DENEYSEL RAT TRİGEMİNAL NEVRALJİ MODELİNDE NANOPARTİKÜLE BAĞLANMIŞ KARBAMAZEPİNİN İNTRANAZAL YOLLA UYGULANMASININ DAVRANIŞSAL ETKİLERİNİN İNCELENMESİ

Abstract

Eker, C. Investigation of the behavioral effects of intranasally administered carbamazepine conjugated with nanoparticles in an experimental rat model of trigeminal neuralgia, Hacettepe University Faculty of Medicine, Department of Neurosurgery, Ankara, 2024 Introduction and Aim: Trigeminal neuralgia (TN) is a neurological disorder characterized by sudden onset, recurrent, unilateral electric shock-like pains. The pain is confined to one or more branches of the trigeminal nerve and is typically triggered by innocuous stimuli. The annual incidence is 4.3 per 100,000, increasing to 45 per 100,000 in individuals over 80 years of age. The first-line treatment for TN is oral carbamazepine (CBZ), considered the gold standard. While CBZ initially provides a treatment response in over 90% of patients, long-term use often leads to side effects such as somnolence and hyponatremia, and rarely to serious adverse effects like Stevens-Johnson Syndrome. Additionally, CBZ loses its efficacy due to autoinduction that accelerates its own metabolism, resulting in decreased treatment response. To overcome these disadvantages, alternative drug delivery systems enhancing bioavailability have been developed. In this context, formulating CBZ within chitosan-based nanoparticles and administering it intranasally has been investigated as a new therapeutic approach, as it can more effectively cross the blood-brain barrier and provide controlled release. Chitosan was chosen for its biocompatibility and its ability to facilitate drug transport across mucosal barriers. In this study, we aimed to test the in vivo efficacy of CBZ-loaded chitosan nanoparticles by behaviorally evaluating the responses to mechanical allodynia in rats with a trigeminal neuralgia model using Von Frey filaments. Materials and Methods: In the in vitro phase, CBZ-loaded nanoparticles were synthesized, thermogravimetric analyses were performed, and loading efficiencies and release profiles were determined using UV-Vis spectroscopy. The size distributions of the nanoparticles were analyzed with a Zeta Sizer, and their morphological properties were examined via electron microscopy. In the in vivo study, trigeminal neuralgia was induced in 30 male Sprague-Dawley rats, which were divided into five groups: a sham group, a control group, and three experimental groups. The experimental groups received a single intranasal dose of either empty chitosan nanoparticles, 2 mg/kg CBZ, or CBZ-loaded chitosan nanoparticles equivalent to 2 mg/kg CBZ, administered 24 hours after infraorbital nerve ligation. Responses to mechanical allodynia were measured using Von Frey filaments preoperatively, postoperatively, and at specified time points (1, 2, 4, 6, 12, 24, 36, and 48 hours after drug administration). All subjects were sacrificed on the 28th day; no tissue samples v were collected as the experiment focused solely on behavioral response assessment. Results: In vitro studies demonstrated that chitosan nanoparticles containing CBZ with a diameter of 75.2 ± 12.9 nm were successfully synthesized. In vivo studies confirmed that the trigeminal neuralgia model was successfully established in all groups except the sham group. In the group administered empty chitosan nanoparticles, there was no significant change in the mechanical allodynia response threshold starting from postoperative 24 hours. In the group given CBZ alone, the pain threshold increased at the 1st and 2nd hours but returned to baseline by the 4th hour. In the group receiving CBZ-loaded chitosan nanoparticles, the pain threshold began to increase from the 1st hour, reached the first peak at the 4th hour, made a second peak at the 24th hour, remained elevated until the 36th hour, and returned to baseline at the 48th hour. Statistical analyses showed that the duration and intensity of the effect were significantly higher for CBZ loaded in nanoparticles compared to CBZ alone. Conclusion: In the rat trigeminal neuralgia model, intranasally administered CBZ-loaded chitosan nanoparticles may represent a potential alternative route for medical treatment due to their extended duration and increased strength of effect. Following this preliminary study, which involved only behavioral measurements and evaluations, we plan to conduct follow-up studies with different protocols that include examination of central nervous system tissues.