Comparing the effects of isoflurane and pentobarbital on the responses of cutaneous mechanoreceptive afferents

Abstract

BackgroundWhile pentobarbital has been used extensively in neurophysiological experiments investigating activity in peripheral nerves, it has fallen out of favor as an anesthetic because of safety concerns and is often replaced with isoflurane. However, the effects of isoflurane on the excitability of mechanoreceptive afferents have yet to be conclusively elucidated.MethodsTo fill this gap, we collected extracellular single-unit recordings of cutaneous mechanoreceptive afferents from the sciatic nerve of 21 rats during vibratory stimulation of the hindpaw. We then compared the strength and temporal structure of the afferent response measured under pentobarbital and isoflurane anesthesia.ResultsWe found that the strength and temporal structure of afferent responses were statistically equivalent whether these were evoked under isoflurane or pentobarbital.ConclusionsWe conclude that, if these two anesthetics have any effect on the responses of mechanoreceptive afferents, their effects are indistinguishable.

Intermittent Failure of Spike Propagation in Primary Afferent Neurons during Tactile Stimulation

“…Skipped spikes would have been expected in those datasets if skipping originated at the spike initiation step. Notably, we observed integer-multiple-patterned spiking across a broad range of stimulus intensities and to different stimulus modalities, all of which is consistent with intermittent failure of spike propagation (Smith and Hatt, 1976;Matzner and Devor, 1993), but integer-multiple-patterned spiking may be due to intermittent failure of spike initiation under other stimulus conditions (Freeman and Johnson, 1982;Gang et al, 1993;Braun et al, 1994;Xing et al, 2001;Coleman et al, 2003;Amir et al, 2005;Cheng et al, 2013).…”

“…The regularity of spiking in SA2 units was crucial for allowing us to recognize that some spikes were "skipped"; similar analysis is not feasible in SA1 units because their repetitive spiking is irregular, or in RA units because their spiking is transient. By applying stimuli as sustained steps, rather than as trains of short pulses, we avoided confusion that might arise from the intermittent failure of spike initiation in response to each pulse; for instance, similar skipping has been observed during vibrotactile stimulation (Coleman et al, 2003;Cheng et al, 2013) but may be due to intermittent failure of spike initiation. Reliable spike initiation can be achieved with supramaximal pulses, but strong pulses risk causing unnaturally synchronized spiking that can lead to ephaptic effects (Jefferys, 1995) or other forms of cross-excitation (Devor and Wall, 1990).…”

Cutaneous Aβ-Non-nociceptive, but Not C-Nociceptive, Dorsal Root Ganglion Neurons Exhibit Spontaneous Activity in the Streptozotocin Rat Model of Painful Diabetic Neuropathy in vivo

“…Another potential limitation of our study is the use of the general anesthetic pentobarbital that my affect the excitability of DRG neurons via modulating some ion channels. However, changes in the excitability of DRG neurons that we see in STZ rats are unlikely to be due to effects of pentobarbital because it was used in both control and STZ rats and because pentobarbital has been shown to have negligible effects on excitability of cutaneous Aβ-mechanoreceptive afferents (Cheng et al, 2013).…”

Sensory computations in the cuneate nucleus of macaques

“…First, the impact of anesthesia tends to be more pronounced in the cortex ( 59 ). Given that the CN is the first recipient of afferent input itself minimally affected by anesthesia ( 60 ), the impact of anesthesia on CN responses, at least those driven by peripheral input, is likely minimal. Second, certain anesthetics have been shown to affect the temporal response properties of neurons in the cortex ( 55 ).…”