Lack of unity of Edinger-Westphal nucleus projections to the ciliary ganglion and spinal cord: a double-labeling approach

Neuromedin U Neurons in the Edinger-Westphal Nucleus Respond to Alcohol Without Interfering with the Urocortin 1 Response

The Edinger-Westphal nucleus (EW) is a midbrain nucleus composed of a preganglionic, cholinergic subpopulation and a densely clustered peptidergic subpopulation (EWcp). The EWcp is one of the few brain regions that show consistent induction of FOS following voluntary alcohol intake. Previous results in rodents point to urocortin 1 (UCN1) as one of the peptides most involved in the control of ethanol intake and preference. Notably, the functions described for UCN1, such as reward processing, stress coping or the regulation of feeding behavior are similar to those described for the neuropeptide neuromedin U (NMU). Interestingly, NMU has been recently associated with the modulation of alcohol-related behaviors. However, little is known about the expression and functionality of NMU neurons in alcohol-responsive areas. In this study, we used the recently developed Nmu-Cre knock-in mouse model to examine the expression of NMU in the subaqueductal paramedian zone comprising the EWcp. We delved into the characterization and co-expression of NMU with other markers already described in the EWcp. Moreover, using FOS as a marker of neuronal activity, we tested whether NMU neurons were sensitive to acute alcohol administration. Overall, we provided novel insights on NMU expression and functionality in the EW region. We showed the presence of NMU within a subpopulation of UCN1 neurons in the EWcp and demonstrated that this partial co-expression does not interfere with the responsivity of UCN1-containing cells to alcohol. Moreover, we proposed that the UCN1 content in these neurons may be influenced by sex.

Background luminance effects on pupil size associated with emotion and saccade preparation

Pupil dilation is consistently evoked by affective and cognitive processing, and this dilation can result from sympathetic activation or parasympathetic inhibition. The relative contributions of the sympathetic and parasympathetic systems on the pupillary response induced by emotion and cognition may be different. Sympathetic and parasympathetic activity is regulated by global luminance level. Higher luminance levels lead to greater activation of the parasympathetic system while lower luminance levels lead to greater activation of the sympathetic system. To understand the contributions of the sympathetic and parasympathetic nervous systems to pupillary responses associated with emotion and saccade preparation, emotional auditory stimuli were presented following the fixation cue whose color indicated instruction to perform a pro- or anti-saccade while varying the background luminance level. Pupil dilation was evoked by emotional auditory stimuli and modulated by arousal level. More importantly, greater pupil dilation was observed with a dark background, compared to a bright background. In contrast, pupil dilation responses associated with saccade preparation were larger with the bright background than the dark background. Together, these results suggest that arousal-induced pupil dilation was mainly mediated by sympathetic activation, but pupil dilation related to saccade preparation was primarily mediated by parasympathetic inhibition.

Autonomic control of the eye

The autonomic nervous system influences numerous ocular functions. It does this by way of parasympathetic innervation from postganglionic fibers that originate from neurons in the ciliary and pterygopalatine ganglia, and by way of sympathetic innervation from postganglionic fibers that originate from neurons in the superior cervical ganglion. Ciliary ganglion neurons project to the ciliary body and the sphincter pupillae muscle of the iris to control ocular accommodation and pupil constriction, respectively. Superior cervical ganglion neurons project to the dilator pupillae muscle of the iris to control pupil dilation. Ocular blood flow is controlled both via direct autonomic influences on the vasculature of the optic nerve, choroid, ciliary body, and iris, as well as via indirect influences on retinal blood flow. In mammals, this vasculature is innervated by vasodilatory fibers from the pterygopalatine ganglion, and by vasoconstrictive fibers from the superior cervical ganglion. Intraocular pressure is regulated primarily through the balance of aqueous humor formation and outflow. Autonomic regulation of ciliary body blood vessels and the ciliary epithelium is an important determinant of aqueous humor formation; autonomic regulation of the trabecular meshwork and episcleral blood vessels is an important determinant of aqueous humor outflow. These tissues are all innervated by fibers from the pterygopalatine and superior cervical ganglia. In addition to these classical autonomic pathways, trigeminal sensory fibers exert local, intrinsic influences on many of these regions of the eye, as well as on some neurons within the ciliary and pterygopalatine ganglia.

