doi: 10.3390/ijms23158543.
Enhancer Regulation of Dopaminergic Neurochemical Transmission in the Striatum
Affiliations
- PMID: 35955676
- PMCID: PMC9369307
- DOI: 10.3390/ijms23158543
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Enhancer Regulation of Dopaminergic Neurochemical Transmission in the Striatum
Int J Mol Sci.
.
Abstract
The trace amine-associated receptor 1 (TAAR1) is a Gs protein-coupled, intracellularly located metabotropic receptor. Trace and classic amines, amphetamines, act as agonists on TAAR1; they activate downstream signal transduction influencing neurotransmitter release via intracellular phosphorylation. Our aim was to check the effect of the catecholaminergic activity enhancer compound ((-)BPAP, (R)-(-)-1-(benzofuran-2-yl)-2-propylaminopentane) on neurotransmitter release via the TAAR1 signaling. Rat striatal slices were prepared and the resting and electrical stimulation-evoked [3H]dopamine release was measured. The releaser (±)methamphetamine evoked non-vesicular [3H]dopamine release in a TAAR1-dependent manner, whereas (-)BPAP potentiated [3H]dopamine release with vesicular origin via TAAR1 mediation. (-)BPAP did not induce non-vesicular [3H]dopamine release. N-Ethylmaleimide, which inhibits SNARE core complex disassembly, potentiated the stimulatory effect of (-)BPAP on vesicular [3H]dopamine release. Subsequent analyses indicated that the dopamine-release stimulatory effect of (-)BPAP was due to an increase in PKC-mediated phosphorylation. We have hypothesized that there are two binding sites present on TAAR1, one for the releaser and one for the enhancer compounds, and they activate different PKC-mediated phosphorylation leading to the evoking of non-vesicular and vesicular dopamine release. (-)BPAP also increased VMAT2 operation enforcing vesicular [3H]dopamine accumulation and release. Vesicular dopamine release promoted by TAAR1 evokes activation of D2 dopamine autoreceptor-mediated presynaptic feedback inhibition. In conclusion, TAAR1 possesses a triggering role in both non-vesicular and vesicular dopamine release, and the mechanism of action of (-)BPAP is linked to the activation of TAAR1 and the signal transduction attached.
Keywords: (−)BPAP; [3H]dopamine release; catecholaminergic activity enhancer effect; rat striatum; trace amine-associated receptor 1.
Conflict of interest statement
The authors declare this work was supported by the Fujimoto Pharmaceutical Corporation, Osaka, Japan.
Figures
The chemical structure of trace amines (phenylethylamine, tryptamine), phenylethylamine analogues (methamphetamine, diethylphenethylamine), and enhancer substances (PPAP, IPAP, BPAP).
(A) The time-course of [3H]dopamine release measured from rat striatum. Filled circles indicate [3H]dopamine release at rest and in response to electrical stimulation. Striatal slices were prepared, loaded with [3H]dopamine and superfused with aerated Krebs-bicarbonate buffer. [3H]Dopamine release was induced by electrical stimulation (40 V, 2 Hz, 2 msec for 3 min) in fractions 4 (S1) and 18 (S2) and was expressed as a fractional rate, i.e., a percentage of the amount of [3H]dopamine in the tissue at the time of the release. The calculated ratio of the electrically stimulated fractional release S2 (2nd stimulation) over fractional release S1 (1st stimulation) (S2/S1) was 0.84 ± 0.04, representing a release of vesicular origin. The calculated ratio of resting fractional release B2 (fraction17) over fractional release B1 (fraction 3) (B2/B1) was 0.72 ± 0.05. When studied, drugs were added to the superfusion buffer between the 1st and 2nd electrical stimulations and maintained through the experiment, mean ± S.E.M., n = 6. (B) The time-course of non-vesicular [3H]dopamine release from rat striatum. Striatal slices were prepared, loaded with [3H]dopamine and superfused with aerated Krebs-bicarbonate buffer. The release of [3H]dopamine was expressed as a fractional rate expressed as percent of content released. [3H]Dopamine release was induced by the addition of drugs to the superfusion buffer and maintained through the experiment. In this experiment, (±)amphetamine as a drug was added in a concentration of 10 µmol/L from fraction 10 and the evoked non-vesicular [3H]dopamine release was 13.88 ± 3.00 percent of content released (calculated between fractions 10 and 25). The calculated [3H]dopamine release was 0.53 ± 0.12 percent of content released in control conditions. Student’s t-statistics for two-means, p < 0.01, mean ± S.E.M., n = 4-4.
