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| Author(s): |
Rita de Cássia de Oliveira Collaço
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Faculdade de Ciências Médicas |
| Defense date: | 2019-02-28 |
| Examining board members: |
Edson Antunes;
Luiz Ricardo de Almeida Kiguti;
Priscila Randazzo de Moura;
Fabio Bucaretchi;
Ana Leonor Abrahão Nencioni
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| Advisor: | Edward Gerard Rowan; Edson Antunes |
| Abstract | |
Scorpionism is frequently accompanied by a massive release of catecholamines and acetylcholine from peripheral nerves caused by neurotoxic peptides present in theses venoms, which have high specificity and affinity for ion channels. Tityus bahiensis (T. bahiensis) is the second most medically important scorpion specie in Brazil (responsible for the major scorpion accidents in Sao Paulo State) but, despite its epidemiological relevance, its venom remains scarcely studied, especially with regarding to its pharmacology on peripheral nervous system. Here, we evaluated the activity of T. bahiensis venom on motor somatic and autonomic neurotransmission using myographic (chick and mouse neuromuscular preparations, and isolated rat vas deferens), electrophysiological (MEPP, EPP, SEJP, resting membrane potentials, perineural waveforms, compound action potentials) and calcium imaging (on DRG neurons and muscle fibres) techniques. Our results show that the major toxic effects of T. bahiensis venom on neuromuscular function are presynaptically driven. Low concentrations of venom prolong the axonal action potential leading to a longer depolarization of the nerve terminals that enhances neurotransmitter release and facilitates nerve-evoked muscle contraction. The venom also stimulates the spontaneous release of neurotransmitters, probably through partial neuronal depolarization. Higher concentration of venom blocks the generation of the action potential and resulting muscle twitches. The venom pharmacology was reversed by low concentrations of TTX, indicating voltage-gated sodium channels as one of the primary target of the venom toxins. These results suggest that major neurotoxicity promoted by T. bahiensis venom are probably caused mainly by 'alpha'- and 'beta'-toxins interacting with presynaptic TTX-sensitive ion channels on both axons and nerve terminals (AU) | |
| FAPESP's process: | 16/11319-6 - The somatic and autonomic activities of Tityus bahiensis scorpion venom and its isolated fractions. |
| Grantee: | Rita de Cássia de Oliveira Collaço |
| Support Opportunities: | Scholarships in Brazil - Doctorate |