Central pupillary light reflex circuits in the cat: II. Morphology, ultrastructure, and inputs of preganglionic motoneurons

Preganglionic motoneurons supplying the ciliary ganglion control lens accommodation and pupil diameter. In cats, these motoneurons make up the preganglionic Edinger-Westphal population, which lies rostral, dorsal, and ventral to the oculomotor nucleus. A recent cat study suggested that caudal motoneurons control the lens and rostral motoneurons control the pupil. This led us to examine the morphology, ultrastructure, and pretectal inputs of these populations. Preganglionic motoneurons retrogradely labeled by introducing tracer into the cat ciliary ganglion generally fell into two morphologic categories. Fusiform neurons were located rostrally, in the anteromedian nucleus and between the oculomotor nuclei. Multipolar neurons were found caudally, dorsal and ventral to the oculomotor nucleus. The dendrites of preganglionic motoneurons within the anteromedian nucleus crossed the midline, providing a possible basis for consensual responses. Ultrastructurally, several different classes of synaptic profiles contact preganglionic motoneurons, suggesting that their activity may be modified by a variety of inputs. Furthermore, there were differences in the synaptic populations contacting the rostral vs. caudal populations, supporting the contention that these populations display functional differences. Anterogradely labeled pretectal terminals were observed in close association with labeled preganglionic motoneurons, particularly in the rostral population. Ultrastructural analysis revealed that these terminals, packed with clear, spherical vesicles, made asymmetric synaptic contacts onto motoneurons in the rostral population, indicating that these cells serve the pupillary light reflex. Thus, the preganglionic motoneurons found in the cat display morphologic, ultrastructural, and connectional differences suggesting that this rostral preganglionic population is specialized for pupil control, whereas more caudal elements control the lens.

CRF family peptides are differently altered by acute restraint stress and chronic unpredictable stress

Corticotropin-releasing factor (CRF) acts to promote stress-like physiological and behavioral responses and is mainly expressed in the paraventricular hypothalamic nucleus (PVN). Urocortin 1 (Ucn1) is also a ligand to CRF type 1 and 2 receptors that has been associated with the stress response. Ucn1 neurons are primarily found in the Edinger-Westphal (EW) nucleus. It has been previously proposed that CRF and Ucn1 differently modulate stress responses to distinct types of stressors. The present study used male Wistar rats to compare the effects of acute restraint stress and unpredictable chronic stress (UCS) through Fos-immunoreactivity (Fos-ir) on CRF-containing neurons of PVN and Ucn1-containing EW centrally projecting neurons. Results showed that PVN neurons responded to both acute restraint and UCS. Also for the PVN, unspecific variables, dependent on the time animals remained in the laboratory, do not seem to alter Fos-ir, since no significant differences between acute and chronic control groups were found. On the other hand, EW neurons were only activated in response to acute restraint stress. Also, for this nucleus a significant difference was found between acute and chronic control groups, suggesting that unspecific variables, dependent on the time animals remain in the laboratory, interfere with the nucleus activation. These results suggest that CRF/Ucn1 neuronal circuits encompass two interconnected systems, which are coordinated to respond to acute stressors, but are differentially activated during chronic unpredictable stress.

About a snail, a toad, and rodents: animal models for adaptation research

Neural adaptation mechanisms have many similarities throughout the animal kingdom, enabling to study fundamentals of human adaptation in selected animal models with experimental approaches that are impossible to apply in man. This will be illustrated by reviewing research on three of such animal models, viz. (1) the egg-laying behavior of a snail, Lymnaea stagnalis: how one neuron type controls behavior, (2) adaptation to the ambient light condition by a toad, Xenopus laevis: how a neuroendocrine cell integrates complex external and neural inputs, and (3) stress, feeding, and depression in rodents: how a neuronal network co-ordinates different but related complex behaviors. Special attention is being paid to the actions of neurochemical messengers, such as neuropeptide Y, urocortin 1, and brain-derived neurotrophic factor. While awaiting new technological developments to study the living human brain at the cellular and molecular levels, continuing progress in the insight in the functioning of human adaptation mechanisms may be expected from neuroendocrine research using invertebrate and vertebrate animal models.

Restraint stress alters the secretory activity of neurons co-expressing urocortin-1, cocaine- and amphetamine-regulated transcript peptide and nesfatin-1 in the mouse Edinger-Westphal nucleus

Central stress regulatory pathways utilize various neuropeptides, such as urocortin-1 (Ucn1) and cocaine- and amphetamine-regulated transcript peptide (CART). Ucn1 is most abundantly expressed in the non-preganglionic Edinger-Westphal nucleus (npEW). In addition to Ucn1, CART and nesfatin-1 are highly expressed in neurons of the npEW, but the way these three neuropeptides act together in response to acute stress is not known. We hypothesized that Ucn1, CART and nesfatin-1 are colocalized in npEW neurons and that these neurons are recruited by acute stress. Using quantitative immunocytochemistry and the reverse transcriptase polymerase chain reaction (RT-PCR), we support this hypothesis, by showing in B6C3F1/Crl mice that Ucn1, CART and nesfatin-1 occur in the same neurons of the npEW nucleus. More specifically, Ucn1 and CART revealed a complete colocalization in the same perikarya, while 90% of these neurons are also nesfatin-1-immunoreactive. Furthermore, acute (restraint) stress stimulates the general secretory activity of these npEW neurons (increased presence of Fos) and the production of Ucn1, CART and nesfatin-1: Ucn1, CART and nesfatin-1(NUCB2) mRNAs have been increased compared to controls by x1.8, x2.0 and x2.6, respectively (p<0.01). We conclude that Ucn1, CART and nesfatin-1/NUCB2 are specifically involved in the response of npEW neurons to acute stress in the mouse.

