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

Leptin coordinates efferent sympathetic outflow to the white adipose tissue through the midbrain centrally-projecting Edinger-Westphal nucleus in male rats

The centrally-projecting Edinger-Westphal nucleus (EWcp) hosts a large population of neurons expressing urocortin 1 (Ucn1) and about half of these neurons also express the leptin receptor (LepRb). Previously, we have shown that the peripheral adiposity hormone leptin signaling energy surfeit modulates EWcp neurons' activity. Here, we hypothesized that Ucn1/LepRb neurons in the EWcp would act as a crucial neuronal node in the brain-white adipose tissue (WAT) axis modulating efferent sympathetic outflow to the WAT. We showed that leptin bound to neurons of the EWcp stimulated STAT3 phosphorylation, and increased Ucn1-production in a time-dependent manner. Besides, retrograde transneuronal tract-tracing using pseudorabies virus (PRV) identified EWcp Ucn1 neurons connected to WAT. Interestingly, reducing EWcp Ucn1 contents by ablating EWcp LepRb-positive neurons with leptin-saporin, did not affect food intake and body weight gain, but substantially (+26%) increased WAT weight accompanied by a higher plasma leptin level and changed plasma lipid profile. We also found that ablation of EWcp Ucn1/LepRb neurons resulted in lower respiratory quotient and oxygen consumption one week after surgery, but was comparable to sham values after 3 and 5 weeks of surgery. Taken together, we report that EWcp/LepRb/Ucn1 neurons not only respond to leptin signaling but also control WAT size and fat metabolism without altering food intake. These data suggest the existence of a EWcp-WAT circuitry allowing an organism to recruit fuels without being able to eat in situations such as the fight-or-flight response.

Gray areas: Neuropeptide circuits linking the Edinger-Westphal and Dorsal Raphe nuclei in addiction

The circuitry of addiction comprises several neural networks including the midbrain - an expansive region critically involved in the control of motivated behaviors. Midbrain nuclei like the Edinger-Westphal (EW) and dorsal raphe (DR) contain unique populations of neurons that synthesize many understudied neuroactive molecules and are encircled by the periaqueductal gray (PAG). Despite the proximity of these special neuron classes to the ventral midbrain complex and surrounding PAG, functions of the EW and DR remain substantially underinvestigated by comparison. Spanning approximately -3.0 to -5.2 mm posterior from bregma in the mouse, these various cell groups form a continuum of neurons that we refer to collectively as the subaqueductal paramedian zone. Defining how these pathways modulate affective behavioral states presents a difficult, yet conquerable challenge for today's technological advances in neuroscience. In this review, we cover the known contributions of different neuronal subtypes of the subaqueductal paramedian zone. We catalogue these cell types based on their spatial, molecular, connectivity, and functional properties and integrate this information with the existing data on the EW and DR in addiction. We next discuss evidence that links the EW and DR anatomically and functionally, highlighting the potential contributions of an EW-DR circuit to addiction-related behaviors. Overall, we aim to derive an integrated framework that emphasizes the contributions of EW and DR nuclei to addictive states and describes how these cell groups function in individuals suffering from substance use disorders. This article is part of the special Issue on 'Neurocircuitry Modulating Drug and Alcohol Abuse'.

Centrally Projecting Edinger-Westphal Nucleus in the Control of Sympathetic Outflow and Energy Homeostasis

The centrally projecting Edinger-Westphal nucleus (EWcp) is a midbrain neuronal group, adjacent but segregated from the preganglionic Edinger-Westphal nucleus that projects to the ciliary ganglion. The EWcp plays a crucial role in stress responses and in maintaining energy homeostasis under conditions that require an adjustment of energy expenditure, by virtue of modulating heart rate and blood pressure, thermogenesis, food intake, and fat and glucose metabolism. This modulation is ultimately mediated by changes in the sympathetic outflow to several effector organs, including the adrenal gland, heart, kidneys, brown and white adipose tissues and pancreas, in response to environmental conditions and the animal's energy state, providing for appropriate energy utilization. Classic neuroanatomical studies have shown that the EWcp receives inputs from forebrain regions involved in these functions and projects to presympathetic neuronal populations in the brainstem. Transneuronal tracing with pseudorabies virus has demonstrated that the EWcp is connected polysynaptically with central circuits that provide sympathetic innervation to all these effector organs that are critical for stress responses and energy homeostasis. We propose that EWcp integrates multimodal signals (stress, thermal, metabolic, endocrine, etc.) and modulates the sympathetic output simultaneously to multiple effector organs to maintain energy homeostasis under different conditions that require adjustments of energy demands.

A possible neural mechanism for photosensitivity in chronic pain

Patients with functional pain disorders often complain of generalized sensory hypersensitivity, finding sounds, smells, or even everyday light aversive. The neural basis for this aversion is unknown, but it cannot be attributed to a general increase in cortical sensory processing. Here, we quantified the threshold for aversion to light in patients with fibromyalgia, a pain disorder thought to reflect dysregulation of pain-modulating systems in the brain. These individuals expressed discomfort at light levels substantially lower than that of healthy control subjects. Complementary studies in lightly anesthetized rat demonstrated that a subset of identified pain-modulating neurons in the rostral ventromedial medulla unexpectedly responds to light. Approximately half of the pain-facilitating "ON-cells" and pain-inhibiting "OFF-cells" sampled exhibited a change in firing with light exposure, shifting the system to a pronociceptive state with the activation of ON-cells and suppression of OFF-cell firing. The change in neuronal firing did not require a trigeminal or posterior thalamic relay, but it was blocked by the inactivation of the olivary pretectal nucleus. Light exposure also resulted in a measurable but modest decrease in the threshold for heat-evoked paw withdrawal, as would be expected with engagement of this pain-modulating circuitry. These data demonstrate integration of information about light intensity with somatic input at the level of single pain-modulating neurons in the brain stem of the rat under basal conditions. Taken together, our findings in rodents and humans provide a novel mechanism for abnormal photosensitivity and suggest that light has the potential to engage pain-modulating systems such that normally innocuous inputs are perceived as aversive or even painful.

The centrally projecting Edinger-Westphal nucleus--I: Efferents in the rat brain

The oculomotor accessory nucleus, often referred to as the Edinger-Westphal nucleus [EW], was first identified in the 17th century. Although its most well known function is the control of pupil diameter, some controversy has arisen regarding the exact location of these preganglionic neurons. Currently, the EW is thought to consist of two different parts. The first part [termed the preganglionic EW-EWpg], which controls lens accommodation, choroidal blood flow and pupillary constriction, primarily consists of cholinergic cells that project to the ciliary ganglion. The second part [termed the centrally projecting EW-EWcp], which is involved in non-ocular functions such as feeding behavior, stress responses, addiction and pain, consists of peptidergic neurons that project to the brainstem, the spinal cord and prosencephalic regions. However, in the literature, we found few reports related to either ascending or descending projections from the EWcp that are compatible with its currently described functions. Therefore, the objective of the present study was to systematically investigate the ascending and descending projections of the EW in the rat brain. We injected the anterograde tracer biotinylated dextran amine into the EW or the retrograde tracer cholera toxin subunit B into multiple EW targets as controls. Additionally, we investigated the potential EW-mediated innervation of neuronal populations with known neurochemical signatures, such as melanin-concentrating hormone in the lateral hypothalamic area [LHA] and corticotropin-releasing factor in the central nucleus of the amygdala [CeM]. We observed anterogradely labeled fibers in the LHA, the reuniens thalamic nucleus, the oval part of the bed nucleus of the stria terminalis, the medial part of the central nucleus of the amygdala, and the zona incerta. We confirmed our EW-LHA and EW-CeM connections using retrograde tracers. We also observed moderate EW-mediated innervation of the paraventricular nucleus of the hypothalamus and the posterior hypothalamus. Our findings provide anatomical bases for previously unrecognized roles of the EW in the modulation of several physiologic systems.

