Comparison of reflex-based and operant methods when evaluating effects of treatment on pain in experimetnal models

Pharmacological treatment of neuropathic pain is still insufficient. Methylphenidate, a psychostimulant that increases the dopamine and noradrenaline levels, is commonly used for treating ADHD. There have been reports of changes in patients pain thresholds by ADHD patients treated with methylphenidate. The aim of the study is to examine if methylphenidate can affect peripheral neuropathic pain. Neuropathic pain has been modelled on laboratory rats by chronic constriction of the ischiatic nerve. The effect of methylphenidate on the evoked pain component was evaluated on control animals and on animals with neuropathic pain using reflex (plantar test, vonFrey test) and operanting test (thermal place preference). The effect of methylphenidate on the spontaneous components of pain was evaluated using the methods of conditioned place preference. This study has proven that methylphenidate in an applicable dose of 1 mg/kg has an antialodynic effect but does not act antinociceptively. This study further confirms that methylphenidate in low doses does not act as attractant and has no effect on spontaneous pain. The last part of the study compares the different methods for pain measurement and comes to the conclusion that the plantar test is not an adequate method for evaluating the effect of analgesics..