Chronic psychosocial stress affects corticotropin-releasing factor in the paraventricular nucleus and central extended amygdala as well as urocortin 1 in the non-preganglionic Edinger-Westphal nucleus of the tree shrew

Stressful stimuli evoke neuronal and neuroendocrine responses helping an organism to adapt to changed environmental conditions. Chronic stressors may induce maladaptive responses leading to psychiatric diseases, such as anxiety and major depression. A suitable animal model to unravel mechanisms involved in the control of adaptation to chronic stress is the psychological subordination stress in the male tree shrew. Subordinate male tree shrews exhibit chronic hypothalamo-pituitary-adrenal (HPA) activation as reflected in continuously elevated cortisol secretion, and structural changes in the hippocampal formation. Corticotropin-releasing factor (CRF) is the major peptide released upon activation of the HPA axis in response to stress. Recent evidence suggests that besides CRF, urocortin 1 (Ucn1) also plays a role in stress adaptation. We have tested the significance of CRF and Ucn1 in adaptation to chronic psychosocial stress in male tree shrews exposed for 35 days to daily psychosocial conflict, by performing semi-quantitative immunocytochemistry for CRF in the parvocellular hypothalamic paraventricular nucleus (pPVN), extended amygdala, viz. central extended amygdala (CeA) and dorsolateral nucleus of the bed nucleus of the stria terminalis (BNSTdl) as well as that for Ucn1 in the non-preganglionic Edinger-Westphal nucleus (npEW). Compared to unstressed animals, psychosocial stress resulted in an immediate and sustained activation of the HPA axis and sympathetic tone as well as reduced testosterone concentration and decreased body and testis weights vs. non-stressed tree shrews. In the pPVN, the number of CRF-immunoreactive neurons and the specific signal density of CRF-immunoreactive fiber terminals in the CeA were strongly reduced (-300 and -40%, respectively; P<0.05), whereas no significant difference in CRF fiber density was found in BNSTdl. The npEW revealed 4 times less Ucn1-immunoreactive neurons (P<0.05). These clear effects on both Ucn1- and CRF-neuropeptide contents may reflect a crucial mechanism enabling the animal to adapt successfully to the stressors, and point to the significance of the pPVN, CeA and npEW in stress-induced brain diseases.

On the role of urocortin 1 in the non-preganglionic Edinger-Westphal nucleus in stress adaptation

The discovery of novel members of the CRF neuropeptide family, urocortin 1 (Ucn1), urocortin 2 and 3 has provided important insights into stress adaptation pathways, and predicted that stress adaptation involves more systems than the HPA-axis alone. This mini-review aims to summarize our recent data and research by others indicating that an important role is played by Ucn1 in the non-preganglionic Edinger-Westphal nucleus (npEW). These results point to an intriguing possibility that CRF/Ucn1 neuronal circuits comprise two separate, but functionally interrelated entities, which are coordinately regulated by acute stressors, but are inversely coupled during chronic stress. Such collaboration between the two systems would implicate a very important role of Ucn1 in adaptation to stress, and, as a consequence, in stress-related disorders like anxiety, major depression and use of drugs of abuse.

Neuropeptide Y activates urocortin 1 neurons in the nonpreganglionic Edinger-Westphal nucleus

Central regulatory pathways promoting stress adaptation utilize various neurotransmitters/neuropeptides, such as urocortin 1 (Ucn1) and neuropeptide Y (NPY). Ucn1 is abundantly expressed in the nonpreganglionic Edinger-Westphal nucleus (npEW), where it is codistributed with NPY-immunoreactive (ir) terminals. A special role for both neuropeptides has been postulated in stress adaptation. Using double-labeling immunohistochemistry, we observed close appositions between NPY-ir terminals and neurons immunoreactive for Ucn1 in the rat, as well as in the human npEW. Therefore, we hypothesized that NPY might control the activity of Ucn1-positive neurons in the npEW. To test this hypothesis, NPY was injected into the lateral cerebral ventricle of rats, resulting in a strong activation of npEW Ucn1 neurons as revealed by Fos immunohistochemistry. Ucn1 mRNA was also upregulated in the npEW 2 hours after the injection of NPY. In a search for the type of NPY receptor that mediates this NPY-induced recruitment of npEW-Ucn1 cells, we found that the great majority of Ucn1 cells exhibited NPY Y5 receptor immunoreactivity, and only a few of the Ucn1 cells coexpressed the Y1 receptor. We concluded that NPY, via NPY Y5 and to a lesser extent via the Y1 receptors, exerts a stimulatory action on Ucn1 cells in the npEW. Further studies are currently in progress to elucidate the significance of this NPY-Ucn1 interaction in the npEW.

