Voltage-Dependent Dopamine Potency at D1-Like Dopamine Receptors

Abstract

In recent years, transmembrane voltage has been found to modify agonist potencies at several G protein-coupled receptors (GPCRs). Whereas the voltage sensitivities of the Ga i/o-coupled dopamine D 2-like receptors (D 2 R, D 3 R, D 4 R) have previously been investigated, the putative impact of transmembrane voltage on agonist potency at the mainly Ga s/olf-coupled dopamine D 1-like receptors (D 1 R, D 5 R) has hitherto not been reported. Here, we assayed the potency of dopamine in activating G protein-coupled inward rectifier potassium (GIRK) channels co-expressed with D 1 R and D 5 R in Xenopus oocytes, at-80 mV and at 0 mV. Furthermore, GIRK response deactivation rates upon dopamine washout were measured to estimate dopamine dissociation rate (k off) constants. Depolarization from-80 to 0 mV was found to reduce dopamine potency by about 7-fold at both D 1 R and D 5 R. This potency reduction was accompanied by an increase in estimated dopamine k off s at both receptors. While the GIRK response elicited via D 1 R was insensitive to pertussis toxin (PTX), the response evoked via D 5 R was reduced by 64% (-80 mV) and 71% (0 mV) in the presence of PTX. Injection of oocytes with Ga s antisense oligonucleotide inhibited the D 1 R-mediated response by 62% (-80 mV) and 76% (0 mV) and abolished the D 5 R response when combined with PTX. Our results suggest that depolarization decreases dopamine affinity at D 1 R and D 5 R. The voltagedependent affinities of dopamine at D 1 R and D 5 R may be relevant to the functions of these receptors in learning and memory.

G protein‐coupled receptor kinase‐2 confers isoform‐specific calcium sensitivity to dopamine D 2 receptor desensitization

“…Injected cells were incubated for 6 days at 12°C in a modified Barth's solution (MBS; in mM: 88 NaCl, 1 KCl, 2.4 NaHCO 3 , 15 HEPES, 0.33 Ca(NO 3 ) 2 , 0.41 CaCl 2 , 0.92 MgSO 4 , 2.5 sodium pyruvate, supplemented with 25 U/ml penicillin and 25 µg/ml streptomycin, adjusted to pH 7.6 with NaOH). Electrophysiological recordings were performed using the parallel eight‐channel, semi‐automated, two‐electrode voltage‐clamp OpusXpress 6000A (Molecular Devices, San José, CA, USA) 18 . Continuous perfusion was maintained at 3.5 ml/min.…”

“…Electrophysiological recordings were performed using the parallel eight-channel, semi-automated, two-electrode voltage-clamp OpusXpress 6000A (Molecular Devices, San José, CA, USA). 18 Continuous perfusion was maintained at 3.5 ml/min. Data were acquired at membrane potentials of −80 mV and sampled at 156 Hz using the OpusXpress 1.10.42 (Molecular Devices) software.…”

Differential voltage-dependent modulation of the ACh-gated K+ current by adenosine and acetylcholine

“…Afterwards, we assessed whether the classical I KACh relaxation can be induced by the activation of A 1 R with Ado, as is characteristic when sub-saturating concentrations of agonist are used [12,13,17,31]. For this purpose, the currents evoked by a sub-saturating (0.3 μM) and a saturating (30 μM) Ado concentration were recorded at -110 mV for 2.5 s, after pre-pulses of 2.5 s between -110 and +50 mV, with 20-mV increments, from a holding potential (V h ) of -50 mV (Fig 3A and 3B).…”

“…Alike as for M 2 R, voltage sensitivity is an emerging property for several other G-proteincoupled receptors (GPCRs) [17][18][19][20][21][22][23][24]. In cardiomyocytes, I KACh is the effector for M 2 R but also for A 1 R and it is currently unknown how voltage affects this latter and how this important potassium current is modulated in consequence.…”

Voltage dependence of the cannabinoid CB1 receptor

“…Several studies have shown, employing different approaches, that not only can GPCRs modulate membrane potential by activating ion channels, but that the membrane potential can modulate the affinity and activity of GPCRs. To date, many GPCRs including cholinergic ( Ben-Chaim et al, 2003 ; Ben-Chaim et al, 2006 ; Navarro-Polanco et al, 2011 ), glutamatergic ( Ohana et al, 2006 ), dopaminergic ( Sahlholm et al, 2008a ; Sahlholm et al, 2008c ; Ågren and Sahlholm, 2020 ), adrenergic ( Rinne et al, 2013 ) and purinergic receptors ( Martinez-Pinna et al, 2004 ; Martinez-Pinna et al, 2005 ) have been shown to be voltage dependent.…”