“The discriminative effects of … mg/kg of caffeine were blocked dose-dependently and completely … alpha adrenergic receptor blocking drugs (phentolamine, prazosin and yohimbine) and were blocked partially by propranolol and by drugs having behavioral depressant … (diazepam, pentobarbital and the adenosine analogs, R-(-)-N6-(2-phenylisopropyl)adenosine, cyclohexyladenosine, 2-chloroadenosine).”