Autonomic regulation of cellular immune function

The nervous system and the immune system (IS) are two integrative systems that work together to detect threats and provide host defense, and to maintain/restore homeostasis. Cross-talk between the nervous system and the IS is vital for health and well-being. One of the major neural pathways responsible for regulating host defense against injury and foreign antigens and pathogens is the sympathetic nervous system (SNS). Stimulation of adrenergic receptors (ARs) on immune cells regulates immune cell development, survival, proliferative capacity, circulation, trafficking for immune surveillance and recruitment, and directs the cell surface expression of molecules and cytokine production important for cell-to-cell interactions necessary for a coordinated immune response. Finally, AR stimulation of effector immune cells regulates the activational state of immune cells and modulates their functional capacity. This review focuses on our current understanding of the role of the SNS in regulating host defense and immune homeostasis. SNS regulation of IS functioning is a critical link to the development and exacerbation of chronic immune-mediated diseases. However, there are many mechanisms that need to be further unraveled in order to develop sound treatment strategies that act on neural-immune interaction to resolve or prevent chronic inflammatory diseases, and to improve health and quality of life.

The Edinger-Westphal nucleus: a historical, structural, and functional perspective on a dichotomous terminology

The eponymous term nucleus of Edinger-Westphal (EW) has come to be used to describe two juxtaposed and somewhat intermingled cell groups of the midbrain that differ dramatically in their connectivity and neurochemistry. On one hand, the classically defined EW is the part of the oculomotor complex that is the source of the parasympathetic preganglionic motoneuron input to the ciliary ganglion (CG), through which it controls pupil constriction and lens accommodation. On the other hand, EW is applied to a population of centrally projecting neurons involved in sympathetic, consumptive, and stress-related functions. This terminology problem arose because the name EW has historically been applied to the most prominent cell collection above or between the somatic oculomotor nuclei (III), an assumption based on the known location of the preganglionic motoneurons in monkeys. However, in many mammals, the nucleus designated as EW is not made up of cholinergic, preganglionic motoneurons supplying the CG and instead contains neurons using peptides, such as urocortin 1, with diverse central projections. As a result, the literature has become increasingly confusing. To resolve this problem, we suggest that the term EW be supplemented with terminology based on connectivity. Specifically, we recommend that 1) the cholinergic, preganglionic neurons supplying the CG be termed the Edinger-Westphal preganglionic (EWpg) population and 2) the centrally projecting, peptidergic neurons be termed the Edinger-Westphal centrally projecting (EWcp) population. The history of this nomenclature problem and the rationale for our solutions are discussed in this review.

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.

Changes in somatodendritic morphometry of rat oculomotor nucleus motoneurons during postnatal development

This work investigates the somatodendritic shaping of rat oculomotor nucleus motoneurons (Mns) during postnatal development. The Mns were functionally identified in slice preparation, intracellularly injected with neurobiotin, and three-dimensionally reconstructed. Most of the Mns (approximately 85%) were multipolar and the rest (approximately 15%) bipolar. Forty multipolar Mns were studied and grouped as follows: 1-5, 6-10, 11-15, and 21-30 postnatal days. Two phases were distinguished during postnatal development (P1-P10 and P11-P30). During the first phase, there was a progressive increase in the dendritic complexity; e.g., the number of terminals per neuron increased from 26.3 (P1-P5) to 47.7 (P6-P10) and membrane somatodendritic area from 11,289.9 microm(2) (P1-P5) to 19,235.8 microm(2) (P6-P10). In addition, a few cases of tracer coupling were observed. During the second phase, dendritic elongation took place; e.g., the maximum dendritic length increased from 486.7 microm (P6-P10) to 729.5 microm in adult Mns, with a simplification of dendritic complexity to values near those for the newborn, and a slow, progressive increase in membrane area from 19,235.8 microm(2) (P6-P10) to 24,700.3 microm(2) (P21-P30), while the somatic area remained constant. In conclusion, the electrophysiological changes reported in these Mns with maturation (Carrascal et al. [2006] Neuroscience 140:1223-1237) cannot be fully explained by morphometric variations; the dendritic elongation and increase in dendritic area are features shared with other pools of Mns, whereas changes in dendritic complexity depend on each population; the first phase paralleled the establishment of vestibular circuitry and the second paralleled eyelid opening.

Unique responses of midbrain CART neurons in macaques to ovarian steroids

CART (cocaine and amphetamine regulated transcript) is a neuropeptide involved in the control of several physiological processes, such as response to psychostimulants, food intake, depressive diseases and neuroprotection. It is robustly expressed in the brain, mainly in regions that control emotional and stress responses and it is regulated by estrogen in the hypothalamus. There is a distinct population of CART neurons located in the vicinity of the Edinger-Westphal nucleus of the midbrain that also colocalize urocortin-1. The aims of this study were 1) to determine the distribution of CART immunoreactive neurons in the monkey midbrain, 2) to examine the effects of estrogen (E) and progesterone (P) on midbrain CART mRNA and peptide expression and 3) to determine whether midbrain CART neurons contain steroid receptors. Adult female rhesus monkeys (Macaca mulatta) were spayed and either treated with placebo (OVX), estrogen alone (E), progesterone alone (P) or E+P. Animals were prepared (a) for RNA extraction followed by microarray analysis and quantitative (q) RT-PCR (n=3/group); (b) for immunohistochemical analysis of CART and CART+tryptophan hydroxylase (TPH), CART+estrogen receptors (ER) or CART+progesterone receptors (n=5/group) and (c) for Western blots (n=3/group). Both E- and E+P-administration decreased CART gene expression on the microarray and with qRT-PCR. Stereological analysis of CART immunostaining at five levels of the Edinger-Westphal nucleus indicated little effect of E or E+P administration on the area of CART immunostaining. However, P administration increased CART-immunopositive area in comparison to the OVX control group with Student's t-test, but not with ANOVA. CART 55-102 detection on Western blot was unchanged by hormone administration. ERbeta and PR were detected in CART neurons and CART fibers appeared to innervate TPH-positive serotonin neurons in the dorsal raphe. In summary, E decreased CART mRNA, but this effect did not translate to the protein level. Moreover, P administration alone had a variable effect on CART mRNA, but it caused an increase in CART immunostaining. Together, the data suggest that CART neurons in the midbrain have a unique steroid response, which may be mediated by nuclear receptors, neuroactive steroids or interneurons.

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.

Expression of c-Fos in the mouse Edinger-Westphal nucleus following ethanol administration is not secondary to hypothermia or stress

Restraint stress, lipopolysaccharide (LPS), and ethanol (EtOH) administration have all been found to induce c-Fos in the brain, and to cause hypothermia. The present study was designed to assess whether the c-Fos expression that occurs in the Edinger-Westphal nucleus (EW) after EtOH administration is independent of the hypothermia or any stress effects that occur. To test this, we used restraint stress and LPS in addition to EtOH, and also examined two control areas, the dorsal raphe nucleus (DRN) and the periaqueductal gray (PAG), in addition to EW. Male C57BL6/J mice were used. Groups of mice received intraperitoneal (IP) injections of EtOH (2 g/kg), LPS (600 microg/kg or 50 microg/kg), or saline. A separate group of mice received no injection, but were placed in plastic restrainers for the entirety of the experiment. For all groups, core temperatures were monitored rectally every 30 min for 3 h postinjection, after which, the animals were sacrificed. Then, the number of Fos-positive cells in the brain regions of the EW, DRN, and PAG was quantified. Both EtOH and restraint stress induced a transient hypothermia, where core temperature (Tc) declined immediately and then rose again. Both doses of LPS induced a slower developing, longer lasting hypothermia, while saline had no effect on Tc. Only EtOH induced a significant amount of c-Fos in EW, while both doses of LPS and restraint stress induced c-Fos in DRN, and only restraint stress caused induction in PAG. These data demonstrate that activation of EW after EtOH is unrelated to hypothermia or stress.

