Developmental changes of cholinesterases and monoamine oxidase in chick embryo spinal and sympathetic ganglia

A comprehensive review of monoamine oxidase inhibitors as Anti-Alzheimer's disease agents: A review

Monoamine oxidases (MAO-A and MAO-B) are mammalian flavoenzyme, which catalyze the oxidative deamination of several neurotransmitters like norepinephrine, dopamine, tyramine, serotonin, and some other amines. The oxidative deamination produces several harmful side products like ammonia, peroxides, and aldehydes during the biochemical reaction. The concentration of biochemical neurotransmitter alteration in the brain by MAO is directly related with several neurological disorders like Alzheimer's disease and Parkinson's disease (PD). Activated MAO also contributes to the amyloid beta (Aβ) aggregation by two successive cleft β-secretase and γ-secretase of amyloid precursor protein (APP). Additionally, activated MAO is also involved in aggregation of neurofibrillary tangles and cognitive destruction through the cholinergic neuronal damage and disorder of the cholinergic system. MAO inhibition has general anti-Alzheimer's disease effect as a consequence of oxidative stress reduction prompted by MAO enzymes. In this review, we outlined and addressed recent understanding on MAO enzymes such as their structure, physiological function, catalytic mechanism, and possible therapeutic goals in AD. In addition, it also highlights the current development and discovery of potential MAO inhibitors (MAOIs) from various chemical scaffolds.

Monoamine oxidase inhibitors: promising therapeutic agents for Alzheimer's disease (Review)

Activated monoamine oxidase (MAO) has a critical role in the pathogenesis of Alzheimer's disease (AD), including the formation of amyloid plaques from amyloid β peptide (Aβ) production and accumulation, formation of neurofibrillary tangles, and cognitive impairment via the destruction of cholinergic neurons and disorder of the cholinergic system. Several studies have indicated that MAO inhibitors improve cognitive deficits and reverse Aβ pathology by modulating proteolytic cleavage of amyloid precursor protein and decreasing Aβ protein fragments. Thus, MAO inhibitors may be considered as promising therapeutic agents for AD.

Acetylcholine synthesis by choline acetyltransferase of a peripheral type as demonstrated in adult rat dorsal root ganglion

pChAT is a splice variant of a peripheral type encoded alternatively by the gene for choline acetyltransferase of the common type (cChAT), the enzyme responsible for acetylcholine synthesis. Immunohistochemistry using pChAT antiserum has successfully visualized many known peripheral cholinergic cells, whereas most cChAT antibodies failed to do so. As, however, accumulating evidence indicates that pChAT expression also occurs in various non-cholinergic neurons, we examined possible acetylcholine production by pChAT in rat dorsal root ganglion as a model. The present study indicated that the ganglion neurons possessed pChAT, but never cChAT, mRNA and protein. Our detailed analysis further showed that, despite low enzyme activities of both choline acetyltransferase and acetylcholinesterase, the level of acetylcholine in the ganglion was as high as to that in various brain regions receiving cholinergic innervation. By using immunoprecipitation methods, we here provide evidence that pChAT definitely has enzyme activity enough to supply physiological concentrations of acetylcholine in the ganglion. We propose that pChAT contributes both to acetylcholine neurotransmission in physiologically identified cholinergic cells and to functions yet unknown in non-cholinergic neurons. Thus pChAT provides a new window on the role of neuronal acetylcholine.

Developmental expression of acetyl- and butyrylcholinesterase in the rat: enzyme and mRNA levels in embryonic dorsal root ganglia

Dorsal root ganglia (DRG) in the adult rat contain acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), enzymes implicated in neural morphogenesis. We used quantitative histochemistry, reverse transcription-PCR (RT-PCR), and in situ hybridization histochemistry to study cholinesterase expression during embryogenesis. Longitudinal sections of rat embryos, embryonic day 9 (E9), E11-E17, and E19, were studied by video microscopy of the stained enzyme reaction products. Both enzymes were detectable in the early DRG (E11-E12), with BChE being most prominent. There was a spatiotemporal change in expression of each cholinesterase within the DRG. From E13 on, AChE expression predominated, especially in the neuronal cell bodies, while BChE was more highly expressed in the surrounding neuropil and the ganglionic roots. This distribution resembled the pattern in adult DRG. AChE mRNA levels, as determined by RT-PCR from DRG collected at days E12-E17, and E19, varied in parallel with the intensity of enzyme stain in the DRG. Overall, these results demonstrate temporally regulated ganglionic expression of cholinesterases, which may be important in the development of the sensory nervous system.

