Fast-spiking Interneurons Contribute to Propofol-induced Facilitation of Firing Synchrony in Pyramidal Neurons of the Rat Insular Cortex

Differential synaptic mechanism underlying the neuronal modulation of prefrontal cortex, amygdala, and hippocampus in response to chronic postsurgical pain with or without cognitive deficits in rats

Chronic Postsurgical Pain (CPSP) is well recognized to impair cognition, particularly memory. Mounting evidence suggests anatomic and mechanistic overlap between pain and cognition on several levels. Interestingly, the drugs currently used for treating chronic pain, including opioids, gabapentin, and NMDAR (N-methyl-D-aspartate receptor) antagonists, are also known to impair cognition. So whether pain-related cognitive deficits have different synaptic mechanisms as those underlying pain remains to be elucidated. In this context, the synaptic transmission in the unsusceptible group (cognitively normal pain rats) was isolated from that in the susceptible group (cognitively compromised pain rats). It was revealed that nearly two-thirds of the CPSP rats suffered cognitive impairment. The whole-cell voltage-clamp recordings revealed that the neuronal excitability and synaptic transmission in the prefrontal cortex and amygdala neurons were enhanced in the unsusceptible group, while these parameters remained the same in the susceptible group. Moreover, the neuronal excitability and synaptic transmission in hippocampus neurons demonstrated the opposite trend. Correspondingly, the levels of synaptic transmission-related proteins demonstrated a tendency similar to that of the excitatory and inhibitory synaptic transmission. Furthermore, morphologically, the synapse ultrastructure varied in the postsynaptic density (PSD) between the CPSP rats with and without cognitive deficits. Together, these observations indicated that basal excitatory and inhibitory synaptic transmission changes were strikingly different between the CPSP rats with and without cognitive deficits.

SCFAs Ameliorate Chronic Postsurgical Pain-Related Cognition Dysfunction via the ACSS2-HDAC2 Axis in Rats

Patients with chronic postsurgical pain (CPSP) frequently exhibit comorbid cognitive deficits. Recent observations have emphasized the critical effects of gut microbial metabolites, like short-chain fatty acids (SCFAs), in regulating cognitive function. However, the underlying mechanisms and effective interventions remain unclear. According to hierarchical clustering and 16S rRNA analysis, over two-thirds of the CPSP rats had cognitive impairment, and the CPSP rats with cognitive impairment had an aberrant composition of gut SCFA-producing bacteria. Then, using feces microbiota transplantation, researchers identified a causal relationship between cognitive-behavioral and microbic changes. Similarly, the number of genera that generated SCFAs was decreased in the feces from recipients of cognitive impairment microbiota. Moreover, treatment with the SCFAs alleviated the cognitive-behavioral deficits in the cognitively compromised pain rats. Finally, we observed that SCFA supplementation improved histone acetylation and abnormal synaptic transmission in the medial prefrontal cortex (mPFC), hippocampal CA1, and central amygdala (CeA) area via the ACSS2 (acetyl-CoA synthetase2)-HDAC2 (histone deacetylase 2) axis. These findings link pain-related cognition dysfunction, gut microbiota, and short-chain fatty acids, shedding fresh insight into the pathogenesis and therapy of pain-associated cognition dysfunction.

Different Anesthetic Drugs Mediate Changes in Neuroplasticity During Cognitive Impairment in Sleep-Deprived Rats via Different Factors

Background

Perioperative neuro-cognitive disorders (PND) are preoperative and postoperative complications of multiple nervous systems, typically manifested as decreased memory and learning ability after surgery. It was used to replace the original definition of postoperative cognitive dysfunctions (POCD) from 2018. Our previous studies have shown that sevoflurane inhalation can lead to cognitive dysfunction in Sprague-Dawley rats, but the specific mechanism is still unclear.

Material/Methods

Thirty-six male Sprague-Dawley rats were randomly divided into 6 groups (n=6): the SD group was given 24-h acute sleep deprivation; Sevoflurane was inhaled for 2 h in the Sevo group. Two mL propofol was injected into the tail vein of rats in the Prop group. The rats in the SD+Sevo group and SD+Prop group were deprived of sleep before intervention in the same way as before.

Results

We noted significant behavioral changes in rats treated with SIK3 inhibitors or tau phosphorylation agonists before propofol injection or sevoflurane inhalation, with associated protein levels and dendritic spine density documented. Sevoflurane anesthesia-induced cognitive impairment following acute sleep deprivation was more pronounced than sleep deprivation-induced cognitive impairment alone and resulted in increased brain SIK3 levels, increased phosphorylation of total tau and tau, and decreased acetylation modifications. After using propofol, the cognitive function returned to baseline levels with a series of reversals of cognitive dysfunction.

Conclusions

These results suggest that sevoflurane inhalation via the SIK3 pathway aggravates cognitive impairment after acute sleep deprivation and that propofol anesthesia reverses the effects of sleep deprivation by affecting modifications of tau protein.