Homeostatic Changes in GABA and Acetylcholine Muscarinic Receptors on GABAergic Neurons in the Mesencephalic Reticular Formation following Sleep Deprivation

Abstract

We have examined whether GABAergic neurons in the mesencephalic reticular formation (RFMes), which are believed to inhibit the neurons in the pons that generate paradoxical sleep (PS or REMS), are submitted to homeostatic regulation under conditions of sleep deprivation (SD) by enforced waking during the day in mice. Using immunofluorescence, we investigated first, by staining for c-Fos, whether GABAergic RFMes neurons are active during SD and then, by staining for receptors, whether their activity is associated with homeostatic changes in GABAA or acetylcholine muscarinic type 2 (AChM2) receptors (Rs), which evoke inhibition. We found that a significantly greater proportion of the GABAergic neurons were positively stained for c-Fos after SD (∼27%) as compared to sleep control (SC; ∼1%) and sleep recovery (SR; ∼6%), suggesting that they were more active during waking with SD and less active or inactive during sleep with SC and SR. The density of GABAARs and AChM2Rs on the plasma membrane of the GABAergic neurons was significantly increased after SD and restored to control levels after SR. We conclude that the density of these receptors is increased on RFMes GABAergic neurons during presumed enhanced activity with SD and is restored to control levels during presumed lesser or inactivity with SR. Such increases in GABAAR and AChM2R with sleep deficits would be associated with increased susceptibility of the wake-active GABAergic neurons to inhibition from GABAergic and cholinergic sleep-active neurons and to thus permitting the onset of sleep and PS with muscle atonia.

Arousal and sleep circuits

“…Orx receptors are found on the most large presumed Glu neurons, but also on some GABA neurons in the pontine and RFMes [11]. In fact, it would appear that the Orx input would enforce W through excitation of some GABA neurons which are W active and involved in preventing PS with muscle atonia [94,95,100,152] (below).…”

“…Yet again here in the medulla and midbrain, GABA (or Gly) inhibitory neurons may play different roles depending upon their activity profile [96], local and distant projections and receptors to the neuromodulators. From c-Fos studies, it is apparent that there are GABA PS-active neurons in some regions and GABA W-active neurons in other regions or overlapping in the same region of the brainstem [97][98][99][100]. These different GABA cell types could be respectively involved in promoting PS with muscle atonia or conversely W with muscle tone and behavioral arousal (Figs.…”

“…2 and 3). Indeed, whereas there is evidence that presumed Glu neurons in the SubLDT (or SLD) which promote muscle atonia are excited by ACh through AChM1Rs [101], GABA neurons in the pontine and mesencephalic RF (PnO and RFMes, along with adjacent vlPAG), which are active during W and can prevent muscle atonia with PS, appear to be inhibited by ACh through AChM2Rs [11,100]…”

REM sleep promotes experience-dependent dendritic spine elimination in the mouse cortex

“…Mammalian sleep cycles compose of non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep 1,2 . Many lines of evidence suggest that sleep is important for regulating neuronal plasticity during brain development and after learning [3][4][5][6][7][8][9] . For example, NREM sleep has been shown to promote synaptic potentiation 10 , synapse formation 11 , and synaptic weakening after wakefulness [12][13][14] .…”

Regulated resurfacing of a somatostatin receptor storage compartment fine-tunes pituitary secretion

“…Cell surface and cytoplasmic levels of SSTR2 were quantified essentially as per the method of Hanieh Toossi and colleagues (Toossi et al, 2018) using ZEN lite software. Briefly, a rectangular box of fixed size was placed over the plasma membrane and another box of the same size over the cytoplasm in each cell.…”