Changes in the Contractile Activity and Reactivity to 5-HT of Smooth Muscles of Rats Following Total Body Irradiation with Accelerated Electrons.

Background: Besides its “classical” neurotransmitter function in the central and peripheral nervous systems, serotonin, or 5-hydroxytryptamine (5-HT) is also a local hormone in a number of tissues, including those of the GI tract. Radiation is known to be able to disrupt certain functions of the tract, modulated by 5-HT-signaling pathways, or the serotonin receptors themselves.

Aim: The present investigation focused on clarifying the nature and extent of influence of an accelerated electron beam with energy of 9 MeV on the serotonergic mediation of healthy smooth muscle gastric tissue of rats following total body irradiation of the animals.

Materials And Methods: The study involved a control group and two experimental groups of animals exposed to 1 and 5 Gy, respectively, using Siemens Primus S/N 3561. Circular smooth muscle tissues were isolated from rats 1 hour and 18 hours after they were exposed to 1 and 5 Gy and also 5 days after irradiation from the rats that received a dose of 5 Gy in order to investigate the action of exogenous serotonin at increasing concentrations from 10-8 to 10-4 mol/l. The contractile reactivity of each group SM preparations was registered isometrically.

Results: Electron beams with energy of 9 MeV did not damage the contractile apparatus of gastric SM of rats and had a stimulating effect on contractility resulting from rapidly developing processes (1 hour) or later occurring once (5 days).

Conclusions: Difference was observed in the importance of the factors of received dose, lapse of time from irradiation to investigation of SM tissues, and exogenous 5-HT concentration for the changes in SM reactivity in serotonin-induced tonic and phasic responses.