Modulation of dopaminergic neurotransmission induced by sublethal Doses of the organophosphate trichlorfon in cockroaches

• Published in: Ecotoxicology and environmental safety Vol. 109; pp. 56 - 62
• Main Authors: Daiane Stu¨rmer, Graziele, de Freitas, Thiago Carrazoni, de Avila Heberle, Marines, de Assis, Dênis Reis, Vinadé, Lúcia, Batista Pereira, Antônio, Luis Franco, Jeferson, André Dal Belo, Cháriston
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 01-11-2014
• Subjects: Acetylcholinesterase; Acetylcholinesterase - metabolism; Alterations; Animals; Brain - enzymology; Cholinergics; Cockroaches - drug effects; Cockroaches - metabolism; Dopaminergic signaling; Grooming - drug effects; Inhibitors; Insecticides - toxicity; Insects; Male; Motor Activity - drug effects; Neurotoxicity; Organophosphates; Phoetalia pallida; Receptors; Synaptic Transmission - drug effects; Toxicity; Trichlorfon; Trichlorfon - toxicity; Phoetalia pallida; Neurotoxicity; Acetylcholinesterase; Dopaminergic signaling; Trichlorfon
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/j.ecoenv.2014.08.006

Organophosphate (OP) insecticides have been used indiscriminately, based on their high dissipation rates and low residual levels in the environment. Despite the toxicity of OPs to beneficial insects is principally devoted to the acetylcholinesterase (AChE) inhibition, the physiological mechanisms underlying this activity remain poorly understood. Here we showed the pharmacological pathways that might be involved in severe alterations in the insect locomotion and grooming behaviors following sublethal administration of the OP Trichlorfon (Tn) (0.25, 0.5 and 1µM) in Phoetalia pallida. Tn inhibited the acetylcholinesterase activity (46±6, 38±3 and 24±6nmol NADPH/min/mg protein, n=3, p<0.05), respectively. Tn (1µM) also increased the walking maintenance of animals (46±5s; n=27; p<0.05). Tn caused a high increase in the time spent for this behavior (344±18s/30min, 388±18s/30min and 228±12s/30min, n=29–30, p<0.05, respectively). The previous treatment of the animals with different cholinergic modulators showed that pirenzepine>atropine>oxotremorine>d-tubocurarine>tropicamide>methoctramine induced a decrease on Tn (0.5µM)-induced grooming increase, respectively in order of potency. Metoclopramide (0.4µM), a DA-D2 selective inhibitor decreased the Tn-induced grooming activity (158±12s/30min; n=29; p<0.05). Nevertheless, the effect of the selective DA-D1 receptor blocker SCH 23390 (1.85µM) on the Tn (0.5µM)-induced grooming increase was significative and more intense than that of metoclopramide (54±6s/30min; n=30; p<0.05). Taken together the results suggest that a cross-talking between cholinergic M1/M3 and dopaminergic D1 receptors at the insect nervous system may play a role in the OP-mediated behavioral alterations.