Cerebral arterial innervation: II. Development of calcitonin-gene-related peptide and norepinephrine in the rat

The pre- and postnatal development of trigeminal calcitonin-gene-related peptide (CGRP)- and sympathetic norepinephrine (NE)-containing nerves supplying the cerebral arteries was studied with immunohistochemistry in rats. At 18-19 days in utero (E 18-19), CGRP fibers were present only as one or two longitudinal bundles zigzagging along the anterior cerebral artery and anterior communicating artery. Growth-cone-like swellings were found at the terminals of individual fibers. In contrast, at this same prenatal age NE fibers were present as a meshwork on all cerebral arteries. The density of NE fibers was higher in the rostral than in the caudal parts of the circle of Willis; growth cones were present on individual fibers at the middle segment of the basilar artery and distal parts of major cerebral arteries. At postnatal day 1-2 (PND 1-2; date of birth = PND 1), the outgrowth of CGRP axons extended along the walls of the middle cerebral and internal carotid arteries. These axons were relatively straight and unbranched. At the same time, NE fibers increased in number and density and continued to form the meshwork pattern on all cerebral arteries. At the end of the first postnatal week, all the longitudinal NE bundles on the rostral part of the circle of Willis began to form circular arborizations. At the end of the second postnatal week, the pattern of NE innervation had completely changed, consisting almost entirely of circumferential rather than tangential fibers. Beginning in the first postnatal week, CGRP fibers increased greatly in number and density and began to form a meshwork pattern. At the second postnatal week, the pattern of CGRP innervation, compared to the pattern at fetal and neonatal stages, had changed significantly, consisting predominantly of a meshwork pattern. By 4 weeks after birth, both the NE and CGRP fiber systems achieved adult densities and patterns. The present results demonstrate the following: 1) Both sympathetic-NE and trigeminal-CGRP innervation of cerebral arteries begin in utero; the NE system innervates corresponding parts of the vessels earlier than the CGRP system. 2) Both NE and CGRP fibers are more dense in the rostral than in the caudal segments of the circle of Willis; this rostrocaudal gradient is expressed in both density and pattern by the earliest fibers of both neurochemical systems and is maintained throughout all developmental stages.(ABSTRACT TRUNCATED AT 400 WORDS)

Anatomic evidence for coexistence of cholinergic and adrenergic neurons in the developing human intestine: new aspects in the pathogenesis of developmental neuronal abnormalities

In order to interpret the interrelation of cholinergic and adrenergic myenteric neural elements in the developing human, histochemical methods were used to demonstrate cholinergic and adrenergic activity independently in consecutive cryostat sections of the esophagus, ileocecal region, and colon of fetuses of 9 to 22 weeks ovulation age. At least some of the neural cells remained plastic, with respect to their transmitter choice, and showed both cholinergic and adrenergic function. These cells were shown to be present first in the ileocecal region (11 weeks) then in the esophagus (12 weeks) and lastly in the colon (14 weeks). Our findings support the hypothesis of a dual gradient of maturation of enteric neurons. The choice of transmitters is influenced by a "microenvironmental" factor, which may also arrest the maturation or cause the death of neurons.

A bipotential neuroendocrine precursor whose choice of cell fate is determined by NGF and glucocorticoids

Adrenal medullary endocrine (chromaffin) cells and sympathetic neurons both derive from the neural crest. We have found that the embryonic adrenal medulla and sympathetic ganglia are both initially populated by precursors expressing neural-specific genes. By birth, however, the medulla consists largely of chromaffin cells. In primary culture, the medullary precursors have three developmental fates: in NGF they continue to mature into neurons and survive, whereas in glucocorticoid they either extinguish their neuronal properties and exhibit an endocrine phenotype, or else continue to develop into neurons but then die. These data suggest that, in vivo, the adrenal medulla develops through both the glucocorticoid-induced differentiation of bipotential progenitors and the degeneration of committed neuronal precursors, which have migrated into the gland.

