Chronic exposure to either @entity1943 (SS) or XXXX , a long-lasting SS analogue, affects SS expression in the postnatal visual cortex of the @entity35 .

@entity1 @entity2390 @entity35 @entity1943 @entity20549
The peptide @entity1943 (SS) is widely distributed in the @entity1 brain where it modulates neuronal activity through interactions with specific membrane-bound receptor subtypes (ssts). Five different ssts were characterized so far (sst1-5) and their selective agonists were developed on the basis of their binding specificity. SS and ssts are transiently expressed in the developing brain, suggesting a functional role of somatostatinergic systems in neuronal maturation. In the present study, we investigated the effects of chronic exposure to either the SS synthetic analogue, @entity20549 or @entity2390 (a long-acting sst2-preferring analogue) on the maturation of SS-immunoreactivity (-ir) in the primary visual cortex of the @entity35 . SS-ir maturation was investigated both by an evaluation of the number of SS-immunoreactive cells and by radioimmunoassay (RIA) to measure the levels of SS in the postnatal visual cortex. In the visual cortex of normal @entity35 , the number of SS-positive cells markedly increased during the second postnatal week and then significantly decreased until the adult value was reached at the third week. Early and repeated intracerebroventricular (i.c.v.) injections of either @entity20549 or @entity2390 prevented the increase in the number of SS-positive cells, with adult values reached at the end of the first postnatal week. Similarly, administration of either @entity20549 or @entity2390 significantly decreased the SS content of the visual cortex, measured at the end of the second postnatal week. These results show that high local concentrations of either @entity20549 or @entity2390 interfere with SS expression in developing cortical neurons in a restricted postnatal period.