Chronic ether stress-induced response of urocortin 1 neurons in the Edinger-Westphal nucleus in the mouse

Urocortin 1 (Ucn1) neurons, most abundantly expressed in the Edinger-Westphal nucleus (E-WN), respond to various acute challenges. In a recent study, we found that acute ether stress resulted in the strongest activation of E-WN Ucn1 cells, as revealed by immunohistochemistry for Fos (often used as a marker for neuronal activation). Although the acute stress responsiveness of E-WN Ucn1 neurons has been widely studied, the activation pattern of Fos in these neurons in response to repeated challenges has not yet been investigated. Therefore, we quantitatively studied Fos activation in E-WN neurons and measured Ucn1 mRNA levels in E-WN neurons after acute and chronic ether stress in mice. Acute stress resulted in a robust Fos response and an increase in Ucn1 mRNA as compared to non-stressed mice. In the chronic stress paradigm, Fos expression was unchanged, whereas after 2 and 3 weeks of daily ether exposure Ucn1 mRNA expression had strongly declined in the E-WN. Fos and Ucn1 mRNA were co-expressed in E-WN neurons in both acutely and chronically stressed animals. This paper is the first to demonstrate that Ucn1 mRNA-expressing neurons in the E-WN show a non-habituating Fos response to a chronic homotypic ether challenge that also resulted in a reliable down-regulation of E-WN Ucn1 mRNA levels vs. acutely stressed animals. Based on these results, we propose that the E-WN-Ucn1 system represents a novel stress adaptation pathway, which may play an important role in coping with chronic challenges.

Urocortin 1 expression in five pairs of rat lines selectively bred for differences in alcohol drinking

RATIONALE

There is accumulating evidence that the neuropeptide urocortin 1 (Ucn1) is involved in alcohol consumption. Thus far, however, most studies have been performed in mice.

OBJECTIVES

The purpose of the present study was to characterize Ucn1 expression in rats selectively bred for either high or low alcohol intake.

METHODS

Brains from naive male rats of five pairs of independently selected lines (iP/iNP, AA/ANA, HARF/LARF, HAD1/LAD1, and HAD2/LAD2) were analyzed by immunohistochemistry.

RESULTS

Significant differences were found between iP/iNP, HARF/LARF, and HAD2/LAD2 in number of Ucn1-containing cells in the Edinger-Westphal (EW) nucleus (the main source of Ucn1 in the brain), whereas no significant differences were found between HAD1/LAD1 and AA/ANA. Similarly, significant differences in the optical density of Ucn1 immunoreactivity in EW were found between iP/iNP, HARF/LARF, and HAD2/LAD2, whereas no differences on this measure were found between HAD1/LAD1 and AA/ANA. In the lateral septum (LS, the main projection area of Ucn1-containing neurons in the rat), significant differences were found only between AA/ANA and HAD2/LAD2; however, a meta-analysis indicated that across all five lines, preferring animals had a significantly greater number of Ucn1-positive fibers than nonpreferring animals.

CONCLUSIONS

These results provide evidence that, in rats, Ucn1 may be involved in regulation of alcohol intake, and that this regulation may occur through the Ucn1 projections to LS.

Cholecystokinin and substance P immunoreactive projections to the paraventricular thalamic nucleus in the rat

Cholecystokinin (CCK) and substance P (SP) are thought to play an important role in a variety of stress responses. Both CCK- and SP-positive fibers innervating the thalamus are found principally in the midline nuclei, including the paraventricular thalamic nucleus (PVT), which has strong reciprocal connections with the medial prefrontal cortex. In the present study, we determined the source of the CCK- and SP-immunoreactive fibers to the PVT, employing combination of retrograde neuronal tracing and immunohistochemistry in the rat. The PVT-projecting neurons showing CCK immunoreactivity were detected in the dorsomedial nucleus of the hypothalamus, and ventral mesencephalic periaqueductal gray, including the Edinger-Westphal nucleus and the dorsal raphe nucleus. Sources of SP afferents to the PVT were detected in the Edinger-Westphal nucleus, the mesopontine tegmentum and the medullary raphe nucleus. CCK- and SP-immunoreactive fibers may exert modulatory influence on the prefrontal cortical activity via the PVT and regulate behavioral components of stress-adaptation responses.

Ethanol versus lipopolysaccharide-induced hypothermia: Involvement of urocortin

The urocortin1 (Ucn1) neurons of the mid-brain-localized Edinger-Westphal nucleus (EW) are robustly responsive to ethanol (EtOH) administration, and send projections to the dorsal raphe nucleus (DRN), which contains corticotropin-releasing factor type 2 receptors (CRF2) that are responsive to Ucn1. In addition, the DRN has been shown to be involved in regulation of body temperature, a function greatly affected by EtOH administration. The goal of the present study was to identify the role that the urocortinergic projections from the EW to the DRN have in mediating EtOH-induced and lipopolysaccharide (LPS)-induced hypothermia. Male C57BL6/J mice were used. Groups of mice underwent cannulation of the DRN, and then received i.p. injections of EtOH (2g/kg) or LPS (600 microg/kg or 400 microg/kg), followed by intra-DRN injections of artificial cerebrospinal fluid (aCSF) or anti-sauvagine (aSVG) (55 pmol), a CRF2 antagonist. Separate groups of mice received single intra-DRN injections of Ucn1 (20 pmol), CRF (20 pmol) or aCSF. For all experiments, core temperatures were monitored rectally every 30 min for several hours post-injection. Both EtOH and LPS induced hypothermia, and aSVG significantly attenuated this effect after EtOH; however, there was no significant attenuation of hypothermia after either dose of LPS. Ucn1 injection also caused hypothermia, while CRF injection did not. These data demonstrate that EtOH-induced hypothermia, but not LPS-induced hypothermia, may involve Ucn1 from EW acting at CRF2 receptors in the DRN.

Lesions of the Edinger-Westphal nucleus in C57BL/6J mice disrupt ethanol-induced hypothermia and ethanol consumption

The Edinger-Westphal nucleus (EW) is a brain region that has recently been implicated as an important novel neural target for ethanol. Thus, the EW is the only brain region consistently showing elevated c-Fos expression following both voluntary and involuntary ethanol administration. Ethanol-induced c-Fos expression in the EW has been shown to occur in urocortin I-positive neurons. Moreover, previous reports using several genetic models have demonstrated that differences in the EW urocortin I system are correlated with ethanol-mediated behaviours such as ethanol-induced hypothermia and ethanol consumption. The aim of this study was to confirm these relationships using a more direct strategy. Thus, ethanol responses were measured following electrolytic lesions of the EW in male C57BL/6J mice. Both EW-lesioned and sham-operated animals were tested for several ethanol sensitivity measures and ethanol consumption in a two-bottle choice test. The results show that lesions of the EW significantly disrupted ethanol-induced hypothermia, while having no effect on pupillary dilation, locomotor activity or ethanol-induced sedation. In addition, EW-lesioned animals showed significantly lower ethanol preference and total ethanol dose consumed in the two-bottle choice test. EW-lesioned animals also consumed less sucrose than sham-operated animals, but did not have altered preferences for sucrose or quinine in a two-bottle choice test. These data support previously observed genetic correlations between EW urocortin I expression and both ethanol-induced hypothermia and ethanol consumption. Taken together, the findings suggest that the EW may function as a sensor for ethanol, which can influence ethanol consumption and preference.

