Early histological maturation in the hippocampus of the guinea pig

The vesicular zinc-rich synaptic systems of the principal neurons of the hi ppocampus are well developed in newborn guinea pigs, a precocial species, I n addition, alvear and fimbrial myelinated fibers as well as significant in hibitory interneurons (i.e. somatostatin, parvalbumin and opioid immunoreac tive hippocampal interneurons) are also well developed, On the contrary, ne ither vesicular zinc synapses nor myelinated fibers nor the above mentioned immunoreactive interneurons are detectable in newborn specimens of other r elated altricial species such as rats or rabbits. These data suggest that e arly maturation of a highly integrative center related to cognitive map bui lding such as the hippocampus is characteristic of precocial species. Copyr ight (C) 2000 S. Karger AG, Basel.