Evidence that urocortin is absent from neurons of the Edinger-Westphal nucleus in pigeons

Abstract

The Edinger-Westphal nucleus (EWN) is a central preganglionic parasympathetic cell group that gives rise to cholinergic input to the ciliary ganglion, thereby regulating several neurovegetative ocular functions. Recently, the supposed presence of the neuropeptide urocortin (UCN) has been reported in EWN neurons in rodent brain. The purpose of the present study was to examine the distribution of UCN in avian brain and to investigate by immunohistochemical analysis the possible use of this substance as an EWN marker in a nonmammalian class of vertebrates. Brain tissue of pigeons was incubated with a specific antibody against UCN and the results showed labeling of many small neurons, forming a double wing in the dorsal mesodiencephalic transition area. Their size and shape, however, differed from those of EWN neurons, and they were preferentially located rostral to the EWN. Double-label experiments employing an antibody against the enzyme choline acetyltransferase (ChAT) showed that UCN is not localized to the cholinergic cells of the EWN and confirmed the rostral distributionof UCN never overlapping the ChAT+ EWN cells. Taken together, these results suggest that, at least in pigeons, the UCN+ population does not belong to the traditionally defined EWN.

Perioculomotor cell groups in monkey and man defined by their histochemical and functional properties: Reappraisal of the Edinger‐Westphal nucleus

“…The present work confirms other studies in bird, mouse, cat, monkey, and human demonstrating that UCNpositive neurons form a distinct cell group within the perioculomotor region, pIII U , which is different from adjacent cholinergic parasympathetic preganglionic neurons (pIII PG ) as shown by the pIII U 's lack of ChAT immunoreactivity (Cavani et al, 2003;Vasconcelos et al, 2003;Ryabinin et al, 2005;Weitemier et al, 2005). Our results confirm the work of May et al (2008) demonstrating that in monkey the pIII U neurons represent a population of loosely packed neurons, which are cytoarchitecturally inconspicuous.…”

“…However, recent studies indicate that UCN is not expressed in cholinergic preganglionic neurons but instead labels adjacent cells, which in some species correspond to the traditional EW as defined by Nissl staining. These species include mouse (Paxinos and Franklin, 2003;Weitemier et al, 2005), rat (Paxinos and Watson, 1986;Yamamoto et al, 1998), cat (Erichsen and May, 2002), and human , but this correspondence is not present in other species, such as monkey (Vasconcelos et al, 2003) and bird (Cavani et al, 2003). Consequently, a new terminology, which differentiates a preganglionic EW from a nonpreganglionic EW has been introduced Weitemier et al, 2005;Ryabinin and Weitemier, 2006).…”

Comparison of the distributions of urocortin‐containing and cholinergic neurons in the perioculomotor midbrain of the cat and macaque

“…Instead, numerous centrally projecting peptidergic populations have been found within the EW in cats, rodents, and even frogs, including neurons immunoreactive for CCK, substance P, urocortin, cocaineand amphetamine-regulated transcript (CART), and neuropeptide B (cat: Maciewicz et al, 1983;Phipps et al, 1983; present data; frog: Kozicz et al, 2002;mouse: Bachtell et al, 2002;Tanaka et al, 2003;rat: Innis and Aghajanian, 1986;Kozicz et al, 1998;Hokfelt et al, 2002;Kozicz, 2003;Dun et al, 2005). In fact, it appears that only in those species in which the preganglionic motoneurons are clustered together do they occupy the cytoarchitecturally defined EW, with urocortin ϩ cells located outside its borders (monkey: Vasconcelos et al, 2003;present data;Horn et al, 2007;pigeon: Reiner et al, 1991;Cavani et al, 2003). However, this cannot be considered even a general primate or bird characteristic, because the cytoarchitecturally defined human EW has recently been shown to contain primarily urocortin ϩ neurons Horn et al, 2007), and too few bird species have been sampled.…”

Urocortin-like immunoreactivity in the primary lymphoid organs of the duck (Anas platyrhynchos)

“…In non-mammalian vertebrates, few data have been reported on the presence and the role of UCN. The molecule, however, may have been conserved during vertebrate evolution, given that it has also been detected in amphibians and birds (Kozicz et al, 2002;Cavani et al, 2003;Boorse et al, 2005;Calle et al, 2005). In amphibians, UCN and CRH receptors have been found in the brain as well as in many other organs and tissues, including the pituitary gland, heart, kidney and alimentary canal (Kozicz et al, 2002;Boorse et al, 2005; thus suggesting a potential role for diverse actions in tissue maintenance and function.…”

“…Moreover, it has been found to act as a cytoprotective factor in tadpole tail during metamorphosis . In birds, UCN-ir has been found in neurons of the pigeon paramedian subgriseal mesencephalon which appear to be part of the brain circuitry involved in sympathetic nervous system-mediated behavioral responses to stress (Cavani et al 2003;Cunha et al, 2007). Intracerebroventricular administered UCN, moreover, has been reported to decrease food intake in the chicken (Zhang et al, 2001).…”