Preganglionic fibers in the rat hypogastric nerve project bilaterally to pelvic ganglia.

Stimulation of the hypogastric nerve (HGN) often evokes bilateral responses in some pelvic organs. Retrograde labeling studies indicate that axons of postganglionic neurons often cross to the opposite side. However, there is little information available as to whether preganglionic fibers in the HGN have a contralateral projection to pelvic ganglia. A retrograde tracer was injected into the left major pelvic ganglion (MPG) in rats receiving various lesions of preganglionic nerves (HGN and pelvic nerve, PN). The lumbar spinal cord was then examined for location and number of dye-filled neurons. In a second approach, the incidence of synaptophysin immunoreactivity (SN-IR) perineuronal profiles (baskets) was examined in the MPG and in the accessory pelvic ganglia (APG) after nerve lesions. Labeled neuronal profiles were found in spinal cord nuclei (Lumbar1-2) after dye injection of the MPG in animals with an intact contralateral HGN. Cutting both HGNs virtually eliminated dye labeling in the lumbar cord, as did severing commissural branches (CB) between pelvic ganglia (leaving the contralateral HGN intact). Some SN-IR baskets were found in the left APG when only the contralateral HGN was intact, but baskets were rare when all four preganglionic nerves were cut. It could not be determined whether the HGN projects to the contralateral MPG, since SN-IR baskets were numerous in the MPG even when all four nerves were cut. This study has shown that some preganglionic fibers in the HGN synapse on neurons in contralateral pelvic ganglia. Both the APG and MPG receive contralateral innervation, but it is likely that neurons in the APG are the primary target of this input. Thus, in addition to crossing postganglionic fibers, a portion of the bilateral control of pelvic tissues is accomplished by preganglionic fibers which target autonomic neurons in contralateral ganglia.

Facial nerve parasympathetic preganglionic afferents to the accessory otic ganglia by way of the chorda tympani nerve in the cat.

The distribution of accessory otic ganglia and connections between the ganglia and the chorda tympani nerve were investigated in the cat in order to determine the parasympathetic preganglionic facial nerve afferents to the otic ganglia using whole mount acetylthiocholinesterase (WATChE) histochemistry. The otic ganglia consist of a single main prominent ganglion and many small accessory ganglia lying on a plexus around the origins of the branches of the mandibular nerve and near the junction of the chorda tympani nerve and lingual nerve. In cell analysis of Nissl-stained preparations, the neurons composing the accessory otic ganglia were morphologically similar to the main otic ganglion neurons. Connecting branches from the chorda tympani nerve to the peripherally located accessory otic ganglia were found and they were not stained by WATChE histochemistry. WATChE-positive connecting branches from the ganglia to the inferior alveolar, lingual, and mylohyoid nerves were also found in the same preparations. The WATChE histochemistry on various autonomic nervous tissues revealed that autonomic postganglionic nerve fibers are selectively stained darkly and that preganglionic fibers remain unstained. Therefore, it is considered that the WATChE-negative connections from the chorda tympani nerve consist chiefly of autonomic preganglionic fibers, whereas the WATChE-positive connections to the branches of the mandibular nerve are mainly postganglionic fibers. This suggests that some of the facial nerve parasympathetic preganglionic fibers in the chorda tympani nerve are mediated in the accessory otic ganglia and then join the branches of the mandibular nerve to supply the target mandibular tissues.

Connections between the vestibular nuclei and brain stem regions that mediate autonomic function in the rat.