The Edinger-Westphal nucleus of the juvenile rat contains transient- and repetitive-firing neurons

Classically, the Edinger-Westphal nucleus is described as containing neurons controlling accommodation and pupillary constriction via projections to the ciliary ganglion. However, in several species including rat, some Edinger-Westphal neurons have ascending or descending CNS projections suggesting that the Edinger-Westphal nucleus might also have non-ocular functions. To further characterize the function of this nucleus we studied the electrophysiological properties of Edinger-Westphal neurons in a slice preparation from juvenile rats. The position of the Edinger-Westphal nucleus was determined using an immunohistochemical procedure directed at the peptide Urocortin, which is expressed in Edinger-Westphal neurons. Passive and active membrane responses were investigated and two different neuron types were identified. One type had a transient firing response to 400 ms depolarizing current pulses and one type had a repetitive firing response. Transient-firing neurons had an outward rectifying response inhibiting firing, possibly due to slowly inactivating I(D)-like potassium channels since low concentrations (200 microM) of the potassium channel blocker 4-aminopyridine elicited repetitive firing. In all neurons, low threshold Ca(2+) spikes were seen and these were blocked by nickel(II) chloride hexahydrate, suggesting that they are mediated via low voltage-activated Ca(2+) channels. Some biocytin-labeled neurons had axons or axonal collaterals projecting laterally or dorsally, suggesting possible non-ocular targets. In conclusion, the rat Edinger-Westphal nucleus contains two separate types of neurons with distinct electrophysiological properties.

Urocortin 1-containing neurons in the human Edinger-Westphal nucleus

The topographical location of neurons containing urocortin 1, a peptide related to corticotropin-releasing factor was investigated in human postmortem brain by immunohistochemistry, and compared with the location of neurons containing choline acetyltransferase, a marker for cholinergic cells. A three-dimensional computer reconstruction of the urocortin 1 and choline acetyltransferase-positive population of neurons within the oculomotor area was made. It was shown that the urocortin 1-positive neurons are located within the area identified as the Edinger-Westphal nucleus according to the human brain stem atlas, and that the neurons identified as Edinger-Westphal nucleus in the atlas are not choline acetyltransferase-positive. This finding agrees with recent animal studies showing that urocortin 1-positive neurons are not identical with the parasympathetic cholinergic neurons projecting to the ciliary ganglion. They indicate that the neurons identified as Edinger-Westphal nucleus in the human brain stem atlas belong to the non-preganglionic Edinger-Westphal nucleus, whereas the location of preganglionic Edinger-Westphal nucleus remains unidentified.

Urocortin 1 distribution in mouse brain is strain-dependent

Urocortin 1 has been implicated in a number of specific behaviors, which include energy balance, stress reactivity and ethanol consumption. To elucidate genetically influenced differences in the mouse urocortin 1 system, we performed immunohistochemical characterization of urocortin 1 distribution in C57BL/6J and DBA/2J mouse brain. Urocortin 1 analysis reveals strain-dependent differences in distribution of urocortin 1 immunoreactive neurons and neuronal fibers. In both strains, the highest number of urocortin 1-positive neurons was observed in the Edinger-Westphal nucleus and lateral superior olive. Urocortin 1-positive neurons were detected in the dorsal nucleus of the lateral lemniscus of DBA/2J mice, but were absent in the C57BL/6J strain. Differences in urocortin 1 fibers were detected in many areas throughout the brain, and were most apparent in the septal areas, thalamic areas, several midbrain regions, and medulla. Strain-dependent distribution of urocortin 1-containing cells and fibers suggests that differences in this neuropeptide system may underlie differences in behavior and physiological responses between these strains. Further, we found that in both mouse strains, urocortin 1 in the Edinger-Westphal nucleus and choline acetyltransferase are not coexpressed. We show that the urocortin 1-positive neurons of this brain area form a separate population of cells that we propose to be called the non-preganglionic Edinger-Westphal nucleus.

Suprachiasmatic nucleus input to autonomic circuits identified by retrograde transsynaptic transport of pseudorabies virus from the eye

Intraocular injection of the Bartha strain of pseudorabies virus (PRV Bartha) results in transsynaptic infection of the hypothalamic suprachiasmatic nucleus (SCN), a retinorecipient circadian oscillator. PRV Bartha infection of a limited number of retinorecipient structures, including the SCN, was initially interpreted as the differential infection of a subpopulation of rat retinal ganglion cells, followed by replication and anterograde transport via the optic nerve. A recent report that used a recombinant strain of PRV Bartha (PRV152) expressing enhanced green fluorescent protein demonstrated that SCN infection actually results from retrograde transneuronal transport of the virus via the autonomic innervation of the eye in the golden hamster. In the present study using the rat, the pattern of infection after intravitreal inoculation with PRV152 was examined to determine if infection of the rat SCN is also restricted to retrograde transsynaptic transport. It was observed that infection in preganglionic autonomic nuclei (i.e., Edinger-Westphal nucleus, superior salivatory nucleus, and intermediolateral nucleus) precedes infection in the SCN. Sympathetic superior cervical ganglionectomy did not abolish label in the SCN after intraocular infection, nor did lesions of parasympathetic preganglionic neurons in the Edinger-Westphal nucleus. However, combined Edinger-Westphal nucleus ablation and superior cervical ganglionectomy eliminated infection of the SCN. This observation allowed a detailed examination of the SCN contribution to descending autonomic circuits afferent to the eye. The results indicate that in the rat, as in the hamster, SCN infection after intraocular PRV152 inoculation is by retrograde transsynaptic transport via autonomic pathways to the eye.

