Colorectal distension-evoked potentials in awake rats: a novel method for studies of visceral sensitivity
Article first published online: 27 AUG 2012
© 2012 Blackwell Publishing Ltd
Neurogastroenterology & Motility
Volume 24, Issue 10, pages 964–e466, October 2012
How to Cite
Hultin, L., Nissen, T. D., Kakol-Palm, D. and Lindström, E. (2012), Colorectal distension-evoked potentials in awake rats: a novel method for studies of visceral sensitivity. Neurogastroenterology & Motility, 24: 964–e466. doi: 10.1111/nmo.12005
- Issue published online: 12 SEP 2012
- Article first published online: 27 AUG 2012
- Received: 22 December 2011 Accepted for publication: 30 July 2012
- cerebral evoked potentials;
- visceral sensitivity
Background Quantification of the visceromotor response induced by colorectal distension (CRD) in rodents is commonly used for preclinical studies of visceral pain. The model is well established but does not fully assess the central response to stimulation. The aim of this study was to establish a novel model assessing cerebral evoked potentials (CEPs) in response to CRD in awake rats.
Methods Epidural recording electrodes were chronically implanted in the skull of female Sprague–Dawley rats. Colorectal distension-induced CEPs were recorded using either rapid balloon distensions (100 ms, 20–80 mmHg) or electric stimulation (1 ms, 1–4 mA) using stimulation probes placed in the distal colon.
Key Results Colorectal distension-induced CEPs were separated in three partly temporally overlapping components consisting of five prominent peaks. Peak latencies at 80 mmHg were (P1, N1) 23 ± 1 and 55 ± 4 ms, (N2, P2a, P2b) 91 ± 3, 143 ± 5 and 174 ± 3 ms, and (P3) 297 ± 3 ms. Amplitudes and latencies were, except for the early component, intensity dependent. Intrarectal administration of lidocaine significantly reduced the amplitude of N2 (by 42 ± 6%, P < 0.001) and P2 (by 34 ± 6%, P < 0.001). Electrically induced CEPs were intensity dependent and had similar topography and latencies as the mechanical evoked potentials (P1: 26 ± 2 ms; N1: 61 ± 1 ms; P2: 84 ± 6 ms; N2: 154 ± 6 ms; P3: 326 ± 10 ms), but there were large variations in amplitudes in between repeated electrical stimulations.
Conclusions & Inferences Colorectal distension-induced CEPs can be recorded reliably in awake rats and may serve as a surrogate marker of colonic sensation and be a useful parameter in studies of visceral sensitivity.