A diverse development of 5-HT1A receptor binding is relevant to behavioral differences observed in adult mice of two genetically closely related inbred strains.

Only few genetic loci were supposed to be crucial for strong behavioral differences, especially in locomotion and aggression, in two closely related mice inbred strains: AB/Halle (ABH) and AB/Gatersleben (ABG). Previously we reported remarkable strain differences in 5-HT1A receptor binding in adult mice. In the present study, we were interested if the strain-specific 5-HT1A receptor binding pattern is already present very early in ontogeny which could indirectly hint at a gene that is differentially regulated in these 2 mouse strains. Since the 5-HT1A receptor is involved in the regulation of locomotion and aggression, one genetic determinate for the behavioral differences in ABH and ABG mice would have been found. Therefore, we measured [³H]8-OH-DPAT specific binding at postnatal day (PND) 1 and 21 (weanlings) using in vitro autoradiography. 5-HT1A receptor binding was not significantly different at PND 1 between strains. However, in weanlings the same 5-HT1A receptor binding pattern was observed as in adults, i.e. ABH mice display a higher forebrain 5-HT1A receptor binding compared to ABG mice. So the strain-specific forebrain 5-HT1A receptor binding pattern develops during the first 3 postnatal weeks and genetically driven mechanisms seem to be crucial. However, early environmental influences, e.g. differences in maternal care, can't be excluded.