Sensory-motor behavioral characterization of an animal model of Maroteaux-Lamy syndrome (or Mucopolysaccharidosis VI)

Sleep loss, caffeine, sleep aids and sedation modify brain abnormalities of mild traumatic brain injury

Little evidence exists about how mild traumatic brain injury (mTBI) is affected by commonly encountered exposures of sleep loss, sleep aids, and caffeine that might be potential therapeutic opportunities. In addition, while propofol sedation is administered in severe TBI, its potential utility in mild TBI is unclear. Each of these exposures is known to have pronounced effects on cerebral metabolism and blood flow and neurochemistry. We hypothesized that they each interact with cerebral metabolic dynamics post-injury and change the subclinical characteristics of mTBI. MTBI in rats was produced by head rotational acceleration injury that mimics the biomechanics of human mTBI. Three mTBIs spaced 48 h apart were used to increase the likelihood that vulnerabilities induced by repeated mTBI would be manifested without clinically relevant structural damage. After the third mTBI, rats were immediately sleep deprived or administered caffeine or suvorexant (an orexin antagonist and sleep aid) for the next 24 h or administered propofol for 5 h. Resting state functional magnetic resonance imaging (rs-fMRI) and diffusion tensor imaging (DTI) were performed 24 h after the third mTBI and again after 30 days to determine changes to the brain mTBI phenotype. Multi-modal analyses on brain regions of interest included measures of functional connectivity and regional homogeneity from rs-fMRI, and mean diffusivity (MD) and fractional anisotropy (FA) from DTI. Each intervention changed the mTBI profile of subclinical effects that presumably underlie healing, compensation, damage, and plasticity. Sleep loss during the acute post-injury period resulted in dramatic changes to functional connectivity. Caffeine, propofol sedation and suvorexant were especially noteworthy for differential effects on microstructure in gray and white matter regions after mTBI. The present results indicate that commonplace exposures and short-term sedation alter the subclinical manifestations of repeated mTBI and therefore likely play roles in symptomatology and vulnerability to damage by repeated mTBI.

Etomidate and Ketamine: Residual Motor and Adrenal Dysfunction that Persist beyond Recovery from Loss of Righting Reflex in Rats

We tested the hypothesis that etomidate and ketamine produce residual effects that modify functional mobility (measured by the balance beam test) and adrenal function (adrenocorticotropic hormone (ACTH) stimulation) immediately following recovery from loss of righting reflex in rats. Intravenous etomidate or ketamine was administered in a randomized, crossover fashion (2 or 4 mg/kg and 20 or 40 mg/kg, respectively) on eight consecutive days. Following recovery of righting reflex, animals were assessed for residual effects on functional mobility on the balance beam, motor behavior in the open field and adrenal function through ACTH stimulation. We evaluated the consequences of the effects of the anesthetic agent-induced motor behavior on functional mobility. On the balance beam, etomidate-treated rats maintained their grip longer than ketamine-treated rats, indicating greater balance abilities (mean ± SD, 21.5 ± 25.1 s vs. 3.0 ± 4.3 s respectively, p < 0.021). In the open field test, both dosages of etomidate and ketamine had opposite effects on travel behavior, showing ketamine-induced hyperlocomotion and etomidate-induced hypolocomotion. There was a significant interaction between anesthetic agent and motor behavior effects for functional mobility effects (p < 0.001). Corticosterone levels were lower after both 40 mg/kg ketamine and 4 mg/kg etomidate anesthesia compared to placebo, an effect stronger with etomidate than ketamine (p < 0.001). Following recovery from anesthesia, etomidate and ketamine have substantial side effects. Ketamine-induced hyperlocomotion with 20 and 40 mg/kg has stronger effects on functional mobility than etomidate-induced hypolocomotion with 2 and 4 mg/kg. Etomidate (4 mg/kg) has stronger adrenal suppression effects than ketamine (40 mg/kg).