IN VITRO CONTRACTIONS OF RAT JEJUNUM FOLLOWING WHOLE-BODY X IRRADIATION AND EVALUATION BY PHARMACOLOGICAL AGENTS
ARMED FORCES RADIOBIOLOGY RESEARCH INST BETHESDA MD
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Adult male rats were sacrificed between 20 minutes and 3 days following 1500 R whole-body x irradiation to record and study the spontaneous contractions of isolated in vitro segments of jejunum. Segments from nonirradiated animals demonstrated a multicomponent irregular pattern of contractions as compared with a single component regular pattern, often associated with an increased contraction amplitude, in segments taken from animals 2 or 3 days after exposure. No increase in the mean rate of spontaneous contractions was noted. The mechanism of this change was studied using pharmacological agents. The ganglionic blocking agent hexamethonium, the anticholinesterase drugs, as well as the neurotoxin tetrodotoxin, when added to the bath containing segments from nonirradiated animals, resulted in a contraction pattern resembling that of segments from animals irradiated 2 or 3 days previously. Evidence is presented, however, which indicates that drug- altered segments differ in some aspects from the irradiation-induced regular segments. The possible mechanisms of the irradiation-induced changes are discussed.
- Anatomy and Physiology