Quantitative prenatal growth of the cervical sympathetic trunk components in sheep (Ovis arise) during the foetal period.

BACKGROUND: Six liner measurements of constant cranial cervical ganglion (CCG), three inconstant main, first, second middle cervical ganglia (MG, MG1, MG2), and interganglionic branch (IGB) were taken to determine normal foetal growth rates and patterns of cervical sympathetic trunk (CST) components in different gestational ages. MATERIALS AND METHODS: Forty sheep foetuses of both sexes aged from 60 to 140 days were divided into four groups and 80 sides of foetuses were examined under a stereomicroscope using a digital calliper. RESULTS: Following findings were obtained: 1) There was no significant difference for the values between sex and body side among all age groups, although sex and laterality differences in CST length and laterality differences in IGB total length and MG1 width were found regardless of age groups. 2) Correlations between dimensions of CST components and crown-rump length (CRL) were always positive during foetal period and decreased with increasing foetal age. 3) The highest growth rate in CST components in foetal sheep took place in the youngest age group because of rapid growth rates in lengths of IGB and CCG. CONCLUSIONS: Based on these detailed findings, comparative prenatal growth rates and patterns of animal organs and body, embryological and histological data as well as neurovertebral relationships among cervical parts of sympathetic trunk, spinal cord, and vertebral column were discussed and compared with previous studies. Although allometric growth of CST in relation to CRL was constant between foetal sheep and pig, there were specific characteristics in prenatal growth of CST components in foetal sheep which were different from those of foetal pig. It seems that only growth pattern in length of CST in sheep during foetal period follows the same growth pattern of CRL, body weight, and length of cervical parts of spinal cord and vertebral column.

Anatomic study of the musculus longus capitis flap.

PURPOSE: To clearly delineate the anatomy of the musculus longus capitis, determine its clinical applications for reconstruction surgery, and provide a safer surgical method of developing the longus capitis muscle flap. METHODS: Anatomical investigations were performed in seven adult cadavers (five cadavers for gross anatomy and two for transparent specimen preparation) with respect to the location, morphology, arterial supply, and innervation of the musculus longus capitis, as well as its spatial relationship with the cervical sympathetic trunk, superior cervical ganglion, carotid sheath, and other surrounding structures. RESULTS: The musculus longus capitis is located anterior to the C1-6 vertebrae, segmentally supplied by branches of the ascending cervical artery, innervated by the C1-5 nerve, and spatially close to the cervical sympathetic trunk, superior cervical ganglion, and carotid sheath. These anatomic findings indicate that the development of a cranial or caudal pedicled longus capitis muscle flap is feasible. CONCLUSION: The musculus longus capitis can be developed into a cranial or caudal pedicled flap for repair of head and neck defects with negligible morbidity of the donor site.

A morphometric analysis of the superior cervical ganglion and its surrounding structures.

PURPOSE: The aim of this cadaveric study was to detect the superior cervical ganglion (SCG) in a topographic manner according to vertebrae and to determine the relationship between the vertebrae, mandibular angle and longus colli muscle through morphometric analysis. METHODS: The present study was performed on 40 SCG of 20 human cadavers (16 males, 4 females). The level of the SCG was determined based on the vertebrae. Ganglion length, width and thickness were detected. Distance to the adjacent vertebra, the mandibular angle and medial side of the longus colli muscle were measured. The results were evaluated statistically. RESULTS: The SCG existing in all cadavers was detected at the C2 vertebra level in 34 cadavers and at the C3 vertebra level in 6 cadavers. The average length, width and thickness of the SCG were 15.18 ± 1.12, 4.62 ± 0.25, and 1.83 ± 0.10 mm, respectively. No statistically significant difference was detected in terms of the distances between the ganglion and anterior tubercle of transverse processes of the vertebrae as well as the mandibular angle on either side. The distance between the SCG and the medial edge of the longus colli muscle was significantly greater on the left side in both men (p < 0.001) and women (p < 0.01). CONCLUSION: Recognition of morphometric characteristics of the SCG and detection of its location according to adjacent formations may serve as a guide for nerve blockage studies and help surgeons to preserve the ganglion in both anterior and anterolateral cervical approaches.

A heat map of superior cervical ganglion location relative to the common carotid artery bifurcation.

