Abstract
Characteristics of the antinociceptive action of phenylethylamine derivatives, amphetamine, β-phenylethylamine (PEA) and β-hydroxyphenylethylamine (OHPEA), were examined. The pain threshold of mice was measured by using the hot plate method. Intraperitoneal administration of α-methyl-p-tyrosine inhibited antinociception induced by PEA and OHPEA, and intracisternal administration of norepinephrine increased antinociception induced by PEA and OHPEA. Intracisternal administration of phentolamine inhibited the antinociception induced by PEA derivatives. The levels of norepinephrine and normetanephrine in the brain were determined by using H PLC. PEA derivatives decreased norepinephrine in the brain and tended to increase normetanephrine at 15 min after the administration of PEA derivatives. These findings indicate that PEA derivatives cause the release of norepinephrine in the central nervous system, and the released norepinephrine induces antinociception.