Vestibular nucleus projections to the Edinger-Westphal and anteromedian nuclei of rabbits

The Edinger-Westphal nucleus (EW), anteromedian nucleus (AM) and adjacent neurons in the ventral tegmental area (VTA) are sources of preganglionic parasympathetic innervation of intraocular smooth muscle, including blood vessels, pupillary muscle and the ciliary body in mammals. They also have central connections that are believed to affect parasympathetic outflow indirectly. This study utilized anterograde transport of biotinylated dextran amine and Phaseolus vulgaris leucoagglutinin to demonstrate direct projections from the vestibular nuclei to the Edinger-Westphal and anteromedian nuclei in rabbits. The rabbit AM and adjacent VTA contain moderate to intensely choline acetyltransferase (ChAT)-immunopositive neurons. The rabbit EW, by contrast, is nearly devoid of ChAT-immunopositive neurons. Vestibular nucleus projections to these regions originate from all levels of the superior, medial and lateral vestibular nuclei, but do show topographic organization. The densest terminations were observed in AM and the ventral and central aspects of EW. The projections to AM terminate in both ipsilaterally and in a narrow paramedian region. Predominantly ipsilateral terminations were observed in VTA. Terminations on ChAT-positive cells in AM and VTA were verified in three rabbits. It is suggested that projections to some intensely ChAT-positive AM and VTA neurons may be a substrate for vestibular influences on lens accommodation, pupillary constriction and regulation of intraocular circulation during changes in posture and gravitoinertial challenges. The projections to ChAT-negative (and weakly immunoreactive) cells in AM, VTA and EW, on the other hand, are likely to contribute vestibular signals to a variety of motor responses via descending pathways.

Localization of preganglionic neurons of the accessory ciliary ganglion in the midbrain: HRP and WGA-HRP studies in the cat

Localization of preganglionic neurons of the accessory ciliary ganglion (ACG), including ectopic intraocular ganglion cells, was investigated in the cat with the aid of horseradish peroxidase (HRP) and HRP-conjugated wheat germ agglutinin (WGA-HRP) methods. When HRP or WGA-HRP was injected into the anterior and posterior chambers of the eye, no retrogradely labeled cells were found in the visceral oculomotor nuclei, although most neurons of the ACG and the main ciliary ganglion (CG) were intensely labeled. When a microsyringe needle was inserted into the ciliary body, the tracer diffused into the suprachoroid lamina and the intraocular ganglion cells, and a small number of labeled neurons appeared in the midplane between each side of the somatic oculomotor nuclei. After injection into the ACG, many labeled neurons were observed in the anteromedian nucleus, Edinger-Westphal nucleus, and midplane between the somatic oculomotor nuclei, their ventral continuations of the ventral tegmental area, and the periaqueductal gray. HRP/WGA-HRP injection into the CG labeled cells in all these areas and in the lateral border zones of the anteromedian, Edinger-Westphal and somatic oculomotor nuclei, and their ventral continuations of the ventral tegmental area. These findings indicate that the visceral oculomotor neurons which project to the ACG tend to be located more medially than those to the CG.

The peripheral and central projections of the Edinger-Westphal nucleus in the rat. A light and electron microscopic tracing study

The peripheral and central efferent projections of the rostral part of the Edinger-Westphal nucleus in the rat were investigated at the light and electron microscopic level by means of iontophoretic injections of the anterograde tracer Phaseolus vulgaris-leucoagglutinin and retrograde tracer injections of Fast blue and Nuclear yellow into the facial nucleus and into the principal olive. Two pathways leaving the rostral part of the Edinger-Westphal nucleus were studied, a peripheral and a central descending pathway. Fluorescent experiments demonstrated that the central pathway fibers originated from distinct individual Edinger-Westphal neurons. These neurons were mainly distributed throughout the rostral part of the Edinger-Westphal nucleus and had fusiform cell bodies. The neurons rarely form collateral projections. The central descending pathway left the Edinger-Westphal nucleus medially and terminated bilaterally in the principal olive, in the subnuclei A, B and C of the inferior olive and ipsilaterally in the medial accessory olive. The central pathway also terminated contralaterally in the lateral parabrachial nucleus, the facial nucleus, the trigeminal brainstem nuclear complex, the lateral reticular nucleus and the rostroventral reticular nucleus. The projection to the facial nucleus provides evidence for the existence of a polysynaptic loop forming the central part of the corneal blink reflex. Projections from the Edinger-Westphal nucleus to the cerebellar cortex or the deep nuclei, as described in cat and primate, could not be confirmed. The peripheral pathway left the Edinger-Westphal nucleus ventrally and terminated on dendrites of ciliary ganglion cells, along smooth muscle cells of ciliary ganglion associated arterioles and in the proximity of ciliary ganglion associated venules. The central and peripheral terminals that originate in the Edinger-Westphal nucleus all had similar ultrastructural features: clear, round vesicles and electron dense mitochondria. The terminals originating from the central descending pathway were often found to be arranged in glomerular-like structures. The central and peripheral terminals made asymmetric synaptic membrane specializations (Gray type one), except terminals innervating the ciliary ganglion associated vessels, which showed no synaptic contacts.

