Estrogen modulates responses of striatal dopamine neurons to MPP+: evaluations using in vitro and in vivo techniques
Creator
Arvin M; Fedorkova L; Disshon K A; Dluzen D E; Leipheimer R E
Publisher
Brain Research
Date
2000
2000-07
Description
In vitro superfusion and in vivo electrochemistry were used to investigate the role of estrogen in modulatings MPP+-induced dopamine output in the corpus striatum and nucleus accumbens of ovariectomized female rats. For in vitro superfusion experiments, dopamine and dihydroxyphenylacetic acid release were determined using HPLC with electrochemical detection from superfusion of corpus striatum fragments with Kreb's ringer phosphate buffer pulsed with MPP+ alone or MPP+ with estrogen. The in vivo electrochemistry experiments recorded the dopamine signal from carbon fiber microelectrodes stereotaxically passed through the corpus striatum and nucleus accumbens. Dopamine release was stimulated by pressure ejection of MPP+ alone or in combination with estrogen through glass micropipettes fastened to the electrodes. Dopamine output from superfusion chambers which received infusion of MPP+ with estrogen showed significantly lower output of dopamine compared with chambers which received MPP+ alone. Outputs of dihydroxyphenylacetic acid did not increase following MPP+ infusions. Data from the electrochemistry experiments demonstrated that estrogen significantly reduced both the amplitude and clearance rates of the MPP+-evokrd dopamine signal in both the corpus striatum and nucleus accumbens. Results of this study demonstrate that: (1) MPP+ evokes striatal dopamine release and this effect is significantly reduced in the presence of estrogen as determined by both in vivo electrochemistry and in vitro superfusion: (2) similar, albeit attenuated effects are observed in the nucleus accumbens as determined with in vivo electrochemistry; (3) estrogen acts to inhibit the clearance of dopamine in both the striatum and nucleus accumbens: and (4) estrogen may function as a neuroprotectant by reducing the uptake of neurotoxin into dopaminergic neurons. (C) 2000 Elsevier Science B.V. All rights reserved.
A neurochemical heterogeneity of the rat striatum as measured by in vivo electrochemistry and microdialysis.
Creator
Yamamoto B K; Pehek E A
Publisher
Brain research
Date
1990
1990-01
Description
The neurochemical heterogeneity of the rat striatum was assessed in vivo by measuring subregional changes in extracellular dopamine and DOPAC by in vivo electrochemistry and microdialysis in response to amphetamine and the D2 antagonist, (-)-sulpiride. Both in vivo electrochemical and microdialysis experiments indicated a significant rostrocaudal gradient in dopamine release following amphetamine. The increase in dopamine release was highest in the rostral areas (over 800% of baseline values) and lowest in the most caudal subregion (425% of baseline). No lateromedial differences in dopamine release were observed. DOPAC levels decreased in dialysates but were similar for all 6 subregions examined. In contrast, D2 blockade with (-)-sulpiride revealed a lateromedial gradient in the increases seen for dopamine and DOPAC such that greater increases were observed in the lateral subregions. (-)-Sulpiride did not produce any differential effects along the rostrocaudal axis. The regional gradients detected in extracellular fluid changes of dopamine and DOPAC indicate that dopamine release is locally regulated by an interaction between the density of dopaminergic innervation to a particular subregion and the D2 receptor density.
In vivo neurochemical and anatomical heterogeneity of the dopamine uptake system in the rat caudate putamen.
Creator
Glynn G E; Yamamoto B K
Publisher
Brain research
Date
1989
1989-03
Description
The neurochemical and anatomical heterogeneity of dopamine uptake blockade was studied at a medial and lateral position in each of 3 rostrocaudal areas of the rat caudate-putamen. In vivo voltammetric measures of extracellular dopamine indicated a lateral-to-medial and rostral-to-caudal gradient in the effect of uptake blockade. The percentage increase in dopamine was greatest in the rostrolateral area (300%) and least in the caudomedial area (10%). The existence of these lateromedial and rostrocaudal gradients was confirmed by tissue content measures of DOPAC and dopamine to DOPAC ratios in each area. The rostrocaudal gradient in the effect of uptake blockade was independent of the rostrocaudal gradient in dopamine tissue content. The regional gradients detected in dopamine uptake blockade may indicate a heterogeneous distribution in the number of uptake sites, a regional variation in the affinity of the uptake site for the blocker and/or altered neuronal activity mediated by an action of the blocker on dopaminergic cell bodies.
An improved and rapid HPLC-EC method for the isocratic separation of amino acid neurotransmitters from brain tissue and microdialysis perfusates.
Creator
Donzanti B A; Yamamoto B K
Publisher
Life sciences
Date
1988
1905-06
Description
An improved, HPLC with electrochemical detection method for the isocratic separation and determination of amino acids from post-mortem brain tissue and from microdialysates of awake-behaving animals is described. Optimal conditions that maximize stability, resolution, and sensitivity were determined for the pre-column derivatization of amino acids using o-phthalaldehyde and
Subject
Dialysis; Male; Animals; Rats; *Brain Chemistry; Chromatography; Electrochemistry; Corpus Striatum/analysis; Amino Acids/*analysis; Neurotransmitter Agents/*analysis; Inbred Strains; High Pressure Liquid/*methods