GLYCOGENOLYTIC RESPONSE OF PRIMARY CHICK AND MOUSE CULTURES OF ASTROCYTES TO NORADRENALINE ACROSS DEVELOPMENT

Glycogen is the brain's largest energy store and it is mainly localise d in astrocytes. Glycogen turnover is extremely rapid in the brain, es pecially during sudden increased demand when glucose supplies are insu fficient. Previous culture studies have reported on the glycogenolytic effect of noradrenaline on 3-4 week-old primary mouse astrocyte cultu res. This effect is believed to be mediated by the beta-adrenergic-cAM P signal transduction system. Recent evidence has shown a drop in fore brain glycogen levels at a specific time point during memory formation for a passive avoidance task in the day-old chick. This 'memory-relat ed' glycogenolysis may be initiated by noradrenaline-induced rises in cAMP occurring around this time point, but it is unknown whether astro cytic glycogenolysis is stimulated by noradrenaline in day-old chicks. This question was approached in the present study and it was shown th at noradrenaline is capable of stimulating both cAMP formation and gly cogen breakdown in chick primary astrocyte cultures at developmental a ge (10-14 days in culture) comparable to the newborn chick. In contras t, noradrenaline did not have a corresponding glycogenolytic effect on 10-day-old mouse astrocyte cultures (equivalent to the 1-week-old mou se), although it induced a considerable amount of glycogen breakdown i n older cultures (18 and 24-26 days).