Oculomotor parasympathetic pathway to the accessory ciliary ganglion bypassing the main ciliary ganglion by way of the trigeminal nerve

When an HRP or WGA-HRP solution was injected into the rostral midbrain including the oculomotor visceral nuclei, densely distributed HRP/WGA-HRP-positive granules were observed around the ganglion neurons in the accessory ciliary ganglion (ACG) and ectopic neurons in the communicating branch from the long ciliary nerve to the ACG. The same injections labeled fibers within the communicating branch as well as the fibers between the ACG and the main ciliary ganglion (CG). These findings indicate that some oculomotor parasympathetic preganglionic fibers reach the ACG bypassing the CG by way of the trigeminal nerve.

Interconnections between the primate cerebellum and midbrain near-response regions

The goal of this study was to determine the pattern of the connections between the midbrain and cerebellum that may play a role in the modulation of the near-response in the macaque. Injection of the retrograde tracer wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP) into the physiologically identified midbrain near-response region, which includes the supraoculomotor area, labelled cells throughout the deep cerebellar nuclei. However, labelled cells were particularly concentrated in the ventrolateral corner of the contralateral posterior interposed nucleus and in the contralateral and, to a lesser extent, the ipsilateral fastigial nuclei. Subsequently, injections of WGA-HRP were used to define the midbrain terminations of the deep cerebellar nuclei. Fastigial nucleus injections labelled terminals in a band along the border between the oculomotor nucleus and the supraoculomotor area that included the Edinger-Westphal nucleus. Injections of the posterior interposed nucleus labelled terminals in the portion of the supraoculomotor area dorsal to the fastigial projection and did not involve the Edinger-Westphal nucleus. In both cases, the terminal label was primarily found contralaterally. In contrast, retrogradely labelled cells were primarily found ipsilaterally within the supraoculomotor area following cerebellar injections. Retrogradely labelled cells projecting to the deep nuclei were also found bilaterally in the anteromedian nucleus, along with sparse terminal label. Taken as a whole, these results demonstrate the presence of a highly specific pattern of labelling in the supraoculomotor area, which may indicate that the posterior interposed nucleus and the fastigial nucleus play different roles in the control of the near-response. Alternatively, these projections may subserve other functions, such as modulating the pupillary light reflex. The fact that the projection from the deep nuclei is primarily contralateral, while the supraoculomotor projection to the deep nuclei is primarily ipsilateral, suggests that this may not be a simple feedback system, but may instead be involved in balancing the gains in the two eyes. In sum, physiological experiments have indicated the presence of near-response neurons in the midbrain supraoculomotor area and have indicated that the cerebellum may play a role in modulating the components of the near-response, as well as activity in the intrinsic eye muscles. The present experiments suggest a pattern of connections that might subserve this cerebellar modulation.

Meso-diencephalic regions projecting to spinal cord and dorsal column nuclear complex in the hedgehog-tenrec, Echinops telfairi

The distribution of neurons projecting to the spinal cord and dorsal column nuclear complex was investigated in the mesodiencephalic regions of the lesser hedgehog-tenrec, Echinops telfairi (Insectivora) by using the retrograde flow technique. While only few neurons projected to the dorsal column nuclear complex, numerous cells were found to give rise to spinal projections. Rubro-spinal neurons of various sizes were distributed over the entire rostrocaudal extent of the contra-lateral nucleus; a few neurons were also located ipsilaterally, Unlike that of the opossum, the projection appeared to be somatotopically organised. Interstitio-spinal neurons were differentiated into several subpopulations according to their location and laterality of projection. In the ipsilateral periventricular grey, in addition, there was a distinct population of cells possibly corresponding to the nucleus of Darkschewitsch. The mesencephalic central grey contained relatively few labeled neurons, the great majority of them being mesencephalic trigeminal, ectopic cuneiform or midline cells. Labeled cuneiform and midline cells, on the other hand, were quite numerous, extending both from a level just caudal to the trochlear nucleus to levels far beyond the rostral tip of the somatic oculomotor nucleus. The discrepancy between the poorly differentiated oculomotor nuclei and the apparently well-developed Edinger-Westphal complex is discussed. Hypothalamo-spinal neurons were essentially restricted to dorsal regions: the hypothalamic paraventricular nucleus (PAV), the dorso-medial (DmHy) and dorso-intermediate cell groups as well as the lateral hypothalamic zone. The latter two cell groups were bilaterally labeled, while the labeled neurons in DmHy and PAV were located predominantly ipsilaterally. Labeled neurons in the amygdala, colliculus superior and mesencephalic trigeminal nucleus were only found following cervical injections; all other mentioned areas and the posterior commissure complex projected to, at least, midthoracic level.

