Neurobehavioural Evaluation of Antidepressant and Anticonvulsant Potentials of Tizanidine in Balb/c Mice

Tizanidine is a selective α2-adrenergic receptor agonist that stimulates the central nervous system through the adrenergic pathway. This study evaluated the antidepressant and anticonvulsant activity of tizanidine in mice. The various limitations of currently available anti-depressive and epileptic drugs and the bidirectional relationship between the two neurological disorders warrant improved pharmacotherapy interventions. 125 Balb/c mice were divided into 75 and 50 for antidepressant and anticonvulsant stud-ies, respectively. Forced swim (FST), tail suspension (TST), and open field (OFT) antidepressant models were used. In each model, twenty-five mice were divided into five groups (n=5); 1 mL/kg dis-tilled water group (negative control), 15 mg/kg imipramine (positive control in FST and TST), 0.05 mg/kg diazepam (positive control for OFT) group, and 1 mg/kg, 2 mg/kg, and 4 mg/kg tizanidine groups respectively. Anticonvulsant screening was conducted using pentylenetetrazole (PTZ) and picrotoxin models of seizure in which mice were treated with 2 mg/kg, 4 mg/kg and 8 mg/kg tizanidine. Tizanidine at all the doses significantly reduced the immobility time of the mice in FST (p≤0.0001) and TST (p≤ 0.05). There was no significant increase in line crossing frequency between tizanidine and 0.05 mg/kg diazepam in the OFT (p˃0.05). Tizanidine significantly delayed the onset of myoclonic jerks (p≤0.001) in the PTZ model but not in the picrotoxin model (p˃0.05). This study showed that tizanidine possesses antidepressant-like activity, but little anticonvulsant activity.