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.

Anxiolytic activity of the MGLU2/3 receptor agonist LY354740 on the elevated plus maze is associated with the suppression of stress-induced c-Fos in the hippocampus and increases in c-Fos induction in several other stress-sensitive brain regions

LY354740 is a potent and selective agonist for group II metabotropic glutamate (mGlu) receptors, mGlu2 and mGlu3 receptors, with anxiolytic activity in several animal models of anxiety, including the elevated plus maze (EPM) test. Here, we studied neuronal activation in mouse brain after EPM exposure in saline- and LY354740-treated mice using c-Fos immunoreactivity as a marker. The effect of LY354740 on c-Fos expression was also studied in cage control (no EPM) mice. Pretreatment with LY354740 (20 mg/kg, s.c.) produced robust anxiolytic behavior on the EPM. LY354740 administration decreased EPM-induced increases in c-Fos expression in the CA3 of the hippocampus, while having no significant effects on basal c-Fos expression in the hippocampus. LY354740 administration significantly increased c-Fos expression in specific limbic regions, including the lateral division of the central nucleus of the amygdala (CeL), lateral parabrachial nucleus, locus coeruleus, and Edinger-Westphal nucleus, whether or not animals were exposed to the EPM. Moreover, LY354740 administration per se significantly increased c-Fos expression in regions processing sensory information, including the paraventricular and lateral geniculate nucleus of the thalamus as well as the nucleus of the optic tract and superior colliculus. In particular, the suppression of fear-evoked neuronal activity in the hippocampus and drug-induced increases in neuronal activation in the CeL have been previously linked to the anxiolytic effects of clinically effective drugs such as benzodiazepines, and thus may contribute to anxiolytic actions of LY354740 in animal models and human anxiety patients.

Urocortin expression in the Edinger-Westphal nucleus is down-regulated in transgenic mice over-expressing neuronal corticotropin-releasing factor

In recent years a large body of evidence has emerged linking chronic stress with increased vulnerability for depression and anxiety disorders. As corticotropin-releasing factor (CRF) is hypersecreted under these psychological conditions, we used our CRF-overexpressing (CRF-OE) mouse line to study underlying brain mechanisms possibly causing these disorders. Urocortin (Ucn), a recently discovered member of the CRF peptide family may play a role in the pathophysiology of stress-induced disorders. Stressors recruit Ucn-immunoreactive neurons in the Edinger-Westphal nucleus (E-WN), which is the major site of Ucn expression. Furthermore, E-WN Ucn mRNA levels are upregulated in CRF-deficient mice. Based on these findings, we hypothesized the down-regulation of E-WN Ucn in CRF-OE mice and consequently, altered responsiveness to stressful stimuli. Our results support this hypothesis as we found weaker immunohistochemical labeling with anti-Ucn and a six times weaker Ucn mRNA signal in E-WN in CRF-OE mice. Moreover, E-WN Ucn-expressing neurons mounted a response to acute challenge in CRF-OE mice too. From these results it is concluded that the CRF and E-WN Ucn neuronal systems work in concert in response to acute challenges, but are inversely regulated in their activities during chronic hyperactivity of the hypothalamo-pituitary-adrenal axis.

Colocalization of urocortin and neuronal nitric oxide synthase in the hypothalamus and Edinger-Westphal nucleus of the rat

Different lines of studies suggest that both the corticotropin-releasing hormone-related peptide Urocortin I (Ucn) and the neuromodulator nitric oxide (NO) are involved in the regulation of the complex mechanisms controlling feeding and anxiety-related behaviors. The aim of the present study was to investigate the possible interaction between Ucn and NO in the hypothalamic paraventricular nucleus (PVN), an area known to be involved in the modulation of these particular behaviors. Therefore, we mapped local mRNA and peptide/protein presence of both Ucn and the NO producing neuronal NO synthase (nNOS). This investigation was extended to include the hypothalamic supraoptic nucleus (SON) and the Edinger-Westphal nucleus area (EW), the latter being one of the major cellular Ucn-expressing sites. Furthermore, we compared the two predominantly used laboratory rat strains, Wistar and Sprague-Dawley. Ucn mRNA and immunoreactivity were detected in the SON and in the EW. A significant difference between Wistar and Sprague-Dawley rats was found in mRNA levels in the EW. nNOS was detected in all brain areas analyzed, showing a significantly lower immunoreactivity in the PVN and EW of Sprague-Dawley versus Wistar rats. Contrary to some previous reports, no Ucn mRNA and only a very low immunoreactivity were detectable in the PVN of either rat strain. Interestingly, double-labeling immunofluorescence revealed that in the SON approximately 75% of all cells immunoreactive for Ucn were colocalized with nNOS, whereas in the EW only approximately 2% of the Ucn neurons were found to contain nNOS. These findings suggest an interaction between Ucn and NO signaling within the SON, rather than the PVN, that may modulate the regulation of feeding, reproduction, and anxiety-related behaviors.

Urocortin in the central nervous system of a primate (Cebus apella): sequencing, immunohistochemical, and hybridization histochemical characterization

The urocortin (UCN)-like immunoreactivity and UCN mRNA distribution in various regions of the nonprimate mammalian brain have been reported. However, the Edinger-Westphal nucleus (EW) appears to be the only brain site where UCN expression is conserved across species. Although UCN peptides are present throughout vertebrate phylogeny, the functional roles of both UCN and EW remain poorly understood. Therefore, a study focused on UCN system organization in the primate brain is warranted. By using immunohistochemistry (single and double labeling) and in situ hybridization, we have characterized the organization of UCN-expressing cells and fibers in the central nervous system and pituitary of the capuchin monkey (Cebus apella). In addition, the sequence of the prepro-UCN was determined to establish the level of structural conservation relative to the human sequence. To understand the relationship of acetylcholine cells in the EW, a colocalization study comparing choline acetyltransferase (ChAT) and UCN was also performed. The cloned monkey prepro-UCN is 95% identical to the human preprohormone across the matched sequences. By using an antiserum raised against rat UCN and a probe generated from human cDNA, we found that the EW is the dominant site for UCN expression, although UCN mRNA is also expressed in spinal cord lamina IX. Labeled axons and terminals were distributed diffusely throughout many brain regions and along the length of the spinal cord. Of particular interest were UCN-immunoreactive inputs to the medial preoptic area, the paraventricular nucleus of the hypothalamus, the oral part of the spinal trigeminal nucleus, the flocculus of the cerebellum, and the spinal cord laminae VII and X. We found no UCN hybridization signal in the pituitary. In addition, we observed no colocalization between ChAT and UCN in EW neurons. Our results support the hypothesis that the UCN system might participate in the control of autonomic, endocrine, and sensorimotor functions in primates.

