Name: Alexandre Frinhani Cunha
Type: MSc dissertation
Publication date: 23/07/2014
Advisor:

Namesort descending Role
Karla Nívea Sampaio Advisor *

Examining board:

Namesort descending Role
Karla Nívea Sampaio Advisor *
Leonardo Resstel Barbosa Moraes Internal Examiner *
Tadeu Uggere de Andrade External Examiner *

Summary: Among the pesticides available for use, the organophosphorus compounds stand out as one of the main responsible for poisonings, suicide attempts and deaths in Brazil. Chlorpyrifos, a widely used pesticide representative of this group, exerts its toxic effect partly due to the inhibition of the acetylcholinesterase enzyme. This inhibition leads to an increase in the amount of acetylcholine available in the cholinergic synapses, promoting various signals and effects which result from an excessive activation of the muscarinic and nicotinic receptors located either peripherally or within the central nervous system. Considering that these compounds are capable of promoting profound changes in many systems in the exposed, rises a particular interest on the effects observed on the cardiovascular system and behavior induced by poisoning with these substances. Therefore, the aim of this study was to evaluate the effects of the acute exposure to sublethal doses of the insecticide chlorpyrifos on three cardiovascular reflexes (baroreflex, Bezold-Jarisch reflex and chemoreflex), on the activity of some enzymes (plasma cholinesterase, creatine kinase MB fraction and lactate dehydrogenase) and on some behavioral parameters in experimental animals (open field test, elevated plus maze and forced swim test). For the cardiovascular tests, animals initially underwent catheterization of the femoral artery and vein and, 24 hours later, were treated with either chlorpyrifos 30 mg/kg or saline. One day after the treatment, cardiovascular recordings were performed for assessment of cardiovascular reflexes. The same animals provided blood samples for all enzymatic measurements, which were collected through the catheter before and after the treatment. For the behavioral tests, animals were treated with either chlorpyrifos at the doses of 20, 25 and 30 mg/kg or saline. And, 24 hours later, were subjected to the open field test, elevated plus maze and forced swim test. In the behavioral tests, the treatment with the organophosphate induced a anxiogenic and depressive-like effect in tested animals. The cholinesterase activity was significantly reduced in treated animals. Some of the treated animals also showed an evidence of cardiovascular injury, represented by the increased activity of CK-MB and LDH enzymes. Regarding cardiovascular tests, the treatment with chlorpyrifos induced an impairment in the bradycardic response of the three reflexes tested. Additionally, exposure to chlorpyrifos decreased the hipertensive response of the chemoreflex, the 16 hypotensive response of the RBJ as well as the range and the baroreflex gain in tested animals.

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