We hypothesize that the entrance from SWS to PS is due to the intrinsic activation of PS-active GABAergic neurons localized in the posterior hypothalamus (co-containing melanin-concentrating hormone), ventrolateral periaqueductal gray and the dorsal paragigantocellular reticular nucleus. 
It was recently proposed that their inactivation during paradoxical sleep is due to a tonic GABAergic inhibition arising from neurons located into the dorsal paragigantocellular reticular nucleus (DPGi).
We also showed that the tonic inhibition of locus coeruleus (LC) noradrenergic and dorsal raphe (DRN) serotonergic neurons during sleep is due to a tonic GABAergic inhibition by neurons localized in the dorsal paragigantocellular reticular nucleus (DPGi) and the ventrolateral periaqueductal gray (vlPAG).
The largest number of CTb/Fos double-labeled cells was found in the dorsal paragigantocellular reticular nucleus (DPGi). It indeed contained 19% of the CTb/Fos double-labeled neurons, whereas the ventrolateral periaqueductal gray (vlPAG) contained 18.3% of these neurons, the lateral paragigantocellular reticular nucleus (LPGi) 15%, the lateral hypothalamic area 9%, the lateral PAG 6.7%, and the rostral PAG 6%.
Four nuclei in the reticular formation of the brain stem demonstrated strong positive labeling: the mesencephalic reticular nucleus, magnocellular reticular nucleus, paragigantocellular reticular nucleus, and gigantocellular reticular nucleus.
IL-1beta expression was also found in the nuclei of afferent nervous pathways of the superior laryngeal nerve, such as the nucleus tractus solitarius, nucleus ambiguus, lateral reticular nucleus, magnocellular reticular nucleus and paragigantocellular reticular nucleus..
The expression of Fos protein in 5-HT-containing neurons (5-HT/Fos co-localized neurons) could be observed in the ventrolateral subdivision of the midbrain periaqueductal grey, interpeduncular nucleus, paramedian raphe nucleus, all of the brainstem raphe nuclei, the alpha part of the gigantocellular reticular nucleus and the lateral paragigantocellular reticular nucleus.
A large number of GAD-negative retrogradely labelled cells was also seen in these structures as well as in the primary motor area of the frontal cortex, the central nucleus of the amygdala, the ventral and lateral bed nucleus of the stria terminalis, the lateral hypothalamic area, the lateral and ventrolateral periaqueductal grey and the lateral paragigantocellular reticular nucleus.
Other regions of the brainstem including the vestibular nuclei, prepositus hypoglossi, dorsal paragigantocellular reticular nucleus, nucleus of the tractus solitarius and locus coeruleus also exhibited altered patterns of Fos labeling following TTX.
The maximal density of stained cells was present within the rostral part of the ventrolateral medulla (VLM), in the region of the lateral paragigantocellular reticular nucleus.
The most robust activation was observed when neurons in or near the lateral paragigantocellular reticular nucleus were microstimulated bilaterally.
Additional CCK8-S immunoreactive terminals were located in the rostroventrolateral medullary reticular nucleus, lateral paragigantocellular reticular nucleus, and the caudal pontine reticular nucleus.
The most robust reflex depression was observed when the lateral paragigantocellular reticular nucleus was microstimulated bilaterally.
The major finding of this study indicates that five brain regions, viz., paraventricular hypothalamic nucleus, perifornical hypothalamic region, A5 catecholamine cell group, rostral ventrolateral medulla, and lateral paragigantocellular reticular nucleus, contain a considerable amount of overlap in cell body labeling.
Last to arrive in the lumbar cord during the prenatal period, at E21, were fibers from the posterior commissural nucleus, the red nucleus, the Edinger-Westphal nucleus, the paragigantocellular reticular nucleus, the medial vestibular nucleus, Roller's nucleus, and the solitary nucleus.
The double labeled neurons were located in the medical part of the NTS, and in the lateral part of the paragigantocellular reticular nucleus and the ventral division of the ambiguus nucleus.
Golgi-staining, retrograde and anterograde tract-tracing, and a two-color immunoperoxidase technique have been employed, at the light- and electron-microscopic levels, to analyze the auditory projections from the cochlear nucleus (CN) to the lateral paragigantocellular reticular nucleus (LPGi) in the rat.
In the medulla oblongata, labeled neurons were found in the nucleus tractus solitarius, area postrema, paratrigeminal nucleus, lateral paragigantocellular reticular nucleus, raphe pallidus and obscurus nuclei, C3 region and scattered cells in the ventral medullary reticular formation.
