nystatin-a1 and chelerythrine

Effects of norepinephrine (NE) on the glycine-mediated inhibitory response were investigated in neurons acutely dissociated from the rat spinal dorsal horn, using nystatin perforated patch recording mode under voltage-clamp conditions. NE reversibly and concentration dependently facilitated Cl(-) current induced by 3 x 10(-5) M glycine. NE neither changed the reversal potential of the glycine response nor affected the affinity of glycine to its receptor. This effect could be mimicked by clonidine (10(-7) M) and blocked by yohimbine (10(-6) M), respectively. N-[2(methylamino)ethyl]-5-isoquinoline sulfonamide dihydrochloride (H-89), an inhibitor of protein kinase A, effectively mimicked the effect of NE on glycine response, whereas chelerythrine (an inhibitor of protein kinase C) failed. NE further enhanced glycine response even in the presence of chelerythrine or stearoylcarnitine chloride (another inhibitor of protein kinase C) or chelerythrine together with stearoylcarnitine chloride. The present results suggest that alpha2-adrenoceptor is involved in the potentiation of NE on glycine response in freshly isolated spinal dorsal horn neurons. Activation of alpha2-adrenoceptor down-regulates the activity of protein kinase A that results in the potentiation of the glycinergic inhibitory effects within the spinal dorsal horn.

Topics: Alkaloids; Animals; Benzophenanthridines; Clonidine; Dose-Response Relationship, Drug; Drug Combinations; Electric Conductivity; Enzyme Inhibitors; Glycine; Isoquinolines; Neurons; Norepinephrine; Nystatin; Patch-Clamp Techniques; Phenanthridines; Posterior Horn Cells; Rats; Rats, Sprague-Dawley; Receptors, Adrenergic, alpha-2; Sulfonamides; Yohimbine

The Role of protein kinase C in the modulatory effect of a mu-opioid receptor agonist, [D-Ala(2),N-Me-Phe(4),Gly(5)-ol]enkephalin (DAMGO), on the glycine-gated Cl(-) current was examined in acutely dissociated rat periaqueductal gray neurons. Using the nystatin-perforated patch-clamp technique, the neurons were voltage-clamped at -60 mV. The glycine-gated Cl(-) current (I(Gly)) was sensitive to strychnine. On pretreatment with 1 microM DAMGO, the 30-microM glycine response increased with time and showed a maximum amplitude of 209+/-37% of control. After a protein kinase C activator, phorbol-12-myristate-13-acetate (PMA, 0.1 microM) as pretreatment, I(Gly) increased to 138+/-6% of control. The DAMGO potentiation of I(Gly) was not altered by coapplication with PMA. Although protein kinase C inhibitors, chelerythrine (3 microM) and 2-[1-(3-dimethylaminopropyl)indol-3-yl]-3-(indol-3-yl) maleimide (GF109203X, 1 microM), did not alter I(Gly), the DAMGO-induced potentiation of I(Gly) was reduced to 161+/-21% or 164+/-31% of the control after coapplication with chelerythrine or GF109203X, respectively. These results indicate that the potentiation of I(Gly) by a mu-opioid receptor agonist is partly mediated by activation of protein kinase C.

Topics: Alkaloids; Animals; Benzophenanthridines; Cells, Cultured; Chlorides; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enzyme Activation; Enzyme Inhibitors; Glycine; Indoles; Maleimides; Narcotics; Neurons; Nystatin; Patch-Clamp Techniques; Periaqueductal Gray; Phenanthridines; Protein Kinase C; Rats; Receptors, Opioid, mu