tokens: In contrast to the protection provided by the putative antagonists , the well - characterized sigma receptor agonist di-o-tolylguanidine ( DTG ) and the novel sigma receptor agonist BD1031 ( 3R-1-[2-(3,4-dichlorophenyl)ethyl]-1,4-diazabicyclo[4.3.0]nonane ) each worsened the behavioral toxicity of cocaine .