Differential development of cholinergic nerve terminal markers in rat brain regions: implications for nerve terminal density, impulse activity and specific gene expression

During critical developmental periods, cholinergic activity plays a key role in programming the development of target cells. In the current study, ontogeny of cholinergic terminals and their activity were contrasted in 4 brain regions of the fetal and neonatal rat using choline acetyltransferase activity, which is unresponsive to changes in impulse flow, and [3H]hemicholinium-3 binding, which labels the high-affinity choline transporter that upregulates in response to increased neuronal stimulation. In all 4 regions (cerebral cortex, midbrain + brainstem, striatum, hippocampus) choline acetyltransferase activity increased markedly from late gestation through young adulthood, but generally did so in parallel with the expansion of total membrane protein, reflective of axonal outgrowth and synaptic proliferation. In contrast, [3H]hemicholinium-3 binding was extremely high in late gestation and immediately after birth, declined in the first postnatal week and then rose again into young adulthood. The ontogenetic changes reflected alterations primarily in the number of binding sites (Bmax) and not in binding affinity. Only the latter phase of development of [3H]hemicholinium-3 binding corresponded to the ontogenetic changes in choline acetyltransferase activity; in the hippocampus, there were disparities even in young adulthood, where [3H]hemicholinium-3 binding showed a spike of activity centered around the 5th to 6th postnatal week, whereas choline acetyltransferase did not. Correction of binding for membrane protein development did not eliminate any of the major differences in developmental patterns between the two markers. These results suggest that development of the choline transporter binding site is regulated independently of the outgrowth of the bulk of cholinergic nerve terminals.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of esterase activities in the chicken before and after hatching

The embryonic chick has long been a model for developmental biology and has often been recommended as a model system in developmental toxicology. More recently, several investigators have shown that the chick embryo also provides a good model for identifying the neurotoxic effects of environmental pollutants, especially cholinesterase-inhibiting pesticides. Although numerous studies detail the structural development of chick embryos, few describe embryonic levels of enzyme synthesis and their changes during development. In this study, the development of esterase activity in chick embryos was measured from day 9 of incubation until 46 days after hatching. Brain acetylcholinesterase (AChE) activity was detected on day 9 of incubation at a concentration of 0.364 mumoles/min/g tissue. An increase between AChE activity and age of the embryos was observed. In the liver, the nonspecific cholinesterases (ChE) and carboxylesterase activities during incubation were not different from activities after the chicks had hatched. Plasma ChE and carboxylesterase activities did not change with age after hatching. Brain neuropathy target esterase (NTE) activity was not detected on day 9 of incubation and was extremely low (6.12 nmoles/15 min/mg protein) the next day, but increased rapidly with increasing age. This study demonstrates that chick embryos have developed esterase activities in the brain and liver by day 10 of incubation and again confirms that the insensitivity of chick embryos and young chicks to organophosphorus ester-induced delayed neurotoxicity is not due to absence of NTE. In addition, the results provide baseline data for evaluating the response of embryonic and immature chicks to neurotoxicants and teratogens.

Ontogeny of acetylcholinesterase, substance P and calcitonin gene-related peptide-like immunoreactivity in chick dorsal root ganglia