Increased expression of PPE-mRNA was more marked in ipsilateral dorsal horn of spinal cord (especially in laminae III-IV and contralateral ventromedial medulla (especially in the lateral paragigantocellular reticular nucleus).
A dense to moderate amount of HA-LI fibers was found distributed in the raphe nuclei, the inferior olive, the nucleus of the solitary tract, vestibular nuclei, and the paragigantocellular reticular nucleus in the medulla oblongata, and the parabrachial nuclei, the Klliker-Fuse nucleus, the pontine nuclei, and the locus coeruleus in the pons.
When injections of FB were made into the lumbar cord at postnatal day (PD) 1, neurons were labeled within several areas of the reticular formation (the retroambiguus nucleus, the ventral and dorsal reticular nuclei of the medulla, the gigantocellular reticular nucleus, the lateral paragigantocellular reticular nucleus, and the pontine reticular nucleus), the presumptive coeruleus complex, and the lateral vestibular nucleus.
Cholinergic neurons in the dorsal paragigantocellular reticular nucleus (DPG) projected bilaterally to each half of the OMC.
FU is a predominantly descending tract, with terminations within (1) the vestibular complex, (2) a column of contiguous medial reticular nuclei from pontine to caudal medullary levels; (3) the plexus of Horsley portion of the parvicellular reticular formation, continuing through the nucleus centralis medullae oblongatae, pars dorsalis, into intermediate layer VII of the cervical spinal cord, down to cervical segment 8-9; (4) the lateral reticular nucleus and the paragigantocellular reticular nucleus; (5) the dorsal lamella of the inferior olive.
Within the rostral portion of the ventrolateral medulla, glutamate-like immunoreactive neurons were found in the lateral wing of the raphe magnus and in the region of the paragigantocellular reticular nucleus.
The results of these experiments demonstrated that numerous substance P-immunoreactive cells in the RMg, gigantocellular reticular nucleus pars alpha and the paragigantocellular reticular nucleus were retrogradely labeled by an injection of Fluoro-Gold into the A7 nucleus.
Using brainstem transections and electrolytic and neurotoxic lesions, we have identified a group of neurons in the paragigantocellular reticular nucleus in the ventral medulla which mediates this descending inhibition.
The high activity neurons in the ventral lateral medulla were predominantly located in the caudal portion of the paragigantocellular reticular nucleus.
Neurons that contained substance P-, thyrotropin-releasing hormone- and/or serotonin-immunoreactivities and that projected to the intermediolateral cell column were present in the nucleus raphe magnus, the nucleus raphe pallidus, the nucleus reticularis magnocellularis pars alpha, the paragigantocellular reticular nucleus and the parapyramidal region.
Enkephalin-immunoreactive neurons that projected to the intermediolateral cell column were present in the raphe magnus, the nucleus reticularis magnocellularis pars alpha, the paragigantocellular reticular nucleus, and the parapyramidal region.
Dual stained catecholamine/WGA perikarya were found in zona incerta, locus coeruleus, substantia nigra, nucleus tractus solitarius and adjacent A2, C2 and C3, lateral paragigantocellular reticular nucleus/C1 and lateral reticular nucleus/A1 following DRN injections and in zona incerta, substantia nigra, nucleus tractus solitarius/A2 and lateral reticular nucleus/A1 after NRM injections.
Major neuron populations with efferent projections to the regions of the dorsal and ventral respiratory groups include the parabrachial nuclear complex (medial parabrachial, lateral parabrachial, and Kölliker-Fuse nuclei), subregions of the lateral paragigantocellular reticular nucleus, subregions of the lateral and magnocellular tegmental fields, inferior central and postpyramidal nuclei of the raphe, and sensory trigeminal nuclei. Neuron populations in the rostral ventrolateral medulla with projections to both the dorsal and ventral respiratory groups, particularly the retrotrapezoid nucleus and neighboring subregions of the lateral paragigantocellular reticular nucleus, are candidate sites for participation in respiratory rhythmogenesis or other critical functions of the brainstem respiratory control system such as intracranial chemoreception..
Within the rostral portion of the ventrolateral medulla, GABA-like immunoreactive neurons were found in the lateral wing of the raphe magnus and in the region of the paragigantocellular reticular nucleus.
Neurons of the CSA were shown electrophysiologically and morphologically to project primarily to the dorsal part of the paragigantocellular reticular nucleus of the contralateral side.
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