The arousal effect of hyperbaric oxygen through orexin/hypocretin an upregulation on ketamine/ethanol-induced unconsciousness in male rats

Roles of orexinergic and noradrenergic neuronal activity in ketamine-induced sedation: a study using an orexin-ataxin-3 transgenic rat model

PURPOSE

To investigate the role of brain noradrenergic and orexinergic activity in ketamine-induced sedation.

METHODS

We used orexin neuron-deficient transgenic rats (orexin/ataxin-3) and wild-type controls. Noradrenaline and orexin levels were measured in the pons, hypothalamus, and cerebral cortex. Ketamine-induced loss-of-righting reflex (LORR) was assessed under modulation of noradrenergic or orexinergic activity.

RESULTS

Wild-type rats had higher noradrenaline and orexin levels than transgenic rats across all regions except hypothalamic noradrenaline. Noradrenaline and orexin were correlated in the pons and cortex. Transgenic rats had a shorter LORR duration than wild-type rats (36.3 ± 10.4 vs. 46.7 ± 5.2 min, P = 0.002). Noradrenergic activation via intraperitoneal yohimbine prolonged LORR in both genotypes (wild-type: 38.8 ± 4.9 vs. 71.9 ± 15.3 min at 3.3 mg/kg, P = 0.002; transgenic: 28.1 ± 3.9 vs. 71.9 ± 24.8 min, P < 0.001). Noradrenergic deactivation by DSP4 reduced LORR duration (wild-type: 43.3 ± 2.18 vs. 36.4 ± 6.0 min, P = 0.005). Intracerebroventricular orexin (1.0 nmol) shortened LORR (44.0 ± 16.7 vs. 30.1 ± 15.5 min, P = 0.001), but co-administration of selective orexin type 1 receptor antagonist YNT-1310 (100 nmol) counteracted this effect. Notably, orexin or DSP4 reduced LORR duration in wild-type rats but prolonged it in transgenic rats (e.g., wild-type: 40.8 ± 6.2 vs. 32.5 ± 5.3 min with orexin, P = 0.0001; transgenic 28.6 ± 6.2 vs. 42.1 ± 5.6 min, P = 0.0026).

CONCLUSION

Orexin-preserved noradrenergic activity supports the typical ketamine-induced sedation profile, highlighting their interactive role in modulating anesthetic depth.

A Behavioral and Electroencephalographic Study of Anesthetic State Induced by MK-801 Combined with Haloperidol, Ketamine and Riluzole in Mice

BACKGROUND

Ketamine is an intravenous anesthetic that acts as a channel blocker on the N-methyl- d -aspartate (NMDA) receptor, a glutamate receptor subtype. MK-801 is the most potent compound among noncompetitive NMDA receptor antagonists. Ketamine induces loss of the righting reflex (LORR) in rodents, which is one of the indicators of unconsciousness, whereas high doses of MK-801 produce ataxia, but not LORR. In contrast, we previously reported that MK-801 combined with a low dose of the dopamine receptor antagonist haloperidol-induced LORR in mice. To assess a neurophysiologically distinct brain state and demonstrate unconsciousness, electroencephalograms (EEG) need to be examined together with LORR. Therefore, we herein investigated EEG changes after the systemic administration of MK-801 alone or in combination with haloperidol, and compared them with those induced by ketamine, the glutamate release inhibitor riluzole, and the γ-aminobutyric acid type A receptor agonist propofol.

METHODS

All drugs were intraperitoneally administered to adult male ddY mice (n = 168). General anesthesia was evaluated based on the righting reflex test. Animals who exhibited no righting for more than 30 seconds were considered to have LORR. In a separate group of mice, EEG of the primary visual cortex was recorded before and after the administration of MK-801 (3.0 mg/kg) alone or in combination with haloperidol (0.2 mg/kg), ketamine (150 mg/kg), riluzole (30 mg/kg), or propofol (240 mg/kg). The waveforms recorded were analyzed using EEG power spectra and spectrograms.

RESULTS

The high dose of MK-801 alone did not induce LORR, whereas MK-801 combined with haloperidol produced LORR in a dose-dependent manner. Ketamine, riluzole, and propofol also dose-dependently induced LORR. In the EEG study, MK-801 alone induced a significant increase in δ power, while MK-801 plus haloperidol exerted similar effects on not only δ, but also θ and α power during LORR, suggesting that increases in δ, θ, and α power were necessary for LORR. The results obtained on MK-801 plus haloperidol were similar to those on ketamine in the behavioral and EEG studies, except for an increase in γ power by ketamine during LORR. Propofol significantly increased δ, θ, α, and β power during LORR. However, the EEG results obtained using riluzole, which produced a unique pattern of lower amplitude activity spanning most frequencies, markedly differed from those with the other drugs.

CONCLUSIONS

This study revealed differences in EEG changes induced by various sedatives. The results obtained on MK-801 alone and MK-801 plus haloperidol suggest the importance of dopamine transmission in maintaining the righting reflex.

Hyperbaric Oxygen Ameliorated Acute Pancreatitis in Rats via the Mitochondrial Pathway

BACKGROUND

Acute pancreatitis (AP) is a common disease of the digestive system. The mechanism of hyperbaric oxygen (HBO) therapy for AP is not completely clear.

AIMS

This study investigated the effects of HBO in AP and whether it acts through the mitochondria-mediated apoptosis pathway.

METHODS

Eighty male Sprague-Dawley rats were randomly assigned to four groups: control (8 rats), sham (24 rats), AP (24 rats), or AP + HBO (24 rats). AP was induced by ligating the pancreatic duct. The AP + HBO group was given HBO therapy starting at 6 h postinduction. Eight rats in each group were killed on days 1, 2, and 3 postinduction to assess pancreatic injury, mitochondrial membrane potential, ATP level, and expression levels of BAX, Bcl-2, caspase-3, caspase-9, and PARP in pancreatic tissue and blood levels of amylase, lipase, and pro-inflammatory cytokines.

RESULTS

HBO therapy alleviated the severity of AP and decreased histopathological scores and levels of serum amylase, lipase, and pro-inflammatory cytokines. Compared to AP induction alone, HBO therapy increased expression of the apoptotic protein BAX, caspase-3, caspase-9, and PARP and ATP levels in tissues and decreased antiapoptotic protein Bcl-2 expression levels and the mitochondrial membrane potential on the first day; the results on the second day were partly consistent with those on the first day, while there was no obvious difference on the third day.

CONCLUSIONS

HBO therapy could induce caspase-dependent apoptosis in AP rats to alleviate pancreatitis, which was possibly triggered by mitochondrial apoptosis pathway regulation of Bcl-2 family members.