Cellular expression of α4 subunit mRNA of the nicotinic acetylcholine receptor in the developing rat telencephalon

doi:10.1016/0304-3940(95)11598-Q

Neuroscience Letters

Volume 192, Issue 1, 2 June 1995, Pages 21-24

https://doi.org/10.1016/0304-3940(95)11598-Q Get rights and content

Abstract

By contrast to adult brain, little is known on the development of nicotinic acetylcholine receptor (nAChR) expression. Using a digoxigenin-labeled riboprobe for in situ hybridization, α4 nAChR subunit mRNA expression was studied in embryonic and postnatal rat neocortex and hippocampus where it was transiently increased in neuronal subpopulations and preceded cholinergic fiber ingrowth. α4 expression was increased in neocortical layer VIb between E20 and P2 and, about birth, in dentate gyrus granule cells subsequently decreasing to adult levels. nAChR mmRNA expression is increased at the developing neuromuscular endplate preceding cholinergic innervation which triggers changes in non-α nAChR isoform expression. It has to be elucidated whether similar changes may occur in the telencephalon.

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Cited by (19)

Cholinergic influences on cortical development and adult neurogenesis
2011, Behavioural Brain Research
Citation Excerpt :
Neuronal nicotinic acetylcholine (ACh) receptors belong to the family of excitatory ligand-gated channels and are pentameric assembled from different combinations of 12 different subunits. Nicotinic receptor subunit mRNAs appear from mid to late embryogenesis throughout the rat cerebral cortex and hence precede the cholinergic innervation from the basal forebrain [8,99,145]. Muscarinic receptors on the other hand are G-protein coupled and appear later.
In this review, we focus on immature neurons and their regulation by the cholinergic system, both during cortical development as well as during adult neurogenesis. We discuss various studies that indicate roles for acetylcholine in precursor development and neuronal differentiation. Cholinergic neurons projecting from the basal forebrain innervate the cerebral cortex during critical periods of neuronal development. Acetylcholine stimulation may help to promote a favourable environment for neuronal maturation. Afferents and their cortical target cells interact and are likely to influence each other during the establishment and refinement of connections. Intracortical cholinergic interneurons similarly have a local effect on cortical circuits. Reduced cholinergic innervation during development hence leads to reduced cortical thickness and dendritic abnormalities. Acetylcholine is also likely to play a critical role in neuronal plasticity, as shown in the visual and barrel cortices. Spontaneous nicotinic excitation is also important during a brief developmental window in the first postnatal weeks leading to waves of neural activity, likely to have an effect on neurite extension, target selection and synaptogenesis. In the hippocampus such activity plays a role in the maturation of GABAergic synapses during the developmental shift from depolarizing to hyperpolarizing transmission. The cholinergic system also seems likely to regulate hippocampal neurogenesis in the adult, positively promoting proliferation, differentiation, integration and potentially survival of newborn neurons.
Structural determinants of the roles of acetylcholine in cerebral cortex
2004, Progress in Brain Research
Citation Excerpt :
It makes it unlikely that transient, ‘instructive’ synapses are being established by the growing ACh neurons. Even though the subcellular distribution of ACh receptors in the developing cortex has not yet been determined, functional receptors of both the nicotinic and muscarinic families are known to be expressed by cortical cells in the late embryonic and early postnatal periods (Ostermann et al., 1995; Zoli et al., 1995; Aubert et al., 1996; Ma et al., 2000; see also Chapter 1). Thus, diffuse transmission and an ambient level of ACh, as discussed above, could participate in the many roles attributed to ACh during corticogenesis (Bear and Singer, 1986; Broide et al., 1996; Zhu and Waite, 1998; Aramakis et al., 2000; Peinado, 2000).