Parasympathetic nuclei

A series of experiments in monkeys using the fluorescent tracer substances Fast Blue and Nuclear yellow as well as wheat germ agglutinin-horseradish peroxidase injected into the ciliary ganglion has demonstrated labeling in 3 distinct regions of the mesencephalon: (1) anterior median nucleus; (2) Edinger-Westphal nucleus; and (3) the nucleus of Perlia. Further it was shown that the caudal extent of the Edinger-Westphal nucleus reaches the level of the central caudal nucleus of the somatic complex and that the lateral visceral column divided into a major and accessory column at the junction of the middle and posterior one-third of the somatic complex.

Direct parasympathetic pathway to the eye: revisited

Intraocular injections of wheat germ agglutinin horseradish peroxidase appeared to confirm previous experimental and clinical data supporting the existence of a direct, non-synapsing, parasympathetic pathway from the mesencephalon to the eye. Quantitative and qualitative differences between the two pathways were noted. The intraocular injection of the fluorescent dyes Fast blue and Nuclear yellow failed to provide mesencephalic labeling. The implications of these findings are discussed.

Identification of the teleost Edinger-Westphal nucleus by retrograde horseradish peroxidase labeling and by electrophysiological criteria

A homolog of the Edinger-Westphal nucleus of other vertebrates is described in two species of serranid basses of the genus Paralabrax, a group possessing a wide range of ocular accommodation but lacking a pupillary reflex to light. The nucleus was found by retrograde labeling from the ciliary ganglion and lies dorsolateral to the ipsilateral oculomotor nucleus. The nucleus consists of 60 to 100 neurons with an average soma diameter of about 20 microns in animals weighing 70 to 150 g. Electrophysiological experiments support the identification. Microstimulation of the nucleus evokes contraction of the ipsilateral lens retractor muscle and slight constriction of the caudal ipsilateral iris. Multi- and single-unit recordings in the nucleus reveal spontaneous firing (about 30 spikes/s in single units), the rate of which decreases during visually-evoked lens retractor relaxations (accommodation to near stimuli). Recordings of muscle fiber activity in the lens retractor show essentially the same behavior, which suggests that the ciliary ganglion and neuromuscular junctions simply relay impulses with little if any synaptic integration. The existence of a discrete Edinger-Westphal nucleus devoted largely to accommodation makes Paralabrax a good model system for the further tracing of central accommodation control pathways.

Disparate visceral neuronal pools subserve spinal cord and ciliary ganglion in the monkey: a double labeling approach

The fluorescent dyes Nuclear yellow, a nuclear marker, and Fast blue, a cytoplasmic marker, were utilized in a double-labeling procedure. One or the other of these dyes was injected sequentially into the cervical spinal cords and ciliary ganglia of 6 cynomolgus monkeys. No double labeling of cells was noted in the anterior median nucleus, Edinger-Westphal nucleus, or nucleus of Perlia in the mid-brain.

The motor nuclei and sensory neurons of the IIIrd, IVth, and VIth cranial nerves in the monitor lizard, Varanus exanthematicus

The motor nuclei of the oculomotor, trochlear, and abducens nerves of the reptile Varanus exanthematicus and the neurons that subserve the sensory innervation of the extraocular muscles were identified and localized by retrograde and anterograde transport of horseradish peroxidase (HRP). The highly differentiated oculomotor nuclear complex, located dorsomedially in the tegmentum of the midbrain, consists of the accessory oculomotor nucleus and the dorsomedial, dorsolateral, intermediate, and ventral subnuclei. The accessory oculomotor nucleus projects ipsilaterally to the ciliary ganglion. The dorsomedial, dorsolateral, and intermediate subnuclei distribute their axons to the ipsilateral orbit, whereas the ventral subnucleus, which innervates the superior rectus muscle, has a bilateral, though predominantly contralateral projection. The trochlear nucleus, which rostrally overlaps the oculomotor nuclear complex, is for the greater part a comma-shaped cell group situated lateral, dorsal, and medial to the medial longitudinal fasciculus. Following HRP application to the trochlear nerve, almost all retrogradely labeled cells were found in the contralateral nucleus. The nuclear complex of the abducens nerve consists of the principal and accessory abducens nuclei, both of which project ipsilaterally. The principal abducens nucleus is located just beneath the fourth ventricle laterally adjacent to the medial longitudinal fasciculus and innervates the posterior rectus muscle. The accessory abducens nucleus has a ventrolateral position in the brainstem in close approximation to the ophthalmic fibers of the descending trigeminal tract. It innervates the retractor bulbi and bursalis muscles. The fibers arising in the accessory abducens muscles form a loop in or just beneath the principal abducens nucleus before they join the abducens nerve root. The afferent fibers conveying sensory information from the extraocular muscles course in the oculomotor nerve and have their perikarya in the ipsilateral trigeminal ganglion, almost exclusively in its ophthalmic portion.

