title: Effects on rats of low intensity and frequency electromagnetic field stimulation on thoracic spinal neurons receiving noxious cardiac and esophageal inputs.
abstract: Objective  Low intensity and low frequency electromagnetic field stimulation (EMFs) provides substantial pain relief in patients with various chronic pains. The aim of this study was to examine the effects of EMFs on the activity of thoracic spinal neurons responding to noxious visceral stimuli. Materials and Methods  Extracellular potentials of single T(3) -T(4)  spinal neurons were recorded in pentobarbital anesthetized male rats. A catheter was placed in the pericardial sac to administer a mixture of algogenic chemicals for noxious cardiac stimulation (0.2 mL, 1 min). Noxious esophageal distension was produced by water inflation (0.4 mL, 20 sec) of a latex balloon. EMFs (0.839-0.952 Hz, 0.030-0.034 µG, 30-40 min) was applied with a pair of Helmholtz coils placed on both sides of the chest. Results  After the onset of EMFs, excitatory neuronal responses to intrapericardial chemicals were reduced in 24/32 (75%) spinal neurons, increased in three neurons and were not affected in five neurons. The inhibitory effect on spinal neurons occurred 10-20 min after the onset of EMFs. Even after termination of EMFs, the suppression of spinal neuronal activity lasted for 1-2 hr. In contrast, excitatory responses of 7/18 (39%) neurons to esophageal distension were inhibited, five (28%) were excited and six (33%) were not affected by EMFs. Conclusions  Results showed that EMFs generally reduced nociceptive responses of spinal neurons to noxious cardiac chemical stimuli, whereas it was not effective for nociceptive responses to esophageal mechanical stimulation.
authors.affiliation: Departments of PhysiologyMedicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma.
authors.forename: Chao
authors.initials: C
authors.lastname: Qin
authors.forename: J Mark
authors.initials: JM
authors.lastname: Evans
authors.forename: William S
authors.initials: WS
authors.lastname: Yamanashi
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Scherlag
authors.forename: Robert D
authors.initials: RD
authors.lastname: Foreman