Postnatal development of somatostatin‐ andneuropeptide y‐immunoreactive neurons in rat cerebralcortex : a double‐labeling immunohistochemical study

Abstract

The postnatal development of somatostatin (SOM)- and neuropeptide Y (NPY)-immunoreactive (ir) neurons was examined in rat cerebral cortex, while considering their coexistence in cortical neurons. Using double immunohistochemical staining for SOM and NPY with diaminobenzidine and benzidine dihydrochloride as chromogens, we subdivided immunoreactive cells into double-labeled SOM/NPY-, SOM only-, and NPY only-ir neurons. SOM/NPY- and SOM only-ir neurons were detectable even at the day of birth, in contrast on NPY only-ir cells which first appeared in most cortices from week two. The morphological features of double-labeled SOM/NPY neurons differed with those of SOM only- and NPY only-ir neurons. No apparent changes in the shape and size of single-labeled neurons occurred with age; throughout their postnatal life they were round and ovoid, had a thin rim of perinuclear cytoplasm, and short processes. However, the features of SOM/NPY-ir neurons were not consistent according to postnatal age; by day P7, these neurons showed immature features and they began to show more advanced neuronal characteristics by week P2, when they had a larger and more intensely-stain cytoplasm. In addition, their processes were longer, thicker and more complex than at earlier ages. At this age, SOM/NPY-ir somata were close to their near maximum size. From week P4, they became smaller and were lightly labeled. SOM/NPY-ir somata were larger than SOM only- and NYP only-ir somata at and after two weeks of age. The present results, showing different postnatal maturation patterns such as time of appearance and morphological features, raise the possibilities that double-labeled SOM/NPY and single-labeled immunoreactive neurons may be different populations regulated by different mechanisms in their development, and with different functional properties during development.

Identification of multiple somatostatin receptors in the rat somatosensory cortex during development

“…From P14 onward, the distribution of somatostatinbinding sites across the cerebral cortex is split at the level of layer IV. This dual repartition of receptors is concomitant with the onset of somatostatin synthesis in GABA interneurons located in layers II-III (McDonald et al, 1982;Cavanagh and Parnavelas, 1988;Eadie et al, 1988;Fitzpatrick-McElligott et al, 1991;Burgunder, 1994;Lee et al, 1998). In fact, the end of the second week postnatal is the period when the concentration of immunoreactive somatostatin in the developing cortex is maximal (McGregor et al, 1982;Fontanesi et al, 1998).…”

Age‐related Change of Somatostatin‐immunoreactive Neurones in the Main Olfactory Bulb of the Rat

“…However, no detailed reports are available concerning age‐related changes in somatostatin‐IR neurones in the olfactory system. Some previous studies (Yamashita and Hayashi, 1996; Cha et al., 1997; Lee et al., 1998) have reported an age‐related change of somatostatin‐IR structures in the cerebral cortex of the rat. Thus, a change of somatostatin in the central nervous system during ageing may be a general principle.…”

Cyto‐ and chemoarchitecture of the cerebral cortex of an echidna (Tachyglossus aculeatus). II. Laminar organization and synaptic density

“…These neurons in the echidna cortex are slightly larger than those reported for the rat (Lee et al, 1998), with soma area averaging up to 100 m 2 in echidna cortex layer V but only 74 m 2 in rodent cortex, but they fall within the range reported for NPY ϩ neurons in cat visual cortex (soma diameter of 16 -20 m; Wahle et al, 1986).…”