The neuronal and extra-neuronal localisations of biogenic amines in the cervical region of the domestic fowl (Gallus gallus domesticus L.)

Carotid labyrinth of amphibians

The amphibian carotid labyrinth is a characteristic maze-like vascular expansion at the bifurcation of the common carotid artery into the internal and external carotid arteries. The carotid labyrinths of anurans are spherical and those of urodeles are oblong. In the intervascular stroma of both anuran and urodelan carotid labyrinths, the glomus cells (type I cells, chief cells) are distributed singly or in clusters between connective tissue cells and smooth muscle cells. In fluorescence histochemistry, the glomus cells emit intense fluorescence for biogenic monoamines. In fine structure, the glomus cells are characterized by a number of dense-cored vesicles in their cytoplasm. The glomus cells have long, thin cytoplasmic processes, some of which are closely associated with smooth muscle cells, endothelial cells, and pericytes. Afferent, efferent, and reciprocal synapses are found on the glomus cells. The morphogenesis of the carotid labyrinth starts in the larvae at the point where the carotid arch descends to the internal gills. Through the early stages of larval development, the slightly expanded region of the external carotid artery becomes closely connected with the carotid arch. By the end of the foot stage, the expanded region becomes globular, and at the final stage of metamorphosis the carotid labyrinth is close to its adult form. In fine structure, the glomus cells appear as early as the initial stage of larval development. At the middle stages of development, the number of dense-cored vesicles increases remarkably. Distinct afferent synapses are found in juveniles, although efferent synapses can be seen during metamorphosis. The carotid labyrinth is innervated by nerve fibers containing several kinds of regulatory neuropeptides. Double-immunolabeling in combination with a multiple dye filter system demonstrates the coexistence of two different neuropeptides. The amphibian carotid labyrinth has been electrophysiologically confirmed to have arterial chemo- and baroreceptor functions analogous to those of the mammalian carotid body and carotid sinus. The ultrastructural characteristics of the glomus cells during and after metamorphosis suggest that the glomus cells contribute to the chemoreception after metamorphosis. The three-dimensional fine structure of vascular corrosion casts suggests that the amphibian carotid labyrinth has the appropriate architecture for controlling vascular tone and the findings throughout metamorphosis reveal that the vascular regulatory function begins at an early stage of metamorphosis. In addition, immunohistochemical studies suggest that the vascular regulation in the carotid labyrinth is under peptidergic innervation. Thus, the multiple functions of the carotid labyrinth underline the importance of this relatively small organ for maintenance of homeostasis and appropriate blood supply to the cephalic region.

Carotid body and glomus cells distributed in the wall of the common carotid artery in the bird

In the bird the carotid body is located between the distal (nodose) ganglion of the vagus nerve and the recurrent laryngeal nerve at the beginning of the common carotid artery, that is, the organ is located at the cervicothoracic border. The chicken carotid body receives numerous branches from the vagus and the recurrent laryngeal nerves. In addition, dense networks of the peptidergic nerve fibers immunoreactive for substance P, calcitonin gene-related peptide (CGRP), vasoactive intestinal peptide (VIP), galanin, and neuropeptide Y (NPY) are distributed in and around the carotid body parenchyma. The substance P- and CGRP-immunoreactive fibers are derived from both the superior and inferior ganglia of the vagus nerve. The VIP-, galanin-, and NPY-immunoreactive fibers originate from the 14th cervical ganglion of the sympathetic trunk. The endocrine organs including the thyroid gland, parathyroid glands, carotid body, and ultimobranchial gland are situated as a continuous series along the common carotid artery. The organs are supplied with arteries arising as one trunk from the common carotid artery. Glomus cells are widely distributed not only in the carotid body but also in the wall of the common carotid artery and around the common trunk and its branches. The glomus cells of the chicken carotid body exhibit intense immunoreactivity for serotonin, tyrosine hydroxylase, and chromogranin A. The cells located in the wall of the common carotid artery further express NPY mRNA and peptide. In the chickens exposed to isocapnic hypoxia for 35 days, 3-4-fold increase of the carotid body volume is induced and the carotid body glomus cells show enhanced synthetic and secretory activities. On the other hand, the cells in the wall of the common carotid artery display little changes after the long-term hypoxia, having different functions from the carotid body. The carotid body rudiment is formed in the lateral wall of the third branchial artery. The neural cells immunoreactive for TuJ1, PGP 9.5, and HNK-1, which are continuous with the inferior vagal (nodose) ganglion, first surround and then invade both the carotid body rudiment and the other portions of the third branchial artery, becoming glomus cells.