BACKGROUND: Determining the superior cervical ganglion's precise anatomical location for local anesthetic block, when stellate block is not feasible or is contraindicated, is difficult. METHODS: We dissected the superior cervical ganglion in 60 embalmed cadaveric specimens. Multiple regressions determined whether subject characteristics predicted the distance between the superior cervical ganglion and common carotid artery bifurcation and the superior cervical ganglion dimensional width and area. Based on these regressions, we mapped the ganglion and common carotid artery bifurcation using a pseudocolor statistical heat map. RESULTS: The statistical model significantly predicted the superior cervical ganglion-common carotid artery bifurcation distance (P = 0.01), and the superior cervical ganglion dimensional width (P = 0.02). CONCLUSION: This study determined that the common carotid artery bifurcation is a good landmark for localizing the superior cervical ganglion for anesthetic block.

Characterization of a cell bridge variant connecting the nodose and superior cervical ganglia in the mouse: Prevalence, anatomical features, and practical implications.

While autonomic ganglia have been extensively studied in rats instead of mice, there is renewed interest in the anatomy of the mouse autonomic nervous system. This study examined the prevalence and anatomical features of a cell bridge linking two autonomic ganglia of the neck, namely, the nodose ganglion (NG) and the superior cervical ganglion (SCG) in a cohort of C57BL/6J mice. We identified a cell bridge between the NG and the cranial pole of the SCG. This cell bridge was tubular shaped with an average length and width of 700 and 240 µm, respectively. The cell bridge was frequently unilateral and significantly more prevalent in the ganglionic masses from males (38%) than females (21%). On each of its extremities, it contained a mixed of vagal afferents and postganglionic sympathetic neurons. The two populations of neurons abruptly replaced each other in the middle of the cell bridge. We examined the mRNA expression for selected autonomic markers in samples of the NG with or without cell bridge. Our results indicated that the cell bridge was enriched in both markers of postganglionic sympathetic and vagal afferents neurons. Lastly, using FluoroGold microinjection into the NG, we found that the existence of a cell bridge may occasionally lead to the inadvertent contamination of the SCG. In summary, this study describes the anatomy of a cell bridge variant consisting of the fusion of the mouse NG and SCG. The practical implications of our observations are discussed with respect to studies of the mouse vagal afferents, an area of research of increasing popularity.

Neuroanatomy of cervical sympathetic trunk: a cadaveric study.

To reduce the risk of iatrogenic injury to sympathetic chain during anterior and anterolateral approaches to the cervical spine, its location has to be well defined and known by surgeons. We analyzed the course of sympathetic chain and its ganglia from C7 up to its entry into the cranial base and its relationship mainly with the longus colli (LC). Formalin fixed 20 human cadavers were dissected under operating microscope. Measurement of the dimensions of the ganglia, distance of the trunk to the LC, and the angles identifying the course of the chain were performed. Superior and inferior cervical/cervicothoracic ganglion were observed in all specimens, the middle cervical ganglion was observed in 48% of the specimens. The middle ganglion consisted of two ganglia in 10% of the dissected sides. Forty percent of the inferior cervical/cervicothoracic ganglion was at the C7 level, 25% was at C7-Th1 disc level, and 35% was at Th1 level. Vertebral ganglion was detected in only 8% of the specimens. The course of the sympathetic trunk converges medially descending from upper cervical levels to the lower levels. Anterior surgical approach to the cervical spine is a commonly used procedure. Although Horner syndrome due to sympathetic injury is not a common sequence of cervical operations, our findings support the current few reports on the subject and should be useful to any surgeon who operates in the cervical region to avoid this uncommon complication.

Potential structures that could be confused with a nonrecurrent inferior laryngeal nerve: an anatomic study.

