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Main Title Thermoregulatory Effects of Chlorpyrifos in the Rat: Long-Term Changes in Cholinergic and Noradrenergic Sensitivity.
Author Gordon, C. J. ;
CORP Author Health Effects Research Lab., Research Triangle Park, NC. Neurotoxicology Div.
Publisher 15 Jul 93
Year Published 1993
Report Number EPA/600/J-94/322;
Stock Number PB94-197142
Additional Subjects Toxicology ; Body temperature regulation ; Cholinergic receptors ; Pesticides ; Dursban ; Norepinephrine ; Rats ; Motor activity ; Heart rate ; Cholinesterase inhibitors ; Scopolamine ; Reprints ;
Library Call Number Additional Info Location Last
NTIS  PB94-197142 Some EPA libraries have a fiche copy filed under the call number shown. 07/26/2022
Collation 12p
Subcutaneous injection of a sublethal dose of chloropyrifos (CHLP), an organophosphate (OP) pesticide, causes long-term inhibition in cholinesterase activity (ChE) of brain, blood, and other tissues. Such prolonged inhibition in ChE should lead to marked behavioral and autonomic thermoregulatory patterns, especially in terms of altered noradrenergic and cholinergic sensitivity. To evaluate the behavioral and autonomic effects of long-term ChE inhibition, Long-Evans rats were implanted with radiotelemetry transmitters that continuously monitored core temperature (Tc), heart rate (HR), and motor activity (MA). These parameters were monitored for 7 days following a single injection of peanut oil (vehicle control) or 280 mg/kg CHLP. CHLP led to a significant reduction in Tc during the first night after treatment but had no other effects on Tc. CHLP also resulted in a significant elevation in HR which lasted for about 72 h. Motor activity was unaffected by CHLP. Cholinergic and noradrenergic drug sensitivity was assessed between 7 and 25 days after CHLP. CHLP-treated rats were more sensitive to norepinephrine as based on a greater hyperthermic response. MA of CHLP-treated rats was more sensitive to scopolamine. On the other hand, the hypothermic effects of oxotremorine (0.4 mg/kg) were nearly abolished by CHLP treatment, indicating tolerance to cholinergic stimulation. The tachycardic effects of methylscopolamine were also greater in the CHLP group. Overall, the acute effects of CHLP are unusual compared to other OPs in that there is no hypothermic response, an attenuated nocturnal elevation in Tc and a prolonged elevation in HR. The CHLP treated rat exhibits a prolonged elevation in HR, hypersensitivity to noradrenergic stimulation and cholinergic antagonism but hyposensitivity to central cholinergic stimulation. (Copyright (c) 1994 Elsevier Science Ltd.)