title: Postnatal manganese exposure alters dopamine transporter function in adult rats: Potential impact on nonassociative and associative processes.
abstract: In the present study, we examined whether exposing rats to a high-dose regimen of manganese chloride (Mn) during the postnatal period would depress presynaptic dopamine functioning and alter nonassociative and associative behaviors. To this end, rats were given oral supplements of Mn (750 microg/day) on postnatal days (PD) 1-21. On PD 90, dopamine transporter (DAT) immunoreactivity and [3H]dopamine uptake were assayed in the striatum and nucleus accumbens, while in vivo microdialysis was used to measure dopamine efflux in the same brain regions. The effects of postnatal Mn exposure on nigrostriatal functioning were evaluated by assessing rotorod performance and amphetamine-induced stereotypy in adulthood. In terms of associative processes, both cocaine-induced conditioned place preference (CPP) and sucrose-reinforced operant responding were examined. Results showed that postnatal Mn exposure caused persistent declines in DAT protein expression and [3H]dopamine uptake in the striatum and nucleus accumbens, as well as long-term reductions in striatal dopamine efflux. Rotorod performance did not differ according to exposure condition, however Mn-exposed rats did exhibit substantially more amphetamine-induced stereotypy than vehicle controls. Mn exposure did not alter performance on any aspect of the CPP task (preference, extinction, or reinstatement testing), nor did Mn affect progressive ratio responding (a measure of motivation). Interestingly, acquisition of a fixed ratio task was impaired in Mn-exposed rats, suggesting a deficit in procedural learning. In sum, these results indicate that postnatal Mn exposure causes persistent declines in various indices of presynaptic dopaminergic functioning. Mn-induced alterations in striatal functioning may have long-term impact on associative and nonassociative behavior.
authors.affiliation: Department of Psychology, California State University, San Bernardino, CA 92407, USA. smcdouga@csusb.edu
authors.forename: S A
authors.initials: SA
authors.lastname: McDougall
authors.forename: C M
authors.initials: CM
authors.lastname: Reichel
authors.forename: C M
authors.initials: CM
authors.lastname: Farley
authors.forename: M M
authors.initials: MM
authors.lastname: Flesher
authors.forename: T
authors.initials: T
authors.lastname: Der-Ghazarian
authors.forename: A M
authors.initials: AM
authors.lastname: Cortez
authors.forename: J J
authors.initials: JJ
authors.lastname: Wacan
authors.forename: C E
authors.initials: CE
authors.lastname: Martinez
authors.forename: F A
authors.initials: FA
authors.lastname: Varela
authors.forename: A E
authors.initials: AE
authors.lastname: Butt
authors.forename: C A
authors.initials: CA
authors.lastname: Crawford
mesh_terms: D000661:Amphetamine / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001245:Association Learning / Q000502:physiology*; D001835:Body Weight / Q000187:drug effects; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D003042:Cocaine / Q000494:pharmacology; D003216:Conditioning, Operant / Q000187:drug effects; D003627:Data Interpretation, Statistical; D004298:Dopamine / Q000378:metabolism; D050483:Dopamine Plasma Membrane Transport Proteins / Q000378:metabolism*; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology; D005260:Female; D008297:Male; D020149:Manganese Poisoning / Q000378:metabolism* / Q000523:psychology*; D017551:Microdialysis; D009043:Motor Activity / Q000187:drug effects; D004856:Postural Balance / Q000187:drug effects; D011597:Psychomotor Performance / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012054:Reinforcement, Psychology; D013239:Stereotyped Behavior / Q000187:drug effects; D013395:Sucrose / Q000494:pharmacology
chemical_list: D000697:Central Nervous System Stimulants; D050483:Dopamine Plasma Membrane Transport Proteins; D018765:Dopamine Uptake Inhibitors; D013395:Sucrose; D000661:Amphetamine; D003042:Cocaine; D004298:Dopamine