Mesopontine organization of cholinergic and catecholaminergic cell groups in the normal and narcoleptic dog

Abstract

Canine narcolepsy is a unique experimental model of a human sleep disorder characterized by excessive daytime sleepiness and cataplexy. There is a consensus recognition of an imbalance between cholinergic and catecholaminergic systems in narcolepsy although the underlying mechanisms remain poorly understood. Possible substrates could be an abnormal organization, numbers and/or ratio of cholinergic to catecholaminergic cells in the brain of narcoleptic dogs. Therefore, we sought to characterize the corresponding neuronal populations in normal and narcoleptic dogs (Doberman Pinscher) by using choline acetyltransferase (ChAT), nicotinamide adenosine dinucleotide phosphate (NADPH)-diaphorase, tyrosine hydroxylase (TH), and dopamine beta-hydroxylase (DBH). Cholinergic cell groups were found in an area extending from the central to the gigantocellular tegmental field and the periventricular gray corresponding to the pedunculopontine tegmental nucleus (PPT), the laterodorsal tegmental nucleus (LDT), and the parabrachial nucleus. An almost perfect co-localization of ChAT and NADPH-diaphorase was also observed. Catecholaminergic cell groups detected included the ventral tegmental area, the substantia nigra, and the locus coeruleus nucleus (LC). The anatomical distribution of catecholaminergic neurons was unusual in the dog in two important aspects: i) TH- and/or DBH-immunoreactive neurons of the LC were found almost exclusively in the reticular formation and not within the periventricular gray, ii) very few, if any TH-positive neurons were found in the central gray and dorsal raphe. Quantitative analysis did not reveal any significant differences in the organization and the number of cells identified in the LDT, PPT, and LC of normal and narcoleptic dogs. Moreover, the cholinergic to catecholaminergic ratio was found identical in the two groups. In conclusion, the present results do not support the hypothesis that the neurochemical imbalance in narcolepsy could result from abnormal organization, numbers, or ratio of the corresponding neuronal populations.

Distribution and morphology of cholinergic, catecholaminergic and serotonergic neurons in the brain of Schreiber's long-fingered bat, Miniopterus schreibersii

“…According to previous reports, the A9 ventral subdivision of the substantia nigra is lacking in carnivores (Tafti et al, 1997), and although reported in the hedgehog, the existence of this group is uncertain since it is represented by a very small number of neurons (Michaloudi and Papadopoulos, 1996). The A9 ventral subdivision has been seen in monotremes, opossum, artiodactyls, dolphin, rodents, tree shrews and primates (Crutcher and Humbertson, 1978;Dahlström and Fuxe, 1964;Hökfelt et al, 1984;Manger et al, 2002bManger et al, , 2004Murray et al, 1982;Østergaard et al, 1992;Tillet and Kitahama, 1998).…”

Distribution and morphology of cholinergic, putative catecholaminergic and serotonergic neurons in the brain of the Egyptian rousette flying fox, Rousettus aegyptiacus

“…Presence of nucleus indicated by '+', absence by 'À', and unknown by '?'. Data taken from: Manger et al (2002b), Crutcher and Humbertson (1978), Michaloudi and Papadopoulos (1996), Maseko and Manger (2007), Østergaard et al (1992), Ruggiero et al (1992), Leshin et al (1995), Tillet and Kitahama (1998), Tillet and Thibault (1989), Manger et al (2003Manger et al ( , 2004, Dahlström and Fuxe (1964), Armstrong et al (1982), Hökfelt et al (1984), Greater canerat (Dwarika, Maseko, Ihunwo, Fuxe, Manger, personal observation), Moon et al (2007), Da Silva et al (2006), Blessing et al (1978), Cheung and Sladek (1975), Poitras and Parent (1978), Reiner and Vincent (1987), Kitahama et al (1990), Henderson (1987), Dormer et al (1993), Tafti et al (1997), Murray et al (1982), Jacobowitz and MacLean (1978), Felten et al (1974), Hubbard and Di Carlo (1974a), Lavoie and Parent (1994), Garver and Sladek (1975), Schofield and Everitt (1981), Satoh and Fibiger (1985), Bogerts (1981), Pearson et al (1983), Halliday et al (1988), Kitahama et al (1996). medullary tegmentum has been reported for monotremes, rats, cats and ferrets (Armstrong et al, 1982Henderson, 1987;Shiromani et al, 1988;<...>…”

“…A medullary tegmental field was not found in the megabat studied. This loose aggregation of cholinergic neurons in the Karasawa et al (2003), Dinopoulos et al (1988), Maseko and Manger (2007), Ferreira et al (2001), Armstrong et al (1983), Tago et al (1989), Da Silva et al (2006), Kimura et al (1981), Vincent and Reiner (1987), Shiromani et al (1988), Henderson (1987), Tafti et al (1997), St-Jacques et al (1996), Everitt et al (1988), Lavoie and Parent (1994), Mesulam et al (1984), Kus et al (2003), Satoh and Fibiger (1985), Mizukawa et al (1986), Mesulam et al (1989). Presence of nucleus indicated by '+', absence by 'À', and unknown by '?'.…”

Distribution of somatostatin-28 (1-12) immunoreactivity in the diencephalon and the brainstem of the dog

“…Somatostatin-positive perikarya have been found in the retrorubral area of the cat and the rat by some authors (Graybiel and Elde 1983;Vincent et al 1985) but not others (Johansson et al 1984;Spangler and Morley 1987). In the dog, labeled cells in this area overlap the ventral extension of the A8 dopaminergic neuronal group that have been suggested to play a key role in the progression of the Parkinson's disease (Arts et al 1996;Tafti et al 1997;García et al 1997). The dense population of labeled cells in the rostral part of the dorsal raphe nucleus of the dog closely resembles a similar population described in the rat (Johansson et al 1984).…”