ethylketocyclazocine 0.01-1 mumol/l and fentanyl 1 and 10 mumol/l but not morphine 1 and 10 mumol/l , met-enkephalin 1 and 4 mumol/l or d-ala2 , d-leu5-enkephalin 0.5 and 5 mumol/l diminished the stimulation-evoked increase in heart rate .
C0014295
met-enkephalin
C0014298
enkephalin