A Novel Approach to Assess Motor Outcome of Deep Brain Stimulation Effects in the Hemiparkinsonian Rat: Staircase and Cylinder Test

Summary

Deep brain stimulation (DBS) is an effective treatment option for Parkinson's disease. We established a study design to screen novel stimulation paradigms in rats. The protocol describes the use of the staircase test and cylinder test for motor outcome assessment in DBS treated hemiparkinsonian rats.

Abstract

Deep brain stimulation of the subthalamic nucleus is an effective treatment option for Parkinson's disease. In our lab we established a protocol to screen different neurostimulation patterns in hemiparkinsonian (unilateral lesioned) rats. It consists of creating a unilateral Parkinson's lesion by injecting 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle, implanting chronic stimulation electrodes into the subthalamic nucleus and evaluating motor outcomes at the end of 24 hr periods of cable-bound external neurostimulation. The stimulation was conducted with constant current stimulation. The amplitude was set 20% below the individual threshold for side effects. The motor outcome evaluation was done by the assessment of spontaneous paw use in the cylinder test according to Shallert and by the assessment of skilled reaching in the staircase test according to Montoya. This protocol describes in detail the training in the staircase box, the cylinder test, as well as the use of both in hemiparkinsonian rats. The use of both tests is necessary, because the staircase test seems to be more sensitive for fine motor skill impairment and exhibits greater sensitivity to change during neurostimulation. The combination of the unilateral Parkinson model and the two behavioral tests allows the assessment of different stimulation parameters in a standardized way.

Introduction

Deep brain stimulation of the subthalamic nucleus (STN) is an effective treatment option for Parkinson's disease¹ and other movement disorders. The underlying mechanisms are still poorly understood and multifactorial, but a key feature is the modulation of neuronal network activity by repetitive depolarization of axons in the vicinity of the stimulating electrode^2-4. High-frequency (>100 Hz) stimulation is required for a beneficial effect in most brain targets and for most indications of DBS. Side effects of deep brain stimulation result from inadvertent coactivation of other fibers, which are covered by the stimulation volume and which s....

Protocol

Animal experiments were approved by the University of Wuerzburg and the legal state authorities of Lower Franconia in accordance with the animal protection guidelines and European Communities Council guidelines (approval number: 55.2-2531.01 76/11). All efforts were made to minimize pain or discomfort of the animals used.

Note: Electrode implantation was performed as described elsewhere¹⁸.

1. Cylinder Test (Figure 2)

1. Prepare a clear plastic glass cylinder (height: 40 cm, diameter: 19 cm) by cleaning the cylinder with a 0.1% acetic acid solution.
2. Prepare cards with date of experime....

Results

All animals underwent a post mortem histological verification of both the dopaminergic lesion and the electrode location. Only animals with correct electrode placement inside the STN (Figure 6) and complete dopaminergic lesion (>90% loss of dopaminergic neurons in substantia nigra) were included into the results section (Figure 7).

The cylinder test performed under lesioned condition showed t.......

Discussion

This article describes a detailed training protocol for the cylinder and staircase test. The latter is designed to assess complex grasping behavior and fine motor movement due to skilled reaching in rats^16,17. The outcome measurement is expressed as number of pellets eaten during the test, which is an objective measurement. The protocol can be used in rat models for Parkinson's disease and other motor disease models. The cylinder test involves a simple approach to evaluate paw use in rats. It requires no t.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Staircase box without lid	Glas Keil, Germany		custom made
Cylinder box	Glas Keil, Germany		custom made
Dustless precision pellets, 45 mg	Bio Serv	F0021