False labelling of dopaminergic terminals in the rabbit caudate nucleus: uptake and release of [³H]‐5‐hydroxytryptamine

Abstract

nomifensine (1, 10 gAM) reduced the tritium accumulation to 65% whereas 6-nitroquipazine (1 JM) was ineffective. The combination of both drugs (1 JAM each) led to a further decrease to about 15%.3 The uptake of [3H]-dopamine into hippocampal slices was blocked by both nomifensine (I JM) and 6-nitroquipazine (I ILM) whereas in caudate nucleus slices only nomifensine (1, 1OtM) reduced the accumulation of [3H]-dopamine. The combination of both drugs was not more effective than nomifensine alone. The different effects of both uptake inhibitors in the hippocampus and caudate nucleus suggest a neurone specific rather than a substrate specific mode of action. 4 In caudate nucleus slices incubated with [3H]-5-HT and superfused continuously the electrically evoked 5-HT release was diminished by the D2-dopamine receptor agonist LY 171555 and enhanced by the D2-receptor antagonist domperidone. If, however, the labelling of caudate nucleus slices was performed in the presence of I JAM or 1OJM nomifensine, the modulation of 5-HT release via D2-receptors was reduced or abolished, respectively. In the hippocampus both LY 171555 and domperidone were completely ineffective in modulating 5-HT release regardless of the absence or presence of nomifensine.

Uptake and Release of Norepinephrine by Serotonergic Terminals in Norepinephrine Transporter Knock-Out Mice: Implications for the Action of Selective Serotonin Reuptake Inhibitors

“…The selectivity of citalopram is the greatest among SSRIs; the K i values for 5-HT, NE, and DA are 14 nM, 32 M, and 41 M, respectively (Hyttel, 1977); therefore, at the concentration (1 M) used in our experiments, only the SERT was effectively inhibited. The hippocampus is densely innervated by noradrenergic and serotonergic varicosities but contains only sparse dopaminergic innervation; the ratio is 30:25:1 for 5-HT/NE/DA (Feuerstein et al, 1986). The average densities of serotonergic (Oleskevich and Descarries, 1990) and noradrenergic (Oleskevich et al, 1989) varicosities are 2.7 and 2.1 million/mm 3 , respectively.…”

“…The connection between dopaminergic and serotonergic uptake has also been described. It has been shown that dopaminergic terminals take up and release [ 3 H]5-HT in the striatum and serotonergic varicosities take up and release [ 3 H]DA in the hippocampus of rabbit (Feuerstein et al, 1986). A paper reported that cocaine place preference persists in DAT or SERT KO mice, but disappears in combined DAT/ SERT KO animals, suggesting that both systems contribute to the rewarding effects of cocaine (Sora et al, 2001).…”

Characterization of the effects of serotonin on the release of [3H]dopamine from rat nucleus accumbens and striatal slices

“…These results strongly suggest that the effect of serotonin on basal 3H overflow is not mediated by serotonin receptors, but appears to involve the DA re-uptake carrier. Serotonin can be transported by the DA reuptake carrier (27,28) and could thus enhance…”

Serotonin-Dopamine Interactions in the Control of Conditioned Reinforcement and Motor Behavior

“…Thus, the 5-HT 3 receptor is a good candidate for modulation of dopamine. However, interaction of 5-HT with carrier-mediated mechanisms via the DA transporter have also been well documented (Feuerstein et al 1986;Schmidt and Black 1989;Yeghiayan et al 1997;Yi et al 1991).…”