Effects of phenylethylamine derivatives on resting [3H]dopamine release from rat striatum. For the experimental procedure, see Figure 2B. (A) The trace amine phenylethylamine (PEA) and the releaser (±)methamphetamine (methamph) induced non-vesicular [3H]dopamine release, whereas N,α-diethylphenylethylamine (DEA) and the enhancer compound (−)PPAP were without effect on [3H]dopamine release. Drugs were added to rat striatal slices from fraction 10 in a concentration of 10 µmol/L, ((±)methamphetamine 6.75 µmol/L) and maintained through the experiment, mean ± S.E.M., n = 4. (B) The enhancer compounds (−)PPAP, (−)IPAP, and (−)BPAP were without effect on non-vesicular [3H]dopamine release. Drugs were added to rat striatal slices from fraction 10 in a concentration of 10 µmol/L and maintained through the experiment, mean ± S.E.M., n = 4. The control for Figure 3A,B is shown in Figure 2B.
A (±)Methamphetamine (methamph) increased both non-vesicular and vesicular [3H]dopamine release from rat striatum. For the experimental procedure, see Figure 2A,B. (A) The releasing effect of (±)methamphetamine on resting [3H]dopamine efflux was concentration-dependent in a range of 1 to 10 µmol/L. The estimated concentration of (±)methamphetamine that increased resting [3H]dopamine release by 50% above control release was 3.2 µmol/L. One-way ANOVA followed by the Dunnett’s test, F(3,20) = 35.14, p < 0.001, (±)methamphetamine in 6.75 and 10 μmol/L concentrations significantly increased non-vesicular [3H]dopamine release, p < 0.01, mean ± S.E.M., n = 4-8. (B) (±)Methamphetamine was added to striatal slices from fraction 8 in a concentration of 6.75 µmol/L and maintained throughout the experiment. Resting [3H]dopamine release (defined as fractional release between fractions 8 and 17) was 0.37 ± 0.08 in control and 4.27 ± 0.46 percent of the content in the presence of (±)methamphetamine, p < 0.001. The electrical stimulation-induced [3H]dopamine release (S2/S1) was 0.89 ± 0.03 in control and 1.86 ± 0.32 in response to (±)methamphetamine, p < 0.01. Student t-statistics for two-means, mean ± S.E.M., n = 8-8.
(−)BPAP increased electrical stimulation-induced [3H]dopamine release from rat striatum. For the experimental procedure, see Figure 2A. When studied, (−)BPAP was added in a concentration of 10−12 mol/L to the superfusion buffer from fraction 8 and maintained throughout the experiment. (A) The release of [3H]dopamine from striatal slices, control experiments. Filled circles indicate [3H]dopamine release at rest and in response to electrical stimulation. The resting [3H]dopamine release (B2/B1) and the electrical stimulation-induced [3H]dopamine release (S2/S1) were 0.92 ± 0.05 and 0.74 ± 0.04 in control conditions. (B) Effect of (−)BPAP (10−12 mol/L) on [3H]dopamine release from rat striatum. Filled circles indicate [3H]dopamine release in the presence and absence of (−)BPAP. (−)BPAP was added to striatal slices from fraction 8 and maintained throughout the experiment. The resting [3H]dopamine release (B2/B1) and the electrical stimulation-induced [3H]dopamine release (S2/S1) were 0.96 ± 0.08 and 1.24 ± 0.13 in the presence of (−)BPAP. These values indicate that (−)BPAP in 10−12 mol/L concentration failed to influence the resting (p = 0.55) but increased the electrically induced [3H]dopamine release (p < 0.01). Student t-statistics for two-means, mean ± S.E.M., n = 7-6.