The Edinger-Westphal-lateral septum urocortin pathway and its relationship to alcohol consumption

Identifying and characterizing brain regions regulating alcohol consumption is beneficial for understanding the mechanisms of alcoholism. To this aim, we first identified brain regions changing in expression of the inducible transcription factor c-Fos in the alcohol-preferring C57BL/6J (B6) and alcohol-avoiding DBA/2J (D2) mice after ethanol consumption. Drinking a 5% ethanol/10% sucrose solution in a 30 min limited access procedure led to induction of c-Fos immunoreactivity in urocortin (Ucn)-positive cells of the Edinger-Westphal nucleus (EW), suppression of c-Fos immunoreactivity in the dorsal portion of the lateral septum (LS) of both strains of mice, and strain-specific suppression in the intermediate portion of the LS and the CA3 hippocampal region. Because the EW sends Ucn projections to the LS, and B6 and D2 mice differ dramatically in EW Ucn expression, we further analyzed the Ucn EW-LS pathway using several genetic approaches. We find that D2 mice have higher numbers of Ucn-immunoreactive processes than B6 mice in the LS and that consumption of ethanol/sucrose in the F2 offspring of a B6D2 intercross positively correlates with Ucn immunoreactivity in the EW and negatively correlates with Ucn immunoreactivity in the LS. In agreement with these findings, we find that alcohol-avoiding male B6.D2 Alcp1 line 2.2 congenic mice have lower Ucn immunoreactivity in the EW than male B6.B6 mice. Finally, we also find that HAP mice, selectively bred for high alcohol preference, have higher Ucn immunoreactivity in EW, than LAP mice, selectively bred for low alcohol preference. Taken together, these studies provide substantial evidence for involvement of the EW-LS Ucn pathway in alcohol consumption.

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.

The efferent connections of the pupillary constriction area in the rat medial frontal cortex

This study investigated, in the rat, the efferent projections of the pupillary constriction area, which is located within the medial frontal cortex. In order to identify the location of the pupillary constriction area, in preliminary experiments the medial frontal cortex was microstimulated. Intracortical microstimulation elicited pupillary constriction in a thin strip of cortex near the interhemispheric fissure and bordering the frontal eye field and vibrissae area of the somatomotor cortex. Seven animals received a single iontophoretic injection of Phaseolus vulgaris leucoagglutinin in the pupillary constriction area. In these cases, anterogradely labelled fibres and terminal-like elements were found in both hemispheres. The densest labeling was seen in several areas of the injected hemisphere, where labeled fibers prevailed in the secondary visual cortex. Dense labeled fibers were also found in the retrosplenial and cingulate cortex. In the thalamus, labeled fibers were seen in the intralaminar nuclei and posterior nuclear group. In the midbrain and pons, labeled fibers were located in the anterior pretectal area, superior colliculus and in the dorsolateral portion of the central gray. Contralaterally to the injection site, labeled fibers were distributed in the homotopic region. These findings led us to assume that, in the medial frontal cortex of the rat, besides controlling pupillary constriction, the pupillary constriction area may also be involved in controlling orientation and exploring behavior.

New neuronal networks involved in ethanol reinforcement

This article represents the proceedings of a symposium at the 2002 ISBRA/RSA meeting in San Francisco. The organizers were Kalervo Kiianmaa and Andrey E. Ryabinin. The chairs were Kalervo Kiianmaa and Jörgen A. Engel. The presentations were (1) The role of opioidergic and dopaminergic networks in ethanol-seeking behavior, by Kalervo Kiianmaa and Petri Hyytiä; (2) Interaction between the dopamine systems in the prefrontal cortex and nucleus accumbens during ethanol self-administration, by Herman H. Samson; (3) Neurochemical and behavioral studies on ethanol and nicotine interactions, by Jörgen A. Engel, Lennart Svensson, Bo Söderpalm, and Anna Larsson; (4) Involvement of the GABA receptor in alcohol reinforcement in sP rats, by Giancarlo Colombo and Giovanni Vacca; (5) Neuroactive steroids and ethanol reinforcement, by Deborah A. Finn, and (6) Potential contribution of the urocortin system to regulation of alcohol self-administration, by Andrey E. Ryabinin and Ryan K. Bachtell.(B)

Reinnervation of the pretectum in adult rats by regenerated retinal ganglion cell axons: anatomical and functional studies

We have investigated the specificity of reinnervation and terminal arborization of injured retinal ganglion cell (RGC) axons in the brainstem with the object of studying in a simple situation the degree to which regenerating axons are able to replicate the characteristic patterns of terminal arborization and restore normal function. We have focussed here on the pathway that is responsible for the pupillary light reflex, which is mediated through the olivary pretectal nucleus (OPN). In adult rats, the left optic nerve was transected and a segment of peripheral nerve (PN) graft was used to bridge between the retina and different regions of the ipsilateral brainstem, including the superior colliculus. After 4-13 months, regenerated RGC axons were examined in coronal sections stained for cholera toxin B subunit. RGC axons were found extending into the ipsilateral brainstem for distances of up to 6 mm. Within the pretectum, axons innervated the OPN and the nucleus of the optic tract preferentially, and formed distinctive terminal arbors within each. Within the SC axons extended laterally into the visual layers and formed a different type of arborization. On testing the pupillary light reflex, it was found in best cases to show response amplitudes which were comparable to those recorded from control intact animals. However, unlike normals, the response amplitude tended to diminish with repeated stimulation and also appeared to deteriorate with age, although responses could still be detected in some cases as long as 15 months after grafting. These results indicate that regenerating axons can selectively reinnervate denervated nuclei, where they form typical terminal arborizations, and provide the substrates for restoring functional circuitry.

Distribution of urocortin-like immunoreactivity in the central nervous system of the frog Rana esculenta

Corticotropin-releasing factor (CRF), sauvagine, and urotensin I are all members of the so-called CRF neuropeptide family. Urocortin (Ucn), a 40-amino-acid neuropeptide recently isolated from the rat brain, is the newest member of this family. Until now, the distribution of Ucn in the central nervous system (CNS) has been studied only in placental mammals. We used a polyclonal antiserum against rat Ucn to determine the distribution of Ucn-like immunoreactivity in the CNS of the green frog, Rana esculenta. The great majority of Ucn-immunoreactive perikarya was seen in the anterior preoptic area, ventromedial thalamic nucleus, posterior tuberculum, nucleus of the medial longitudinal fasciculus, and Edinger-Westphal nucleus. Urocortin-immunoreactive nerve cells were also observed in the motor nuclei of the trigeminal and facial nerves and in the hypoglossal nucleus. Immunoreactive fibers were found in the medial and lateral septal nuclei, bed nucleus of the stria terminalis, many of the thalamic and hypothalamic nuclei, mesencephalic tectum, tegmental nuclei, torus semicircularis, and dorsal horn and central field of the spinal cord. Only scattered Ucn-immunoreactive axon terminals were observed in the external zone of the medial eminence. The densest accumulations of Ucn-immunoreactive nerve terminals were seen in the granular layer of the cerebellum and cochlear nuclei. Our results suggest that an ortholog of mammalian Ucn occurs in the CNS of the green frog. The distribution of Ucn-like immunoreactivity in Rana esculenta showed many similarities to the distribution in placental mammals. The distribution of Ucn-like immunoreactivity in the anuran CNS was different from that of CRF and sauvagine, so our results suggest that at least three different lineages of the CRF neuropeptide family occur in the anuran CNS.

Strain differences in urocortin expression in the Edinger-Westphal nucleus and its relation to alcohol-induced hypothermia

The Edinger-Westphal nucleus is the primary source of urocortin in rodent brain. Mapping of inducible transcription factors has shown that the Edinger-Westphal nucleus is preferentially sensitive to ethanol self-administration. In the present study we have immunohistochemically compared expression of urocortin and c-Fos in naive and ethanol-treated C57BL/6J and DBA/2J mouse inbred strains. We found that C57BL/6J mice possess significantly higher numbers of urocortin-expressing cells in the Edinger-Westphal compared to DBA/2J mice. Subsequent histological analysis confirmed a lower number of large neurons in the DBA/2J Edinger-Westphal nucleus. Surprisingly, despite the differences in structure, no strain differences were observed in the number of c-Fos-containing cells after acute (0.6-4.8 g/kg, i.p.) and repeated (2.4 g/kg, 14 days, one injection/day) administration of ethanol. Double-label immunohistochemistry showed that ethanol-induced c-Fos expression is present in different sets of Edinger-Westphal cells between the strains. Specifically, expression of c-Fos in C57BL/6J mice is preferentially induced in urocortin cells, while c-Fos in DBA/2J mice occurs in a mixed population of cells. Behavioral analysis of the B6D2 F2 intercross, a heterogeneous mouse strain, showed that the number of urocortin cells is positively correlated with basal temperatures and ethanol-induced hypothermia. Involvement of the Edinger-Westphal in alcohol-induced hypothermia is further confirmed by analysis of urocortin cells in the HOT/COLD selected lines. These results provide evidence that C57BL/6J and DBA/2J mice have structural differences in the Edinger-Westphal that can result in activation of different populations of neurons upon alcohol intoxication contributing to differential thermoregulation between these inbred strains.

