Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterised by deficits in social communication and repetitive behaviour. The BTBR T+tf/J strain is a well-characterised mouse model of ASD which has genetic alterations also found in human ASD. Previous studies have shown that ASD may be associated with functional bowel disease and a reduction in myenteric neurons 1,2 . The aim of this study was to investigate the function of the enteric nervous system (ENS) and the extrinsic afferent innervation of the gut in the BTBR model of ASD. Peristaltic motor complexes were measured using an isovolumetric Trendelenburg organ bath in which intraluminal pressure was recorded at rest. To assess the extrinsic innervation of the gut, afferent nerve firing from isolated segments of the jejunum were measured using electrophysiological multi-unit recording of mesenteric nerve bundles in response to mechanical and chemical stimuli. Afferent responses to application of the TRPV1 agonist capsaicin (1μM), or an inflammatory soup composed of; bradykinin, serotonin, histamine and prostaglandin E2 (5μM final concentration) was recorded. Data are presented as mean ±SEM and significance was confirmed with t-test or two-way ANOVA as appropriate. Tissues from C57 control mice exhibited a regular and consistent pattern of peristaltic motility with a mean contraction amplitude of 49.2 ± 4.356 mmHg and an average contraction duration of 44.5 ± 4.581 seconds (n = 6). Conversely, tissues from BTBR mice (n=6) had disordered motility with irregular, inconsistent contractions. Both peak contraction amplitude and contraction duration were significantly decreased (P<0.05, independent t-test). Ramp distension of the jejunum evoked a graded increase in afferent nerve firing due to the activation of mechanosensitive nerves. However, the magnitude of the afferent response was significantly reduced in preparations from BTBR mice (P<0.005, 2 way ANOVA). Peak afferent nerve firing at 50 mmHg was 92.68±12.80 imp/s-1 in recordings from C57 mice (n = 10) and 76.49 ±15.44 imp/s-1 in tissues from the BTBR mice (n = 9). Moreover, BTBR afferents showed a significantly prolonged response to capsaicin compared to C57 afferents. An increase in the time taken to for the fibres to desensitize was also observed (P=<0.0001, BTBR n = 5; C57 n = 5). Preparations from BTBR mice (n = 5) also exhibited an increase in the afferent response to the inflammatory soup (P<0.05). These results suggest that the BTBR model of ASD exhibits significant deficits in gut motility and alterations in jejunal extrinsic afferent nerve firing in response to mechanical and chemical stimuli. These data may suggest that both extrinsic and intrinsic innervation of the GI tract is altered in the BTBR mouse model of ASD. Further studies are now warranted to investigate the mechanisms by which ASD effects visceral sensitivity.