Concentration-dependent effect of (−)BPAP on resting and electrical stimulation-induced [3H]dopamine release from rat striatum. For the experimental procedure, see Figure 2A. (−)BPAP was added in a concentration range from 10−15 to 10−5 mol/L to the superfusion buffer from fraction 8 and maintained through the experiment. (A) The S2/S1 ratio indicates the effect of (−)BPAP on electrical stimulation-induced [3H]dopamine release determined in 1st (absence of drug, S1) and 2nd (presence of drug, S2), stimulations were carried out in fractions 4 and 18. The S2/S1 value was 0.79 ± 0.04 in control experiments (c). One-way ANOVA followed by the Dunnett’s test, F(11,48) = 10.16, p < 0.0001, * p < 0.05, ** p < 0.01, mean ± S.E.M., n = 4-8. (B) The B2/B1 ratio indicates the effect of (−)BPAP on resting fractional [3H]dopamine release determined in fractions 3 (absence of drug, B1) and 17 (presence of the drug, B2). The B2/B1 value was 0.91 ± 0.05 in control experiments (c). One-way ANOVA followed by the Dunnett’s test, F(11,48) = 1.171, p = 0.331, mean ± S.E.M., n = 4-8.
Effect of nomifensine on [3H]dopamine release from rat striatum. For the experimental procedure, see Figure 2A. (A) Filled circles indicate [3H]dopamine release in the presence and absence of nomifensine. Nomifensine was added to striatal slices from fraction 8 in a concentration of 10 µmol/L and maintained throughout the experiment. The B2/B1 ratio for resting release was 0.78 ± 0.02 in control and it was 0.80 ± 0.07 in the presence of nomifensine, not differing significantly. The S2/S1 ratio for electrical stimulation-induced release was 0.89 ± 0.05 in control and nomifensine increased this release to 1.27 ± 0.16 (p < 0.05). Student t-statistics for two-means, mean ± S.E.M., n = 8-4. (B) Nomifensine concentration dependently increased the electrically induced (vesicular) but not the resting (non-vesicular) [3H]dopamine release in striatal slices. One-way ANOVA followed by the Dunnett’s test, F(2,16) = 0.212, p = 0.812 for resting release and F(2,16) = 4.993, p = 0.02, * p < 0.05 for electrically stimulated release, mean ± S.E.M., n = 4-8.
(A) Nomifensine (Nomif) reversed the (±)methamphetamine (methamph)-induced [3H]dopamine release from rat striatum. For the experimental procedure, see Figure 2B. (±)Methamphetamine was added to striatal slices from fraction 10 in a concentration of 6.75 µmol/L, nomifensine was added to the slices from fraction 5 in a concentration of 10 µmol/L and the drugs were maintained throughout the experiment. The (±)methamphetamine-induced [3H]dopamine release was 12.73 ± 2.20 and nomifensine decreased this release to 1.15 ± 0.26 percent of content (p < 0.01). Student t-statistics for two means, mean ± S.E.M., n = 4-4. (B) Nomifensine inhibited (±)methamphetamine-induced non-vesicular [3H]dopamine release in a concentration-dependent manner. (±)Methamphetamine was added to striatal slices from fraction 10 in a concentration of 6.75 µmol/L, nomifensine was added to the slices in a concentration of 1 or 10 µmol/L from fraction 1 and the drugs were maintained throughout the experiment. One-way ANOVA followed by the Dunnett’s test, F(3,12) = 15.58, p = 0.0002, * p < 0.05 mean ± S.E.M., n = 4.
Effect of nomifensine on (−)BPAP-induced [3H]dopamine release in rat striatum. For the experimental procedure, see Figure 2A. (−)BPAP was added to striatal slices from fraction 8 in a concentration of either 10−11 mol/L in the presence and absence of nomifensine. When used, nomifensine was added to striatal slices from fraction 1 in a concentration of 1 µmol/L and drugs were maintained throughout the experiment. One-way ANOVA followed by the Dunnett’s test, F(3,12) = 4.784, p = 0.020, control vs. (−)BPAP effect * p < 0.05. Student t-statistics for two-means, (−)BPAP vs. (−)BPAP and nomifensine effect # p < 0.01, mean ± S.E.M., n = 4.