Urocortin-deficient mice display normal stress-induced anxiety behavior and autonomic control but an impaired acoustic startle response

Corticotropin-releasing hormone (Crh) plays an important role in modulating physiological and behavioral responses to stress. Its actions are mediated through two receptors, Crhr1 and Crhr2. Urocortin (Ucn), a Crh-related neuropeptide and the postulated endogenous ligand for Crhr2, is a potential mediator of stress responses. We generated Ucn-deficient mice using embryonic stem cell technology to determine its role in stress-induced behavioral and autonomic responses. Unlike Crhr1- or Crhr2-deficient mice, Ucn-deficient mice exhibit normal anxiety-like behavior as well as autonomic regulation in response to stress. However, the mutant mice display an impaired acoustic startle response that is not due to an obvious hearing defect. Thus, our results suggest that Ucn does not play an essential role in stress-induced behavioral and autonomic responses. Ucn may modulate the acoustic startle response through the Ucn-expressing neuron projections from the region of the Edinger-Westphal nucleus.

Functional circuitry involved in the regulation of whisker movements

Neuroanatomical tract-tracing methods were used to identify the oligosynaptic circuitry by which the whisker representation of the motor cortex (wMCx) influences the facial motoneurons that control whisking activity (wFMNs). Injections of the retrograde tracer cholera toxin subunit B into physiologically identified wFMNs in the lateral facial nucleus resulted in dense, bilateral labeling throughout the brainstem reticular formation and in the ambiguus nucleus as well as predominantly ipsilateral labeling in the paralemniscal, pedunculopontine tegmental, Kölliker-Fuse, and parabrachial nuclei. In addition, neurons in the following midbrain regions projected to the wFMNs: superior colliculus, red nucleus, periaqueductal gray, mesencephalon, pons, and several nuclei involved in oculomotor behaviors. Injections of the anterograde tracer biotinylated dextran amine into the wMCx revealed direct projections to the brainstem reticular formation as well as multiple brainstem and midbrain structures shown to project to the wFMNs. Regions in which retrograde labeling and anterograde labeling overlap most extensively include the brainstem parvocellular, gigantocellular, intermediate, and medullary (dorsal and ventral) reticular formations; ambiguus nucleus; and midbrain superior colliculus and deep mesencephalic nucleus. Other regions that contain less dense regions of combined anterograde and retrograde labeling include the following nuclei: the interstitial nucleus of medial longitudinal fasciculus, the pontine reticular formation, and the lateral periaqueductal gray. Premotoneurons that receive dense inputs from the wMCx are likely to be important mediators of cortical regulation of whisker movements and may be a key component in a central pattern generator involved in the generation of rhythmic whisking activity.

Characterization of the central nervous system innervation of the rat spleen using viral transneuronal tracing

Splenic immune function is modulated by sympathetic innervation, which in turn is controlled by inputs from supraspinal regions. In the present study, the characterization of central circuits involved in the control of splenic function was accomplished by injecting pseudorabies virus (PRV), a retrograde transynaptic tracer, into the spleen and conducting a temporal analysis of the progression of the infection from 60 hours to 110 hours postinoculation. In addition, central noradrenergic cell groups involved in splenic innervation were characterized by dual immunohistochemical detection of dopamine-beta-hydroxylase and PRV. Infection in the CNS first appeared in the spinal cord. Splenic sympathetic preganglionic neurons, identified in rats injected with Fluoro-Gold i.p. prior to PRV inoculation of the spleen, were located in T(3)-T(12) bilaterally; numerous infected interneurons were also found in the thoracic spinal cord (T(1)-T(13)). Infected neurons in the brain were first observed in the A5 region, ventromedial medulla, rostral ventrolateral medulla, paraventricular hypothalamic nucleus, Barrington's nucleus, and caudal raphe. At intermediate survival times, the number of infected cells increased in previously infected areas, and infected neurons also appeared in lateral hypothalamus, A7 region, locus coeruleus, subcoeruleus region, nucleus of the solitary tract, and C3 cell group. At longer postinoculation intervals, infected neurons were found in additional hypothalamic areas, Edinger-Westphal nucleus, periaqueductal gray, pedunculopontine tegmental nucleus, caudal ventrolateral medulla, and area postrema. These results demonstrate that the sympathetic outflow to the spleen is controlled by a complex multisynaptic pathway that involves several brainstem and forebrain nuclei.

Selective cell loss in Edinger-Westphal in asymptomatic elders and Alzheimer's patients

Exaggerated pupillary response to a low concentration of cholinergic antagonists has been suggested as an early marker for Alzheimer's Disease (AD). To examine the anatomic basis of this phenomenon, we determined possible neuropathological changes in the Edinger-Westphal (EW) nucleus, a midbrain neural center with a significant functional role in the control of pupil size. Stereologically determined neuronal numbers within the EW were counted in individuals with pathologically confirmed AD, control cases with no AD-type pathology, and subjects with AD pathology not meeting diagnostic criteria for AD. The EW of AD patients displayed a marked and striking neuronal loss when compared with controls. In contrast, the number of neurons in the somatic portion of the nucleus of the third cranial nerve (NCNIII) remained intact. The EW in brains from clinically normal individuals with evidence of early AD-type pathology also displayed a significant and selective loss of neurons. The magnitude of EW neuronal loss in the latter group was smaller than that observed in AD. These findings suggest that pupillary hypersensitivity in AD may be caused by abnormalities in the EW. Neuronal loss and pathology within the EW in a subpopulation of clinically silent controls with pathologic findings consistent with early-stage AD constitutes a possible explanation for the reported exaggerated pupil response in some normal elderly subjects.

The activation of urocortin immunoreactive neurons in the Einger-Westphal nucleus following stress in rats

Urocortin, a member of the corticotropin releasing factor (CRF) peptide family, has a 45%sequence identity to CRF. Urocortin is ten-times more potent than CRF in increasing CAMP in cells expressing the CRF, receptor, therefore it was postulated to be an endogenous ligand for this receptor. Urocortin possesses the biological activity of CRF, and by activating the CRF(2) receptors, it can directly affect autonomic functions and play an important role in modifying the efferent components of endocrine, immune and behavioral responses to stress.Although urocortin's distribution in the rat brain has been described, with the most abundant urocortin-ir perikarya present in the Edinger-Westphal nucleus (E-WN), little is known about the physiological significance of brain urocortin. Since immediate early gene expression is seen in several midbrain regions, such as in the E-WN, following acute stress, we hypothesized that acute pain stress can result in the activation of the urocortinergic neurons in the E-WN.Fos immunoreactivity, the protein product of the immediate early gene c-fos, was used as a marker of cellular activity. Double-label immunohistochemical and double label immunofluorescence techniques were used in an acute pain stress model to reveal the colocalization of Fos-immunopositivity with urocortin-immunoreactivity (ir) within the E-WN.Our results showed that acute pain stress resulted in the activation of urocortin-ir neurons in the E-WN, peaking at 4 h after acute pain stress, based on the colocalization of Fos-ir with urocortin-ir, and the upregulation of urocortin mRNA transcripts in the E-WN. Based on these results, we suggest that the E-WN is a brain area that shows sustained activation by a painful stressor.