This chapter reviews the results of light and electron microscopic immunocytochemical studies, carried over the last several years, which have provided basic information on the regional distribution and relational features of the cortical acetylcholine (ACh) innervation in both the adult and the postnatal rat neocortex. The chapter discusses the ultrastructural features of the ACh innervation in both the primary somatosensory cortex and CA1 stratum radiatum of adult rat. In the parietal cortex, an extensive examination of the intrinsic and relational features of the ACh (choline acetyltransferase (ChAT)-immunostained) axon varicosities was carried out in serial as well as single thin sections. Among other findings, this thorough analysis revealed that, in all layers of the parietal cortex, only a small fraction of all ACh varicosities were endowed with a junctional complex, that is, a straightening of apposed membranes with or without post-synaptic thickening on either side of a slightly widened extracellular space.
The cholinergic innervation develops early and rapidly in the rat cerebral cortex: A quantitative immunocytochemical study
2001, Neuroscience
A recently developed method for determining the length of cholinergic axons and number of cholinergic axon varicosities (terminals) in brain sections immunostained for choline acetyltransferase was used to estimate the areal and laminar densities of the cholinergic innervation in rat frontal (motor), parietal (somatosensory) and occipital (visual) cortex at different postnatal ages. This cortical innervation showed an early beginning, a few immunostained fibers being already present in the cortical subplate at birth. In the first two postnatal weeks, it developed rapidly along three parameters: a progressive increase in the number of varicosities per unit length of axon, and a lengthening and branching of the axons. Between postnatal days 4 and 16, the number of varicosities increased steadily from two to four per 10 μm of cholinergic axon. The mean densities of cholinergic axons increased from 1.4 to 9.6, 1.7 to 9.3 and 0.7 to 7.2 m/mm³, and the corresponding densities of varicosities from 0.4 to 3.9, 0.4 to 3.5, and 0.2 to 2.6×10⁶/mm³ in the frontal, parietal and occipital areas, respectively. The rate of growth was maximal during these first two weeks, after which the laminar pattern characteristic of each area appeared to be established. Adult values were almost reached by postnatal day 16 in the parietal cortex, but maturation proceeded further in the frontal and particularly in the occipital cortex.
These quantitative data on the ingrowth and maturation of the cholinergic innervation in postnatal rat cerebral cortex substantiate a role for acetylcholine in the development of this brain region and emphasize the striking growth capacity of individual cholinergic neurons.
Expression of the α4 isoform of the nicotinic acetylcholine receptor in the fetal human cerebral cortex
2001, Developmental Brain Research
Nicotinic acetylcholine receptors are likely to play an important role in neuronal migration during development. Furthermore, the α4 receptor subunit gene is related to a hereditary juvenile form of epilepsy. Only little information is available, however, on the expression of cerebrocortical nicotinic acetylcholine receptors during human fetal development. Using non-isotopic in situ hybridization and immunohistochemistry, we have studied the distribution of the α4 subunit of the nicotinic acetylcholine receptor mRNA and protein in the human frontal cortex at middle (17–24 weeks of gestation) and late (34–42 weeks of gestation) fetal stages. Both, α4 receptor mRNA and α4 receptor protein were observed beginning during week 17–18 of gestation. At this time of development, a few weakly labeled mRNA-containing cells were present mainly in the ventricular zone, the subplate and the cortical plate. A similar distribution pattern was found for the receptor protein. Around week 38 of gestation, the distribution in the cerebral cortex of α4 subunit-containing cells was similar to that of adult human cortices with the highest densities of labeled neurons found in layers II/III, followed by layers V and VI. Nicotinic acetylcholine receptor-containing neurons appear rather early in human fetal development. Given functional maturity, they may interact during cortical development with acetylcholine released from corticopetal fibers or other yet unknown sources subserving the process of neuronal migration and pathfinding.
Functional nicotinic acetylcholine receptor expression in stem and progenitor cells of the early embryonic mouse cerebral cortex
2001, Developmental Biology