The distribution of acetylcholinesterase and of two neuropeptide (substance P and calcitonin gene-related peptide) immunoreactivities has been investigated in sensory neurons of lumbosacral dorsal root ganglia during chick embryo development, combining immunolocalization of neuropeptides with simultaneous histochemical detection of acetylcholinesterase, in order to study co-localization of the two peptides and their relations with acetylcholinesterase. Acetylcholinesterase at E7 of development appears in only a few neurons, usually the larger ones located in the lateroventral region of the ganglia. As development proceeds the number of neurons and intensity of staining increase. Until E12-13 acetylcholinesterase positivity is limited to the region of the ganglion containing larger neurons. At later stages (E20) it spreads progressively, leading to staining of cells over the whole ganglion. Substance P-like immunoreactivity appears at E6 and for calcitonin gene-related peptide at E7. These immunoreactivities progressively increase with development, remaining limited to the small neuron compartment of the dorsomedial region of the ganglion. Immunoreactivity for both neuropeptides reaches a maximum around E10-13 and then declines. Using simultaneous double immunostaining, calcitonin gene-related peptide and substance P-like immunoreactivities are largely co-localized, although their distribution is not completely coincident. Neuropeptide-positive cells are usually devoid of any acetylcholinesterase activity until E15. They become positive for the enzyme at later stages. The significance of acetylcholinesterase expression in sensory neurons and the possible relation of its appearance and neuron size is discussed.

Acetylcholinesterase in the development of chick dorsal root ganglia

Acetylcholinesterase is expressed in chick dorsal root ganglia neurons very early in development. Since the physiological role of the enzyme in these cells is still obscure, it appeared of interest to investigate its modifications in the course of development. The specific activity of acetylcholinesterase in chick dorsal root ganglia increases, during in ovo development, from day E5 to day E13; after day E13 there is a decrease. Conversely, when acetylcholinesterase activity was expressed on a per ganglion basis, a continuous increase in the level of the enzyme until day E20 was observed. Acetylcholinesterase is a polymorphic enzyme and its molecular forms have different cellular localizations. Two globular forms, a tetramer (G4) and a dimer (G2), are present in the ganglia, as in chick brain. G4 is the major form at day E5, where it represents about 85% of the activity. This form shows a progressive decrease since day E8, and at day E20 exhibits activity levels similar to those of G2. It is known that acetylcholinesterase-producing cells are also able to release the enzyme in the extracellular space. We determined the release of acetylcholinesterase by cultured dorsal root ganglia neurons at various developmental stages: acetylcholinesterase release is significantly increased at day E20, as compared to younger stages, and 90% of the enzyme released is G4.

Multiple molecular forms of soluble esterases in the digestive system of the developing chicken

Soluble esterases in tissues of endodermic origin and of various developmental ages of Gallus gallus were analysed by polyacrylamide slab gel electrophoresis and characterized as carboxylesterases, acetylesterases and cholinesterases. Esterase bands were observed from day 9 in the liver and from day 6 in stomach, intestine and yolk sac. The electrophoretic profiles became more complex after hatching with concomitant increase in the staining intensity. On isoelectric focusing of liver extracts only a major form with pI 5.4 was observed. An eserine sensitive band designated EL-1 was found to be tissue (liver) and age (upon hatching) specific. EL-1-like isozymes were also observed in other species of the Galliformes order.

Ontogeny of glucose metabolism in sympathetic ganglia of chickens. Changes in the carbon fluxes to CO2, lactate, and tissue constituents from 8 to 19 days of embryonic age

Chains of sympathetic ganglia were excised from the lumbar region of white Leghorn chicken embryos, 8-19 days of age. The chains were incubated for 5 h at 36 degrees C in a bicarbonate-buffered physiological salt solution containing 5.55 mM unlabeled glucose and tracer amounts of glucose labeled either uniformly or at carbon-1 or carbon-6. Glucose uptake and labeled lactate output were both highest in ganglia from the youngest embryos studied and declined progressively with increasing age. The output of labeled CO2 rose to a peak rate at an incubation age of 10-12 days in the presence of either [U-14C]glucose or [1(-14)C]glucose, but changed relatively little with age in the presence of [6(-14)C]glucose. The incorporation of 14C into tissue constituents was fastest at 10-12 days with all three labeled glucoses. It is concluded that the hexosemonophosphate shunt is most active at an incubation age of 10-12 days, after glycolysis has greatly slowed. The literature on morphological and biochemical changes in the sympathetic ganglia during development is briefly reviewed and discussed in relation to the observed metabolic changes. The early high glycolytic rate may be related to the normal developmental delay in vascularization of the sympathetic chains.

