
Keywords: DOP; δ opioid receptor; EM-1; endomorphin-1; EM-2; endomorphin-2; i.c.v.; intracerebroventricular; i.p.; intraperitoneal; i.t.; intrathecal; KOP; κ opioid receptor; MOP; μ opioid receptor; MPE; maximum possible effect; s.c.; subcutaneous; Spinal antino