Efficacy of Tricaine Methanesulfonate (MS-222) as an Anesthetic Agent for Blocking Sensory-Motor Responses in Xenopus laevis Tadpoles

Abstract

Anesthetics are drugs that reversibly relieve pain, decrease body movements and suppress neuronal activity. Most drugs only cover one of these effects; for instance, analgesics relieve pain but fail to block primary fiber responses to noxious stimuli. Alternately, paralytic drugs block synaptic transmission at neuromuscular junctions, thereby effectively paralyzing skeletal muscles. Thus, both analgesics and paralytics each accomplish one effect, but fail to singularly account for all three. Tricaine methanesulfonate (MS-222) is structurally similar to benzocaine, a typical anesthetic for anamniote vertebrates, but contains a sulfate moiety rendering this drug more hydrophilic. MS-222 is used as anesthetic in poikilothermic animals such as fish and amphibians. However, it is often argued that MS-222 is only a hypnotic drug and its ability to block neural activity has been questioned. This prompted us to evaluate the potency and dynamics of MS-222-induced effects on neuronal firing of sensory and motor nerves alongside a defined motor behavior in semi-intact in vitro preparations of Xenopus laevis tadpoles. Electrophysiological recordings of extraocular motor discharge and both spontaneous and evoked mechanosensory nerve activity were measured before, during and after administration of MS-222, then compared to benzocaine and a known paralytic, pancuronium. Both MS-222 and benzocaine, but not pancuronium caused a dose-dependent, reversible blockade of extraocular motor and sensory nerve activity. These results indicate that MS-222 as benzocaine blocks the activity of both sensory and motor nerves compatible with the mechanistic action of effective anesthetics, indicating that both caine-derivates are effective as single-drug anesthetics for surgical interventions in anamniotes.

Galvanic Vestibular Stimulation: Cellular Substrates and Response Patterns of Neurons in the Vestibulo-Ocular Network

“…This surgical procedure anatomically preserved all vestibular endorgans within the otic capsule on both sides (Fig. 1 A, B), the CNS, the extraocular motor innervation, and eye muscles and allowed prolonged in vitro experimentation (Ramlochansingh et al, 2014), including an in vivo-like activation of the VOR during motion or electrical stimulation (Straka and Simmers, 2012).…”

“…This system was mounted on top of the experimental setup to visualize the motion of one eye from above during natural or galvanic vestibular stimulation at a video capture frame rate of 30 Hz with the FlyCap2 software (version 2.3.2.14). Eye motion profiles and parameters were extracted from the captured video sequences using a custom video-processing algorithm written in Matlab (for details, see Ramlochansingh et al, 2014). To calculate the motion of the eye, an ellipse was drawn around the eyeball and the angle between the minor axis of the ellipse and the longitudinal axis of the head was calculated in each frame of a given video sequence .…”

Sex differences and endocrine regulation of auditory-evoked, neural responses in African clawed frogs (Xenopus)

“…One potential alternative is benzocaine, which does not appear to have the same detrimental effects on hair cell activity as MS222 (Balak et al 1990; Meyers et al 2003) but is also associated with more health risks and mortality (Cakir and Strauch 2005; Cacala et al 2007). In contrast to curare, a recent paper reports that both benzocaine and MS-222 block sensory nerve activity in Xenopus (Ramlochansingh et al 2014), again supporting the use of alternative means of immobilization for recordings of neural activity.…”

A new substance to relax polychaete worms (Annelida) prior to morphological study

“…MS-222, Tricaine methanesulfonate (a chemical commonly used for anesthesia, sedation, or euthanasia of fish) (Wayson 1976), has also been used to relax polychaetes prior to examination (Fauchald 1977; Fidalgo e Costa 1999). MS-222 can simultaneously block pain sensation, paralyze the animal by muscle relaxation and exert a general anesthesia by blocking Na + -conductance of cellular elements comprising the neuromuscular system (brain and muscles) (Ramlochansingh et al 2014). A 0.05 percent solution of MS-222 in sea-water completely anesthetizes medium-sized worms within 5–7 minutes (Clark 1961).…”