In vitro and in vivo characterization of a novel negative allosteric modulator of neuronal nAChRs.
In this study, we compared the in vitro and in vivo neuronal nicotinic acetylcholine receptor (nAChR) properties of 1,2,3,3a,4,8b-hexahydro-2-benzyl-6-N,N-dimethylamino-1-methylindeno[1,2,-b]pyrrole (HDMP, 4) to that of negative allosteric modulator (NAM), PCP. Patch-clamp experiments showed that HDMP exhibited an inhibitory functional activity at α7 nAChRs with an IC(50) of 0.07 μM, and was 357- and 414-fold less potent at α4β2 and α3β4 nAChRs, with IC(50)s of 25.1 and 29.0 μM, respectively. Control patch-clamp experiments showed that PCP inhibited α7, α4β2 and α3β4 nAChRs with IC(50)s of to 1.3, 29.0 and 6.4 μM, respectively. Further, HDMP did not exhibit any appreciable binding affinity to either α7 or α4β2 nAChRs, suggesting its action via a non-competitive mechanism at these neuronal nAChR subtypes. The in vivo study showed that HDMP was a potent antagonist of nicotine-induced analgesia in the tail-flick (AD(50)=0.008 mg/kg), but not in the hot-plate test. All together, our in vitro and in vivo data suggest that HDMP is a novel NAM of neuronal nAChRs with potent inhibitory activity at α7 nAChR subtype at concentrations ≤ 1μM that are not effective for α4β2 and α3β4 nAChRs.
Abdrakhmanova
Galya R
GR
Department of Pharmacology and Toxicology, Virginia Commonwealth University, 1112 E. Clay Str., P.O. Box 980524, Richmond, VA 23298, USA. gabdrakhmano@vcu.edu
Blough
Bruce E
BE
Nesloney
Carey
C
Navarro
Hernán A
HA
Damaj
M Imad
MI
Carroll
F Ivy
FI
D000494:Allosteric Regulation / Q000187:drug effects / Q000502:physiology; D000818:Animals; D057809:HEK293 Cells; D006801:Humans; D007192:Indenes / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D010147:Pain Measurement / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D010622:Phencyclidine / Q000494:pharmacology; D011758:Pyrroles / Q000494:pharmacology*; D011978:Receptors, Nicotinic / Q000378:metabolism*
C555106:1,2,3,3a,4,8b-hexahydro-2-benzyl-6-N,N-dimethylamino-1-methylindeno(1,2-b)pyrrole; D007192:Indenes; D011758:Pyrroles; D011978:Receptors, Nicotinic; D010622:Phencyclidine