Functional histamine H 3 and adenosine A 2A receptor heteromers in recombinant cells and rat striatum

Abstract

In the striatum, histamine H receptors (HRs) are co-expressed with adenosine A receptors (ARs) in the cortico-striatal glutamatergic afferents and the GABAergic medium-sized spiny neurons that originate the indirect pathway of the basal ganglia. This location allows HRs and ARs to regulate the striatal GABAergic and glutamatergic transmission. However, whether these receptors can physically interact has not yet been assessed. To test this hypothesis, a heteromer-selective in vitro assay was used to detect functional complementation between a chimeric AR-Gα and wild-type HRs in transfected HEK-293T cells. HR activation with the agonist RAMH resulted in Ca mobilization (pEC 7.31 ± 0.23; maximal stimulation, Emax 449 ± 25% of basal) indicative of receptor heterodimerization. Functional HR-AR heteromers were confirmed by co-immunoprecipitation and observations of differential cAMP signaling when both receptors were co-expressed in the same cells. In membranes from rat striatal synaptosomes, HR activation decreased AR affinity for the agonist CGS-21680 (pKi values 8.10 ± 0.04 and 7.70 ± 0.04). Moreover, HRs and ARs co-immunoprecipitated in protein extracts from striatal synaptosomes. These results support the existence of a HR-AR heteromer with possible physiological implications for the modulation of the intra-striatal transmission.

The Systemic Administration of the Histamine H1 Receptor Antagonist/Inverse Agonist Chlorpheniramine to Pregnant Rats Impairs the Development of Nigro-Striatal Dopaminergic Neurons

“…The density of dopamine D 2 receptors in striatal nerve terminals was evaluated in a synaptosomal membrane preparation obtained as described in detail elsewhere (Márquez-Gómez et al, 2018) from a pool of P21 males or females (four pups per determination for a total of three experiments per group). Synaptosomes were lysed in a hypotonic solution (10 mM Tris–HCI, 1 mM EGTA, pH 7.4), the suspension was centrifuged (20,000 × g , 4°C, 20 min) and the pellet (membranes) was re-suspended in 0.5 ml incubation buffer (50 mM Tris–HCI, 10 mM KCl, 4 mM MgCl 2 , 1 mM EDTA, 100 μM ketanserin, pH 7.4).…”

Striatal histamine mechanism in the pathogenesis of restless legs syndrome

“…At presynaptic terminals, H3R not only acts as a heteroreceptor, which suppresses transmitter release [ 36 ] and modulates striatal medium spiny neuron (MSN) activity [ 37 ], but also forms with adenosine A 2a receptor (A 2a R) as the heteromers [ 38 ]. Activation of H3R increases the A 2a R activity-induced cAMP formation [ 38 ], and causes neurotransmitter release [ 39 ]. Adenosine A 2a R has been shown to increase glutamatergic release from corticostriatal terminals [ 40 , 41 ].…”

Adenosine A2A and histamine H3 receptors interact at the cAMP/PKA pathway to modulate depolarization-evoked [3H]-GABA release from rat striato-pallidal terminals

“…Coronal slices (300 μm thick) were then obtained with a vibratome (World Precision Instruments, Sarasota, FL), and the pallidal tissue was carefully dissected from the slices [16]. The composition of the Krebs-Henseleit solution was (mM) NaCl 116, KCl 3, MgSO 4 1, KH 2 PO 4 1.2, NaHCO 3 25, and D-glucose 11 (pH 7.4 after saturation with O 2 /CO 2 , 95:5% v/v). This solution did not contain CaCl 2 in order to reduce excitotoxicity.…”

“…In transfected cells, H 3 Rs form heteromers with dopamine D 1 and D 2 receptors, and in striatal membranes, H 3 R activation decreases the affinity of D 2 receptors for agonists [23], whereas in SK-N-MC cells shifts the coupling of D 1 receptors from Gα s to Gα i/o proteins and therefore from stimulation to inhibition of cAMP formation [24]. We recently showed that endogenous and transfected H 3 and A 2A receptors form heterodimers [25], which could therefore underlie the interaction H 3 R/A 2A R in GABA release.…”