DEVELOPMENTAL EXPRESSION OF ALPHA(7) NEURONAL NICOTINIC RECEPTOR MESSENGER-RNA IN RAT SENSORY CORTEX AND THALAMUS

Citation
Rs. Broide et al., DEVELOPMENTAL EXPRESSION OF ALPHA(7) NEURONAL NICOTINIC RECEPTOR MESSENGER-RNA IN RAT SENSORY CORTEX AND THALAMUS, Neuroscience, 67(1), 1995, pp. 83-94
Citations number
49
Categorie Soggetti
Neurosciences
Journal title
ISSN journal
03064522
Volume
67
Issue
1
Year of publication
1995
Pages
83 - 94
Database
ISI
SICI code
0306-4522(1995)67:1<83:DEOANN>2.0.ZU;2-L
Abstract
The distribution of alpha(7) messenger RNA expression was characterize d in developing rat cortex and thalamus. Northern blot analysis of neo natal and adult cortex revealed a single messenger RNA transcript of 5 .7 kb. Using in situ hybridization with both full length and short S-3 5-labeled alpha(7) riboprobes, a distinct transient expression of mess enger RNA within sensory cortex and thalamus, during early postnatal d evelopment, was observed. alpha(7) transcripts were expressed in low l evels as early as embryonic day 13 in the ventricular zone of the neoc ortex, and as early as embryonic day 15 in the thalamic neuroepitheliu m. A marked increase in messenger RNA levels was observed during the l ate prenatal period in both sensory and non-sensory regions of the cor tex and thalamus. Moderate to high levels of messenger RNA were mainta ined into the first postnatal week, followed by a decline into adultho od. alpha(7) messenger RNA expression was significantly higher in the anterodorsal, lateral dorsal, ventral posterior medial and ventral pos terior lateral thalamic nuclei of postnatal day 7 pups than in adult b rains. Expression of messenger RNA within dorsal lateral geniculate, v entral lateral geniculate and medial geniculate did not show a signifi cant reduction with age. Within the developing cortex, messenger RNA e xpression delineated the primary somatosensory, auditory and visual co rtices in a unique laminar pattern that was consistently and significa ntly higher than in the adult in superficial layer VI. Higher levels o f expression were also observed in retrosplenial cortex at postnatal d ay 7 than in the adult. Tangential sections through postnatal day 7 co rtex revealed low levels of alpha(7) messenger RNA expression delineat ing the primary sensory areas in layer IV, corresponding to acetylchol inesterase-labeled thalamocortical afferents. However, these sensory a reas exhibited higher levels of alpha(7) messenger RNA expression and were more clearly defined in layer VI, but not by acetylcholinesterase staining. The distribution of alpha(7) messenger RNA within the devel oping thalamocortical system parallels the distribution of alpha-bunga rotoxin binding sites and suggests that the receptor is localized on b oth thalamic cells and their cortical target neurons. This transient a nd distinct pattern of distribution of the alpha(7) neuronal nicotinic receptor, which coincides with the major phase of thalamocortical dev elopment, suggests that it may play a functional role in the developme nt of cortical circuitry.