Melatonin is synthesized from serotonin by the action of arylalkylamine N-acetyltransferase (AANAT) and hydroxyindole-O-methyltransferase. In this study, we observed cellular changes of arylalkylamine N-acetyltransferase (EC 126.96.36.199; AANAT) in the hippocampal CA1 region at various time points after ischemia/reperfusion. In vehicle-treated sham group, AANAT immunoreaction was detected in pyramidal neurons of the CA1 region. AANAT immunoreactivity in the neurons was highest 2 days and disappeared from 4 days after ischemia/reperfusion. From 3 days after ischemia/reperfusion, AANAT immunoreaction was expressed in astrocytes in the strata oriens and radiatum of the CA1 region. AANAT protein and mRNA levels were significantly increased 2 days after ischemia/reperfusion, and markedly decreased from 5 days after ischemia/reperfusion. The repeated administration of melatonin (10 mg/kg, i.p.) 3 times (once a day) to gerbils before ischemia/reperfusion significantly reduced ischemia-induced hyperactivity as well as neuronal death compared to those in the vehicle-treated ischemia group. Melatonin treatment also maintained AANAT immunoreactivity and its protein levels in the CA1 region after ischemia/reperfusion. These results suggest that the reduction of AANAT in ischemic CA1 region is associated with delayed neuronal death following transient ischemia, and melatonin treatment shows neuroprotection with maintenance of AANAT levels in the ischemic CA1 region.
Bibliographical noteFunding Information:
The authors would like to thank Mr. Suek Han, Seung Uk Lee and Ms. Hyun Sook Kim for their technical help in this study. This work was supported by the Regional Core Research Program funded by the Korea Ministry of Education, Science and Technology (Medical & Bio-material Research Center) and by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD) ( KRF-2006-E00142 ).
All Science Journal Classification (ASJC) codes
- Clinical Neurology