Pharmacological and behavioral properties of A-349821, a selective and potent human histamine H3 receptor antagonist.
Histamine H3 receptors regulate the release of a variety of central neurotransmitters involved in cognitive processes. A-349821 ((4'-(3-((R,R)2,5-dimethyl-pyrrolidin-1-yl)-propoxy)-biphenyl-4-yl)-morpholin-4-yl-methanone) is a novel, non-imidazole H3 receptor ligand, displaying high affinity for recombinant rat and human H3 receptors, with pKi values of 9.4 and 8.8, respectively, and high selectivity for the H3 receptor versus H1, H2, and H4 histamine receptors. A-349821 is a potent H3 receptor antagonist in a variety of models using recombinant human and rat receptors, reversing agonist induced changes in cyclic AMP formation (pKb= 8.2 and pKb= 8.1, respectively), [35S]-GTPgammaS binding (pKb= 9.3 and pKb= 8.6, respectively) and calcium levels (human pKb= 8.3). In native systems, A-349821 competitively reversed agonist induced inhibition of electric field stimulated guinea-pig ileum (pA2= 9.5) and histamine-mediated inhibition of [3H]-histamine release from rat brain cortical synaptosomes (pKb= 9.2). Additionally, A-349821 inhibited constitutive GTPgammaS binding at both rat and human H3 receptors with respective pEC50 values of 9.1 and 8.6, demonstrating potent inverse agonist properties. In behavioral studies, A-349821 (0.4 mg/kg-4 mg/kg) potently blocked (R)-alpha-methylhistamine-induced dipsogenia in mice. The compound also enhanced cognitive activity in a five-trial inhibitory avoidance model in spontaneously hypertensive rat (SHR) pups at doses of 1-10mg/kg, with the 1mg/kg dose showing comparable efficacy to a fully efficacious dose of ciproxifan (3mg/kg). These doses of A-349821 were without effect on spontaneous locomotor activity. Thus, A-349821 is a novel, selective non-imidazole H3 antagonist/inverse agonist with balanced high potency across species and favorable cognition enhancing effects in rats.
Abbott Laboratories, Global Pharmaceutical Research Division, Department of Neuroscience Research, Abbott Park, IL 60064, USA. tim.esbenshade@abbott.com
Timothy A
TA
Esbenshade
Gerard B
GB
Fox
Kathleen M
KM
Krueger
John L
JL
Baranowski
Thomas R
TR
Miller
Chae Hee
CH
Kang
Lynne I
LI
Denny
David G
DG
Witte
Betty B
BB
Yao
Jia Bao
JB
Pan
Ramin
R
Faghih
Youssef L
YL
Bennani
Michael
M
Williams
Arthur A
AA
Hancock
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D001713:Biphenyl Compounds / Q000494:pharmacology*; D004285:Dogs; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006168:Guinea Pigs; D006632:Histamine / Q000378:metabolism*; D006633:Histamine Antagonists / Q000494:pharmacology*; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D018377:Neurotransmitter Agents / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D017207:Rats, Sprague-Dawley; D018100:Receptors, Histamine H3 / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors; D013462:Sulfur Radioisotopes
C489829:A349821; D001713:Biphenyl Compounds; D006633:Histamine Antagonists; D018377:Neurotransmitter Agents; D018100:Receptors, Histamine H3; D011994:Recombinant Proteins; D013462:Sulfur Radioisotopes; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006632:Histamine