Synaptic control of motoneuronal excitability

Movement, the fundamental component of behavior and the principal extrinsic action of the brain, is produced when skeletal muscles contract and relax in response to patterns of action potentials generated by motoneurons. The processes that determine the firing behavior of motoneurons are therefore important in understanding the transformation of neural activity to motor behavior. Here, we review recent studies on the control of motoneuronal excitability, focusing on synaptic and cellular properties. We first present a background description of motoneurons: their development, anatomical organization, and membrane properties, both passive and active. We then describe the general anatomical organization of synaptic input to motoneurons, followed by a description of the major transmitter systems that affect motoneuronal excitability, including ligands, receptor distribution, pre- and postsynaptic actions, signal transduction, and functional role. Glutamate is the main excitatory, and GABA and glycine are the main inhibitory transmitters acting through ionotropic receptors. These amino acids signal the principal motor commands from peripheral, spinal, and supraspinal structures. Amines, such as serotonin and norepinephrine, and neuropeptides, as well as the glutamate and GABA acting at metabotropic receptors, modulate motoneuronal excitability through pre- and postsynaptic actions. Acting principally via second messenger systems, their actions converge on common effectors, e.g., leak K(+) current, cationic inward current, hyperpolarization-activated inward current, Ca(2+) channels, or presynaptic release processes. Together, these numerous inputs mediate and modify incoming motor commands, ultimately generating the coordinated firing patterns that underlie muscle contractions during motor behavior.

Urocortin expression in the Edinger-Westphal nucleus is up-regulated by stress and corticotropin-releasing hormone deficiency

Urocortin is a 40-amino acid mammalian peptide related to CRH and urotensin. The physiological role of urocortin is unknown, but it has been postulated to serve some of the functions previously attributed to CRH. We had earlier found that urocortin messenger RNA (mRNA) expression within the mouse brain is confined to the region of the Edinger-Westphal (EW) nucleus of the midbrain. To further characterize the regulation of the urocortin gene, we first cloned and sequenced the mouse gene, confirming the presence of a single gene in the murine genome. A general survey of mouse tissues using Northern blot analysis revealed the presence of urocortin mRNA only within the midbrain. By in situ hybridization analysis, we found that urocortin mRNA expression in the EW nucleus is responsive to stress, as mRNA levels increased approximately 3-fold after 3 h of restraint. Chronic glucocorticoid treatment, although not affecting basal levels, blocked the stress-induced rise in urocortin mRNA. Using CRH-deficient [knockout (KO)] mice, we examined the effect of combined CRH and glucocorticoid deficiency upon urocortin mRNA expression. As in wild-type (WT) mice, we had previously found that urocortin expression in CRHKO mouse brain was not detected outside of the EW nucleus. However, we found that urocortin expression within the EW of CRHKO mice is up-regulated 2- to 3-fold compared with that in WT mice. This up-regulation is not due to a lack of inhibition by glucocorticoids, as urocortin mRNA levels in the EW nucleus of CRHKO mice did not change after glucocorticoid supplementation. As the EW does not project to any brain regions known to be involved in the behavioral responses to stress, urocortin expressed in this site is unlikely to mediate stress-induced behaviors. On the other hand, as the EW nucleus may play a role in the regulation of the autonomic nervous system and projects to various brain stem nuclei that express the CRH receptor, urocortin originating in the EW may play a role in the regulation of the autonomic nervous system during stress.

Differential distribution of urocortin- and corticotropin-releasing factor-like immunoreactivities in the rat brain

Urocortin, a novel 40 amino acid neuropeptide, is a member of the corticotropin-releasing factor family. With 45% homology to corticotropin-releasing factor, urocortin binds with similar affinity to the corticotropin-releasing factor- and corticotropin-releasing factor-2 receptors and may play a role in modulating many of the same systems as corticotropin-releasing factor. To assess whether urocortin and corticotropin-releasing factor are localized in the same regions of the brain, we compared the distribution of urocortin- and corticotropin-releasing factor-like immunoreactivities in the rat central nervous system. Polyclonal antibodies to rat corticotropin-releasing factor and rat urocortin were generated and utilized to map the distribution of corticotropin-releasing factor- and urocortin-like immunoreactivities throughout the rat forebrain and brainstem. Characterization of the antibodies by radioimmunoassay showed no cross-reactivity with related peptides. Male Sprague-Dawley rats were treated with colchicine for 18-24 h. Following colchicine treatment, the rats were perfused with paraformaldehyde-lysine-periodate fixative and their brains removed. Serial coronal sections were taken throughout the rat brain and processed for either corticotropin-releasing factor- or urocortin-like immunoreactivity. Urocortin-like immunoreactivity shows a discrete localization within several regions including the supraoptic nucleus, the median eminence, Edinger-Westphal nucleus and the sphenoid nucleus. This is in contrast to the more abundant corticotropin-releasing factor-like immunoreactivity. Regions containing high levels of corticotropin-releasing factor immunoreactivity include the lateral septum, paraventricular nucleus of the hypothalamus, median eminence and locus coeruleus. There are a few regions that contain both urocortin-immunoreactive and corticotropin-releasing factor-immunoreactive cells, such as the supraoptic nucleus and the hippocampus. Therefore, urocortin and corticotropin-releasing factor appear to have different distribution patterns which may be indicative of their respective physiological functions.

Stress-induced behaviors require the corticotropin-releasing hormone (CRH) receptor, but not CRH

Corticotropin-releasing hormone (CRH) is a central regulator of the hormonal stress response, causing stimulation of corticotropin and glucocorticoid secretion. CRH is also widely believed to mediate stress-induced behaviors, implying a broader, integrative role for the hormone in the psychological stress response. Mice lacking the CRH gene exhibit normal stress-induced behavior that is specifically blocked by a CRH type 1 receptor antagonist. The other known mammalian ligand for CRH receptors is urocortin. Normal and CRH-deficient mice have an identical distribution of urocortin mRNA, which is confined to the region of the Edinger-Westphal nucleus, and is absent from regions known to mediate stress-related behaviors. Since the Edinger-Westphal nucleus is not known to project to any brain regions believed to play a role in anxiety-like behavior, an entirely different pathway must be postulated for urocortin in the Edinger-Westphal nucleus to mediate these behaviors in CRH-deficient mice. Alternatively, an unidentified CRH-like molecule other than CRH or urocortin, acting through the CRH receptors in brain regions believed to mediate stress-induced behaviors, may mediate the behavioral response to stress, either alone or in concert with CRH.

Extent and duration of recovered pupillary light reflex following retinal ganglion cell axon regeneration through peripheral nerve grafts directed to the pretectum in adult rats

The functional reinnervation of the olivary pretectal nucleus (OPN) was studied in adult rats with peripheral nerve (PN) grafts bridging the interrupted retinopretectal pathway. Functional recovery was assessed quantitatively using established pupillometry techniques. The effect of intravitreal tuftsin fragment 1-3 (tuftsin 1-3) injections during the grafting procedure was also studied. A total of 53 adult rats received autologous PN grafts connecting the ocular stump of the transected optic nerve to the ipsilateral OPN. The contralateral eye was enucleated to remove the input from that eye to the OPN. A pupillary light reflex was elicited from 35 of the 53 PN-grafted animals and in the best cases, a response was obtained which compared closely to that recorded from control animals. Tuftsin 1-3 was found to increase the rate of recovery of the response. The response amplitude of PN-grafted rats was generally found to diminish with repeated stimulus presentation and also appeared to deteriorate with age. This was in contrast to control animals' responses. However, a PLR could still be elicited in 3 of the 6 animals studied 15 months after PN-grafting. These findings indicate that a near-normal PLR function can be restored using a peripheral nerve graft, but there are a number of factors that are likely to compromise optimal outcome.