OBJECTIVES: Study and detailed description of the large connections between the normally recurrent inferior laryngeal nerve (RILN) and the sympathetic trunk (ST) because these may be mistaken for a nonrecurrent inferior laryngeal nerve (NRILN). STUDY DESIGN: Morphologic study of adult human necks. METHODS: The necks of 144 human, adult, embalmed cadavers were examined (68 males, 76 females). They had been partially dissected by Cambridge preclinical medical students and then further dissected by the authors using magnification. The RILN, the ST, and their branches were identified and dissected. A total of 277 RILNs and STs (137 rights, 140 lefts) were observed. RESULTS: A communicating branch (CB) with a similar diameter to the RILN occurred between the ST and the RILN in 48 of the 277 (17.3%) dissections, 24 from the 137 (17.5%) right dissections, and 24 from the 140 (17%) left dissections. In 12 cases, the CB was bilateral. The CB arose from the superior cervical sympathetic ganglion in 3 of the 48 (6.25%) cases, from the middle ganglion in 10 (21%) cases, from the stellate ganglion in 3 (6.25%) cases, and from the ST in 32 (66.6%) cases. One (0.36%) NRILN associated with a right retro-esophageal subclavian artery (arteria lusoria) was found. CONCLUSIONS: 1) The CB between the RILN and the ST may have a diameter and course similar to an NRILN and may be confused with it. 2) The occurrence of the CB is greater than the occurrence referred to in previous studies. 3) The occurrence of the CB is similar by side and sex. 4) The CB may arise at different levels from the cervical ST and ganglia and end in the thyroid area. 5) Other neural elements may also be confused with an RILN, such as the cardiac nerves and the collateral branches from an NRILN to the trachea and esophagus.

Postganglionic horner syndrome in three patients with coincident middle ear infection.

Three patients developed a postganglionic Horner syndrome during the course of an ipsilateral uncomplicated middle ear infection. The mechanism may be an effect on the middle ear caroticotympanic sympathetic plexus, for which there is considerable anatomic and physiologic evidence. Why Horner syndrome does not occur more often after middle ear infection is a mystery.

The cranial cervical ganglion and its branches in the yak (Bos grunniens).

The heads and necks of 10 yaks were dissected to study the shape, location, arrangement, and branches of the cranial cervical ganglion. The ganglion was a greyish fusiform structure, mean length 19.72 mm, width 7.65 mm and depth 4.55 mm, located on the rostrolateral surface of the m. longus capitis. Approximately 25% of the ganglion was covered by the tympanic bulla, the rest by the m. stylohyoideus. The branches of the cranial cervical ganglion included the internal and external carotid nerves, sympathetic trunk and the branches connecting with the glossopharyngeal, vagus and hypoglossal nerves. In one animal the right cranial cervical ganglia was a greyish pyramidal structure 10 mm long, 8 mm wide and 5 mm thick but the left ganglion was similar to those found in the other specimens examined.

Age-related structural and neurochemical changes of the human superior cervical ganglion.

The aim of this study was to investigate age-related morphological and neurochemical changes in the human superior cervical ganglion (SCG). Thirty-seven superior sympathetic human cervical ganglia of young, adult, and aged subjects were examined using morphometric analysis, biotin-streptavidin immunohistochemistry for detecting neurofilament, myelin protein, protein gene product 9.5, nerve growth factor receptor p75 in sympathetic neurons and nerve fibers. Morphometric parameters of neurons (area, long and short axis, shape factor of the neuron body, nucleus, cytoplasm, and lipofuscin) were investigated in every sixth serial section of the ganglion. Seven hundred neurons with clearly visible nuclei were measured in each studied group. The present study showed that human SCG of older subjects had larger areas of neuron body, cytoplasm and nucleus, a lower shape factor, an increased amount of lipofuscin, and a greater number of large-size neurons, as compared to SCG obtained from young subjects. Neuronal cytoskeletal alterations manifested themselves through a decreased number of neurofilament-positive neurons were detected in old human SCG. The amount of myelinated fibers decreased with age, although the amount of myelinated fibers in the young and the adult subjects varied from few to a moderate number. PGP 9.5 immunoreactivity varied in different age groups. A marked reduction of nerve growth factor receptor p75 in old human sympathetic neurons was detected. In conclusion, the findings of this study confirm age-related morphological changes in the human SCG. Structural neuronal changes may influence the deterioration of neuronal functional capacity, neuronal plasticity, and regenerative characteristics.

The gross anatomy of the cranial cervical ganglion in the guinea pig (Cavia porcellus).

The right and left cranial cervical ganglia in the heads of 10 adult guinea pigs (5 male, 5 female) were dissected in detail. The cranial cervical ganglion (CCG) was located on the caudo-ventral aspect of the distal ganglion of the vagus nerve, and medial to the digastric and styloglossal muscles. It was present also ventral to the tympanic bulla, ventro-lateral to the longus capitis muscle, and between the ascending pharyngeal and the internal carotid arteries. The branches of the CCG included the internal and external carotid nerves, the jugular nerve and connecting branches to the pharynx, vagus, glossopharyngeal, accessory, cranial laryngeal, first and second cervical nerves, and vessels in the carotid body region. The number of nerves ramifying from the CCG of the guinea pig varied among cases. Compared to other species, there are also differences in the number of nerve branches and the course patterns. No sex differences are present as far as the guinea pig CCG is concerned.