Morphometric study of pre- and post-hatching nerve cell bodies of lumbar spinal ganglia of Gallus domesticus

A cytomorphometric study was performed in lumbar spinal ganglia neurons of Gallus domesticus on the 10th and 18th incubation days and 8th, 35th, 61st, and 120th post-hatching days. The absolute volume of nucleus and relative volume of cytoplasm were respectively estimated by the Bach caryometric method and by point-counting volumetry, carried out in 0.5 micrometer thick araldite sections. The relative volume, the surface-to-volume ratio and the total surface of RER, SER, mitochondria, dense bodies, Golgi complex and the relative volume of hyaloplasm inside and outside the Nissl bodies were estimated from electronmicrographs by the Weibel et al. method. The conclusions were: a) there was an increase of the cell volume and a decrease of the nucleo-cytoplasmic ratio, particularly between the first two ages; b) the relative volumes of RER and SER change inversely with respect to each other: the RER increases before hatching, decreasing progressively afterwards; the changes of relative volume of dense bodies are similar to those of the RER, and the mitochondria show relatively small variations concerning the same parameter; c) the relative volume of hyaloplasm inside the Nissl bodies decreases while those outside increases; d) the surface-to-volume ratio drops sharply for all organelles from the 10th to the 18th day of incubation; after hatching, a tendency to increase is observed; e) the membrane surface-to-cytoplasmic volume ratio decreases for all organelles from the 10th to the 18th day of incubation; after hatching, this ratio increases slightly for mitochondria and Golgi complex, sharply for SER, dropping for dense bodies. The RER values alternate regularly.

Developmental distributive pattern of acetylcholinesterase in chick embryo ciliary ganglion

AChE cytochemistry was performed in the chick ciliary ganglion (CG) during various embryonic stages. AChE first appeared in the RER of the neurons at 5 days of incubation (d.i.). Synaptic AChE appeared only later, parallely to the appearance of the calyciform synapses, i.e. at 9 d.i. At first AChE was mainly localized at the calyx side facing the satellite cell, thereafter extending to the neuronal side and especially labeling synaptic contacts occurring at points along the presynaptic membrane. Finally, at 15 d.i., i.e. when the calyx is morphologically mature, AChE reaction labels the whole contour of the calyciform nerve terminal. At 10 d.i., limited AChE-positive extrasynaptic areas of the ciliary neurons surface first appeared, thereafter extending up to affect at 15 d.i. large neuronal surfaces. Some hypotheses can be drawn from our results: (i) the earliest appearance of cytoplasmic AChE seems somehow independent of the establishing of functional synaptic contacts; (ii) the pattern of development of neuronal AChE suggests the existence of a sort of transynaptic control by presynaptic nerve terminals. However, it is possible that concomitant retrograde iris-dependent influences on ganglionic AChE concur in modulating neuronal AChE; (iii) the functional role possibly played by AChE localized at extra-synaptic level still remains to be clarified.

Synaptogenesis in chick paravertebral sympathetic ganglia: a morphometric analysis

Synaptogenesis was studied in lumbar sympathetic ganglia of chicken by light and electron microscopic morphometric methods. At 10 days in ovo, fewer than 1% of the adult number of synapses are present. The total numbers of synapses and of synaptic vesicles per ganglion increase progressively with age; however, the majority of both are formed after 30 days after hatching. The average number of synaptic vesicles per synapse increases several fold after hatching. The numbers of synapses and of synaptic vesicles per ganglion increase roughly in concert with biochemical markers of presynaptic development (activity of choline acetyltransferase and levels of acetylcholine) as well as postsynaptic development (tyrosine hydroxylase; based on biochemical data reported elsewhere). The amount of acetylcholine and activity of choline acetyltransferase per synaptic vesicle at 10 days in ovo are 8 and 27 times the corresponding adult values. By 1 day after hatching, these ratios have fallen to near adult levels. These data are consistent with the early presence of cholinergic neuroblasts, as suggested by others, and suggest further that such cholinergic neuroblasts are eliminated, or their cholinergic properties suppressed, before hatching.