The effect of GM1 ganglioside on coerulospinal, noradrenergic, adult neurons and on fetal monoaminergic neurons transplanted into the transected spinal cord of the adult rat

GM1 ganglioside, thyroxine and hydrocortisone were tested for their ability to improve the survival and growth of fetal locus coeruleus noradrenergic neurons in the transected, adult spinal cord. GM1 alone was also tested for its effect on fetal mesencephalic dopaminergic neurons implanted into a small dorsolateral cavity at the L2 region of the cord previously transected at the T9-T10 region. None of the substances tested had any measurable effect on either of the fetal implants. However, in the GM1- and thyroxine-treated animals the somatic dendrites of the axotomized, noradrenergic, coerulospinal neurons appeared more robust, and more intensely fluorescent, compared to their appropriate controls. GM1 also caused a pronounced sprouting of the axotomized monoaminergic (catecholaminergic and serotonergic) fibres in the rostral region of the cord adjacent to the transection site. All of the mesencephalic dopaminergic implants survived in both the GM1-treated animals and their saline-injected controls. However, their development was apparently not influenced by GM1. The results indicate that GM1 and thyroxine can enhance those aspects of the reactive mechanisms of mature, axotomized, noradrenergic coerulospinal neurons that promote their regeneration. As such, GM1 could become a useful tool in current attempts to foster the regeneration of damaged monoaminergic neurons in the mammalian CNS.

Developmental regulation of phenylethanolamine N-methyl transferase in avian sympathetic nerves

The presence of the catecholamine synthetic enzyme, phenylethanolamine N-methyl transferase (PNMT), has been detected in the expansor secundariorum, a smooth muscle of the avian wing. The concentration of the enzyme was estimated over a 10-week time course from 17 days incubation to 9 weeks posthatch and found to increase rapidly up until hatch in parallel with dopamine beta-hydroxylase activity, but then to fall precipitously to very low levels. The time course of the initial increase in activity corresponds to the presence of ingrowing sympathetic nerve fibres, and denervation of the expansor results in loss of greater than 80% of the PNMT activity. It is concluded that during the period of innervation the growing nerves contain the enzyme PNMT and therefore have the capacity to synthesize adrenaline, but that shortly after innervation is complete the capacity to synthesize adrenaline is lost. Several alternate mechanisms are proposed to explain the observations.

[Cholinergic and adrenergic innervation of human intracerebral arteries in ontogenesis]

The intracerebral branches of the anterior, medial and posterior cerebral arteries in the cerebral tissue sections or revealed by means of the preparation method have been studied in cortical parts of the acoustic, optic and motor analyzers at various age periods (from the second half of pregnancy up to 86 years of age). On the intracranial arteries of all the age groups, the adrenergic and cholinergic fibers are revealed in the radial arteries and their large branches. Differences in the maturation rate and in involution of neural conductors have been stated between the cholinergic (revealed by means of reactions for acetylcholinesterase) and adrenergic (reaction with glyoxylic acid) conductors.

The development of adrenergic innervation in some human foetal blood vessels

The development of adrenergic innervation was examined in saphenous and brachial veins, femoral, brachial and superficial temporal arteries from human foetuses of 7-19 weeks gestation. Fluorescence histochemical and electron microscopic techniques were used on transverse sections of the vessels. No specific adrenergic fluorescence was detected within any of the vessels before 11 weeks gestation, by which time the arteries showed specific adrenergic fluorescence. However, there was no evidence of adrenergic innervation of veins even at 19 weeks gestation. Incubation of the vessels with alpha-methylnoradrenaline did not lead to earlier detection of fluorescence. Electron microscopy showed that the adrenergic nerves found in the arteries were arranged as bundles of axons partially enclosed within Schwann cell processes, often lying close to capillaries in the outer regions of the tunica adventitia.

A histochemical study of the cholinergic and adrenergic innervation of the developing teeth and oral tissues in the mouse

The dental follicle and papilla are innervated at different stages of tooth development. The type of nerves innervating these structures at different stages was investigated using an enzymic method for acetylcholinesterase (AChE) and direct visualization for noradrenaline on fetal and neonatal stages up to 7 days after birth. Glandular and muscular tissue were positive for AChE in 17-day fetuses but no reaction was observed in the teeth or supporting tissues up to 7 days after birth. Noradrenaline was detected in blood vessels at 18 days and in glandular tissue at birth but was not observed in the teeth within the period covered. It is unlikely that AChE plays any role in the innervation of teeth; the adrenergic nerve supply probably develops later.