Developmental Morphology and Topography of the Components of the Cervical Sympathetic Trunk in Sheep (Ovis aries) During the Fetal Period.

The objective of this study was to clarify the typical architecture and morphological variations of cervical sympathetic trunk (CST) in sheep during fetal period. Components of CST were examined on both sides of 40 male and female sheep fetuses aged from 60 to 140 days under a stereomicroscope. Skeletotopy and frequency of presence of cranial cervical ganglion (CCG), syntopy of cervical ganglia, and composition and topography of vagosympathetic trunk were consistent among specimens whereas the shape of cervical ganglia, the skeletotopy and number of three middle cervical ganglia (MG), and the frequency of communicating branches of CCG to the first cervical spinal nerve exhibited differences during fetal period. A reduction in the number of MG and the caudal movement of main MG were noted by increasing fetal age. Based on these detailed findings, comparative and developmental anatomy and evolutionary changes are discussed and compared with previous studies. The number of MG, skeletotopy of CCG and main MG, the number and range of communicating branches of CCG to spinal nerves, and the association of vagus and sympathetic nerves in fetal sheep were fundamentally different from those of mostly reported species. These results suggest that data obtained from CST of fetal sheep are significantly different from those obtained from humans, and it is problematic to apply them to humans because of the more cranial position of CCG, very narrow contribution of CCG to spinal nerve, absence of the vertebral ganglion, existence of multiple MG, and no communicating branches from MG to spinal nerves. Anat Rec, 300:2250-2262, 2017. © 2017 Wiley Periodicals, Inc.

Size and number of binucleate and mononucleate superior cervical ganglion neurons in young capybaras.

The total number of neurons in the superior cervical ganglion (SCG) of adult capybaras is known from a previous study, where a marked occurrence of binucleate neurons (13%) was also noted. Here, distribution, number and fate of binucleate neurons were examined in younger, developing capybaras, aged 3 months. The mean neuronal cross-sectional area was 575.2 microm2 for mononucleate neurons and 806.8 microm2 in binucleate neurons. Frequency of binucleate neurons was about 36%. The mean ganglion volume was about 190 mm3 in young capybaras and the mean neuronal density was about 9,517 neurons/mm3. The total number of neurons per ganglion was about 1.81 mill. Neuronal cell bodies constituted 22.5% of the ganglion volume and the average neuronal volume was 23,600 microm3. By comparing the present data with those previously published the conclusion is drawn that the maturation period was characterized by the following points: a 26% remarkable decrease in neuronal density which was significant (P < 0.05) and a significant 16% (P < 0.05) decrease in the total number of SCG neurons accompanied by a 23% decrease in the total number of SCG binucleate neurons.

Network of the sympathetic nervous system: focus on the input and output of the cervical sympathetic ganglion.

Unlike the thoracic and lumbar sympathetic nervous systems with paravertebral ganglions in individual spinal segments, the cervical sympathetic nervous system lacks segmental structures corresponding to the spinal segments and only three ganglions, namely the upper and middle cervical ganglions and the stellate ganglion, are present. Single axons have been observed in the ganglions using an anterograde-labeling method to analyze their expansion in order to investigate the relationship between the cervical sympathetic ganglions and the spinal cord in rats. Although segmental structures were not confirmed in the upper cervical ganglion, segmental structures were demonstrated in the stellate ganglion. Next, it was determined that some sympathetic preganglionic neurons, nitric oxide synthetase-positive preganglionic neurons, form dense nerve endings on the upper cervical ganglion neurons that project onto organs closely related to glandular secretion in the head and neck region. Finally, the relationship between the cell body size of upper cervical ganglion neurons and the size of the target was investigated for the three major salivary glands in rats and it was determined that no direct relationship was present.

Detailed Anatomy of the Cranial Cervical Ganglion in the Dromedary Camel (Camelus dromedarius).

