THE EFFECTS OF BIFIDOBACTERIUM LONGUM NCC3001 ON AH NEURON EXCITABILITY AND SLOW WAVE ACTIVITY OF THE MOUSE INTESTINE By

TITLE: The effects of Bifidobacterium longum NCC3001 on AH neuron excitability and slow wave activity of the mouse intestine ABSTRACT The small intestine holds an intrinsic ability to digest and absorb nutrients from the food we intake without intervention from the central nervous system. This ability is made possible by the population of cells that inhabit the gut, particularly interstitial cells of Cajal of the myenteric plexus and sensory primary intrinsic neurons (AH cells), which ultimately influence muscle function and motility. The AH cells are the first neurons in the hierarchy of sensory neurons in the gut and are therefore a perfect candidate to test the effects of Bifidobacterium longum NCC3001 supernatant since in a physiological setting the metabolites secreted by this bacterium can interact with the AH cells directly or indirectly through absorption by the mucosa. The probiotic Bifidobacterium longum NCC3001 has been shown to normalize anxiety-like behaviour and hippocampal brain derived neurotropic factor (BDNF) levels in mice infected with Trichuris muris in a model of infectious colitis. Utilizing a chronic model of colitis, a study was conducted to decipher whether or not the anxiolytic effects of Bifidobacterium longum NCC3001 involved the vagus. My specific objective in this study was to find evidence for interaction between B.longum NCC3001 and myenteric neurons as a potential route for B.longum NCC3001 to influence CNS function. We assessed a cell's electro-responsiveness through spike discharge, which is the number of action potentials elicited in response to a supra-threshold depolarizing current injection. The electro-responsiveness of neurons perfused with B. longum NCC3001 supernatant (conditioned medium; n = 4) was significantly reduced compared to the control group (those perfused with Krebs solution; n = 5; P = 0.016). The electro-responsiveness of neurons perfused iv with the conditioned medium was also significantly lower than that of neurons perfused with unconditioned group (MRS growth medium alone) group (n = 4; P = 0.029). In comparing the excitabilities of the neurons in the control group with that of the control media group, there was no statistical difference (P = 0.29). In subsequent studies, the objective was to identify the AH cells and to determine the effect of B. longum NCC3001 conditioned medium on this population of cells. The electro-responsiveness as measured through spike discharge of AH cells perfused with the conditioned medium (n = 5) was significantly reduced compared to neurons perfused with the unconditioned medium (n = 5; P …