Clinical observations have long indicated a vestibular influence on autonomic function. Neuroanatomical studies in the rabbit and in the cat have identified descending vestibulo-autonomic pathways from the caudal portion of the medial vestibular nucleus and the inferior vestibular nucleus to the dorsal motor nucleus of the vagus nerve, the nucleus of the solitary tract, and some brain stem medullary sympathetic regions. This study describes vestibulo-autonomic pathways in rats. One group of Long-Evans rats received injections of tetramethylrhodamine dextran into the caudal aspect of the vestibular nuclear complex. Anterogradely labeled descending fibers were traced bilaterally to lateral, ventrolateral, and intermediate subnuclei of the nucleus of the solitary tract and the dorsal motor nucleus of the vagus nerve. A small number of axons also projected bilaterally to the nucleus ambiguus, the ventrolateral medulla, and the nucleus raphe magnus. Finally, anterogradely labeled ascending fibers were traced from the caudal medial vestibular nucleus and the inferior vestibular nucleus to the medial, lateral, ventrolateral, and Kolliker-Fuse regions of parabrachial nucleus. A second group of rats received iontophoretic injections of Fluoro-gold into the nucleus of the solitary tract to identify the cells of origin of the vestibulo-solitary projection. Similar to findings in the rabbit (Balaban and Beryozkin, 1994), retrogradely labeled cells were observed in the caudal medial vestibular nucleus and the inferior vestibular nucleus. These findings are consistent with the hypothesis that a common pattern of vestibular nuclear projections to autonomic regions is shared by rabbits, cats, and rats.

Spinal and vagal projections to the sympathetic trunk of the wrasse, Halichoeres poecilopterus.

The sympathetic preganglionic neurons of the teleost, Halichoeres poecilopterus, were identified by retrograde axonal tracing. After horseradish peroxidase was applied to the sympathetic trunk, labeled neurons were found at the caudalmost level of the medulla, in the spinal cord near the fourth spinal nerve root (rostral spinal group), and in the spinal cord from rostral to the sixth spinal nerve root to caudal to the tenth spinal nerve root (caudal spinal group). The rostral spinal group has three cell columns segregated mediolaterally from the central gray zone to the lateral funiculus. Labeled neurons were found predominantly on the side ipsilateral to the application. In the caudal spinal group, labeled neurons were found bilaterally in the central gray zone. This condition is different from that previously reported in the puffer fish and filefish. The labeling in the medulla suggests that the preganglionic neurons in the brainstem may send fibers to the sympathetic trunk of this fish, although their peripheral targets are unknown.

Distribution of vagal preganglionic neurons in the rat brain innervating thoracic and abdominal organs revealed by retrograde DiI tracing.

To investigate the distribution and number of preganglionic neurons which regulate motility and secretion in thoracic and abdominal organs in the vagal parasympathetic nervous system, the neuronal tracer DiI was injected into the organs and the distribution of retrogradely labeled neurons was examined in the rat brainstem. The stomach received the vast majority of efferent projections from the dorsal motor nucleus of the vagus nerve (DMV). The cecum and the duodenum also received projections from the DMV, but they originated from a smaller number of preganglionic neurons. Preganglionic neurons projecting to the stomach occupied the middle part of the DMV, those projecting to the cecum occupied the lateral part of the DMV, and those projecting to the duodenum were found in the medial edge of the DMV. The ventral and dorsal sides of the stomach wall were innervated by the left and right vagus nerves, respectively. However, immediately after passing the boundary between the stomach and duodenum, the left and right vagal nerve fibers mixed in the ventral and dorsal walls of the distal gastrointestinal tract. The nucleus ambiguous is a mixture of parasympathetic preganglionic neurons and motoneurons. In this study, we revealed that the major targets of these preganglionic neurons were the lungs and other thoracic organs.

The spinal sympathetic preganglionic cell column in the puffer fish, Takifugu niphobles.

Little is known about the spinal sympathetic organization in teleosts. We examined the location of the sympathetic preganglionic neurons with horseradish peroxidase (HRP) labeling. After HRP application to the sympathetic trunk or celiac ganglion, labeled neurons were found just dorsal - dorsolateral to the central canal. They form a cell column (central autonomic nucleus) at the level of the posterior rootlet of the first spinal nerve to the third spinal nerve. HRP application to the sympathetic trunk produced labeling in almost the entire central autonomic nucleus, but HRP application to the celiac ganglion produced labeling in only the rostral half of the central autonomic nucleus. These results suggest that there is some topographical arrangement in the rostrocaudal part of the central autonomic nucleus. On the other hand, the fact that the sympathetic preganglionic neurons are within a single cell column and have no mediolateral segregation means that the target-related or function-associated mediolateral arrangement found in tetrapods is lacking in this species. We also found some labeling in the central autonomic nucleus after HRP application to the cranial nerves. This may indicate that the preganglionic neurons project to the cranial nerves.

