Synthesis, nicotinic acetylcholine receptor binding, and antinociceptive properties of 2'-fluoro-3'-(substituted phenyl)deschloroepibatidine analogues. Novel nicotinic antagonist.
A series of 2'-fluoro-3'-(substituted phenyl)deschloroepibatidine analogues (5a-k) showed high affinity for alpha4beta2 binding with no affinity at alpha7 nAChRs. The most potent compound was 2'-fluoro-3'-(4-nitrophenyl)deschloroepibatidine (5g) which possessed a Ki value of 0.009 nM. Surprisingly, none of the compounds showed agonist effects in pain tests and body temperature changes in mice even when tested at 10-15 mg/kg with the exception of 5b, which showed only very weak agonist effects. In contrast, all the compounds were potent functional antagonists of nicotine-induced antinociception. Interestingly, the 3'-substituted phenyl analogues 5b-k were 10-870-fold more effective as antagonists in the tail-flick test versus the hot-plate procedure. They failed to antagonize nicotine-induced hypothermia. The 4-chlorophenyl analogue (5e) (AD50 = 0.0003 in the tail-flick test) was the most potent and selective analogue. These results suggest that these compounds will be highly useful for identifying which specific receptor subtypes are involved in each of nicotine's pharmacological effects. These compounds also deserve consideration as potential pharmacotherapies for treatment of smoking cessation.
Carroll
F Ivy
FI
Chemistry and Life Sciences, Research Triangle Institute, P.O. Box 12194, Research Triangle Park, North Carolina 27709, USA. fic@rti.org
Ware
Roy
R
Brieaddy
Lawrence E
LE
Navarro
Hernán A
HA
Damaj
M I
MI
Martin
Billy R
BR
D000700:Analgesics / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001831:Body Temperature / Q000187:drug effects; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology; D002540:Cerebral Cortex / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D008297:Male; D051379:Mice; D018733:Nicotinic Antagonists / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology; D010146:Pain / Q000517:prevention & control; D011485:Protein Binding; D011725:Pyridines / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology; D011869:Radioligand Assay; D051381:Rats; D011978:Receptors, Nicotinic / Q000378:metabolism*; D013329:Structure-Activity Relationship
D000700:Analgesics; D019086:Bridged Bicyclo Compounds, Heterocyclic; D018733:Nicotinic Antagonists; D011725:Pyridines; D011978:Receptors, Nicotinic; C082748:epibatidine