Morphology of environmentally induced synaptic plasticity in vomeronasal system.

Adult male hamsters and rats were reared for 2 months in either an isolated condition (IC) or a social condition (SC). The lengths of synaptic active zones (SAZ) of synapses in the granule cell layer of the accessory olfactory bulb were measured as an indicator of synaptic size in perforated and non-perforated synapses. In the hamster, the SAZ of both perforated and non-perforated synapses were larger in animals reared in the SC, compared to those of animals reared in the IC. In the rat, only the SAZ of non-perforated synapses was larger in the SC animals, compared with those reared in IC. These results indicate that rearing conditions affect synaptic structure, with the morphological change being more pronounced in hamsters than in rats.