Effect of EPPTB on [3H]dopamine release from rat striatum. For the experimental procedure, see Figure 2A. (A) Filled circles indicate [3H]dopamine release in the presence and absence of EPPTB. EPPTB was added to striatal slices from fraction 8 in a concentration of 1 µmol/L and maintained through the experiment. The B2/B1 ratio for resting release was 0.85 ± 0.05 in control and it was 0.88 ± 0.07 in the presence of EPPTB, not differing significantly. The S2/S1 ratio for electrical stimulation-induced release was 0.94 ± 0.02 in control and it was 0.95 ± 0.03 in the presence of EPPTB. This difference was not significant: Student t-statistics for two-means, p > 0.05, mean ± S.E.M., n = 3-3. (B) Concentration-dependent effect of EPPTB on electrical stimulation-induced [3H]dopamine release in rat striatum. EPPTB was added to striatal slices from fraction 8 in concentrations varied from 0.01 to 1 µmol/L and maintained through the experiment. One-way ANOVA followed by the Dunnett’s test, F(3,13) = 1.757, p = 0.204, mean ± S.E.M., n = 3-8.
(A) EPPTB decreased the (±)methamphetamine (methamph)-induced non-vesicular [3H]dopamine release in rat striatum. For the experimental procedure, see Figure 2B. (±)Methamphetamine (10 µmol/L) was added to striatal slices from fraction 12 and maintained through the experiment in the presence and absence of EPPTB. EPPTB (1 µmol/L) was added to striatal slices from fraction 3 and maintained throughout the experiment. (±)Methamphetamine-induced [3H]dopamine release was 12.42 ± 1.46 and this release was decreased to 4.20 ± 1.62 percent of content by 1 µmol/L EPPTB, p < 0.01; Student t-statistics for two-means, mean S.E.M., n = 4-8. (B) EPPTB (0.1 and 1 µmol/L) antagonized the effect of (±)methamphetamine on resting but not on electrical stimulation-induced [3H]dopamine release in rat striatum. For the experimental procedure, see Figure 2A,B. (±)Methamphetamine was added to striatal slices from fraction 8 in a concentration of 6.75 µmol/L. When used, EPPTB was added to the slices in a concentration of 0.1 or 1 µmol/L from fraction 1 and drugs were maintained throughout the experiment. Resting [3H]dopamine release (defined as the fractional release between fractions 8 and 17) was 0.37 ± 0.08 in control and 4.27 ± 0.46 percent of content in the presence of (±)methamphetamine, this release was decreased by EPPTB. The electrical-induced [3H]dopamine release (S2/S1) was 0.89 ± 0.03 in control and 1.86 ± 0.32 in the presence of (±)methamphetamine; this release was not altered by EPPTB. One-way ANOVA followed by the Dunnett’s test, F(3,26) = 13.990, p < 0.001 for resting [3H]dopamine release and F(3,26) = 5.554, p < 0.004 for electrical stimulation-induced [3H]dopamine release, # p < 0.05 control vs. (±)methamphetamine effect, * p < 0.05 (±)methamphetamine vs. (±)methamphetamine and EPPTB effect, mean ± S.E.M., n = 6-8.
EPPTB reversed the (−)BPAP-induced [3H]dopamine release in rat striatum. For the experimental procedure, see Figure 2A. (−)BPAP was added to striatal slices from fraction 8 in a concentration of either 10−12 (A) or 10−11 mol/L (B) in the presence and absence of EPPTB. When used, EPPTB was added to striatal slices from fraction 1 in a concentration of either 0.01 or 0.1 µmol/L and drugs were maintained through the experiment. (A) One-way ANOVA followed by the Dunnett’s test, F(3,28) = 12.310, p < 0.001, # p < 0.01; Student t-statistics for two-means, control vs. (−)BPAP effect p < 0.05, (−)BPAP vs. (−)BPAP, and EPPTB (0.01 and 0.1 µmol/L) effects * p < 0.01, mean ± S.E.M., n = 7-10. (B) One-way ANOVA followed by the Dunnett’s test, F(3,23) = 3.890, p = 0.022, Student t-statistics for two-means, control vs. (−)BPAP effect # p < 0.01, (−)BPAP vs. (−)BPAP and EPPTB (0.1 µmol/L) effect * p < 0.01, mean ± S.E.M., n = 6-8.