Innervation of the chicken parathyroid glands: immunohistochemical study with the TuJ1, galanin, VIP, substance P, CGRP and tyrosine hydroxylase antibodies

The innervation of the chicken parathyroid glands was studied by immunohistochemistry using various antibodies. The parathyroid glands, as well as the carotid body and ultimobranchial gland, received branches originating from the vagus nerve. Numerous nerve fibers immunolabeled with the monoclonal antibody (TuJ1) against neuron-specific class III beta-tubulin isotype were found in the connective tissue capsule and septa penetrating into the parathyroid parenchyma. They were also prominent in the wall of blood vessels. Peptidergic nerve fibers immunoreactive for galanin, vasoactive intestinal polypeptide (VIP), substance P and calcitonin gene-related peptide (CGRP) were densely distributed in the capsule, septa and blood vessel walls of the parathyroid glands. In addition, some TuJ1-, substance P- and CGRP-immunoreactive fibers were detected in close association with the parenchymal cells of parathyroid glands. Tyrosine hydroxylase-immunoreactive fibers were concentrated around blood vessels and also in connective tissue stroma.

Distribution of serotonin-immunoreactive cells around arteries arising from the common carotid artery in the chicken

By using an immunoperoxidase method with antiserotonin antiserum, the distribution of serotonin-immunoreactive cells in the carotid body region was investigated in chickens. The thyroid gland, cranial and caudal parathyroid glands, carotid body, and ultimobranchial gland of chickens were located along the common carotid artery as a continuous series and were supplied with branches arising from the artery. Almost all chief cells of the chick carotid bodies were immunoreactive for serotonin. Furthermore, numerous serotonin-immunoreactive cells were widely distributed in the adventitial connective tissue around those arteries that issued from the common carotid artery to supply each endocrine organ, i.e., the carotid body artery, the esophagotracheobronchial artery, the ascending esophageal artery, and the inferior thyroid artery. These arteries usually arose by one trunk from the lateral aspect of the middle portion of the common carotid artery. The serotonin cells were most numerous around the carotid body artery and were dispersed along the whole length of the artery. In addition, they were detected around the common trunk of each artery and the roots of the ascending esophageal artery, the inferior thyroid artery, and the esophagotracheobronchial artery. The serotonin cells were also distributed in the tunica media of the common carotid artery. In that place, they were concentrated around the origin of the common trunk of each artery and were scattered below the origin along the longitudinal axis and on the opposite side of the origin. The serotonin-immunoreactive cells distributed around and in the arteries may be involved in the control of blood flow and may have chemoreceptive properties.

Innervation of the serotonin-immunoreactive cells distributed in the wall of the common carotid artery and its branches in the chicken

In the chicken, serotonin-immunoreactive cells were widely distributed not only in the carotid body but also in the wall of the common carotid artery and around each artery arising from the common carotid artery. Almost all of the serotonin cells in the wall of the common carotid artery were intensely immunoreactive to the neuropeptide Y, met- and leu-enkephalin antisera, whereas in the carotid body only a few cells were immunoreactive to these antisera. Innervation of the serotonin cells in and around arteries of chickens was investigated by immunohistochemistry and electron microscopy, in comparison with that of the carotid body. The serotonin cell groups in and around arteries, as well as the carotid body, received numerous peptidergic nerve fibers. Calcitonin gene-related peptide (CGRP)- and substance P-immunoreactive varicose nerve fibers were densely distributed, and somatostatin-immunoreactive fibers were moderately distributed in the serotonin cell groups. Galanin- and vasoactive intestinal peptide (VIP)-immunoreactive fibers were sparsely distributed in the cell groups. By electron microscopy, the serotonin cells in and around arteries were characterized by the presence of numerous dense-cored vesicles, 70-220 nm in diameter. The granule-containing cells were in close association with numerous axons. Naked axons regarded axon terminals were frequently apposed on the granular cells. The axon terminals were usually long and often partly invested the granular cells. Numerous synaptic junctions were detected along the contact between the granular cells and axon terminals. Most of the synaptic junctions showed afferent morphology; the secretory granules were accumulated near and attached to the asymmetrical membrane thickenings. Thus, the serotonin cells in and around arteries, like the carotid body, constitute chemoreceptive tissue.

Distribution of CGRP-, somatostatin-, galanin-, VIP-, and substance P-immunoreactive nerve fibers in the chicken carotid body

An immunoperoxidase method was used to investigate and compare the distribution of neuropeptide-immunoreactive (ir) nerve fibers and neurofilament-ir fibers in chick carotid body. The vagus nerve and its branches were intensely immunoreactive with an antiserum against chick neurofilaments. The branches from the vagus and the recurrent laryngeal nerves anastomosed within the connective tissue encircling the carotid body, and then entered the organ to form a network of neurofilament-ir fibers. Immunoreactivities for CGRP, somatostatin, galanin, VIP and substance P were found in the carotid body; they were located within varicose fibers. Immunoreactivity for each peptide was discretely and characteristically distributed. Dense networks of varicose CGRP-ir nerve fibers were found throughout the carotid body in close proximity to clusters of carotid body cells and to blood vessels. Substance P-ir fibers were distributed similarly to CGRP-ir fibers. Somatostatin-ir fibers appeared as patches distributed around chief cells. Numerous galanin- and VIP-ir nerve fibers were observed in the connective tissue surrounding the carotid body, but they occurred in only moderate densities in the parenchyma.