Anatomical demonstration of vagal input to nicotinamide acetamide dinucleotide phosphate diaphorase-positive (nitrergic) neurons in rat fundic stomach.

Recent pharmacological evidence suggests that the nonadrenergic, noncholinergic (NANC) vagal inhibitory input responsible for receptive relaxation of the fundic stomach is mediated by nitric oxide-synthesizing enteric neurons. To demonstrate anatomically such direct vagal inputs to neurochemically identified enteric neurons, we utilized the nicotinamide acetamide dinucleotide phosphate (NADPH)-diaphorase histochemical reaction in conjunction with selective anterograde labeling of vagal efferents or afferents. Approximately 30% of all myenteric neurons of the fundic myenteric plexus stained positive for NADPH diaphorase, and the principal recipient of axonal projections from NADPH diaphorase-positive neurons was the circular muscle layer. In a group of animals showing the most complete labeling of vagal efferent preganglionics with the carbocyanine dye DiA, quantitative analysis of the half of the ventral fundic wall closer to the greater curvature revealed that 46.8% +/- 4.4% of all myenteric neurons received some degree of vagal contacts and that 30.5% +/- 6.6% of such vagally contacted neurons were also NADPH diaphorase positive. In another group of rats with the most successful selective labeling of vagal afferents through DiI injections into the left nodose ganglion, analysis of select ganglia throughout the ventral fundic wall revealed that, of a total of 454 neurons with vagal afferent contacts, 34.8% +/- 2.8% were NADPH diaphorase positive. These findings support the view that, in the fundic stomach, some vagal preganglionic efferents terminate on nitric oxide-synthesizing neurons that, in turn, project to and relax the external smooth muscle layers. Furthermore, vagal afferent endings also contact NADPH diaphorase-positive neurons, suggesting the possibility of local axon reflexes originating from smooth muscular in-series tension receptors and terminating on nitrergic neurons of the myenteric plexus.

Location, distribution and projections of intracardiac ganglion cells in the rat.

Physiological studies indicate that cardiac parasympathetic nerves may act selectively at discrete cardiac sites. To determine anatomical sites at which selective integration of cardiac nerve activity may occur, the present study identified and described the location, distribution, and projections of intracardiac ganglion cells in the rat. The estimated 3992 ganglion cells per rat heart were located in 4 distinct groups, all above the atrioventricular groove: (1) between the superior vena cava and aorta (2.5% of total), (2) in the region of the superior interatrial septum (49.9%), (3) posterior to the left atrium (24.0%), and (4) posterior to the inferior interatrial septum and right atrium (23.5%). Only a few ganglion cells were located subepicardially within the infolding of the dorsal interatrial septum. Retrogradely transported fluorescent tracers injected into the left or right ventricles demonstrated that different groups of ganglion cells projected to discrete or selective regions of the heart. Projections to the left ventricle originate only from ganglion cells located posterior to the interatrial septum and the left atrium. In the rat, intracardiac ganglion cells, confined to 4 atrial regions, appear to have discrete sites of termination within the heart. It is proposed that selective activation of different intracardiac ganglion cell groups may elicit specific regional changes in cardiac parasympathetic nerve activity.

Morphology of labeled efferent fibers in the guinea pig cochlea.

