Developmental Progression of Electrical Activity Throughout the Anterior-Posterior Axis of Xenopus laevis Spinal Cord and Skeletal Musculature

Spontaneous Ca²⁺-mediated electrical activity manifests during nervous system and muscle development and is important for neuronal and muscle cell differentiation. Previous studies have shown that Ca²⁺ -mediated electrical activity manifests in the Xenopus developing spinal cord from the moment the neural tube closes (22 h post fertilization, hpf) until the embryo hatches (32 hpf). Similarly, developing muscle cells exhibit Ca²⁺ transients during an embryonic period that correlates with somitogenesis. After hatching, Xenopus larvae develop a tail which allows for effective swimming of the tadpole. Whether the spontaneous embryonic Ca²⁺-mediated electrical activity is recreated in the most posterior tissues of the larva’s tail remains unknown. We investigated the developmental progression of Ca²⁺-mediated electrical activity in anterior and tail tissues of the Xenopus tadpole. Anterior and posterior muscle and spinal cord were dissected from stages 33, 37 and 41 (44, 54, 72 hpf, respectively) tadpoles and dissociated cells were loaded with a Ca²⁺-sensitive dye followed by time-lapse imaging with a confocal microscope. Preliminary results show that Ca²⁺ transients are evident in cells derived from tail tissues with the highest incidence of active cells at stage 33 decreasing to undetectable levels by stage 41. Cells derived from anterior spinal cord and muscle do not exhibit spontaneous activity. These results indicate that expression of Ca²⁺-mediated electrical activity in neuronal and muscle cells of the tail is developmentally regulated and suggest that this activity may be relevant for appropriate tail development as well as for the regenerative capacity of these tissues after injury.