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 .