Antiopioid activity of the cardioexcitatory peptide in central modulation of cardiovascular functions

Intracerebroventricular (i.c.v.) injection of [D-Ala2,Leu5]enkephalin produced depressor and bradycardiac responses which were prevented by naloxone or FMRF-NH2 pretreatment. Intrathecal injection of FMRF-NH2 to rats in hemorrhagic shock resulted in a slight but significant increase in blood pressure, and prevented the further decrease in heart rate which was observed in the control group. It is concluded that FMRF-NH2 may act as an antiopioid substance in central modulation of cardiovascular functions.