Novel Benzodioxan Derivative, 5-{ 3- [((2S)-1, 4-Benzodioxan-2-ylmethyl)amino] propoxy} -1, 3-benzodioxole HC1 (MKC-242), with a Highly Potent and Selective Agonist Activity at Rat Central SerotoninlA Receptors

Abstract

The present study characterizes the neurochemical profile of the newly synthesized compound 5-{3-[((2S)-1, 4-benzodioxan-2-ylmethyl)amino]propoxy}-1, 3-benzodioxole HC1 (MKC-242). In in vitro experiments, MKC-242 had high affinity for serotonin_1A (5-HT_1A) receptors (K₁: 0.35 nM) and moderate affinity for α₁-adrenoceptors (K_i: 21 nM), whereas it had no appreciable affinity for any other neurotrans-mitter recognition sites studied and 5-HT transporter. MKC-242 (0.3-3.0 mg/kg, s.c.; 1-10 mg/kg, p.o.) caused presynaptic 5-HT_1A-receptor-mediated responses (decreases in 5-HT turnover and 5-HT release) and postsynaptic 5-HT_1A-receptor-mediated responses (hypothermia, an increase in serum corticosterone level and 5-HT_1A behavioral syndrome). The effects of MKC-242 on decarboxylase inhibitor-induced 5-hydroxytryptophan accumulation and rectal temperature were blocked by the 5-HT_1A-receptor antagonist N-tert-butyl-3-(4-(2-methoxyphenyl)piperazin-1-yl)-2-phenylpropanamide. The comparative studies on the in vivo responses induced by MKC-242 and the 5-HT_1A-receptor full agonist 8-hydroxy-2-(di-n-propyl-amino)tetralin (8-OH-DPAT) showed that MKC-242 and 8-OH-DPAT had similar efficacy at presynaptic 5-HT_1A receptors, whereas the former had less efficacy than the latter at postsynaptic 5-HT_1A receptors. Furthermore, MKC-242 partially inhibited forskolin-stimulated adenylate cyclase activity in hippocampal membranes. These findings suggest that MKC-242 acts as a full and partial agonist at pre- and postsynaptic 5-HT_1A receptors, respectively, in the central nervous system.