Serotonin and vasoactive intestinal peptide antagonists attenuate rotavirus diarrhoea

Abstract

Background and aims: The mechanisms underlying intestinal secretion in rotavirus diarrhoea remain to be established. We previously reported that rotavirus evokes intestinal fluid and electrolyte secretion by activation of the enteric nervous system. We now report that antagonists for the 5-hydroxytryptamine 3 receptor (5-HT(3)) and vasoactive intestinal peptide (VIP) receptor, but not antagonists for 5-hydroxytryptamine 4 receptor or the muscarinic receptor, attenuate rotavirus induced diarrhoea.

Methods: Neurotransmitter antagonists were administered to wild-type or neurokinin 1 receptor knockout mice infected with homologous (EDIM) or heterologous (RRV) rotavirus.

Results: While RRV infected mice had diarrhoea for 3.3 (0.2) days (95% confidence interval (CI) 3.04-3.56), the 5-HT(3) receptor antagonist (granisetron) and the VIP receptor antagonist (4Cl-D-Phe(6),Leu(17))-VIP both reduced the total number of days of RRV induced diarrhoea to 2.1 (0.3) (95% CI 1.31-2.9) (p<0.01). EDIM infected mice treated with granisetron had a significantly shorter duration of diarrhoea (5.6 (0.4) days) compared with untreated mice (8.0 (0.4) days; p<0.01). Experiments with neurokinin 1 receptor antagonists suggest that this receptor may possibly be involved in the secretory response to rotavirus. On the other hand, rotavirus diarrhoea was not attenuated in the neurokinin 1 receptor knockout mice.

Conclusions: Our results suggest that the neurotransmitters serotonin and VIP are involved in rotavirus diarrhoea; observations that could imply new principles for treatment of this disease with significant global impact.

Figure 1

Number of days with diarrhoea (NDD) after treatment with a vasoactive intestinal peptide receptor antagonist (VIPa) (0.5, 1.5, and 4.5 mg/kg) and atropine (3, 10 mg/kg). Non-treated RRV infected mice served as controls. Numbers in columns indicate number of mice. Values are means (SEM). **p<0.01 compared with controls (Student’s t test).

Figure 2

Prevalence of mice with diarrhoea after rotavirus infection (RRV) plotted versus hours post inoculation. Saline treated RRV infected mice (number of litter = 8) were compared with mice treated with granisetron (2 mg/kg; number of litter = 4) or vasoactive intestinal peptide receptor antagonist (VIPa) (0.5 mg/kg; number of litter = 2). Values are means (SEM). *p<0.05, **p<0.01 compared with controls (Student’s t test).

Figure 3

Number of days with diarrhoea (NDD) after treatment of rotavirus infected mice with the 5-HT₃ receptor antagonist granisetron, the 5-HT₄ receptor antagonist RS 39604, or a combination of a vasoactive intestinal peptide receptor antagonist (VIPa) (1.5 mg/kg) and granisetron (2 mg/kg) (Granis+VIP). Non-treated rotavirus infected mice served as controls. Values in columns indicate the number of mice. Values are means (SEM). *p<0.05, **p<0.01 compared with controls (Student’s t test).

Figure 4

Comparison between saline treated and granisetron treated EDIM infected mice. Granisetron was given at a dose of 2 or 5 mg/kg/day or 2 mg/kg twice a day (2×2 mg/kg). Values are means (SEM). **p<0.01 compared with controls (Student’s t test).

Figure 5

Effect of substance P (SP) on the number of days with rotavirus diarrhoea (NDD). SP receptor antagonism was studied using neurokinin 1 receptor knockout mice (NK-1 R−/−), the SP receptor antagonist (D-Pro2, D-Trp7, 9)-SP (SP-ant), and NK-1 receptor antagonists (Sendide and CP-96,345). Values above the columns indicate the number of mice. Values are means (SEM). **p<0.01 compared with controls (Student’s t test).