can be used to identify recorded cells immediately after impalement and greatly facilitates recordings of human myenteric neurons in freshly dissected specimens of tissue. It can also be combined with immunohistochemical labeling of recorded cells. The advanced method described in this study allows electrophysiological characterization of human enteric neurons with simultaneous identification of their morphology which greatly facilitates recordings of human myenteric neurons. The aim of the study was to develop the technique using a fluorescent dye carboxyfluorescein in microelectrodes to record from human enteric neurons and identify their morphology in situ. Myenteric neurons were identified with carboxyfluorescein as Dogiel type I, II, or filamentous; their morphologies were matched with S and AH type electrophysiological properties. This classification was confirmed after fixation, in combination with immunohistochemical characterization.