Autonomic nerves in the mammalian choroid plexus and their influence on the formation of cerebrospinal fluid

The choroid plexuses of all ventricles receive a well-developed adrenergic and cholinergic innervation reaching both the secretory epithelium and the vascular smooth muscle cells. Also peptidergic nerves, containing vasoactive intestinal polypeptide, are present but primarily associated only with the vascular bed. A sympathetic inhibitory effect on the plexus epithelium has been indicated in determinations of carbonic anhydrase activity and by studies of various aspects of active transport in isolated plexus tissue. Pharmacological analysis in vitro has shown the choroidal arteries to possess both vasoconstrictory alpha-adrenergic and vasodilatory beta-adrenergic receptors. Electrical stimulation of the sympathetic nerves, which originate in the superior cervical ganglia, induces as much as 30% reduction in the net rate of cerebrospinal fluid (CSF) production, while sympathectomy results in a pronounced increase, about 30% above control, in the CSF formation. There is strong reason to believe that the choroid plexus is under the influence of a considerable sympathetic inhibitory tone under steady-state conditions. From pharmacological and biochemical experiments it is suggested that the sympathomimetic reduction in the rate of CSF formation is the result of a combined beta-receptor-mediated inhibition of the secretion from the plexus epithelium and a reduced blood flow in the choroid plexus tissue resulting from stimulation of the vascular alpha-receptors. The choroid plexus probably also represents an important inactivation site and gate mechanism for sympathomimetic amines, as evidenced by considerable local activity of catechol-O-methyl transferase and monoamine oxidase, primarily type B. The CSF production rate is also reduced by cholinomimetic agents, suggesting the presence of muscarinic-type cholinergic receptors in the choroid plexus.

Innervation of rabbit fetal lungs

Nerve fibers, autonomic ganglia, and neuroepithelial bodies of the lungs of rabbit fetuses, 17 to 31 days gestational age, were studied with neurohistological techniques including silver impregnation, acetylcholinesterase histochemistry, and glyoxylic-acid-induced histofluorescence for monoamines. The silver impregnation method showed that nerve fibers and ganglia accompanied the bronchi and large pulmonary blood vessels to enter the developing lungs by the 17th day of gestation. Cholinergic and adrenergic nerves began to appear in the walls of the bronchi on the 21st day. The developing pulmonary arteries had accompanying adrenergic nerves on the 25th day. Acetylcholinesterase-positive parasympathetic ganglia were seen on the 27th day. Silver-impregnated nerve fibers in the developing alveolar walls and pleura were found on the 25th day. Neuroepithelial bodies and specialized single cells which were argyrophilic, acetylcholinesterase-positive, and fluorescent could be demonstrated in 19--21-day-old and older fetuses; and some of these structures were innervated by sensory and autonomic motor fibers. These observations indicated that nervous tissue and neuroepithelial bodies appeared in the lungs during the glandular stage of the lung development and that differentiation of adrenergic and cholinergic nerves began in the late glandular stage.

Selective loss of noradrenergic phenotypic characters in neuroblasts of the rat embryo

To define the fate of embryonic neuroblasts in rat gut, which transiently express several noradrenergic traits, we investigated the high-affinity uptake of norepinephrine. At 12.5 days of gestation, these cells exhibited immunoreactivity to tyrosine hydroxylase [tyrosine 3-monoxygenase; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2] and endogenous catecholamine fluorescence. However, by 13.5 days these noradrenergic neurotransmitter phenotypic characters essentially disappeared. In contrast, norepinephrine uptake, which was also apparent at 12.5 days, persisted at least through 17.5 days. These observations indicate that norepinephrine uptake develops as an additional noradrenergic characteristic in these cells and persists after the disappearance of other noradrenergic traits. Consequently, neurotransmitter phenotypic characters may be transiently displayed during normal development in vivo.

