Organic cation transporter 3 and the dopamine transporter differentially regulate catecholamine uptake in the basolateral amygdala and nucleus accumbens

Abstract

Regional alterations in kinetics of catecholamine uptake are due in part to variations in clearance mechanisms. The rate of clearance is a critical determinant of the strength of catecholamine signaling. Catecholamine transmission in the nucleus accumbens core (NAcc) and basolateral amygdala (BLA) is of particular interest due to involvement of these regions in cognition and motivation. Previous work has shown that catecholamine clearance in the NAcc is largely mediated by the dopamine transporter (DAT), but clearance in the BLA is less DAT-dependent. A growing body of literature suggests that organic cation transporter 3 (OCT3) also contributes to catecholamine clearance in both regions. Consistent with different clearance mechanisms between regions, catecholamine clearance is more rapid in the NAcc than in the BLA, though mechanisms underlying this have not been resolved. We compared the expression of DAT and OCT3 and their contributions to catecholamine clearance in the NAcc and BLA. We found DAT protein levels were ~ 4-fold higher in the NAcc than in the BLA, while OCT3 protein expression was similar between the two regions. Immunofluorescent labeling of the two transporters in brain sections confirmed these findings. Ex vivo voltammetry demonstrated that the magnitude of catecholamine release was greater, and the clearance rate was faster in the NAcc than in the BLA. Additionally, catecholamine clearance in the BLA was more sensitive to the OCT3 inhibitor corticosterone, while clearance in the NAcc was more cocaine sensitive. These distinctions in catecholamine clearance may underlie differential effects of catecholamines on behavioral outputs mediated by these regions.

Cocaine Augments Dopamine-Mediated Inhibition of Neuronal Activity in the Dorsal Bed Nucleus of the Stria Terminalis

“…Thus, the observed uptake rates for evoked catecholamine signals are standardized to dopamine-DAT affinity and do not provide a kinetic analysis of norepinephrine uptake rates specifically, or the contribution of noncanonical transporter species to catecholamine removal (Holleran et al, 2020). This K m value was applied consistently across recordings to provide a qualitative comparison of basal catecholamine signal uptake rates in the dBNST versus the caudate regions, where uptake rate is dominated by DAT function (Holleran et al, 2020).…”

General Overview of Organic Cation Transporters in Brain

“…The monoamine neurotransmitter transporters exhibit transmitter/Na + /Cl À stoichiometries of 1:1:1 (NET), 1:2:1 (DAT), and 1:1:1 (SERT) (Kristensen et al 2011;Torres et al 2003). In SERT cotransport of 5-HT with Na + Net: (Lorang et al 1994;Pacholczyk et al 1991;Schroeter et al 2000;Torres et al 2003), Dat: (Cerruti et al 1993;Ciliax et al 1995;Freed et al 1995;Hersch et al 1997;Hoffman et al 1998;Holleran et al 2020;Lorang et al 1994;Nirenberg et al 1996Nirenberg et al , 1997aRevay et al 1996;Torres et al 2003), Sert: (Bengel et al 1998;Brust et al 2000;Hoffman et al 1998;Pickel and Chan 1999;Qian et al 1995;Sur et al 1996;Tao-Cheng and Zhou 1999;Zhou et al 1998) (Bengel et al 1998;Brust et al 2000;Cerruti et al 1993;Chang et al 1996;Hoffman et al 1998;Pickel and Chan 1999;Qian et al 1995;Sur et al 1996;Tao-Cheng and Zhou 1999;Torres et al 2003;Zhou et al 1998), Oct1: (Baganz et al 2008;Choudhuri et al 2003;Duan and Wang 2013;Lin et al 2010;Sekhar et al 2019;…”

“…After Oct3 removal in mice, the concentrations of DA and NE in the SN and the ventral tegmental area and the concentration of histamine in thalamus and hypothalamus were decreased (Vialou et al 2008). Employing cocaine and corticosterone as inhibitors the involvement of Oct3 in the clearance of catecholamines (DA and NE) after neuronal activation was investigated in rats (Holleran et al 2020). Cocaine is a high affinity inhibitor of DAT whereas corticosterone inhibits rOct3 and rOct2 with higher affinity compared to rPmat (Table 4).…”

Effectiveness and Relationship between Biased and Unbiased Measures of Dopamine Release and Clearance

“…Interestingly, with increased stimulation intensity, dopamine clearance rate in DATKO slices was increased, suggesting additional recruited mechanisms of clearance. The organic cation transporter 3 (OCT3) has been implicated in catecholamine clearance in the striatum and basolateral amygdala . DATKO mice have previously been used as a model of diffusion, but recent evidence demonstrates that OCT3 is active and even upregulated in DATKO transgenic rats .…”

“…The organic cation transporter 3 (OCT3) has been implicated in catecholamine clearance in the striatum 61 and basolateral amygdala. 62 DATKO mice have previously been used as a model of diffusion, but recent evidence demonstrates that OCT3 is active and even upregulated in DATKO transgenic rats. 63 While not tested exclusively herein, it is possible that increased stimulation intensity is recruiting this alternate uptake mechanism.…”