title: Increased hippocampal excitability produced by amitraz.
abstract: The present study characterized the effect of the formamidine pesticide, amitraz, upon hippocampal function in male Long-Evans rats. Animals were chronically prepared with a stimulating electrode in the perforant path and field potentials were recorded from a bipolar electrode situated across the granule cell layer of the dentate gyrus. Input/output functions and paired pulse inhibition were monitored in unrestrained, unanesthetized animals over a number of days following acute administration of 100 mg/kg of amitraz. Input/output functions revealed a decrease in excitatory postsynaptic potential (ESP) slope and an increase in population spike height 4 and 24 hr after treatment, with return to baseline by 48 hr. Tests of inhibition using pairs of stimulus pulses delivered at intervals ranging between 20 and 100 msec revealed a decrease in inhibition following amitraz. Both of these effects could be mimicked by administration of 0.1 mg/kg of the alpha-2 agonist clonidine, supporting this mode of action of amitraz on CNS function. These results indicate that systemic amitraz treatment produced a transient enhancement of excitatory and reduction of inhibitory processes in a CNS pathway.
authors.affiliation: Northrop Services Inc., Research Triangle Park, NC 27709.
authors.forename: M E
authors.initials: ME
authors.lastname: Gilbert
authors.forename: R S
authors.initials: RS
authors.lastname: Dyer
mesh_terms: D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D007306:Insecticides / Q000494:pharmacology*; D008297:Male; D051381:Rats; D012016:Reference Values; D013997:Time Factors; D014052:Toluidines / Q000494:pharmacology*
chemical_list: D007306:Insecticides; D014052:Toluidines; C014983:amitraz; D003000:Clonidine