Contact inhibition of righting reflex
The rats were positioned supine on a horizontal surface, and another
horizontal surface was placed slightly in touch with the supine animal’s
feet soles. The rating was done as follows: 0-the animal successfully
righted itself (normal), 1-partial righting, in which the animal exerts
some effort (intermediate response), and 2-complete loss of righting, in
which the animal faces up its feet and walks on the upper surface
(severe response).
Ketamine (75-90 mg/kg, Ketalar, Pfizer, Istanbul, Turkey) and xylazine
(5-8 mg/kg, Rompun, Bayer, Leverkusen, Germany) were used to anesthetize
the rats intraperitoneally. The pedal reflex was used to determine the
depth of anaesthesia, and further anaesthesia was provided in half-dose
increments as needed. Each rat’s external ear canal and tympanic
membrane were examined following general anaesthesia using a zero-degree
rigid Karl Storz surgical scope. Rats with abnormal external ear canals
or a perforated tympanic membrane were excluded from this study.
After the baseline vestibular parameters testing, an endoscopic-guided
transtympanic instillation of aqueous and ethanol henna extract was
conducted into the right middle ear of the rats in Group A and B,
respectively (Figure 3). At the same time, normal saline was instilled
in the right middle ear of rats in Group C. A total of 0.1ml
instillation of aqueous, ethanol extract, and saline for each rat was
sufficient to fill the whole middle ear cavity of the rat.
The rats were given time to recover from the anaesthesia. The four
vestibular parameters testing were assessed on the rat’s
post-instillation of transtympanic Henna at intervals of 4 hours, 24
hours, 48 hours, 72 hours, one week, two weeks, and three weeks.
The rats would then be euthanized intraperitoneally with thiopental
sodium (200 mg/kg Pentothal; Abboth, Campoverde di Aprilla, Italy).