TY - JOUR
T1 - Design, synthesis, and dopamine receptor modulating activity of spiro bicyclic peptidomimetics of L-prolyl-L-leucyl-glycinamide
AU - Khalil, Ehab M.
AU - Ojala, William H.
AU - Pradhan, Ashish
AU - Nair, Venugopalan D.
AU - Gleason, William B.
AU - Mishra, Ram K.
AU - Johnson, Rodney L.
PY - 1999/2/25
Y1 - 1999/2/25
N2 - In the present study, the synthesis of the 5.5.6. and 5.6.5. spiro bicyclic lactam PLG peptidomimetics, compounds 3 and 4, respectively, was undertaken. These peptidomimetics were designed to examine the following: (1) the effect that changing the size of the thiazolidine and lactam ring systems would have on the ability of these systems to mimic the type-IIβ-turn and (2) the effect that these structural perturbations would have on the ability of the peptidomimetics to modulate dopamine receptors. Through the use of the [3H]spiroperidol/N-propylnorapomorphine (NPA) dopamine D2 receptor competitive binding assay, 3 and 4, at a concentration of 100 nM, decreased the dissociation constant of the high-affinity state of the dopamine receptor for the agonist. These effects were observed when either Gpp(NH)p was absent or present and they were comparable to those produced by PLG at a concentration of 1 μM. Peptidomimetics 3 and 4 also increased the percentage of D2 receptors that existed in the high-affinity state. Even with Gpp(NH)p present, 3 and 4 were able to return the R(H)/R(L) ratios to values observed in the respective controls where Gpp(NH)p was absent. Furthermore, both peptidomimetics were able to attenuate the Gpp(NH)p-induced shift to the low- affinity state to a greater extent than PLG. Peptidomimetics 3 and 4 were evaluated in vivo as modulators of apomorphine-induced rotational behavior in the 6-hydroxydopamine-lesioned rat model of hemiparkinsonism, and each affected the rotational behavior in a bell-shaped dose-response relationship producing increases of 95 ± 31% (0.01 mg/kg, ip) and 88 ± 14% (0.001 mg/kg, ip), respectively. In comparison, the previously reported 5.5.5. spiro bicyclic lactam 2 increased rotational behavior by 25 ± 11% (0.01 mg/kg, ip).
AB - In the present study, the synthesis of the 5.5.6. and 5.6.5. spiro bicyclic lactam PLG peptidomimetics, compounds 3 and 4, respectively, was undertaken. These peptidomimetics were designed to examine the following: (1) the effect that changing the size of the thiazolidine and lactam ring systems would have on the ability of these systems to mimic the type-IIβ-turn and (2) the effect that these structural perturbations would have on the ability of the peptidomimetics to modulate dopamine receptors. Through the use of the [3H]spiroperidol/N-propylnorapomorphine (NPA) dopamine D2 receptor competitive binding assay, 3 and 4, at a concentration of 100 nM, decreased the dissociation constant of the high-affinity state of the dopamine receptor for the agonist. These effects were observed when either Gpp(NH)p was absent or present and they were comparable to those produced by PLG at a concentration of 1 μM. Peptidomimetics 3 and 4 also increased the percentage of D2 receptors that existed in the high-affinity state. Even with Gpp(NH)p present, 3 and 4 were able to return the R(H)/R(L) ratios to values observed in the respective controls where Gpp(NH)p was absent. Furthermore, both peptidomimetics were able to attenuate the Gpp(NH)p-induced shift to the low- affinity state to a greater extent than PLG. Peptidomimetics 3 and 4 were evaluated in vivo as modulators of apomorphine-induced rotational behavior in the 6-hydroxydopamine-lesioned rat model of hemiparkinsonism, and each affected the rotational behavior in a bell-shaped dose-response relationship producing increases of 95 ± 31% (0.01 mg/kg, ip) and 88 ± 14% (0.001 mg/kg, ip), respectively. In comparison, the previously reported 5.5.5. spiro bicyclic lactam 2 increased rotational behavior by 25 ± 11% (0.01 mg/kg, ip).
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U2 - 10.1021/jm980525q
DO - 10.1021/jm980525q
M3 - Article
C2 - 10052970
AN - SCOPUS:0033602130
SN - 0022-2623
VL - 42
SP - 628
EP - 637
JO - Journal of medicinal chemistry
JF - Journal of medicinal chemistry
IS - 4
ER -