Flavia Valladao Thiesen (1), Helena M.T. Barros (2,*), Mario Tannhauser
(2) and Semiramis L. Tannhauser (2)
(1) Center of Applied Toxicology, Pontificia Universidade Catolica do Rio
Grande do Sul, Av. Ipiranga, 6681 -Predio 12, Porto Alegre, 90619-900 Brazil
(2) Division of Pharmacology, Fundacao Faculdade Federal de Ciencias Medicas
de Porto Alegre, Sarmento Leite, 245-Porto Alegre, 90050-170 Brazil
(*) To whom correspondence should be addressed.
Abstract: Early assessment of neurological and behavioral effects
is extremely valuable for early identification of intoxications because
preventive measures can be taken against more severe or chronic toxic consequences.
The time course of the effects of an oral dose of the anticholinesterase
agent propoxur (8.3 mg/kg) was determined on behaviors displayed in the
open-field and during an active avoidance task by rats and on blood and
brain cholinesterase activity. Maximum inhibition of blood cholinesterase
was observed within 30 min after administration of propoxur. The half-life
of enzyme-activity recovery was estimated to be 208.6 min. Peak brain cholinesterase
inhibition was also detected between 5 and 30 min of the pesticide administration,
but the half-life for enzyme activity recovery was much shorter, in the
range of 85 min. Within this same time interval of the enzyme effects, diminished
motor and exploratory activities and decreased performance of animals in
the active avoidance task were observed. Likewise, behavioral normalization
after propoxur followed a time frame similar to that of brain cholinesterase.
These data indicate that behavioral changes that occur during intoxication
with low oral doses of propoxur may be dissociated from signs characteristic
of cholinergic over-stimulation but accompany brain cholinesterase activity
inhibition.
Keywords: Propoxur, Anticholinesterase agent, Behavioral toxicology,
Pharmacokinetics, Cholinesterase