The detailed morphology and topography of the cranial cervical ganglion (CCG) with its surrounding structures were studied in 10 sides of five heads of adult one-humped camel to determine its general arrangement as well as its differences and similarities to other animals. The following detailed descriptions were obtained: (1) the bilateral CCG was constantly present caudal to cranial base at the rostroventral border of the occipital condyle over the caudolateral part of nasopharynx; (2) the CCG was always in close relations medially with the longus capitis muscle, rostrolaterally with the internal carotid artery, and caudally with the vagus nerve; and (3) the branches of the CCG were the internal carotid and external carotid nerves, jugular nerve, cervical interganglionic branch, laryngopharyngeal branch, carotid sinus branch and communicating branches to the vagus, and first spinal nerves. In conclusion, there was no variation regarding topography of dromedary CCG among the specimens, in spite of typical variations in number, and mainly in origin of nerve branches ramifying from the CCG. In comparative anatomy aspect, the close constant relations, and presence of major nerves (internal/external carotid and jugular nerves) of dromedary CCG exhibited a typical reported animal's pattern. However, the shape, structures lateral to the CCG, the origin and course pattern of external carotid and jugular nerves, the number of the major nerves branches, the communicating branches of the CCG to the spinal and cranial nerves, and the separation of most rostral parts of vagosympathetic trunk of dromedary were different from those of most reported animals.

Immunohistochemical localization of tyrosine hydroxylase in corneal nerves.

The sympathetic innervation of the mammalian cornea is thought to play an important role in the regulation of epithelial ion transport, mitogenesis, and wound healing following corneal injuries. Anatomically, the three-dimensional organization and relative density of corneal sympathetic innervation in many species remains inadequately described. In the present study, the sympathetic innervation of five different mammals (guinea pig, rat, mouse, hamster, and human) was studied in corneas sectioned parallel to the main axis of fiber orientation by labeling the fibers immunohistochemically with antiserum against tyrosine hydroxylase and an avidin-biotin-diaminobenzidine technique. The results showed that each species displayed a distinctive pattern and density of tyrosine hydroxylase immunoreactive (TH-IR) corneal innervation that was unique to that species. The overall level of TH-IR innervation was highest in the guinea pig, moderate in the human, hamster, and rat, and lowest in the mouse. In all species examined, TH-IR nerves were most numerous in the corneoscleral limbus where they either formed intimate associations with blood vessels or coursed through the connective tissue matrix apparently unrelated to vascular elements. Other TH-IR nerves entered the cornea proper in radially directed stromal nerve bundles to give rise to subepithelial plexuses of varying complexity. Occasional intraepithelial penetrations were observed in the guinea pig, human, and rat. Removal of the superior cervical ganglion resulted in the total loss of TH-IR staining from guinea pig and hamster corneas and in the substantial but incomplete loss of TH-IR staining from rat and mouse corneas, thus demonstrating their predominantly sympathetic origin. Combined sympathetic and sensory ocular denervation in the rat eliminated almost all corneal and limbal TH-IR immunostaining, thus suggesting a minor TH-IR sensory component in this species. In agreement with this conclusion, small numbers of TH-IR sensory neurons and an abundance of TH-IR fibers were observed in the trigeminal ganglia of the rat and guinea pig. Removal of the rat main ciliary ganglion resulted in the loss of additional TH-IR fibers from the chamber angle and iris, thereby confirming a partial parasympathetic contribution to the rat iridial TH-IR innervation. Following unilateral removal of the superior cervical ganglion in rats and guinea pigs, the contralateral cornea contained increased numbers of TH-IR nerves, suggesting an upregulation of tyrosine hydroxylase (TH) expression in some contralateral axons.(ABSTRACT TRUNCATED AT 400 WORDS)

The "false" nonrecurrent inferior laryngeal nerve.

BACKGROUND: Communicating branches between the cervical sympathetic system and the inferior laryngeal nerve (ILN) have been described. They usually originate from the middle cervical sympathetic ganglion (MCSG). These branches (sympathetic-inferior laryngeal anastomotic branch [SILAB]), usually thin, sometimes have the same diameter as the ILN. In this study we prospectively evaluated the frequency of this condition and its implications during surgical neck exploration. METHODS: From November 1998 to October 1999, 791 patients underwent surgical neck exploration, and 1253 ILNs were dissected: 656 on the right side (52.3%) and 597 on the left side (47.7%). RESULTS: On the right side, a nonrecurrent ILN was found in 3 cases (0.46%), and a large SILAB was found in 10 cases (1.5%). The SILAB originated from the superior cervical sympathetic ganglion in 2 cases and directly from the sympathetic trunk above the MCSG in 8 cases. No anomalous branch was found on the left side. CONCLUSIONS: The SILAB may originate not only from the MCSG but also from the superior cervical sympathetic ganglion or directly from the sympathetic trunk. When the SILAB is as large as the ILN, it could be mistaken for a nonrecurrent ILN. The awareness of this anatomic condition during neck dissection may help to avoid injuries of the genuine ILN running in the usual pathway.

