Cortical Representation of Hyperalgesia Induced by Nerve Growth Factor (LOGIN_NGF)

Intraepidermal injection of nerve growth factor results in a non-inflammatory hyperalgesia for thermal and mechanical stimuli. This hyperalgesia is similar to the pathological ailments of patients with neuropathic pain. The mechanisms of the cognitive modulation of pain and hyperalgesia are not yet understood in this group of patients. The investigators plan to use NGF injection as a model of non-inflammatory neuropathic pain in healthy subjects to investigate the underlying neuronal mechanisms of this hyperalgesia using functional magnetic resonance imaging and resting state network analysis.

injection of 50 µl NGF, once into the left volar forearm and injection of 50 µl NaCl (sodium chloride) once into the right volar forearm

Activation of the resting state network (using functional magnetic resonance imaging (fMRI) and a standard echo planar imaging (EPI) sequence) as well as acitvation of the pain processing network (using fMRI and a standard EPI sequence) in response to painful stimulation, will be measured before and after injection of NGF into the volar forearm of the participant. Particants are measured 0-4 days before injection (baseline) and then again 4-7 days after injection (to measure changes due to NGF injection).

Pain will be applied by using impact stimulation to the side where NGF was injected as well as a control side. Pain and tolerance thresholds as well as 3 ratings of intensity/unpleasantness and suffering will be obtained immediately after stimulation. This will take place before NGF injection (baseline, 0-4 days) and after NGF injection (4-7 days). Ratings will be conducted on visual analog scale from 0 (no pain/unpleasantess/suffering) to 100 (worst pain/unpleasantness/suffering imaginable).

Inclusion Criteria: no acute or chronic disease no acute or chronic pain age: 18-60 years male no medication use Exclusion Criteria: metallic parts in the body claustrophobia drug or substance abuse