β-Endorphin Response in Blood and Cerebrospinal Fluid after Single and Multiple Irradiation with HeNe and GaAs Low-Power Laser

Abstract

Low-power laser (LL) irradiation causes biological effects such as analgesia. Cerebrospinal fluid (CSF) and blood immunoreactive β-endorphin (Iβ-E) delivery is involved; however, there are no opioid dose–response curves for different laser energy densities (ED) irradiation. In this work we try to determine dose–response curves for single and multiple HeNe and GaAs LL irradiation in both CSF and plasma Iβ-E contents, irradiating peripheral tissues. Single irradiation with HeNe or GaAs LL did not modify CSF Iβ-E concentrations. An ED of 12 J/cm² caused a statistically significant (p < 0.001) tendency to decrease the opioid peptide using the HeNe laser. Blood Iβ-E concentrations grow incrementally in single laser EDs (HeNe and GaAs). The most effective EDs were 9 to 10.8 J/cm²; higher EDs decreased the biological response. As a result of chronic stress suffered in mutiple LL irradiation (multiple intraperitoneal chloral hydrate administration is involved), CSF and blood basal Iβ-E concentrations increased. A tendency for Iβ-E to decrease (normalizing) in CSF and blood followed mutiple HeNe and GaAs LL irradiation using an ED of 10.8 J/cm². A higher ED was less effective. GaAs LL not only failed to normalize, but increased blood opioid concentrations; however, HeNe LL irradiation behaved as in CSF.