Edinger-Westphal nucleus: cells that project to spinal cord contain corticotropin-releasing factor

Combined retrograde transport and immunocytochemical methods were used to determine whether neurons in the Edinger-Westphal complex (EW) that project to the spinal cord also demonstrate corticotropin-releasing factor-like immunoreactivity (CRF-LI). Large injections of horseradish peroxidase (HRP) into cervical spinal cord retrogradely labeled cells throughout the extent of the EW complex. Most retrogradely labeled EW neurons also exhibited CRF-LI, evidence that EW is the origin of a direct CRF-containing pathway which links the rostral mesencephalon with spinal cord.

Choline acetyltransferase immunocytochemistry of Edinger-Westphal and ciliary ganglion afferent neurons in the cat

The distribution of cholinergic neurons in the region of the cat Edinger-Westphal nucleus (EW) was determined by immunocytochemical localization of the acetylcholine-synthesizing enzyme choline acetyltransferase (ChAT). Neurons containing ChAT-like immunoreactivity (ChAT-LI) were densely distributed within EW, the anteromedian nucleus (AM), and the oculomotor nucleus (III), and were also present in immediately adjacent regions of the periaqueductal gray and ventral tegmental region. The majority of labelled neurons in EW and AM showed a markedly lower intensity of ChAT-LI than the labelled neurons in III and adjacent regions. To determine the relationship of cells with ChAT-LI to the distribution of ciliary ganglion afferent neurons, a double labelling immunocytochemistry/retrograde transport technique was also used. These experiments showed that many of the cells located outside of III that stained intensely for ChAT-LI project to ciliary ganglion. Very few ciliary ganglion afferent neurons were found in EW or AM itself; instead, the distribution of lightly labelled ChAT-LI-positive neurons in EW and AM more closely matched the known distribution of peptide-containing cells that have descending, central projections.

Afferents to the lateral reticular nucleus from the oculomotor region. I. The Edinger-Westphal nucleus

By means of retrograde axonal transport of the wheat germ agglutinin-horseradish peroxidase complex, a projection from the Edinger-Westphal nucleus to the lateral reticular nucleus was demonstrated in the cat. Following small tracer ejections in the main part of the lateral reticular nucleus, a significant number of labelled neurons were found bilaterally throughout the Edinger-Westphal nucleus. Most of the labelled cells were located on the ipsilateral side. The projecting neurons are spindle-shaped to round with a maximum diameter of the cell body between 15 and 30 microns. The findings are discussed in relation to other Edinger-Westphal efferent projections, and some comments are made concerning the cytoarchitecture and delineation of the feline Edinger-Westphal nucleus.

Edinger-Westphal nucleus: cholecystokinin immunocytochemistry and projections to spinal cord and trigeminal nucleus in the cat

Immunocytochemical methods were used to determine the distribution of cells with cholecystokinin-like immunoreactivity (CCK-LI) in the cat Edinger-Westphal complex (EW). Numerous cells with CCK-LI are found throughout the length of EW. The distribution and frequency of such cells are similar to the pattern of EW neurons that show substance P-like immunoreactivity (SP-LI). Companion retrograde transport experiments reveal that EW neurons which project to spinal cord or the region of the caudal trigeminal nucleus are found throughout the length of EW, and that some EW neurons which project to spinal cord also show CCK-LI.

Cortical neurons with collateral projections to both the caudate nucleus and the centromedian-parafascicular thalamic complex: a fluorescent retrograde double labeling study in the cat

The retrograde fluorescent technique was used to label cortical neurons which project to both the caudate nucleus and also to the centromedian-parafascicular (CM-Pf) thalamic nuclear complex. After experimentation with many other pairs of fluorescent tracers, Evans Blue (EB) and Fast Blue (FB) were chosen as the best combination for studying the systems involved. Following injections of EB into the caudate nucleus and FB into the CM-Pf complex, doubly labeled medium-sized pyramidal neurons were present within layer V and VI of specific cortical regions. These cells were found on the inferior bank of the cruciate sulcus, in the anterior limbic area, in the cingulate and anterior sylvian gyri and within the buried cortex of the presylvian sulcus. The doubly labeled cells were relatively few in number compared to the more numerous singly labeled FB (corticothalamic) cells found in layers V and VI, and the very numerous singly labeled EB (corticostriatal) neurons, located in layers II, III, V, and VI.

Edinger-Westphal neurons that project to spinal cord contain substance P

Combined retrograde transport and immunocytochemical methods were used to determine whether Edinger-Westphal neurons projecting to spinal cord also demonstrate substance P-like immunoreactivity (SPLI). Large injections of horseradish peroxidase (HRP) into cervical and lumbar enlargements retrogradely labeled cells throughout the length of the Edinger-Westphal complex (EW). Nearly all HRP-labeled EW neurons also stained for SPLI, evidence that EW is the origin of a direct substance P pathway linking rostral mesencephalon with spinal cord.