High plasma calcitonin gene-related peptide and serum pituitary adenylate cyclase-activating polypeptide levels in patients with neuropathic pain.

INTRODUCTION: Based on animal studies, calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are thought to play a role in neurobiological events such as neuropathic pain, neuroprotection, neurotransmission, neural plasticity, and neurotrophic effects. The aim of the study is to investigate whether there is a change in the blood level of CGRP and PACAP in patients with neuropathic pain and to look for clues about the utility of these peptides as pharmacological targets in the treatment of neuropathic pain in humans. METHODS: The study included 60 polyneuropathy patients with neuropathic pain, 30 polyneuropathy patients without neuropathic pain (NNP) and 29 healthy subjects as control group. Polyneuropathy patients with neuropathic pain were divided into two groups as diabetic (D-PNP) and non-diabetic polyneuropathy (ND-PNP) patients. Plasma CGRP and serum PACAP levels were measured from venous blood samples of the patients and healthy controls. RESULTS: The CGRP level was significantly higher in the D-PNP and ND-PNP groups compared to the control and NNP groups (P<0.05). PACAP levels were significantly higher in the D-PNP and ND-PNP groups compared to the control and NNP groups (P<0.05). There was no significant correlation between CGRP and PACAP levels and neuropathic pain scale (NPS). CONCLUSIONS: This study is the first to demonstrate elevated plasma CGRP and serum PACAP levels in polyneuropathy patients with neuropathic pain. The results of this study are important in terms of showing that both CGRP and PACAP can be new pharmacological targets in the treatment of neuropathic pain and polyneuropathy in humans.