EVOLUTION of NOCICEPTION in elasmobranchs

The University Corporation, Northridge, Northridge CA

Investigators

Abstract

One striking ability of individual sharks is their survival in the face of serious injuries, which has led many people who study them to speculate that sharks do not perceive pain. Pain perception (also called nociception) relies upon specialized sensory neurons to detect noxious (injurious) stimuli. Pain is a survival-enhancing experience that enables animals to avoid injury; the lack of evidence for pain perception in seriously injured sharks suggests that they lack nociception. The goal of this project is to definitively determine whether or not sharks experience pain by using molecular biological and histological techniques to identify whether sharks possess cell types and cell structures that are specifically associated with nociception in other vertebrate animals. The findings from this research will lead towards a better understanding about both the evolution and function of nociceptors in vertebrate animals. This project will also provide training to underrepresented minority undergraduate students in fundamental laboratory bench and bioinformatics techniques, as well as allowing them to participate in cutting-edge transcriptomics research. It will also expand the bioinformatics capacity and training of collaborating California State University Northridge faculty. In order to feel pain and avoid injury, animals need specialized sensory (“nociceptive”) neurons to detect noxious stimuli. Nociceptive neurons originate from neural crest cells that give rise to peripheral sensory ganglia, and previous work has classified these cells into two primary morphological types (C-fiber or Aδ-fiber neurons). In principle, all vertebrates have nociceptors since they all have full-fledged neural crest cells. Sharks belong to a vertebrate group called elasmobranchs, along with skates and rays There exists a gap in scientific knowledge regarding elasmobranch nociception because of disagreements about the types and numbers of nociceptors that elasmobranchs are thought to possess Some previous researchers have proposed that elasmobranchs lack full-scale nociception because of low numbers of C-Fiber neurons, and their disregard for serious bodily injury. The goal of the present study is to whether true nociceptive neurons exist in elasmobranchs by 1) looking at the shark genomes to identify specific nociceptor sequences; 2) Isolating shark Dorsal Root Ganglia/Trigeminal Ganglia (where nociceptive cell bodies reside) and analyzing their transcriptome to find pain receptors profiles; 3) Using immunohistochemistry to label nociceptors in the Dorsal Root Ganglia of sharks; 4) Looking at the promoters of two key nociceptor transcription factors, and studying their regulatory elements to determine differences between elasmobranchs and other vertebrates, and differences between the Trigeminal Ganglia and Dorsal Root Ganglia. This project is expected to uncover the extant capabilities for nociception in elasmobranchs; as well as contributing towards a better understanding about the evolution of sensory pain perception in vertebrates. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.