Intrathecal catheter implantation and drug administration

The experiments were conducted in 5-week-old male Sprague-Dawley rats. A polyethylene lumbar intrathecal catheter (PE 10, 0.61 mm OD; Intramedic, Clay Adams, Becton Dickinson and Company, NJ) was inserted between the L5 and L6 vertebrae and advanced 3.5 cm rostrally under isoflurane (2–3% in O₂) anesthesia, as described in detail previously [10]. The proper location of the tip of the catheter was tested 24 h before the pharmacological experiments by assessing the motor blockade following intrathecal injection of 30 μl of lidocaine (50 mg/ml).