The adult cerebral cortex contains nicotinic acetylcholine (ACh) receptors vital to cortical function. However, little is known about the assembly of embryonic nicotinic receptor subunits into functional receptors or whether they play an active role in cortical development. We now report evidence of functional nicotinic acetylcholine receptor channels in fetal mouse cerebral cortex as early as embryonic day 10 (E10), when the cortex consists of dividing stem and progenitor cells. Patch–clamp electrophysiological measurements indicate that nicotine and ACh evoke sizable inward currents characteristic of nicotinic receptors, that are strongly rectifying with a reversal potential near 0 mV. Three different nicotinic agonists, ACh, nicotine, and dimethylphenylpiperazinium, evoked cytosolic Ca²⁺ signals. Agonist-evoked Ca²⁺ signals and electrophysiological responses were found in greater than 70% of all E10–E11 cells tested and were blocked by nicotinic receptor antagonists. The Ca²⁺ response to nicotinic agonists was markedly prolonged in cells from early embryonic stages relative to later stages of development. α3, α4, and α7 receptor subunit proteins were detected immunocytochemically in cortical cells from E10 to birth. The incidence of each subunit declined with embryonic age, suggesting a role in early development. We discuss the possible function of nicotinic receptors in early cortical development and their role as a target for nicotine in the developmental pathologies associated with the fetal tobacco syndrome.
Survival and mitogenesis of neuroepithelial cells are influenced by noradrenergic but not cholinergic innervation in cultured embryonic rat neopallium
2000, Brain Research
Citation Excerpt :
Experimental elimination of this projection results in altered neuronal migration patterns amongst lower cortical laminae in neonates [15]. However, appearance of muscarinic binding sites [34] and expression of nicotinic receptor subunits [29] occurs throughout all the layers of rat cortex in foetal life, and muscarinic (principally m3) receptor activation promotes the survival of neurons which develop in both postnatal [41] and prenatal periods [24]. Neural precursor cells in the rat foetal cortex express ChAT [7], but it has not been established whether these cells can release acetylcholine locally to activate its receptors.
α-Adrenoreceptors are present in the ventricular (VZ) and subventricular (SVZ) zones of the mammalian embryonic forebrain, and contribute towards cell cycle controls in the germinal neuroepithelium [Pabbathi et al., Brain Res. 760 (1997) 22–33.]. Since noradrenaline-containing fibres from the locus coeruleus (LC) and other brainstem nuclei innervate many parts of the CNS from an early stage of embryogenesis, we have used heterochronic cocultures to investigate whether noradrenergic innervation may be the source of trophic support. Dorsal neopallium from E13 rat embryo was cultured in proximity to E15 rostral pons (RP), enabling rapid innervation of the neuroepithelium by differentiated noradrenergic neurons of the LC. The projection of interconnecting fibres into germinal areas of the cortex was established in vitro by retrograde tracing and dopamine β-hydroxylase (DBH) immunocytochemistry. When functional innervation was prevented by transection of axons connecting the explants, the number of apoptotic (TUNEL-positive) cells in the neopallium was increased. Bromodeoxyuridine (BrdU) double-labelling confirmed that germinal cells were amongst those which underwent apoptosis. When cortical explants were innervated by a source of non-monoaminergic (cholinergic) axons from the E18 basal forebrain diagonal band/septum complex (DS), numbers of apoptotic cells were comparable to those in non-innervated cultures. α1 and α2 adrenoreceptor antagonists included in the medium of cortical cocultures innervated by noradrenergic axons reversed the survival-promoting effect of innervation. Blockade of α1 but not of α2 receptors also reduced the numbers of S-phase nuclei in the cortex. The results provide evidence that local delivery of neurotransmitter from embryonic noradrenergic axons terminating in the neocortex can regulate survival and proliferation of neuroepithelial cells.

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^☆: This study was supported by the Deutsche Forschungsgemeinschaft (Schr 283/8-2).

¹: We are greatly indebted to Prof. S. Heinemann, La Jolla, for providing the clones used for probe construction. We would like to thank Prof. P.G.M. Luiten, Groningen, for valuable comments. We thank A. Jeske, S. Nowacki and K. Pilz for excellent technical assistance, I. Koch for photographical and A. Kirchmayer for secretarial work.

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Cellular expression of α4 subunit mRNA of the nicotinic acetylcholine receptor in the developing rat telencephalon☆

Abstract

Cell

Brain Res. Bull.

Mol. Brain Res.

Neuroscience

Dev. Biol.

Mol. Brain Res.