Effect of Ro31-8220 on [3H]dopamine release from rat striatum. For the experimental procedure, see Figure 2A. (A) Filled circles indicate [3H]dopamine release in the presence and absence of Ro31-8220. Ro31-8220 was added to striatal slices from fraction 8 in a concentration of 1 µmol/L and maintained throughout the experiment. Resting release expressed by the B2/B1 ratio was 0.81 ± 0.03 in control and it was 0.90 ± 0.09 in the presence of Ro31-8220, the difference was not significant. The electrical stimulation-induced release expressed by the S2/S1 ratio was 0.80 ± 0.07 in control and it was 0.47 ± 0.10 in the presence of Ro31-8220, p < 0.05. Student t-statistics for two-means, mean ± S.E.M., n = 3-4. (B) Ro31-8220 concentration-dependently decreased electrical stimulation-induced [3H]dopamine release from rat striatum. Ro31-8220 was added to striatal slices from fraction 8 in concentrations varied from 0.1 to 10 µmol/L and maintained through the experiment. 10 µmol/L Ro31-8220 reduced electrical stimulation-induced [3H]dopamine release, * p < 0.01. One-way ANOVA followed by the Dunnett’s test, F(3,13) = 4.489, p = 0.022, mean ± S.E.M., n = 3-6.
Ro31-8220 decreased the (±)methamphetamine (methamph)-induced non-vesicular. [3H]dopamine release in rat striatum. For the experimental procedure, see Figure 2B. (±)Methamphetamine was added to striatal slices from fraction 12 in a concentration of 10 μmol/L in the presence and absence of Ro31-8220. Ro31-8220 (1 µmol/L) was added to striatal slices from fraction 4 and drugs were maintained through the experiment. (±)Methamphetamine-induced non-vesicular [3H]dopamine release was 13.31 ± 2.67 and this release was decreased to 4.57 ± 1.48 percent of content by 1 µmol/L Ro31-8220, p < 0.05. Student t-statistics for two-means, mean ± S.E.M., n = 4-4.
Ro31-8220 reversed (−)BPAP-induced [3H]dopamine release in rat striatum. For the experimental procedure, see Figure 2A. (−)BPAP was added to striatal slices from fraction 8 in a concentration of 10−12 mol/L in the presence and absence of Ro31-8220. When used, Ro31-8220 was added to striatal slices from fraction 1 in a concentration of 1 µmol/L and drugs were maintained throughout the experiment. One-way ANOVA followed by the Dunnett’s test, F(3,21) = 9.235, p < 0.001, control vs. (−)BPAP effect # p < 0.05. Student t-statistics for two-means, (−)BPAP vs. (−)BPAP plus Ro31-8220 effect * p = 0.001, mean ± S.E.M., n = 3-8.
Phorbol 12-myristate 13-acetate (PMA) increased electrical stimulation-induced [3H]dopamine release from rat striatum. For the experimental procedure, see Figure 2A. PMA was added to striatal slices from fraction 8 in a concentration range varied from 0.01 to 1 µmol/L and maintained through the experiment. Resting release expressed by the B2/B1 ratio was 0.79 ± 0.03 in control and it was 0.71 ± 0.23 in the presence of 1 µmol/L PMA, not differing significantly. 1 µmol/L PMA increased the electrical stimulation-induced [3H]dopamine release, * p < 0.01. One-way ANOVA followed by the Dunnett’s test, F(3,12) = 7.196, p = 0.0051, * p < 0.01, mean ± S.E.M., n = 4.
Phorbol 12-myristate 13-acetate (PMA) potentiated the (−)BPAP-stimulated [3H]dopamine release in rat striatum. For the experimental procedure, see Figure 2A. (−)BPAP was added to striatal slices from fraction 8 in a concentration of 10−12 mol/L. PMA was added to striatal slices from fraction 12 at a concentration of 1 µmol/L, and drugs were maintained throughout the experiment. One-way ANOVA followed by the Dunnet’s test, F(3,28) = 82.75, p < 0.0001, * p < 0.05. Student t-statistics for two-means, PMA vs. PMA plus (−)BPAP effect # p < 0.0001, mean ± S.E.M., n = 8.
