Presence of cannabinoid binding sites in the brain from early postnatal ages.

The present study demonstrates the presence of cannabinoid receptors in the brain from early postnatal ages. Specific and saturable binding was observed in the forebrain and remaining brain from early postnatal ages (2 and 5 days after birth). Female neonate forebrain exhibited a higher receptor density at 2 days after birth than males, but this trend was inverted at 5 days. From postnatal day 10, the receptors could be measured in more defined brain areas, i.e. the striatum, limbic forebrain and ventral mesencephalon. The ontogeny of the receptors in these three areas was relatively similar, exhibiting a progressive increase which maximised on days 30 or 40 and then subsequently decreased to adult values. Subtle sexual dimorphism was found in the striatum and ventral mesencephalon but not the limbic forebrain.