Laser-evoked cortical responses in freely-moving XXXX reflect the activation of C-fibre afferent pathways.

@entity19 @entity35 @entity1 @entity158
UNASSIGNED: The limited success of translating basic animal findings into effective clinical treatments of @entity158 can be partly ascribed to the use of sub-optimal models. @entity19 models of @entity158 often consist in recording (1) threshold responses (like the tail-flick reflex) elicited by (2) non-nociceptive specific inputs in (3) anaesthetized animals. The direct cortical recording of laser-evoked potentials (LEPs) elicited by stimuli of graded energies in freely-moving rodents avoids these three important pitfalls, and has thus the potential of improving such translation. @entity19 LEPs are classically reported to consist of two distinct components, reflecting the activity of A  - and C-fibre afferent pathways. However, we have recently demonstrated that the so-called "A  -LEPs" in fact reflect the activation of the auditory system by laser-generated ultrasounds. Here we used ongoing white noise to avoid the confound represented by the early auditory response, and thereby comprehensively characterized the physiological properties of C-fibre LEPs recorded directly from the exposed surface of the @entity35 brain. Stimulus-response functions indicated that response amplitude is positively related to the stimulus energy, as well as to nocifensive behavioral score. When displayed using average reference, @entity19 LEPs consist of three distinct deflections, whose polarity, order, and topography are surprisingly similar to @entity1 LEPs. The scalp topography of the early N1 wave is somatotopically-organized, likely reflecting the activity of the primary somatosensory cortex, while topographies of the later N2 and P2 waves are more centrally distributed. These results indicate that recording LEPs in freely-moving @entity35 is a valid model to improve the translation of animal results to @entity1 physiology and pathophysiology.
