Application of fast-scan cyclic voltammetry for the in vivo characterization of optically evoked dopamine in the olfactory tubercle of the rat brain

Abstract

The olfactory tubercle (OT), as a component of the ventral striatum, serves as an important multisensory integration center for reward-related processes in the brain. Recent studies show that dense dopaminergic innervation from the ventral tegmental area (VTA) into the OT may play an outsized role in disorders such as psychostimulant addiction and disorders of motivation, increasing recent scientific interest in this brain region. However, due to its anatomical inaccessibility, relative small size, and proximity to other dopamine-rich structures, neurochemical assessments using conventional methods cannot be readily employed. Here, we investigated dopamine (DA) regulation in the OT of urethane-anesthetized rats using in vivo fast-scan voltammetry (FSCV) coupled with carbon-fiber microelectrodes, following optogenetic stimulation of the VTA. The results were compared with DA regulation in the nucleus accumbens (NAc), a structure located adjacent to the OT and which also receives dense DA innervation from the VTA. FSCV coupled with optically evoked release allowed us to investigate the spatial distribution of DA in the OT and characterize OT DA dynamics (release and clearance) with subsecond temporal and micrometer spatial resolution for the first time. In this study, we demonstrated that DA transporters play an important role in regulating DA in the OT. However, the control of extracellular DA by uptake in the OT was less than in the NAc. The difference in DA transmission in the terminal fields of the OT and NAc may be involved in region-specific responses to drugs of abuse and contrasting roles in mediating reward-related behavior.

Heterogeneous extracellular dopamine regulation in the subregions of the olfactory tubercle

“…Here, as an extension of our recent work and others (Wakabayashi et al 2016, Robinson et al 2005), we identified for the first time the major catecholamine evoked in the OT by the electrical stimulation of the VTA as DA and subsequently determined how the regulation of extracellular DA release and clearance differed in the amOT, alOT and pOT with pharmacological manipulation.…”

“…Glass-encased cylindrical carbon-fiber microelectrodes were prepared as described earlier (Cahill & Wightman 1995). T-650 untreated carbon fibers (Thornel, Amoco Corp., Greenville, SC) with an exposed length of 75 – 100 μm and 7 μm nominal diameter were used (Wakabayashi et al 2016). FSCV was computer-controlled and the experimental setup for dual measurement has been described previously (Park et al 2011, Zachek et al 2010).…”

“…Temporal responses were determined by monitoring the current at the peak oxidation potential for DA in successive voltammograms. As the carbon-fiber microelectrode was used to generate a lesion for histological verification, detailed below, the average post-calibration factor (9.2 ± 1.1 pA/(μM·μm 2 ) was obtained in vitro with known concentrations of DA from our recent study (n = 8 electrodes) to determine DA concentrations in the OT (Wakabayashi et al 2016).…”

Role of trace amine-associated receptor 1 in nicotine’s behavioral and neurochemical effects

“…In vivo fast-scan cyclic voltammetry Rats were anesthetized with urethane (1.5 g/kg) and placed in a stereotaxic frame for implantation of a Ag/AgCl reference electrode, a carbon-fiber microelectrode (NAc core: AP 1.2 mm; ML 1.3 mm; DV~−7.5 mm), and a stimulating electrode [32,33]. A bipolar stimulating electrode (Plastics One, Roanoke, VA, USA) positioned above the VTA (AP −5.2 mm; ML 1.0 mm; DV~−8.0 mm) [34].…”

Contrasting Regulation of Catecholamine Neurotransmission in the Behaving Brain: Pharmacological Insights from an Electrochemical Perspective

“…Early studies used voltammetry in anesthetized rats to reveal an apparent heterogeneity of release and uptake in compartments of the striatum and basolateral amygdala (BLA) (May and Wightman, 1989;Garris and Wightman, 1994b). Dopamine regulation also differs between the NAc and the olfactory tubercle (OT) (Wakabayashi et al, 2016). Dopamine release reaches smaller concentrations in the OT as compared with the NAc, and DAT inhibition produces Contrasting Regulation of Catecholamines Fig.…”