Objectives: This study investigated the antinociceptive effects of co-administration of lithium chloride (LiCl) and vitamin E (Vit. E) on chronic constriction injury (CCI)-induced peripheral neuropathy in male Wistar rats. It further explored the anti-inflammatory and neuroprotective properties of LiCl and Vit. E which may be complementary to the antinociceptive effects of the two substances.
Methods: Thirty-six male Wistar rats, 190.00 ± 10.00 g of body weight (b.w) were randomly assigned to six experimental groups and administered with either normal saline, Vit. E, LiCl, or their combination, once daily for twenty-one (21) days. CCI was used to induce NP and mechanical allodynia was assessed using von Frey filaments and pinprick test. Open field maze (OFM) was used to assess the exploratory behaviour. Biochemical parameters were assessed in the dorsal root ganglion (DRG) after twenty-one days of treatment.
Results: Mechanical allodynia was developed in rats following CCI. Co-administration of LiCl and Vit.E. synergistically reduced mechanical hyperalgesia in rats which were significantly different compared with the single administration of either Vit.E. or LiCl. Combined doses of Vit.E. and LiCl significantly increases the explorative behaviour in the OFM. CCI increased malondialdehyde (MDA), tumour necrotic factor-alpha (TNF-α), calcitonin gene-related polypeptide (CGRP), calcium ion (Ca2+ ), and reduced superoxide dismutase (SOD) activities. Co-administration of LiCl and Vit.E. significantly reduced MDA, TNF-α, but increased SOD compared with ligated control.
Discussion: The findings revealed that the synergistic effects of the co-administration of Vit. E and LiCl in ameliorating neuropathic pain are mediated by their anti-inflammatory and antioxidant properties.