Histochemical study of the cholinesterase activity in cat myenteric ganglia during postnatal development

The changes in the cholinesterase activity of cat myenteric ganglia during the postnatal development are studied histochemically. During early postnatal development, the increase in enzyme activity is particularly pronounced in the perikarya of the myenteric neurones. Intensification of the reaction in the neuropile is characteristic after the 14th postnatal day and also persists in adult animals. The localization and intensity of the histochemical reaction in the individual neurones of a single ganglion is variable. The changes in enzyme activity are not identical in dynamics and localization in the myenteric ganglia in the areas of the alimentary tract examined, this difference being observed throughout the entire postnatal development.

Development of the multiple molecular forms of acetylcholinesterase in chick paravertebral sympathetic ganglia: an in vivo and in vitro study

The development of acetylcholinesterase (AChE) activity and the distribution of this enzyme among its multiple forms was studied in both tissue extracts and dissociated cell cultures of chick paravertebral sympathetic ganglia. In agreement with previous findings, total AChE (expressed either per ganglion or per microgram protein) increased in vivo between the time of formation of the paravertebral chain (embryonic day 7; E7) to hatching (E20-E21). After this time, enzyme activity changed much more slowly. Sucrose gradient sedimentation analysis of AChE in ganglia of post-hatching chicks revealed multiple forms of AChE with S values of approximately 6.5, 11 and 19.5. Developmental studies showed that 6.5 S and 11 S forms are present as early as day E7. Much of the pre-hatching increase in total AChE is due to increased levels of the 6.5 S form of the enzyme. By hatching, this form comprised approximately 85-90% of the total AChE activity. In contrast, during the first week after hatching, the activity of the 11 S form increased several-fold while that of the 6.5 S remained approximately unchanged. The 19.5 S form, which is thought to be associated with the synaptic membrane, was not detected prior to day E17 and reached adult levels (2-3% of total AChE activity) by the first week after hatching. Development of AChE was also studied in dissociated cell cultures of embryonic ganglia. Essentially all the AChE activity in such cultures was found to be associated with the neurons. Total AChE activity of cultured E11 ganglia increased in a pattern which was both qualitatively and quantitatively similar to that which occurred in vivol. Furthermore, it was found that development of both the 6.5 and 11 S forms of AChE took place in vitro. In cultures of E8, E11, E15 and E19 ganglia, the distribution of activity between the two forms after various times in vitro was similar to that which was found for in vivo ganglia at an equivalent embryonic stage. Such changes were not affected by the elimination of nonneuronal cells from the cultures. Two aspects of in vitro development, however, differed from that which occurred in vivo. First, an increase in 11 S AChE did not occur at ages equivalent to the first week post-hatching. Second, the 19.5 S form did not develop (even after several weeks) in cultures of E8, E11 and E15 ganglia, nor was this form (which was removed during dissociation of the ganglia) regenerated in cultures of E19 ganglia. Such findings suggest that the pattern of development of AChE and its multiple forms in chick sympathetic neurons is in part intrinsically programmed into these cells at an early stage of development as well as in part regulated by extrinsic signals that these cells receive from their chemical and cellular environment.

Effect of cholinesterase inhibitors on differentiation of cultured sympathicoblasts

The 2 cholinesterase inhibitors, eserine and BW 284C 51, inhibited the nerve fibre growth and differentiation of immature sympatheticoblasts at low concentrations. The effect was nerve cell-specific and appeared in the course of the in vitro development, indicating that cholinesterases might play an important role in the early differentiation of sympathicoblasts.

A correlative histofluorescence and light microscopic study of the formation of the sympathetic trunks in chick embryos

The appearance and development of the primary and secondary sympathetic trunks in staged chick embryos was studied using the Falck-Owman histochemical method for the demonstration of primary monoamines. The earliest appearance of catecholamine (stage 20) was in individual fluorescent cells located in the region of the dorsal root ganglia about two stages prior to the formation of primary trunk aggregates. These cells are believed to be sympathetic precursor cells and correspond to formaldehyde-induced fluorescent cells observed in recent explantation experiments. Aggregates of fluorescent cells had formed bilaterally dorsolateral to the aorta at stage 22. These aggregates became continuous to form primary trunks by stage 24. The secondary sympathetic trunks were first seen in stage 25 and appeared to form at least partially by dorsal migration of cells from the primary trunks. Fluorescent cell processes were first observed at this stage. Secondary trunk formation was essentially complete by stage 28, and the primary trunks had become small and discontinuous. Definite rami communicantes could be observed by the early part of stage 28 in silver preparations. The significance of the development of two successive trunks in avians is discussed.

