Effect of dihydroxyphenylalanine, imipramine and coffeine on the light induced decrease in nocturnal serotonin N-acetyltransferase in the rat pineal gland.
The s.c. administration of 150mg L-dihydroxphyenylalaine/kg b.w. 15 min before the decapitation prevents the light induced decrease in nocturnal serotonin N-acetyltransferase activity in the rat pineal gland. The s.c. administration of 50mg imipramine/kg b.w., resp. 100mg/kg b.w., 15 min before the decapitation, slows down, or prevents the light induced fall in the activity. The maintenance of a sufficient level of active norepinephrine on beta-receptors, either by displacement of norepinephrine in the nerve endings by dopamine, or by the inhibition of norepinephrine reuptake by imipramine, thus slows down or prevents the decrease in serotonin N-acetyltransferase activity after exposure to light during the night. The i.p. administration of a phosphodiesterase inhibitor coffeine citrate in a dose 200mg/kg 90 min after switching off the light for the night stimulated serotonin N-acetyltransferase activity 270 min after the light and been switched off, but did not influence the abrupt decrease induced in nocturnal activity by exposure to light.
D000123:Acetyltransferases / Q000378:metabolism*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D003624:Darkness; D004295:Dihydroxyphenylalanine / Q000494:pharmacology*; D007099:Imipramine / Q000494:pharmacology*; D008027:Light; D008297:Male; D010870:Pineal Gland / Q000201:enzymology*; D051381:Rats; D012701:Serotonin / Q000378:metabolism*
D012701:Serotonin; D002110:Caffeine; D004295:Dihydroxyphenylalanine; D000123:Acetyltransferases; D007099:Imipramine