Transient expression of S-100beta immunostaining in developing thalamus and somatosensory cortex of rat.

Serotonin is thought to affect the development of barrel fields in somatosensory cortex of rat and transient expression of the serotonin transporter has been reported in relevant thalamic (ventral posterior) and cortical (layer IV of parietal) regions in support of this. Much of the developmental role of serotonin is mediated by release of the neurotrophic protein S-100beta. The current work was thus undertaken to determine if S-100beta also shows a transient expression pattern in thalamus and barrel fields. Male Sprague-Dawley rats were examined immunocytochemically for S-100beta expression on postnatal days (PD) 1, 7, 15 and 22. Expression of S-100beta selectively peaked in the ventral posterior nucleus of the thalamus at PD 7, and in layer IV of the parietal cortex from PD 7 to 15, in a 'barrel-like' pattern. Our findings suggest that S-100beta could indeed be the mediator of serotonin's effects on barrel field formation.