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Course: MCAT > Unit 2

Lesson 3: Foundation 3: Organ Systems

Nervous/immune systems: Effects of vagotomy on immune response


The vagus nerve is part of the parasympathetic division of the autonomic nervous system and influences many biological processes, such as digestion, heart rate, and immune function.
Scientists performed an experiment to explore the relationship between vagal activity and rats’ immune response to lipopolysaccharide (LPS), an antigen found in the outer membrane of Gram-negative bacteria. LPS normally elicits a strong immune response in animals, because the O-antigen is a target for recognition by host antibodies.
For this experiment, 40 rats were collected and separated into two groups. The vagal trunks were removed from the rats in one group (vagotomy, Vx). The other group was subjected to a surgery in which the rats’ vagus nerve was exposed but not cut (sham). Both groups were given one month to recover from their surgery, and the weight of both groups was measured.
After weighing, rats from both groups were given injections of either saline or LPS. Two hours after injection, the rats were decapitated, and concentrations of interleukin-1β (IL-1β) mRNA were measured in the hippocampus, hypothalamus, and pituitary. Neither group had significant levels of IL-1β mRNA in the pituitary. Levels of IL-1β mRNA in the hippocampus and hypothalamus are shown in Figure 1.
Figure 1 Effects of vagotomy on interleukin concentrations in the hippocampus (A) or hypothalamus (A)
The stomachs of the rats were also removed and weighed. This information, along with the original body weights after surgery, is shown in Table 1.
Table 1 Body weight and stomach weight of vagotomized and sham-operated rats.
Source: Bluthe, R. Combe, C. Dantzer, R. Keith, K. Kent, S. Laye, S. Medina, C. Parnet, P. (1995).
Why did the researchers measure IL-1β levels in mice?
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