Threshold of Pain in Chronic Magnetic Field- (50 Hz, 17.9 μT) Exposed Rats: Effect of Sucrose Ingestion

Abstract

Both magnetic field (MF) exposure and sucrose ingestion produce opioid mediated analgesia, independently. This article addresses the query whether or not sucrose ingestion potentiates the analgesia of MF exposure. The pain threshold, as reflected by withdrawal of tail (thresholds of tail flick, TF), vocalization during stimulus (VD), and vocalization after stimulus (VA) were determined in 7 sessions at 0, 5, 10, 15, 30, 45, and 60 min, respectively (control rats). After an interval of 24 h the rats were provided with sucrose solution and were allowed to ingest it for 10 min. The pain thresholds were determined (Control sucrose-fed rats). The rats then received exposure to magnetic field (50 Hz, 17.9 μT) for 7 d (8 h/d) (MF-exposed rats) and the effect of sucrose ingestion was repeated (MF-Sucrose-fed rats). The basal threshold of pain did not vary in between the control and MF-exposed rats. Pain threshold during sessions II–VII did not vary in control rats but it increased in MF rats. Moreover, the pain thresholds were elevated in MF rats as compared to control rats. Sucrose-ingestion elevated the threshold of TF in controls but not in MF-exposed rats; while the thresholds of VA and VD were elevated more in control than MF rats. The results suggest that the MF exposure (50 Hz, 17.9 μT, 8 h/d) for 7 d did not affect the basal thresholds of pain, increased stress induced analgesia, and attenuated the sucrose ingestion-induced analgesia.

Keywords:

• Chronic MF exposure
• Sucrose-fed analgesia
• Pain threshold stress-induced analgesia
• Stress