With the increasing popularity of contact sports, cognitive deficits caused by mild traumatic brain injury have been receiving attention from researchers.
In this rodent study, researchers from the Kunming Medical University in China built upon existing literature that rosemary extract enhances cognitive function in rats. They argued that such research is important because “despite the high incidence and serious consequences of cognitive deficits following mild traumatic brain injury, effective therapeutic drugs are limited.”
What the researchers are doing differently in this current one is that there hasn’t been any studies published or tests conducted to examine the effect rosemary extract has on mild traumatic brain injury patients. Thus, for this study, they investigated the extract’s potential mechanisms that occur in the hippocampus of rats induced with mild traumatic brain injuries.
Study design
Seventy-two Sprague-Dawley rats were struck three times, once per day on consecutive days, on the closed parietal occipital skull with a single metallic pendulum to establish the mild traumatic brain injury model.
The rats were divided randomly into six groups, and physiologic parameters were recorded and scored. Only rats that fell into the criteria for mild traumatic brain injuries after the strikes underwent the subsequent treatments.
Rosemary extract by Kunming Pharmaceutical Co., which isn’t on the market, was dissolved in 1% Tween-80 to prepare a suspension in different concentrations (20 mg/mL, 40 mg/mL, and 80 mg/mL). After the third strike conducted on the rats, the different concentrations were administered intragastrically on the rats for seven days. A control group was administered only 1% Tween-80.
Running through a maze
The rat’s ability to navigate through a Morris water maze shows the “crucial role of the hippocampus in learning and memory,” the researchers wrote.
To measure the rats’ cognitive function, they were put through the Morris water maze on days 1-16 post-injury. They were randomly placed on the north, south, east, or west starting points at each trial, and on days 1-14, each rat was placed into a pool 2 m in diameter and had to locate a hidden platform to escape the water. ”Latency to find the platform and time spent in each quadrant were recorded using an automated tracking system,” the researchers wrote.
In addition, an immunohistochemistry test was also administered. On post-injury day 17, the rats were anesthetized and their brains post-fixed for 48 hours in 4% paraformaldehyde and then stored in a 30% sucrose solution, before dissecting the brains to study it more.
Results
During the maze test, animals with the induced brain trauma took longer to find the platform throughout the testing period compared to another set of rats that bypassed the brain strikes.
Among the rats with the mild brain trauma, all rats supplemented with the various concentrations of rosemary extract took less time than the group supplemented with only Tween, but there were no statistically significant differences between the different extract concentration groups. With this observation, the researchers concluded that “rosemary extract improved the spatial learning and memory deficits induced by mild traumatic brain injury,” they wrote.
Through the brain dissection, they also found that rosemary extract reduced the number of degenerated rat hippocampal neurons that were increased by the trauma. They attribute this to the “anti-inflammatory activity of the central nervous system,” induced by the extract’s carnocic acid’s anti-oxidative properties.
“To the best of our knowledge, this is the first study to demonstrate that [rosemary extract] improves cognitive deficits in [mild traumatic brain injury-induced] rats because of its neuroprotective action via the anti-oxidative stress and anti-inflammatory activities,” they wrote.
They recommend further research in the pharmacological mechanism behind the improvement in cognitive deficits, as well as the relationship between the rosemary extract dose and improvement in cognitive deficits.
Source: Neuroscience Letters
Published online and print, doi:10.1016/j.neulet.2016.04.048
"Rosemary extract improves cognitive deficits in a rats model of repetitive mild traumatic brain injury associated with reduction of astrocytosis and neuronal degeneration in hippocampus"
Authors: Hai Song, et al.