Efferent axons to the guinea pig cochlea were labeled by extracellular injections of horseradish peroxidase into the intraganglionic spiral bundle within the spiral ganglion. The terminal fibers formed by these axons were classified according to their patterns of termination within the basal turn of the cochlea. A class of terminal fibers designated "autonomic" forms a highly branched plexus in the osseous spiral lamina but does not enter the organ of Corti. The termination of single autonomics includes blood vessels as well as areas of the osseous spiral lamina not adjacent to blood vessels. Two major classes of efferent axons from the olivocochlear bundle enter the cochlea by way of the vestibulocochlear anastomosis and terminate either in areas near inner hair cells (IHC efferents) or onto outer hair cells (OHC efferents). The IHC efferents have thin axons throughout their course within the cochlea and can be divided into two subclasses. The most numerous subclass of IHC efferents (unidirectional) enters the inner spiral bundle and turns to spiral in only one direction for less than 1 mm and then forms a discrete termination including many en passant and terminal swellings that are within both the inner and tunnel spiral bundles. A less common subclass of IHC efferents (bidirectional) bifurcates upon entry into the inner spiral bundle to send branches both apically and basally. These terminal fibers take spiral courses that are greater than 1 mm in extent, often course in the tunnel spiral bundle for a large portion of the spiral, and form terminals throughout their extended spiral course. None of the IHC efferent fibers send branches to cross the tunnel to innervate the outer hair cells. A second major class of olivocochlear fibers, OHC efferent fibers, forms large boutons on the outer hair cells, and although they sometimes spiral beneath the IHCs for some length, they do not give off terminals to this region. The OHC efferent axons are thick and myelinated as they enter the cochlea, and they branch near the spiral ganglion to form several terminal fibers. Some of these terminal fibers are thin as they travel from the intraganglionic spiral bundle across the osseous spiral lamina to the organ of Corti, whereas others are thick and obviously myelinated as far peripheral as the habenula.(ABSTRACT TRUNCATED AT 400 WORDS)

The location of descending fibres to sympathetic neurons supplying the eye and sudomotor neurons supplying the head and neck.

Evidence is given of the location in man of the fibres going to the sympathetic neurons of the lateral horn that supply the intrinsic and extrinsic muscles of the eye and the sweat glands of the head and neck. For the region of the pons and medulla, the evidence is abstracted from the literature. For the cervical spinal cord, the evidence is from our cases of anterolateral cordotomy. In the medulla, thrombosis of the artery of the fossette latérale destroys the fibres; this locates the fibres in the posterolateral retro-olivary area. But not all fibres to the sudomotor neurons lie there: some run elsewhere, though they probably remain ipsilateral. In the cervical cord, the fibres supplying the sympathetic neurons of the intrinsic and extrinsic muscles of the eye run near the posterior angle of the anterior horn. Most of the fibres supplying the sudomotor neurons lie in the same region, though some lie outside this area but on the same side of the cord.

Origin of the parasympathetic preganglionic fibers to the distal colon of the rabbit as demonstrated by the horseradish peroxidase method.

The extrinsic innervation of the rabbit distal colon was studied by the use of the horseradish peroxidase (HRP) tracing technique. After injection of HRP, labelled cells were observed in sacral spinal cord segments S2-S5, primarily in the lateral intermediate grey matter. Labelled neurons were also observed in the lateral funiculus and sometimes in the ventral horn. No labelled cells were found in the vagal nuclei, contrary to the reports of earlier investigators. Anterograde transport of HRP resulted in labelling of visceral afferent neurons in dorsal root ganglia, whilst the central processes of afferent neurons entered Lissauer's tract and formed a collateral pathway along the lateral edge of the dorsal horn which terminated in close apposition to labelled preganglionic efferent neurons.

Sympathoadrenal preganglionic neurons: their distribution and relationship to chemically-coded fibers in the kitten intermediolateral cell column.

The location of those sympathetic preganglionic neurons in the spinal cord that project to the adrenal medulla--the sympathoadrenal preganglionic (SAP) neurons--was studied by the method of retrograde axonal transport of the fluorescent dye Fast Blue. The distribution of chemically-coded fibers and their relationship to the SAP neurons was also investigated using the indirect immunofluorescence technique. In kittens, 5 microliters of a 1% solution of Fast Blue was injected into the medulla of the left adrenal gland. After a survival period of 5 days, the spinal cords from C8 to L5 were sectioned and processed for the localization of enkephalin-, neurophysin-, oxytocin-, serotonin-, substance P- and somatostatin-like immunoreactivity. Retrogradely labeled neurons were found in the ipsilateral intermediolateral cell column (IML) (89.8% of all retrogradely labeled neurons) from T1 to L4, and in the contralateral IML (10.2%) from T1 to L4. The enkephalin, serotonin and substance P immunoreactive fibers appeared to surround both the retrogradely labeled and unlabeled IML neurons. The somatostatin immunoreactive fibers were observed only in proximity to the retrogradely labeled neurons. Only a sparse population of neurophysin and oxytocin immunoreactive fibers were observed in IML, and were not seen to be in apposition to the retrogradely labeled neurons.

