The anxiolytic and analgesic properties of fenobam, a potent mGlu5 receptor antagonist, in relation to the impairment of learning.
Fenobam [N-(3-chlorophenyl)-N'-(4,5-dihydro-1-methyl-4-oxo-1H-imidazole-2-yl)urea] was suggested to possess anxiolytic actions 30 years ago. Hoffmann-La Roche researchers recently reported that it is a selective and potent mGlu5 receptor antagonist, acting as a negative allosteric modulator. In the present study, we show that fenobam readily penetrates to the brain, reaching concentrations over 600 nM, clearly above the affinity for mGluR5 receptors. Fenobam (at 10, 30, and 100 mg/kg) did not affect horizontal locomotor activity in the open field test. Anxiolytic-like activity in the context freezing test was seen at 30 mg/kg, while fenobam was not active in the elevated plus maze test at the tested concentrations. Fenobam had antinociceptive actions in the formalin test at 10 and 30 mg/kg, but failed to attenuate mechanical allodynia in the chronic constriction injury model. Impairment of learning was revealed in the passive avoidance test at 30 mg/kg. Fenobam also impaired performance in both the Morris water maze and in the contextual fear conditioning test at the doses of 30 and 10 mg/kg, respectively. Prepulse inhibition, used as a model of psychomimetic activity, was not affected by fenobam at doses of up to 60 mg/kg. Our results indicate that the beneficial effects of fenobam occur in a similar dose range as the potential side-effects.
In Vivo Pharmacology, Merz Pharmaceuticals GmbH, Frankfurt am Main, Germany.
Wolfgang
W
Jacob
Andreas
A
Gravius
Malgorzata
M
Pietraszek
Jens
J
Nagel
Irina
I
Belozertseva
Elena
E
Shekunova
Andrey
A
Malyshkin
Sergio
S
Greco
Caroline
C
Barberi
Wojciech
W
Danysz
D018712:Analgesics, Non-Narcotic / Q000494:pharmacology*; D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D001362:Avoidance Learning / Q000187:drug effects; D001921:Brain / Q000187:drug effects*; D003214:Conditioning, Classical / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005239:Fear; D046352:Freezing Reaction, Cataleptic / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology*; D007858:Learning / Q000187:drug effects*; D008124:Locomotion / Q000187:drug effects; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D010146:Pain / Q000188:drug therapy; D010147:Pain Measurement; D010812:Physical Stimulation; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors*
D018712:Analgesics, Non-Narcotic; D014151:Anti-Anxiety Agents; C578937:Grm5 protein, rat; D007093:Imidazoles; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; C032794:fenobam