Abstract
Rapid enzyme inactivation and atraumatic animal sacrifice are necessary to protect many labile neurochemicals from degradation. To compare sacrifice methods as they affect the steady state levels of brain norepinephrine (NE), dopamine (DA) and serotonin (5-HT) at various times of day, 25-30 g ICR Sprague-Dawley mice were sacrificed at 8 AM, 12 Noon, 4 PM, 8 PM, 12 midnight and 4 AM by microwave irradiation (MWR) or by decapitation (DC). During the dark cycle (7 PM to 7 AM), mice were sacrificed in infrared light. All brains were removed within 5 minutes, frozen in liquid nitrogen and stored in a freezer at 7minus;70°C. The concentrations of NE, DA and 5-HT in whole brain were determined by HPLC coupled with an electrochemical detector. Whole brain NE content following microwave irradiation was significantly higher at 12 Noon, 8 PM, 12 PM and 4 AM. However, NE did not exhibit circadian rhythm in either the group sacrificed by decapitation or the group sacrificed by microwave irradiation. DA levels were significantly higher in brains of mice sacrificed by MWR at 12 Noon, 12 PM and 4 AM. The maximum increase of 15% was observed at 4 AM. Analysis of variance showed no significant circadian rhythm in brain dopamine content in either group. Mice sacrificed by microwave irradiation showed a significant increase in whole brain serotonin content at all times examined when compared to those sacrificed by decapitation. A maximum increase of 48% in serotonin content between these two groups was observed at midnight. From the data presented in this paper we can conclude that a circadian rhythm in serotonin content is observed only in mice sacrificed by the DC method. Further, we have shown that an increase in serotonin content in whole brain following heating could be a result of an increased amount of free serotonin content, which is readily extracted as compared to a bound form. It appears that in normal brain, serotonin maintains a balance between the free and bound form. It is conceivable that observed circadian variations in serotonin content could be due to fluctuations in levels of the bound form of serotonin.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
