Levels of vasoactive intestinal peptide, cholecystokinin and calcitonin gene-related peptide in plasma and jejunum of rats following traumatic brain injury and underlying significance in gastrointestinal dysfunction.

Abstract

To study the alterations of brain-gut peptides following traumatic brain injury (TBI) and to explore the underlying significance of these peptides in the complicated gastrointestinal dysfunction. Rat models of focal traumatic brain injury were established by impact insult method, and divided into 6 groups (6 rats each group) including control group with sham operation and TBI groups at postinjury 3, 12, 24, 72 h, and d 7. Blood and proximal jejunum samples were taken at time point of each group and gross observations of gastrointestinal pathology were recorded simultaneously. The levels of vasoactive intestinal peptide (VIP) in plasma, calcitonin gene-related peptide (CGRP) and cholecystokinin (CCK) in both plasma and jejunum were measured by enzyme immunoassay (EIA). Radioimmunoassay (RIA) was used to determine the levels of VIP in jejunum. Gastric distension, delayed gastric emptying and intestinal dilatation with a large amount of yellowish effusion and thin edematous wall were found in TBI rats through 12 h and 72 h, which peaked at postinjury 72 h. As compared with that of control group (247.8+/-29.5 ng/L), plasma VIP levels were significantly decreased at postinjury 3, 12 and 24 h (106.7+/-34.1 ng/L, 148.7+/-22.8 ng/L, 132.8+/-21.6 ng/L, respectively), but significantly increased at 72 h (405.0+/-29.8 ng/L) and markedly declined on d 7 (130.7+/-19.3 ng/L). However, Plasma levels CCK and CGRP were significantly increased through 3 h and 7 d following TBI (126-691% increases), with the peak at 72 h. Compared with control (VIP, 13.6+/-1.4 ng /g; CGRP, 70.6+/-17.7 ng/g); VIP and CGRP levels in jejunum were significantly increased at 3 h after TBI (VIP, 35.4+/-5.0 ng/g; CGRP, 103.8+/-22.1 ng/g), and declined gradually at 12 h and 24 h (VIP, 16.5+/-1.8 ng/g, 5.5+/-1.4 ng/g; CGRP, 34.9+/-9.7 ng/g, 18.5+/-7.7 ng/g), but were significantly increased again at 72 h (VIP, 48.7+/-9.5 ng/g; CGRP, 142.1+/-24.3 ng/g), then declined in various degrees on d 7 (VIP, 3.8+/-1.1 ng/g; CGRP, 102.5+/-18.1 ng/g). The CCK levels in jejunum were found to change in a similar trend as that in plasma with the concentrations of CCK significantly increased following TBI (99-517% increases) and peaked at 72 h. Traumatic brain injury can lead to significant changes of brain-gut peptides in both plasma and small intestine, which may be involved in the pathogenesis of complicated gastrointestinal dysfunction.