Projections of upper structure to the spinal cardioacceleratory center in cats: an HRP study using a new microinjection method.

We studied, with the horseradish peroxidase (HRP) method, the supraspinal structure projections to the cardioacceleratory center in the intermediolateral nucleus (ILN) of T3-4 segments of the cat spinal cord. A fiber-filled double-barrel coaxial electrode was devised. The inner barrel electrode, filled with 3 M NaCl solution, was used for stimulating intraspinal structures to determine the cardioacceleratory center. The outer barrel electrode with an Agar stop, filled with a 20% HRP solution, was used for injecting HRP by pulses of positive electric current. In every experiment, HRP was injected into 3 points within the cardioacceleratory center at intervals of 1 mm. Out of 36 experiments, 10 showed that the HRP injection sites were centered in and almost confined to the ILN, and the population of the HRP-labeled cells was not less than 50. Some 1146 HRP-labeled cells were thus identified. They were distributed in the medulla oblongata (72.1%), pons (10.2%), midbrain (8.5%) and hypothalamus (9.2%). They were concentrated in the medullary reticular formation (37.8%), median raphe (26.9%) and pontine reticular formation (10.2%). Contrary to expectation, the HRP-labeled cells were few in the nucleus tractus solitarii (3.7%), paraventricular hypothalamic area (3.3%) and nucleus locus coeruleus (none).

Central connections of the hepatic branch of the vagus nerve: a horseradish peroxidase histochemical study.

The hepatic branch of the vagus nerve has been implicated as an important source of afferent input controlling both physiological and behavioral homeostasis. In addition, it is clear that parasympathetic efferents to the liver can significantly alter hepatic functions. In order to begin physiological studies on the nature of hepatic afferent and efferent relations, it will be necessary to understand the central anatomical organization of the components of this small visceral nerve. By carefully exposing and dissecting the hepatic branch of the vagus and applying crystalline horseradish peroxidase (HRP) to it, we were able to elucidate a predominant pattern of afferent terminations within the left subnucleus gelatinosus, the medial division of the left solitary nucleus and the left lateral edge of the area postrema. Efferent nuclei were concentrated in the left dorsal motor nucleus of the vagus (DMN) with a few scattered neurons located in the right DMN as well as the left anterior nucleus ambiguous.

Retrograde transport of horseradish peroxidase by regenerating preganglionic axons in the cat's cervical sympathetic trunk.

Horseradish peroxidase (HRP) was applied to the proximal stumps of regenerating (7 days postsectioned) and freshly cut cervical sympathetic trunks of cats. Counts of HRP-labeled neurons in the spinal cord showed that regenerating sympathetic axons were just as capable, if not better able, of taking up and retrogradely transporting HRP, as freshly cut normal sympathetic axons.

Cardiac vagal preganglionic fibers in neonatal rats: a comparison with cervical vagal components.

Origins of cardiac innervation were determined by injection of horseradish peroxidase (HRP) into the myocardium of rats. Bilaterally labeled efferent cells in the brainstem were found in the rostral nucleus ambiguus (NA) with fewer cells in the dorsal motor nucleus (DMN). No afferent labeling was seen. In young rats, but not in adults, there was labeling in the ventral horn of the cervical spinal cord. A unilateral vagotomy prior to the HRP injection resulted in labeled cells in the brainstem contralateral to the vagotomy while cells in the spinal cord remained bilateral. Thus the label in these spinal cord cells may represent HRP uptake by fibers of passage. These results were compared to the afferent and efferent vagal components of the entire cervical vagus nerve.