Elsevier

Brain Research

Volume 643, Issues 1–2, 18 April 1994, Pages 343-348
Brain Research

Modulation of dopamine D3 receptor binding by N-ethylmaleimide and neurotensin

https://doi.org/10.1016/0006-8993(94)90045-0Get rights and content

Abstract

GTP or G protein inactivation by N-ethylmaleimide reduced the Bmax value but not the KD value of 7-[3H]hydroxy-N,N-di-n-propyl-2-aminotetralin ([3H]7-OH-DPAT) binding in the rat subcortical limbic area. Neurotensin (10 nM) increased the KD and the Bmax values of [3H]7-OH-DPAT binding, and these effects persisted also following N-ethylmaleimide pretreatment. N-Propylnorapomorphine, quinpirole, raclopride, and remoxipride inhibited [3H]7-OH-DPAT binding with Ki values of 0.093, 1.97, 10.6, and 710 nM, respectively. These findings indicate that the D3 receptor is coupled to G proteins in the brain, and that neurotensin can modulate D3 agonist binding by a G protein-independent mechanism.

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      In support of this, application of NT into the PFC has been shown to enhance the spontaneous activity of DA neurons in the VTA (Rompre et al., 1998; Fatigati et al., 2000). Third, NT1 receptors may reduce the inhibitory influence of D2 pre- and post-synaptic receptors (Agnati et al., 1983; von Euler et al., 1989; von Euler et al., 1990; Liu et al., 1994) either through an allosteric receptor/receptor interaction involving second messengers (von Euler et al., 1991; Fuxe et al., 1992; Jomphe et al., 2006) or by direct noncompetive binding of NT to the D2 receptor (Mandell et al., 1998). In support of this, Beauregard et al. (1992) found that iontophoretic application of DA and NT into the PFC and NAC in urethane-anesthetized rats decreased the inhibitory effects of DA in 74% of the PFC and 48% of the NAC neurons tested.

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    This work was supported by a grant from the Swedish Medical Research Council (14X-10377-01).

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