Ambiguous effect of signals transmitted by the vagus nerve on fibrosarcoma incidence and survival of tumor-bearing rats

While the parasympathetic nervous system appears to be involved in the regulation of tumor progression, its exact role is still unclear. Therefore, using a rat BP6-TU2 fibrosarcoma tumor model, we investigated the effect of (1) reduction of vagal activity produced by subdiaphragmatic vagotomy; and (2) enhancement of vagal activity produced by continuous delivery of electric impulses to the cervical part of the vagus nerve on tumor development and survival of tumor-bearing rats. We also evaluated the expression of cholinergic receptors within in vitro cultivated BP6-TU2 cells. Interestingly, we found that both, vagal stimulation and subdiaphragmatic vagotomy slightly reduced tumor incidence. However, survival of tumor-bearing rats was not affected by any of the experimental approaches. Additionally, we detected mRNA expression of the α1, α2, α5, α7, and α10 subunits of nicotinic receptors and the M1, M3, M4, and M5 subtypes of muscarinic receptors within in vitro cultivated BP6-TU2 cells. Our data indicate that the role of the vagus nerve in modulation of fibrosarcoma development is ambiguous and uncertain and requires further investigation.