Nitroglycerine (NTG) induced migraine-like pain behaviors in female C57Bl/6 mice. (A) Procedure for evaluating the conditioned place preference (CPP) using a single-trial conditioning on the day of last NTG treatment. (B) The peptide antagonist of calcitonin gene related peptide (CGRP), α-CGRP (8-37) (0.8 mg/kg, i.v.) effectively elicited pain relief-induced CPP and blocked ongoing pain in NTG-treated mice. (C) Difference score analysis (test time-preconditioning time spent in the drug paired chamber) confirmed α-CGRP (8-37)-induced CPP in NTG-treated mice. (D) After four intermittent treatments with NTG, mice displayed significantly reduced paw withdrawal threshold to von Frey filaments probing when compared with the vehicle-treated control mice. * P < 0.05, *** P < 0.001, n = 6 for each group.