The trajectory of the sympathetic nerve fibers to the rat cochlea as revealed by anterograde and retrograde WGA-HRP tracing.

Wheat germ agglutinin-horseradish peroxidase conjugate was injected in the unilateral superior cervical ganglion (SCG), and the projection pathways of postganglionic sympathetic nerve fibers innervating the cochlea were traced in the rat. The labeled axons advanced along the internal carotid artery (ICA), and a few advanced caudally in the major petrosal nerve (MPN) and entered the facial nerve, while the majority ran rostral to the pterygopalatine ganglion at the point where they crossed the MPN in the carotid canal. The rest of the labeled fibers remained on the surface of the ICA and advanced to the cranial cavity. Most of the labeled fibers along the facial nerve joined the cochlear nerve and finally reached the osseous spiral lamina through the spiral ganglion. Some of the labeled fibers ran along the anterior inferior cerebellar artery from the basilar artery which was previously thought to have been the only pathway. We could not find any labeled fiber on the modiolar artery from anterior inferior cerebellar artery in the cochlea. These observations are consistent with our hypothesis that the sympathetic fibers innervating the neural tissues or related structures follow nerve fibers and meninges as matrices of projection pathways rather than arteries.

Superior cervical ganglionic origin of sympathetic fibers in the facial nerve, and their preganglionic spinal inputs: a WGA-HRP study in Macaca fuscata.

The origin of sympathetic fibers in the facial nerve of Macaca fuscata was demonstrated using the HRP method. WGA-HRP injection into the facial nerve resulted in heavy labeling in the ipsilateral superior cervical ganglion. The majority of labeled neurons in the superior cervical ganglion had sizes ranging from 20 to 35 microns. In the present study it was of particular interest that labeled neurons are also found in the intermediolateral nucleus and lateral funiculus ipsilaterally at the level from the C8 to T4 spinal cord segments. Many labeled neurons in the lateral funiculus were located in close vicinity to the intermediolateral nucleus, and, characteristically, a few of these had a long dendrite extending to the lateral surface of the spinal cord. The labeling in the spinal cord appears to be caused by transneuronal transport of WGA-HRP.

Co-expression of tyrosine hydroxylase, dopamine beta-hydroxylase and neuropeptide Y in the sympathetic neurons projecting to the submandibular gland in the sheep.

Sympathetic neurons projecting to the ovine submandibular gland (SMG) from the superior cervical ganglion (SCG) and middle cervical ganglion (MCG) were identified using retrograde tracing with fluorescent dye (Fast Blue). Antibodies to tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DbetaH) and neuropeptide Y (NPY) were used to determine the immunochemical characteristics of SMG-innervating sympathetic neurons. Immunohistochemistry combined with the retrograde tracing revealed that the population of SMG-projecting neurons consist of four distinct sub-populations, but taking into account their possible different physiological properties only three major sub-populations can be distinguished. The vast majority of neurons in both ganglia are noradrenergic in nature (co-express TH and DbetaH). All examined TH-immunoreactive (IR) neurons also show immunoreactivity to DbetaH. Sub-population of noradrenergic neurons can be divided into NPY-IR and non-NPY-IR. Noradrenergic neurons expressing NPY may act as vasoconstrictors. The second sub-population of SMG projecting neurons in the ganglia studied consists of non-noradrenergic neurons (containing NPY, but not TH). It is known that these kinds of neurons may play a vasodilatory role. In both examined ganglia the third sub-population consists of non-TH-IR and non-NPY-IR neurons of unknown physiological function. Since no DbetaH immunoreactivity was found in any of TH- neurons these nerve cells can also be regarded as non-noradrenergic. It is possible that some neurons of the second as well as the third sub-population are cholinergic and some of them are non-noradrenergic/non-cholinergic in character.