Alteration of a small-intestine mechanoreceptor response by beta radiation

Abstract

The data presented are pertinent for identification of abdominal neural components capable of responding promptly to ionizing radiation. Responses of 37 receptors located at the serosal surface of the small intestine were obtained from anesthetized cats. None of these receptors exhibited spontaneous activity. None of the 21 irradiated receptors, each receiving about 0.5 rad/sec from a 25-mc strontium-yttrium-90 beta source, exhibited neural activity as a consequence of irradiation alone. Poststimulus-time histograms (PSTH) revealed characteristic patterns of neural activity upon mechanical stimulation. Quantitative comparison of the PSTH for six irradiated and six nonirradiated receptors that remained viable for at least five periods of mechanical stimulation revealed radiation induced sustained decreases (three receptors) or sustained increases (one receptor) in total spike activity. These sustained alterations in response to mechanical stimulation were not seen in any of the six control receptors. These alterations were all developed during the first of two 100-rad exposures. The second exposure did not materially affect the magnitude of the altered response, indicating that there was no cumulative dose effect of radiation on these receptors with doses less than about 200 rad. The data also suggest that the extremely stable latency of the first spikes induced by mechanical stimulation of these receptors becomes more variable after exposure to radiation. It appears that radiation can affect the level of response to an experimental analog of normal adequate stimulus, but that radiation does not induce neural activity in a quiescent small intestine mechanoreceptor.