Preparation of pure neuronal and non-neuronal cultures from embryonic chick sympathetic ganglia: a new method based on both differential cell adhesiveness and the formation of homotypic neuronal aggregates

A new method has been developed for the preparation of essentially pure primary cultures of neurons and non-neuronal cells from 11-day embryonic chick sympathetic ganglia. This method utilizes (1) differences in cell-to-substrate adhesiveness between neurons and non-neuronal cells and (2) the capacity of neurons to form homotypic aggragates. The maximum difference in adhesiveness between neuronal and non-neuronal cells occurred when the ganglia were dissociated with trypsin following collection in a salt solution lacking divalent cations. This difference allowed the preparation of highly purified non-neuronal cultures and 85-90% pure neuronal cultures. Intermittent agitation during the period of cell separation markedly increased the purity of the neuronal cultures by (1) inhibiting neuronal but not non-neuronal cell attachment and (2) facilitating the formation of homotypic neuronal aggregates in the supernatant. Neuronal and non-neuronal cultures prepared under these conditions were more than 99% pure on the basis of both morphological and biochemical analyses. Both cell types exhibited attachment efficiencies greater than 95% and have been maintained for several weeks in vitro. Thus, completely isolated neuronal and non-neuronal cultures can be prepared and maintained for prolonged periods in the absence of cells of the other type.

Binding of alpha-bungarotoxin to chick sympathetic ganglia: properties of the receptor and its rate of appearance during developement

Studies were carried out on the binding of [125I]alpha-bungarotoxin (alphaBT) to membrane fragments of chick sympathetic ganglia. Specific binding of toxin was saturable with a KD of 1.1 nM. The rates of association and dissociation of the toxin from ganglionic membranes were 4.3 X 10(4) M-1 sec-1 and 4.6 X 10(-5) sec-1 (t 1/2 = 4.2 h). respectively. Binding was inhibited (by up to 95%) by low concentrations of nicotinic, but not by a muscarinic cholinergic ligand. The properties of the ganglionic binding site for alphaBT were consistent with its being a nicotinic acetylcholine receptor. The development of toxin receptors in chick ganglia was also studied. From days 7 to 11 in ovo, few receptors were present; from days 12 to 20 in ovo, there was a 10-fold increase in receptor number per ganglion; from hatching to maturity, the receptor number per ganglion slowly increased and reached a maximum of 14 fmoles. The ontogeny of receptors for alphaBT in sympathetic ganglia appears to correlate with the cytological maturation and innervation of the principal neurons.

Developmental variations of tyrosine hydroxylase and acetylcholinesterase in embryonic and post-hatching chicken sympathetic ganglia

The developmental variations of tyrosine hydroxylase (TH) and of acetylcholinesterase (AChE) were studied in embryonic and post-hatching chicken sympathetic ganglia. Different levels of TH activity were found in two different flocks of White Leghorn chicken, which are probably dependent on genetic differences. These enzymatic differences, however, do not become apparent before hatching and may indicate a combined effect of genetic variation and functional demands. During the period of incubation, TH activity is characterized by a pronounced and steady increase from the twelfth day of incubation up to day 2 after hatching. This corresponds to a period of intense maturation of the sympathetic neuron. In the period following hatching, the 'fourth day fall phenomenon' previously described by us for DOPA decarboxylase (DDC), dopamine-beta-hydroxylase (DBH), and monoamine oxidase (MAO) is not seen in the TH curve. Instead, TH activity tends to remain constant between days 2 and 14 after hatching (ah). Both ganglionic protein and weight remain constant in this period, indicating a phase of general pause in protein synthesis. AChE activity increases steadily from the eighth until the twenty-first day of incubation. A sudden and significant drop in AChE activity was found at day 2 ah followed by a period of rapid increase at day 3 ah and a levelling of activity up to day 30 ah. Comparing the present variations to those observed in our previous studies on DBH, a temporal relationship between TH and DBH activity is observed during the phases of synaptogenesis and maturation but not during the phase of intense functional activity. Our results strongly suggest that before hatching in chick embryo sympathetic ganglia, the cholinergic presynaptic terminals play a role in regulating the development of the adrenergic neurons. In the period following hatching, however, the DBH and TH levels in cell bodies seem to be principally regulated by the functional activity. This results in depletion of DBH, but not TH, through liberation along with the neurotransmitter at the periphery. Depletion of DBH at the terminals may result in increased transport and thereby depletion in the cell body. This mechanism is probably responsible for the difference in the profiles of activity of DBH and TH in the cell bodies observed in the first week after hatching.