Chronic guanethidine treatment of female rats including effects on the fetus

Adult virgin female rats were injected daily with low doses (5 or 10 mg/kg) or a high dose (30 mg/kg) of guanethidine for 12 or 18 weeks respectively. 'Short' and 'long' noradrenergic neurones were unaffected by low doeses. This contrasts markedly to earlier findings in male rats in which long-term damage of 'short' noradrenergic neurones occurred, and indicates a basic difference between 'short' noradrenergic neurones in male and female rats. Widespread degeneration of both types of neurones followed treatment with high doses and little reinnervation was observed 8 weeks after cessation of treatment. Fertility, pregnancy and litter size were apparently unaffected. Some teratogenic effects were observed in the offspring of female rats treated with guanethidine (10 or 25 mg/kg/day) before and throughout pregnancy. However, these effects had largely disappeared by the time the offspring were 10 weeks old. Since noradrenergic neurones of newborn rats are particularly sensitive to damage by guanethidine it would appear that either very little guanethidine crosses the placental barrier or that noradrenergic neurones are not susceptible during prenatal development to the cytotoxic effects of guanethidine.

Sites of transition between functional systemic and cerebral arteries of rabbits occur at embryological junctional sites

The vascular smooth muscle of cerebral blood vessels is relatively insensitive to sympathomimetic stimulation compared with muscle from systemic vessels. The transition in the vertebral artery occurs just rostral to the emergence of that artery from the foramen of the lateral process of the atlas and in the internal carotid artery just before it enters the carotid canal. These sites in the adult correspond to embryological junctions between segments of the vertebral and internal carotid arteries derived from the primitive dorsal aortas and their branches with vessels originating locally from the bilateral longitudinal neural arteries. Topographic patterns of vascular properties may in some cases be explained by the different sites of origin of their primordial mesodermal cells.

Methylazoxymethanol treatment of fetal rats results in abnormally dense noradrenergic innervation of neocortex

A single injection of methylazoxymethanol in pregnant rats at 15 days of gestation results in severe cortical atrophy in the offspring. In the adult offspring, the neurochemical markers for the cortical gamma-aminobutyric acid-containing neurons are severely reduced, whereas the noradrenergic markers are minimally altered. Immunohistofluorescence microscopy demonstrates a marked increase in the density of noradrenergic axons which have an abnormal pattern of distribution in the atrophic cortex. The results suggest that the central noradrenergic neurons determine the number of axons to be formed early in brain development, but local factors in the terminal field regulate the ultimate distribution of the noradrenergic axons.

Pre- and postnatal development of catecholamine-containing and cholinesterase-positive nerves of the rat cornea and iris

Glyoxylic acid-induced fluorescence technique and a copper thiocholine method were used to investigate the ontogenesis of the catecholamine-containing and cholinesterase-positive nerves of the rat iris and cornea. First fluorescent nerve fibres appeared in the iris on the 18th gestation day and in the cornea on the 19th day. A rapid increase in the density of the adrenergic nerve fibres of the iris continued to the age of three weeks, while the number of such fibres were small in the cornea. Acetylcholinesterase-positive fibres appeared both in the cornea and in the iris on the 19th gestation day. Their density increased more rapidly in the iris, especially in the sphincter muscle, than in the cornea. Non-specific cholinesterase activity was localized in the Schwann cells and the reaction was more intense during development than in the nerves of the cornea of adult rats.

Data regarding the structural feature of nervous elements in the bile ducts during intrauterine life

The nervous elements of the extrahepatic bile ducts were studied on serial sections prepared from rabbit and human embryos and foetuses, using silver impregnation techniques. In the gallbladder of rabbit embryos and foetuses, the nervous elements are absent, whereas the bile ducts possess a dense parasympathetic vegetative plexus. In human embryos, the muscular layers and submucosa of the gallbladder and bile ducts have well developed parasympathetic plexuses and a sympathetic subserous plexus, without nerve cells, respectively. The histotopical identification of nervous elements in the bile ducts allows the distinction of parasympathetic plexuses from the sympathetic ones.

Adrenergic innervation of the mouse heart revealed at an early stage using alpha-methylnoradrenaline

The development of noradrenergic innervation was studied in the mouse heart using fluorescence histochemistry. Following incubation of hearts with alpha-methylnoradrenaline fluorescent nerve fibres were seen as early as 13 days in utero. It is suggested that the neuronal uptake mechanism for noradrenaline is functional at an early stage.