Synaptic Currents in Xenopus laevis Tectal Neurons: A Study on Whole-Cell Patch Clamp Electrophysiology

Electrophysiology is the study of the electrical properties of cells and tissues. In neuroscience research, it involves the measurement of the electrical activity of neurons. Xenopus laevis tadpoles have previously been used for electrophysiological experimentation because tadpole neural circuit organization has been well-characterized. In addition, the neural connections within the retinotectal circuit of the tadpole—from the eye to the brain to the optic tectum—mirror what can be seen in many mammalian sensory circuits. The optic tectum is a region of interest in many electrophysiological studies that use tadpoles, as it is a highly accessible midbrain structure important for the transformation of sensory input into movement output. When paralyzing tadpoles for electrophysiology work, a neuromuscular blocker called pancuronium is often used. Within the peripheral nervous system, it causes muscle relaxation and paralysis by blocking the neurotransmitter acetylcholine from binding to the nicotinic acetylcholine receptors at the neuromuscular junction. However, there is evidence that if pancuronium enters the central nervous system, it may affect the brain cell features relevant to electrophysiology data—like synaptic currents—due to the process of binding to neuronal-type acetylcholine receptors. This could compromise the reliability of pancuronium as a paralytic agent for in vivo studies of the brain that use tadpoles, nematodes, and fish. The goal of this project was to use electrophysiology to measure features of synaptic currents—evoked postsynaptic currents and spontaneous (miniature) postsynaptic currents—of individual neural cells in the tadpole optic tectum upon exposure to pancuronium to assess how the paralytic influences excitatory and inhibitory activity of these currents while keeping the cellular voltage constant. However, due to the semester ending prematurely, I was unable to complete data collection. Therefore, the results are inconclusive