Effect of N-ethylmaleimide (NEM) on [3H]dopamine release from rat striatum. For the experimental procedure, see Figure 2A. (A) Filled circles indicate [3H]dopamine release in the presence and absence of NEM. NEM was added to striatal slices from fraction 8 in a concentration of 30 µmol/L and maintained through the experiment. Resting release expressed by the B2/B1 ratio was 0.93 ± 0.06 in control, and it was 1.07 ± 0.07 in the presence of NEM, not differing significantly. The electrical stimulation-induced release expressed by the S2/S1 ratio was 0.88 ± 0.06 in the control and 1.63 ± 0.23 in the presence of 30 µmol/L NEM, p = 0.009. Student t-statistics for two-means, mean ± S.E.M., n = 7-7. (B) NEM increased electrical stimulation-induced [3H]dopamine release in rat striatum. NEM was added to striatal slices from fraction 8 in a concentration range varied from 10 to 100 µmol/L and maintained through the experiment. One-way ANOVA followed by the Dunnett’s test, F(3,11) = 13.32, p = 0.006, * p < 0.05, mean ± S.E.M., n = 3-4.
Effect of N-ethylmaleimide (NEM) on [3H]dopamine release from rat striatum. For the experimental procedure, see Figure 2A. (A) Filled circles indicate [3H]dopamine release in the presence and absence of NEM. NEM was added to striatal slices from fraction 8 in a concentration of 30 µmol/L and maintained through the experiment. Resting release expressed by the B2/B1 ratio was 0.93 ± 0.06 in control, and it was 1.07 ± 0.07 in the presence of NEM, not differing significantly. The electrical stimulation-induced release expressed by the S2/S1 ratio was 0.88 ± 0.06 in the control and 1.63 ± 0.23 in the presence of 30 µmol/L NEM, p = 0.009. Student t-statistics for two-means, mean ± S.E.M., n = 7-7. (B) NEM increased electrical stimulation-induced [3H]dopamine release in rat striatum. NEM was added to striatal slices from fraction 8 in a concentration range varied from 10 to 100 µmol/L and maintained through the experiment. One-way ANOVA followed by the Dunnett’s test, F(3,11) = 13.32, p = 0.006, * p < 0.05, mean ± S.E.M., n = 3-4.
N-Ethylmaleimide (NEM) NEM potentiated the (−)BPAP-stimulated [3H]dopamine release in rat striatum. For the experimental procedure, see Figure 2A. (−)BPAP was added to the slices from fraction 8 in a concentration of 10−12 mol/L. NEM was added to the slices from fraction 12 in a concentration of 30 µmol/L and drugs were maintained throughout the experiment. One-way ANOVA followed by the Dunnett’s test, F(3,26) = 8.740, p = 0.048, control vs. NEM and (−)BPAP effect # p < 0.05. Student t-statistics for two-means, control vs. NEM effect * p < 0.01, NEM vs. NEM and (−)BPAP effect * p < 0.05, (−)BPAP vs. (−)BPAP/NEM effect * p < 0.05, mean ± S.E.M., n = 7-8.
(−)BPAP reversed tetrabenazine (TBZ)-induced inhibition of [3H]dopamine release from rat striatum. Rats were injected with saline, TBZ (1 mg/kg), (−)BPAP (0.0001 mg/kg), and TBZ (1 mg/kg) plus (−)BPAP (0.0001 mg/kg) sc 60 min before the experiments. Striatal slices were prepared, loaded with [3H]dopamine and superfused. The resting and the electrical stimulation (40 V, 10 Hz, 2-msec for 3 min in fraction 4)-induced [3H]dopamine release was determined. Electrical stimulation markedly increased the release of [3H]dopamine from striatal slices obtained from saline-treated rats, this release was inhibited by injection of TBZ. (−)BPAP reversed the inhibitory effect of TBZ on [3H]dopamine release in the striatum of rats concomitantly treated with the two drugs. (−)BPAP treatment did not alter electrical stimulation-induced [3H]dopamine release. One-way ANOVA followed by the Dunnett’s test, F(3,26) = 8.617, p = 0.0004, saline vs. TBZ pretreated groups * p < 0.01. Student t-statistics for two means, TBZ vs. TBZ and (−)BPAP effect # p < 0.001, mean ± S.E.M., n = 7-8.
