The objective of this proposal is to characterize the neuronal circuits that mediate the peristaltic reflex in normal and inflamed colon, and determine the effect of inflammatory cytokines (IL-1beta and IL-6) and neurotrophins (GDNF and BDNF) on neurotransmitter expression and neuronal remodeling. Previous studies and preliminary experiments have lead us to identify neuronal circuits within the myenteric plexus consisting of modulatory neurons coupled to motor neurons that mediate the reciprocal activity of circular and longitudinal muscle. The experimental approach exploits novel preparations that enable identification of the neural pathways: (1) compartmented intestinal segments to measure release of sensory (CGRP), modulatory neural pathways: (1) compartmented intestinal segments to measure release of sensory (CGRP), modulatory (somatostatin, GABA, [Met]enkephalin], and excitatory (ACh and SP) or inhibitory (IP, PACAP and NO) motor neurotransmitters in animals and humans; (2) longitudinal muscle strips with adherent myenteric plexus to identify the coupling of interneurons to each other and to excitatory motor neurons; (3) circular muscle strips with axonal remnants, and synaptosomes derived from these strips to identify pre-synaptic regulation of neurotransmitter release; (4) freshly dispersed and cultured myentric ganglia to examine feedback regulation of somatostatin interneurons and neuronal remodeling by neurotrophins; (5) organotypic cultures of smooth muscle to identify the interplay of cytokines and neurotrophins; (5) organotypic cultures of smooth muscle to identify the interplay of cytokines and neurotrophins in normal and TNBS-induced colitis.
The Specific Aims of the proposal are: (1) to characterized the modulatory roles of somatostatin, GRP and NPY in the ascending and descending phases of the peristaltic reflex, and identify the pre- synaptic interactions between motor neurons; (2) to characterize the sensory pathways activated by chemical stimuli and identify the 5-HT4 receptor splice variant mediating desensitization of the reflex; (3) to characterize the roles of the cytokines, IL-1beta and IL-6, and trophic (GDNF) and anti-trophic (BDNF) neurotrophins in mediating changes in peristaltic neurotransmission and neuronal remodeling in TNBS-induced colitis.
The aims are supported by preliminary studies and will provide a deeper understanding of neurotransmission in health and disease.
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