Immunoregulatory properties of (+)-pentazocine and sigma ligands

(+)-Pentazocine, phencyclidine, and other sigma ligands including 1,3-di-(o)-tolylguanidine (DTG), (+)-1-propyl-3-(3-hydroxyphenyl) piperidine [(+)-PPP] and haloperidol were investigated for their potential immunoregulatory properties. High concentrations (10(-5) M) of DTG and haloperidol were found to suppress in vitro murine splenocyte natural killer activity while equivalent concentrations of (+)-pentazocine, (-)-pentazocine and (+)-PPP were without effect. In a reciprocal fashion, lower doses (10(-9) M) of DTG enhanced natural killer activity. Sigma ligands were also found to affect in vitro polyclonal immunoglobulin production following mitogen stimulation. Specifically, high concentrations (10(-6) M) of haloperidol significantly (P < 0.001) suppressed pokeweed mitogen (PWM)-stimulated IgG and IgM production, yet enhanced lipopolysaccharide (LPS)-stimulated IgM production by murine splenocytes. Lower concentrations (10(-8) to 10(-10) M) enhanced (two- to fourfold) PWM-induced IgM production and LPS-stimulated IgG and IgM production. At high concentrations (10(-6)), (+)-pentazocine suppressed (P < 0.01) LPS-induced polyclonal IgG and IgM but enhanced (P < 0.01) PWM-induced IgM production. Both DTG and (-)-pentazocine (10(-8) to 10(-10) M) significantly augmented (two- to threefold) LPS-stimulated murine splenocyte production of polyclonal IgM. Intracellularly, (-)-pentazocine (10(-9) M), haloperidol (10(-7) M), DTG (10(-7) M) and (+)-PPP (10(-5) to 10(-9) M) enhanced forskolin (10(-6) M)-induced cAMP production in splenic lymphocytes while (+)-pentazocine was without effect. Collectively, the data suggest functional and biologically relevant sigma receptors on cells of the immune system.