Precerebellar and vestibular nuclei of the short-beaked echidna (Tachyglossus aculeatus)

Role of REM Sleep, Melanin Concentrating Hormone and Orexin/Hypocretin Systems in the Sleep Deprivation Pre-Ischemia

STUDY OBJECTIVES

Sleep reduction after stroke is linked to poor recovery in patients. Conversely, a neuroprotective effect is observed in animals subjected to acute sleep deprivation (SD) before ischemia. This neuroprotection is associated with an increase of the sleep, melanin concentrating hormone (MCH) and orexin/hypocretin (OX) systems. This study aims to 1) assess the relationship between sleep and recovery; 2) test the association between MCH and OX systems with the pathological mechanisms of stroke.

METHODS

Sprague-Dawley rats were assigned to four experimental groups: (i) SD_IS: SD performed before ischemia; (ii) IS: ischemia; (iii) SD_Sham: SD performed before sham surgery; (iv) Sham: sham surgery. EEG and EMG were recorded. The time-course of the MCH and OX gene expression was measured at 4, 12, 24 hours and 3, 4, 7 days following ischemic surgery by qRT-PCR.

RESULTS

A reduction of infarct volume was observed in the SD_IS group, which correlated with an increase of REM sleep observed during the acute phase of stroke. Conversely, the IS group showed a reduction of REM sleep. Furthermore, ischemia induces an increase of MCH and OX systems during the acute phase of stroke, although, both systems were still increased for a long period of time only in the SD_IS group.

CONCLUSIONS

Our data indicates that REM sleep may be involved in the neuroprotective effect of SD pre-ischemia, and that both MCH and OX systems were increased during the acute phase of stroke. Future studies should assess the role of REM sleep as a prognostic marker, and test MCH and OXA agonists as new treatment options in the acute phase of stroke.

Identification of Sleep-Modulated Pathways Involved in Neuroprotection from Stroke

STUDY OBJECTIVES

Sleep deprivation (SDp) performed before stroke induces an ischemic tolerance state as observed in other forms of preconditioning. As the mechanisms underlying this effect are not well understood, we used DNA oligonucleotide microarray analysis to identify the genes and the gene-pathways underlying SDp preconditioning effects.

DESIGN

Gene expression was analyzed 3 days after stroke in 4 experimental groups: (i) SDp performed before focal cerebral ischemia (IS) induction; (ii) SDp performed before sham surgery; (iii) IS without SDp; and (iv) sham surgery without SDp. SDp was performed by gentle handling during the last 6 h of the light period, and ischemia was induced immediately after.

SETTINGS

Basic sleep research laboratory.

MEASUREMENTS AND RESULTS

Stroke induced a massive alteration in gene expression both in sleep deprived and non-sleep deprived animals. However, compared to animals that underwent ischemia alone, SDp induced a general reduction in transcriptional changes with a reduction in the upregulation of genes involved in cell cycle regulation and immune response. Moreover, an upregulation of a new neuroendocrine pathway which included melanin concentrating hormone, glycoprotein hormones-α-polypeptide and hypocretin was observed exclusively in rats sleep deprived before stroke.

CONCLUSION

Our data indicate that sleep deprivation before stroke reprogrammed the signaling response to injury. The inhibition of cell cycle regulation and inflammation are neuroprotective mechanisms reported also for other forms of preconditioning treatment, whereas the implication of the neuroendocrine function is novel and has never been described before. These results therefore provide new insights into neuroprotective mechanisms involved in ischemic tolerance mechanisms.

Nonphosphorylated neurofilament protein is expressed by scattered neurons in the vestibular and precerebellar brainstem

Vestibular information is essential for the control of posture, balance, and eye movements. The vestibular nerve projects to the four nuclei of the vestibular nuclear complex (VNC), as well as to several additional brainstem nuclei and the cerebellum. We have found that expression of the calcium-binding proteins calretinin (CR) and calbindin (CB), and the synthetic enzyme for nitric oxide synthase (nNOS) define subdivisions of the medial vestibular nucleus (MVe) and the nucleus prepositus (PrH), in cat, monkey, and human. We have asked if the pattern of expression of nonphosphorylated neurofilament protein (NPNFP) might define additional subdivisions of these or other nuclei that participate in vestibular function. We studied the distribution of cells immunoreactive to NPNFP in the brainstems of 5 cats and one squirrel monkey. Labeled cells were scattered throughout the four nuclei of the VNC, as well as in PrH, the reticular formation (RF) and the external cuneate nucleus. We used double-label immunofluorescence to visualize the distribution of these cells relative to other neurochemically defined subdivisions. NPNFP cells were excluded from the CR and CB regions of the MVe. In PrH, NPNFP and nNOS were not colocalized. Cells in the lateral vestibular nucleus and RF colocalized NPNFP and a marker for glutamatergic neurons. We also found that the cholinergic cells and axons of cranial nerve nuclei 3, 4, 6, 7,10 and 12 colocalize NPNFP. The data suggest that NPNFP is expressed by a subset of glutamatergic projection neurons of the vestibular brainstem. NPNFP may be a marker for those cells that are especially vulnerable to the effects of normal aging, neurological disease or disruption of sensory input.

Development of the vestibular apparatus and central vestibular connections in a wallaby (Macropus eugenii)

We have studied the early development of the vestibular apparatus and its central connections in the tammar wallaby (Macropus eugenii) in order to determine whether the vestibular system anatomy is sufficiently mature at birth to assist in climbing to the pouch. Structural development was studied with the aid of hematoxylin and eosin stained sections and immunoreactivity for GAP-43, whereas the development of vestibular system connections was examined by carbocyanine dye tracing. At the time of birth, the otocyst has distinct utricle, saccule and semicircular canals with immature sensory regions receiving innervation by GAP-43 immunoreactive fibers. Vestibular nerve fibers can be traced into the brainstem to the developing vestibular nuclei, which are not yet cytoarchitectonically distinct. The vestibular nuclei do not contribute direct projections to the lower cervical spinal cord at birth; most bulbospinal projections in the newborn appear to be derived bilaterally from the gigantocellular, lateral paragigantocellular reticular and ventral medullary nuclei. A substantial bilateral projection to the vestibular ganglion and apparatus from the region of the gigantocellular and lateral paragigantocellular nuclei was seen at birth, but not in subsequent ages. This is similar to a projection seen in newborn Ameridelphians. By postnatal day (P) 5, the vestibular apparatus had extensive projections to all vestibular nuclei and neurons projecting in the lateral vestibulospinal tract could be identified in the lateral vestibular nucleus. Cytoarchitectonic differentiation of the vestibular nuclei proceeded over the next 3 to 4 weeks with the emergence of discrete parvicellular and magnocellular components of the medial vestibular nucleus by P19. GAP-43 immunoreactivity stayed high in the lateral vestibulospinal tract for several months after birth, suggesting that the development of this tract followed a prolonged timecourse. Our findings indicate that central and peripheral connections of the vestibular ganglion are present at birth, but that there is no direct projection from the vestibular nuclei to the cervical spinal cord until P5. Nevertheless, the possibility remains that an indirect projection between the vestibular nuclei and the medial reticular formation is present at birth and mediates control of the climb.