Phorbol 12-myristate 13-acetate (PMA) reversed the inhibitory effect of tetrabenazine (TBZ) on [3H]dopamine release in rat striatum. Striatal slices were prepared from non-treated and TBZ-pretreated (1 mg/kg sc 60 min before the experiment) rats, loaded with [3H]dopamine and superfused. The resting and the electrical stimulation (40 V, 10 Hz, 2-msec for 3 min in fraction 16)-induced [3H]dopamine release was determined as a fractional rate. (A) PMA was added from fraction 10 in a concentration of 1 µmol/L to striatal slices obtained from TBZ-pretreated rats and was maintained throughout the experiment. (B) TBZ pretreatment decreased the electrical stimulation-induced [3H]dopamine release from striatum: the release was 2.78 ± 0.19 in control and 1.21 ± 0.19 percent of content in tetrabenazine-pretreated rat striatum, # p < 0.05. PMA (1 µmol/L) increased the electrical stimulation-induced [3H]dopamine release in non-treated and TBZ-pretreated rat striatum by 178 and 475%, respectively. Student t-statistics for two-means, * p < 0.05, ** p < 0.01, mean ± S.E.M., n = 6-8.
EPPTB reversed the sulpiride-induced increase of [3H]dopamine release from rat striatum. For the experimental procedure, see Figure 2A. EPPTB or sulpiride was added to the slices from fraction 8 in a concentration of 0.1 or 10 µmol/L, respectively. When EPPTB and sulpiride were added in combination, EPPTB (0.1 µmol/L) was added from fraction 1 and sulpiride (10 µmol/L) was added from fraction 8 and drugs were maintained throughout the experiment. Sulpiride did not alter resting [3H]dopamine release on its own. One-way ANOVA followed by the Dunnett’s test, F(3,21) = 21.65, p = 0.001, control vs. sulpiride treated groups * p < 0.05. Student t-statistics for two means, sulpiride vs. sulpiride and EPPTB effect # p < 0.05, mean ± S.E.M., n = 4-7.
Hypothetical model of the trace amine-associated receptor 1 (TAAR1) signaling involved in the regulation of presynaptic dopaminergic neurotransmission. Activation of the Gs protein-coupled TAAR1 by classical or trace amines and exogenous releaser drugs (amphetamines) results in adenylyl cyclase activation followed by an increased intracellular cAMP production and, as a consequence, an increase in PKA/PKC-mediated intracellular phosphorylation. Activation of PKC phosphorylates plasma membrane dopamine transporter (DAT) as well as proteins involved in SNARE core complex assembly leading to non-vesicular and vesicular dopamine release, respectively. Moreover, PKC also phosphorylates vesicular monoamine transporter 2 (VMAT2) and the increased dopamine accumulation causes elevated vesicular dopamine content and release. Dopamine released into the synaptic cleft activates D2 autoreceptor-mediated presynaptic feedback inhibition, which then leads to the opening of GIRK and the resulted hyperpolarization of the cell membrane suspends further release of dopamine. Our working hypothesis is that TAAR1 possesses a central role in the regulation of DAT, dopamine-containing vesicle operation, readily releasable pool and SNARE core complex assembly and feedback inhibition of dopamine release also. We have speculated that the enhancer drugs ((−)BPAP) activate TAAR1 signaling and the reserpine-sensitive PKC pool and phosphorylation of the proteins in SNARE core complex and VMAT2 leads to increased vesicular dopamine release, i.e., enhancer effect.
References
-
- Borowsky B., Adham N., Jones K.A., Raddatz R., Artymyshyn R., Ogozalek K.L., Durkin M.M., Lakhlani P.P., Bonini J.A., Pathirana S., et al. Trace amines: Identification of a family of mammalian G-protein-coupled receptors. Proc. Natl. Acad. Sci. USA. 2001;98:8966–8971. doi: 10.1073/pnas.151105198. - DOI - PMC - PubMed
-
- Bunzow J.R., Sonders M.S., Arttamangkul S., Harrison L.M., Zhang G., Quigley D.I., Darland T., Suchland K.L., Pasumamula S., Kennedy J.L., et al. Amphetamine, 3,4-methylenedioxymethamphetamine, lysergic acid diethylamide, and metabolites of the catecholamine neurotransmitters are agonists of a rat trace amine receptors. Mol. Pharmacol. 2001;60:1181–1188. doi: 10.1124/mol.60.6.1181. - DOI - PubMed
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