Influence of development and aging on nicotinic receptor subtypes in rodent brain

The influence of development and aging on nicotinic receptor subtypes in rodent brain was investigated. 3H-nicotine and 3H-acetylcholine (3H-ACh) were used as receptor ligands. Specific binding sites for 3H-nicotine and 3H-ACh were detected in mouse brain during the late prenatal period. A drop in the number of 3H-nicotine and 3H-ACh binding sites was measured shortly after birth. The 3H-nicotine and 3H-ACh binding sites showed different time courses during prenatal development. Competition experiments using unlabelled (-)nicotine and 3H-nicotine revealed one population of high affinity nicotinic binding sites in the cortex of 1-day and 5-day-old mice whereas both a set of high and low affinity binding sites were found in adult mice. The proportion of cortical high and low affinity nicotinic binding sites did not change with aging although the absolute amount of high affinity nicotinic binding sites decreased. The 3H-nicotine binding showed different temperature dependence in rat brain of different ages. The results illustrate dynamic changes in nicotinic receptor properties during life span of rodents.