An FSCV Study on the Effects of Targeted Typical and Atypical DAT Inhibition on Dopamine Dynamics in the Nucleus Accumbens Shell of Male and Female Mice

Abstract

Understanding the neurochemistry underlying sex differences in psychostimulant use disorders (PSUD) is essential for developing related therapeutics. Many psychostimulants, like cocaine, inhibit the dopamine transporter (DAT), which is largely thought to account for actions related to their misuse and dependence. Cocaine-like, typical DAT inhibitors preferentially bind DAT in an outward-facing conformation, while atypical DAT inhibitors, like modafinil, prefer a more inward-facing DAT conformation. Modafinil and R-modafinil have emerged as potential therapeutic options for selected populations of individuals affected by PSUD. In addition, analogs of modafinil (JJC8-088 and JJC8-091) with different pharmacological profiles have been explored as potential PSUD medications in preclinical models. In this work, we employ fast scan cyclic voltammetry (FSCV) to probe nucleus accumbens shell (NAS) dopamine (DA) dynamics in C57BL/6 male and female mice. We find that cocaine slowed DA clearance in both male and female mice but produced more robust increases in evoked NAS DA in female mice. R-Modafinil produced mild increases in evoked NAS DA and slowed DA clearance across the sexes. The modafinil analog JJC8-088, a typical DAT inhibitor, produced increases in evoked NAS DA in female and male mice. Finally, JJC8-091, an atypical DAT inhibitor, produced limited increases in evoked NAS DA and slowed DA clearance in both sexes. In this work we begin to tease out how sex differences may alter the effects of DAT targeting and highlight how this may help focus research toward effective treatment options for PSUD.

Keywords: Dopamine; FSCV; dopamine transporter; modafinil; sex differences; substance use disorder.

Figure 1:. Cocaine administration increases evoked DA release and slows DA clearance in the NAS.

(A) Representative color plots of evoked NAS DA for a female mouse treated with 10 mg/kg Cocaine. (B) The averaged evoked NAS DA response in male and female mice at control levels (shown in grey), 10 min (male: green, female: orange), 30 min (male: teal, female: purple), and 90 min (male: blue, female: red) post cocaine administration of 3 mg/kg; i.p. and (C) 10 mg/kg; i.p. Stimulation is marked by green box below the plots and traces. Data is shown as the average with SEM in correspondingly colored error bars (n=6 for each treatment).

Figure 2:. Cocaine administration increases evoked DA release and slows DA clearance in the NAS.

(A) Averaged normalized change in NAS DA_max and (B) DA clearance (t_1/2) in male and female mice. DA was analyzed every five min and after 4 consistent control files, cocaine (3 or 10 mg/kg; i.p.) was administered. DA was analyzed for 120 min after drug administration. (n=6 for each treatment group).

Figure 3:. R-modafinil (R-MOD) administration increases evoked DA release and slows DA clearance in the NAS.

(A) Representative color plots of evoked NAS DA for a female mouse treated with 10 mg/kg R-modafinil. (B) The averaged evoked NAS DA response in male and female mice at control levels (shown in grey), 30 min (male: teal, female: purple), and 90 min (male: blue, female: red) post R-modafinil administration of 10 mg/kg; i.p. and (C) 32 mg/kg; i.p. Stimulation is marked by green box below the plots and traces. Data is shown as the average with SEM in correspondingly colored error bars (n=7 for each treatment group).

Figure 4:. R-modafinil administration increases evoked DA release and slows DA clearance in the NAS.

(A) Averaged normalized change in NAS DA_max and (B) DA clearance (t_1/2) in male and female mice. DA was analyzed every five min and after 4 consistent control files, R-modafinil (10 or 32 mg/kg; i.p.) was administered. DA was analyzed for 120 min after drug administration. (n=7 for each treatment group).

Figure 5:. JJC8-088 administration increases evoked DA release and slows DA clearance in the NAS.

(A) Representative color plots of evoked NAS DA for a female mouse treated with 10 mg/kg JJC8-088. (B,C) The averaged evoked NAS DA response in male and female mice at control levels (shown in grey), 30 min (male: teal, female: purple), and 90 min (male: blue, female: red) post JJC8-088 administration (10 and 32 mg/kg; i.p.). Stimulation is marked by green box below the plots and traces. Data is shown as the average with SEM in correspondingly colored error bars (n=7 for each treatment group).

Figure 6:. JJC8-088 administration increases evoked DA release and slows DA clearance in the NAS.

(A) Averaged normalized change in NAS DA_max and (B) DA clearance (t_1/2) in male and female mice. DA was analyzed every five min and after 4 consistent control files, JJC8-088 (10 and 32 mg/kg; i.p.) was administered. DA was analyzed for 120 min after drug administration. (n=7 for each treatment group).

Figure 7:. JJC8-091 administration increases evoked DA release and slows DA clearance in the NAS.

(A) Representative color plots of evoked NAS DA for a female mouse treated with 10 mg/kg JJC8-091. (B,C) The averaged evoked NAS DA response in male and female mice at control levels (shown in grey), 30 min (male: teal, female: purple), and 90 min (male: blue, female: red) post JJC8-091 administration (10 and 32 mg/kg; i.p.). Stimulation is marked by green box below the plots and traces. Data is shown as the average with SEM in correspondingly colored error bars (n=7 for each treatment group).

Figure 8:. JJC8-091 administration increases evoked DA release and slows DA clearance in the NAS.

(A) Averaged normalized change in NAS DA_max and (B) DA clearance (t_1/2) in male and female mice. DA was analyzed every five min and after 4 consistent control files, JJC8-091 (10 and 32 mg/kg; i.p.) was administered. DA was analyzed for 120 min after drug administration. (n=7 for each treatment group).