tokens: This response was significantly reduced by the intravenous ( i . v . ) injection of guanethidine ( 5 mg ) , hexamethonium ( 10 mg ) or phentolamine ( 5 mg ) , and conversely , potentiated by i . v . desmethylimipramine ( 0 . 3 mg ) , while propranolol ( 0 . 5 mg ) i . v . selectively inhibited the enlargement of pulse pressure and the tachycardia following i . c . carbachol ( 1 mug ) .