Differential postnatal development of μ-, δ- and χ-opioid binding sites in mouse brain

Abstract With selective labelling techniques and analysis of saturation curves it is shown that in rat brain the concentrations of μ-, δ- and χ-binding sites increase differentially during postnatal development. There are no changes in the binding affinities. The concentration (pmol/g brain) of χ-sites are first to reach adult levels, namely between 7 and 14 days after birth. Adult levels of μ-sites are attained between 14 and 21 days after birth. The most striking finding is that development of δ-sites, which are not detectable 3 days after birth by the method used, lags markedly behind that of μ- and χ-sites. The profile of development in rat brain is compared to that found previously in mouse brain.