Mediation and mechanisms of the hypotensive effect of L-dopa in the sea-gull: Larus argentatus

We have investigated the mediation of the hypotensive action of L-DOPA after peripheral DOPA decarboxylase (DC) inhibition in the sea-gull, Larus argentatus. Vagotomy prevented the bradycardia and hypotension occurring after L-DOPA in birds pretreated with an inhibitor of peripheral DC. L-DOPA alone, given to intact birds, resulted in a slight increase in blood pressure (BP), accompanied by a tendency to bradycardia. Spinal transection in combination with vagotomy reversed the bradycardia and reinforced the increase in BP seen in intact birds after L-DOPA. The dopamine receptor antagonist spiroperidol did not alter the hypotension and bradycardia after L-DOPA in birds pretreated with a peripherally acting DC inhibitor. Yohimbine antagonized the effects of L-DOPA, restoring the BP to near basal values within 5 min after i.v. injections, while prazosin had no such effect. The heart rate returned towards basal values after both yohimbine and prazosin. We conclude that L-DOPA elicits its hypotensive action in the sea-gull via activation of central alpha-adrenoceptors, which may belong to the alpha 2-subtype. The bradycardia may involve central activation of adrenoceptors of both the alpha 1- and alpha 2-types. The hypotension and bradycardia are mediated via vagal activation and probably also inhibition of sympathetic nervous output. The functional significance of sympathetic fibres running along with the vagus nerve is suggested.

Autonomic innervation of the ocular choroid membrane in the chicken: a fluorescence-histochemical and electron-microscopic study

The distribution pattern of adrenergic fibres innervating the ocular choroid membrane of the chicken was studied by means of fluorescence and electron microscopy. In addition, the origin of these fibres was investigated after superior cervical ganglionectomy. Adrenergic axons reach the choroid, partly forming the perivascular plexuses and partly running in the choroid nerves and the choroidal branches of the ciliary nerves. The axon terminals distribute to the smooth muscle cells of the arterial wall and to the extensive system of smooth muscle cells of the intervascular stroma. After unilateral ganglionectomy, fluorescent fibres almost completely disappeared, and degenerative changes could be observed in the terminal varicosities on both smooth muscle cell populations. These findings suggest that the adrenergic axons either originate from neurones within the ipsilateral superior cervical ganglion, or pass through this ganglion. The persistence of normal terminals in short- and long-term ganglionectomised animals shows that the vasal and intervascular muscle cells of the choroid membrane are provided with both an adrenergic and a cholinergic innervation.

Innervation of the parathyroid in the European starling (Sturnus vulgaris)

Anatomical studies were conducted to characterize the source, type, and distribution of parathyroid gland innervation in European starlings. Denervation experiments demonstrated that the parathyroid glands and adjacent carotid bodies are innervated by nerve fibers originating in the nodose ganglion of the vagus nerve. In the parathyroid parenchyma, these fibers terminate adjacent to chief cells or near vascular smooth muscle. Vagal fibers also form synapses with catecholamine-containing glomus cells of the carotid body. Blood parenchyma. These observations suggest that vagal innervation may influence parenchyma. These observations suggest that vagal innervation may influence parathyroid function in starlings either through direct chief cell innervation or through alteration of vascular perfusion. A neurohemal relationship also may exist between the carotid body and parathyroids.

Development of chick paravertebral sympathetic ganglia. I. Fine structure and correlative histofluorescence of catecholaminergic cells

Paravertebral sympathetic ganglia from the lumbosacral region of a series of chick embryos have been studied with electron microscopic methods, including aldehyde-osmium and permanganate fixatives, and correlative histofluorescence (Grillo et al, '74). Our purpose was to assess the differentiation of catecholaminergic (CA) cells during histogenesis in ovo. Examination of comparable adult ganglia as a baseline for differentiating stages confirmed that the principal sympathetic neuron (PN) is similar to those of other species in that it contains predominately small dense-cored vesicles (SDCV) preserved only by permanganate, and does not histofluoresce following the method of Grillo et al. ('74). At embryonic day (E) 7--8, when ganglia have just formed, areas fluorescing bright yellow-green are correlated with two types of cells: 1) Neuroblasts with vesicular nuclei and large dense-cored vesicles (LDCV) are common. As the neuroblasts grow and differentiate, LDCV move away from perikaryal cytoplasm into developing processes. Around E13-15, LDCV appear in the neuroblasts which continue to develop until they resemble miniature adult PN in late embryos and hatchlings. 2) Granule (GR) cells with clumped chromatin and sparse cytoplasm are clustered in te ganglionic periphery at E7-8, but are rare. The GR cells increase somewhat in size and numbers by E11, but retail essentially the same characteristics as at earlier stages. Neither bright fluorescence nor GR cells appear later than stages E13-15. These results are interpreted to mean that when chick sympathetic stem cells have migrated from the primary ganglia into the paravertebral ganglia, they give rise to two separate lines of CA cells, one of which is not maintained and subsequently disappears. The results are significant as a basis for understanding how a mixed population of CA cells might arise within sympathetic ganglia in situ.

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.