Methylamine and benzylamine induced hypophagia in mice: Modulation by semicarbazide-sensitive benzylamine oxidase inhibitors and aODN towards Kv1.1 channels

Abstract

1 In starved mice, the anorectic activity of methylamine (MET) and benzylamine (BZ), both substrates of semicarbazide-sensitive benzylamine oxidases (Bz-SSAO), was compared with that of the potassium channel blocking agents charybdotoxin (ChTX), tetraethylammonium (TEA), gliquidone (GLI), ammonium chloride (NH4+) and of the anoressants amphetamine (AMPH) and nicotine (NIC). After i.c.v. administration, an approximate ranking order of potency was: ChTX ≥ AMPH > NIC = TEA ≥ GLI ≥ MET > BZ > NH4+. 2 Clorgyline (2.5 mg kg-1 i.p.) or deprenyl (10 mg kg-1 i.p.) potentiated the anorectic effect of i.c.v.-administered BZ, NIC and AMPH. The effect of TEA was increased only by deprenyl, while MET, NH4+, ChTX and GLI were not affected by either of the inhibitors. 3 The Bz-SSAO inhibitors α-aminoguanidine (50 mg kg-1 i.p.), B24 (100 mg kg-1 i.p.) and MDL 72274 (2.5 mg kg-1 i.p.) potentiated the effect of i.p., but not of i.c.v.-administered MET. 4 Antisense oligodeoxyribonucleotides (aODN) to Kv1.1 potassium channels abolished the effect of BZ and TEA, but was ineffective in reducing the activity of MET and other compounds. 5 These results suggest that MET is endowed with peculiar hypophagic effects at dosage levels that are not able to affect gross behaviour in mice. The effect of MET, differently from BZ, seems unrelated to an increase in the central release of monoaminergic mediators, as well as to a Kv1.1 blocking activity. Through a reduction of the endogenous breakdown of MET, Bz-SSAO inhibitors enhance the central pharmacological activity of this amine.