Investigation of the presence and antinociceptive function of muscarinic acetylcholine receptors in the African naked mole-rat (<i>Heterocephalus glaber</i>)

The present study investigated the cholinergic system in the African naked mole-rat (Heterocephalus glaber) with focus on the muscarinic acetylcholine receptor subtypes M(1) and M(4). The protein sequences for the subtypes m(1–5) of the naked mole-rat were compared to that of the house mouse (Mus musculus) using basic local alignment search tool (BLAST). The presence and function of M(1) and M(4) was investigated in vivo, using the formalin test with the muscarinic receptor agonists xanomeline and VU0152100. Spinal cord tissue from the naked mole-rat was used for receptor saturation binding studies with [(3)H]-N-methylscopolamine. The BLAST test revealed 95 % protein sequence homology showing the naked mole-rat to have the genetic potential to express all five muscarinic acetylcholine receptor subtypes. A significant reduction in pain behavior was demonstrated after administration of 8.4 mg/kg in the formalin test. Administration of 50 mg/kg VU0152100 resulted in a non-significant tendency towards antinociception. The antinociceptive effects were reversed by the muscarinic acetylcholine receptor antagonist atropine. Binding studies indicated presence of muscarinic acetylcholine receptors with a radioligand affinity comparable to that reported in mice. In conclusion, muscarinic acetylcholine receptor subtypes are present in the naked mole-rat and contribute to antinociception in the naked mole-rat

Synthesis and pharmacological characterization of the selective GluK1 radioligand (S)-2-amino-3-(6-[³H]-2,4-dioxo-3,4-dihydrothieno.3,2-d] pyrimidin1(2H)- yl) propanoic acid ([³H]-NF608)

The kainic acid receptors belong to the class of ionotropic glutamate receptors and comprise five subunits named GluK1-5. Radioligands are essential tools for use in binding assays aimed at ligand-receptor structure-activity-relationship studies. Previous work has led to the synthesis of GluK1 radioligands [3H]-SYM2081, [3H]-UBP310 and [3H]-ATPA, however all strategies were work-intensive and thus not attractive. Herein, we report the synthesis of [3H]-NF608 and subsequent pharmacological evaluation at homomeric recombinant rat GluK1 receptors. Binding affinities of a series of standard GluK1 ligands were shown to be in line with previously reported affinities obtained by use of already reported radioligands

Chemo-enzymatic synthesis of a series of 2,4-syn-functionalized (S)-glutamate analogues: new insight into the structure-activity relation of ionotropic glutamate receptor subtypes 5, 6, and 7.

International audience(S)-Glutamic acid (Glu) is the major excitatory neurotransmitter in the central nervous system (CNS) activating the plethora of ionotropic Glu receptors (iGluRs) and metabotropic Glu receptors (mGluRs). In this paper, we present a chemo-enzymatic strategy for the enantioselective synthesis of five new Glu analogues 2a−f (2d is exempt) holding a functionalized substituent in the 4-position. Nine Glu analogues 2a−j are characterized pharmacologically at native 2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA), kainic acid (KA), and N-methyl-D-aspartic acid (NMDA) receptors in rat synaptosomes as well as in binding assays at cloned rat iGluR5−7 subtypes. A detailed in silico study address as to why 2h is a high-affinity ligand at iGluR5−7 (Ki = 3.81, 123, 57.3 nM, respectively), while 2e is only a high affinity ligand at iGluR5 (Ki = 42.8 nM). Furthermore, a small series of commercially available iGluR ligands are characterized in iGluR5−7 bindin