Differentiation of sympathicoblasts in cultures of chick ganglia: light and electron microscopic, fluorescence and enzyme histochemical observations

Immature sympathetic ganglia prepared from 5 1/2-or 6-day-old chick embryos were cultured up to one month. The in vitro development was followed by phase microscopy, electron microscopy and using histochemistry for catecholamines, monoamine oxidase and cholinesterases. During the first week of culture extensive plexuses of nerve fibres were formed between and around the clusters of nerve cells. Mature-looking neurons were observed in the cultures by phase microscopy after three weeks, at which age the mean diameter of the perikarya was more than doubled. Varying catecholamine fluorescence was observed in the perikarya during the entire culture period. The nerve fibres showed usually only weak fluorescence, but, in the older cultures, bright varicosities were regularly found in the fibres. Monoamine oxidase activity was demonstrated already at three days of culture and the reaction was maintained positive. Weak or moderate acetyl-cholinesterase activity was demonstrated in the sympathicoblasts and young sympathetic neurons and their processes. The axolemma showed acetylcholinesterase activity also around the nerve terminals containing small dense cored vesicles. Reactions for the non-specific cholinesterases were negative. Electron microscopy of the 30-day-old cultures revealed that the clusters of nerve cells consisted of mature sympathetic neurons, which contained large (60-200 nm) and small (35-60 nm) granular catecholamine-storing vesicles. Glial cells were almost totally lacking. Large numbers of nerve terminals containing both large and small granular vesicles were observed in the clusters, often in synaptic contact with the sympathetic neurons. It is concluded that the primitive sympathicoblasts are, in favourable conditions, capable of differentiation in culture up to mature sympathetic neurons.

Neuronal control of neurotransmitters biosynthesis during development

Studies on neuronal control mechanisms of neurotransmitters biosynthesis during the development of peripheral and central autonomic synapses are reviewed. Particular emphasis is placed on investigations of developing peripheral sympathetic ganglia and brain in chick embryo and chick. Studies on the development of autonomic neurons and synapses under different pharmacological conditions are reported. Principally the effect of a) the administration of drugs and precursors such as L-dopa, 3H-dopa, 6-OH dopa; b) the prenatal administration of reserpine; c) the blockade of cholinergic receptors; d) the nerve growth factor (NGF) is analyzed. Results of developmental studies on chick ciliary ganglia are summarized. The review particulary underlines the importance of combining the use of sensitive microchemical methods to pharmacological tools in exploring the development of regulatory mechanisms at the cellular level.

Effects of a snake alpha-neurotoxin on the development of innervated skeletal muscles in chick embryo

The evolution of the cholinergic (nicotinic) receptor in chick muscles is monitored during embryonic development with a tritiated alpha-neurotoxin from Naja nigricollis and compared with the appearance of acetylcholinesterase. The specific activity of these two proteins reaches a maximum around the 12th day of incubation. By contrast, choline acetyltransferase reaches an early maximum of specific activity around the 7th day of development, and later continuously increases until hatching. Injection of alpha-toxin in the yolk sac at early stages of development causes an atrophy of skeletal and extrinsic ocular-muscles and of their innervation. In 16-day embryos treated by the alpha-toxin, the endplates revealed by the Koelle reaction are almost completely absent. The total content and specific activities of acetylcholinesterase and choline acetyltransferase in atrophic muscles are markedly reduced.