Connections of the rostral ventral respiratory neuronal cell group: an anterograde and retrograde tracing study in the rat

The connections of the rostral ventral respiratory cell group (VRG) were retrogradely and anterogradely determined after discrete injections of a mixture of the fluorescent tracers Fast Blue (FB) and Fluoro Ruby (FR) into the physiologically identified rostral inspiratory cell group. Retrogradely FB-labeled neurons and/or anterogradely FR-labeled fibers and terminal fields were located bilaterally in a variety of brain areas. Both retrograde and anterograde labelings were mainly found in: 1) the deep cerebellar nuclei; 2) the lateral lemniscus and paralemniscal nuclei, deep gray, and white intermediate layers of the superior colliculus, tegmental (laterodorsal and microcellular) nuclei, and central gray; and 3) the septohypothalamic nucleus, and lateral and posterior hypothalamic areas. The FR-labeled terminal-like elements were found in: 1) Crus 2 of the ansiform lobule, and the simple, 2, and 3 cerebellar lobules; 2) the subcoeruleus, deep mesencephalic, and Edinger-Westphal nuclei; and 3) the premammillary, lateral, and medial mammillary nuclei, retrochiasmatic part of the supraoptic nucleus, and the zona incerta. The FB-labeled neurons were found in: 1) the parapedunculopontine tegmental and cuneiform nuclei, caudal linear nucleus of the raphe, and adjacent area of the cerebral peduncle; 2) the thalamic posterior nuclear group and subparafascicular, parafascicular, and gelatinosus thalamic nuclei; 3) the parastrial amygdaloid and subthalamic nuclei; and 4) the olfactory tubercle, granular, and agranular insular cortex, parietal and lateral orbital cortices. The connections of the rostral VRG with several cerebellar, midbrain, diencephalic, and telencephalic regions could provide an anatomical substrate for a role of these regions in the control of respiratory-related functions.

Distribution of urocortin-like immunoreactivity in the central nervous system of the rat

Urocortin was recently cloned from the rat midbrain. Urocortin is a member of the corticotropin releasing factor (CRF) peptide family and shows 45% sequence identity to CRF and 63% sequence identity to urotensin. It binds with a high affinity to CRF1 and CRF2 receptors, resulting in the stimulation of their adenylate cyclase activity. We used a polyclonal antibody against rat urocortin to define the distribution of urocortin-like immunoreactivity in the rat central nervous system. Several immunostained cell bodies were found in the supraoptic, paraventricular, and ventromedial hypothalamic nuclei. A large number of neurons with urocortin-like immunoreactivity were seen in the dorsolateral tegmental nucleus, in the linear and dorsal raphe nuclei, and in the substantia nigra. The most abundant immunoreactive (ir) perikarya were found in the Edinger-Westphal nucleus. Some neurons showed immunoreactivity in the interstitial nucleus of Cajal, the nucleus of Darkeschewitsch, and the periaqueductal gray. A dense immunoreactive fiber network was found in the lateral septal area. Some faintly stained axon terminals were observed among urocortin-ir perikarya in the supraoptic and paraventricular nuclei, in the central and periaqueductal gray, and in the Edinger-Westphal nucleus. No fibers with urocortin-ir were seen in the median eminence or the posterior pituitary. The distribution of urocortin-ir overlapped with the expression of the mRNA for the CRF2 receptor in several brain areas. These data support the hypothesis that this peptide is the endogenous ligand for the CRF2 receptor. Urocortin has been implicated in various endocrine responses, such as blood pressure regulation, as well as in higher cognitive functions.

Axosomatic synapses of the rat ciliary ganglion

We have identified four different types of axosomatic synapses within the rat ciliary ganglion, and present the three-dimensional relationships of both pre- and postsynaptic elements. The majority of axosomatic synapses are situated on small postsynaptic spines that simply appose the axon (termed somatic spine), or are situated within an axonal invagination (termed invaginating somatic spine). The somatic spine synapse predominates, composing 70% of the population, which may be due to simplicity of construction as it usually forms only one active zone. In contrast, the invaginating somatic spine forms multiple active zones and accounts for only 22% of the population. Synapses involving a regular nonspinous portion of the cell membrane were rarely encountered (6%; termed somatic), as were those of axon branches situated within tubular invaginations of the cell body (2%; termed tunnelling). Synapses were differentially distributed, occurring four times more frequently on that portion of neuronal cell body membrane adjacent to the glial cell perinuclear area. However, there was no preferred location by synapse type, suggesting that this unequal distribution was the result of a general mechanism. The neuronal cells of the rat ciliary ganglion apparently constitute a single population, at least on the basis of cell size, shape, and organelle content.

Interactive events subserving the pupillary light reflex in pigmented and albino rats

The consensual pupilloconstrictor response requires the intensity information that is delivered to each eye to be integrated to produce an averaged response such that the pupillary diameter in each eye is equal. Here we have examined how luminance information from each eye is integrated in the rat and where the integration occurs, using a pupillometry system to record pupillary diameter after illumination of one or both eyes. In albino rats the size of the uncrossed optic pathway to the pupilloconstrictor centre, the olivary pretectal nucleus, is reduced three-fold and there is a concomitant but less dramatic reduction in the size of the consensual response. Unilateral lesions of the olivary pretectal nucleus in pigmented rats restrict all optic input to the opposite pretectum. Stimulation of one or both eyes in these animals suggests that integration occurs not only at the level of the olivary pretectal nucleus, but also downstream in the Edinger-Westphal nucleus. Parallels with human studies and the opportunity to perform secondary lesions suggests the rat may provide a good model in which to study the substrates of the pupilloconstrictor response and mechanisms of integration of convergent parallel inputs in general.

Efferent synaptic organization of the olivary pretectal nucleus in the albino rat. An ultrastructural tracing study

In this study an ultrastructural analysis was made of the efferent projections of the olivary pretectal nucleus in the rat. The anterograde tracer Phaseolus vulgaris leucoagglutinin was injected iontophoretically into the olivary pretectal nucleus. Ascending and descending pathways were studied. In the descending pathway special attention was paid to the fine structural features of the olivary pretectal nucleus efferents projecting to the Edinger-Westphal nucleus, the interstitial nucleus of Cajal, the nucleus of Darkschewitsch and the periaqueductal gray. The projection to the superior colliculus and the pontine nucleus was also studied at the ultrastructural level. All the labeled terminals in the descending pathway showed ultrastructurally similar features: clear, round vesicles and electron dense mitochondria. The terminals made asymmetric synaptic membrane specializations (Gray type I), the postsynaptic profiles were dendritic. In the interstitial nucleus of Cajal and the superior colliculus the terminals are organized in glomerulus-like structures. The terminals in the descending pathway were enwrapped by astrocytic processes, also in the glomerulus-like structures. In the ascending pathway the projection to the ventral part of the lateral geniculate nucleus was studied. Almost all terminals in the ascending pathway showed similar ultrastructural features as in the descending pathway: electron dense mitochondria, clear, round vesicles and asymmetric synaptic membrane specializations (Gray type I). The terminals are organized in glomerulus-like structures. To identify the projecting neurons in the interstitial nucleus of Cajal and the Edinger-Westphal nucleus, retrograde tracing experiments were performed. Therefore the beta subunit of cholera toxin conjugated with horseradish peroxidase was injected into the facial nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)