tokens: The antinociception produced by (+/-)- PG-9 was prevented by the unselective muscarinic antagonist atropine , the M1 - selective antagonists pirenzepine and dicyclomine and the acetylcholine depletor hemicholinium-3 , but not by the opioid antagonist naloxone , the gamma-aminobutyric acidB antagonist 3-aminopropyl-diethoxy-methyl-phosphinic acid , the H3 agonist R-(alpha)-methylhistamine , the D2 antagonist quinpirole , the 5-hydroxytryptamine4 antagonist 2-methoxy-4-amino-5-chlorobenzoic acid 2-(diethylamino)ethyl ester hydrochloride , the 5-hydroxytryptamin1A antagonist 1-(2-methoxyphenyl)-4-[4-(2-phthalimido)butyl]piperazine hydrobromide and the polyamines depletor reserpine .