Objective: Environmental deprivation, a type of childhood maltreatment, has been reported to constrain the cognitive developmental processes such as associative learning and implicit learning, which may lead to functional and morphological changes in the ventral pallidum (VP) and pessimism, a well-known cognitive feature of major depression. We examined whether neonatal isolation (NI) could influence the incidence of learned helplessness (LH) in a rat model mimicking the pessimism, and the number of vesicular glutamate transporter 2 (VGLUT2)-expressing VP cells and Penk-expressing VP cells. Methods: The number of escape failures from foot-shocks in the LH test was measured to examine stress-induced depression-like behavior in rats. The number of VGLUT2-expressing VP cells and Penk-expressing VP cells was measured by immunohistochemistry. Results: In NI rats compared with Sham rats, the incidence of LH in adulthood was increased and VGLUT2-expressing VP cells but not Penk-expressing VP cells in adulthood were decreased. VGLUT2-expressing VP cells were decreased only in the LH group of NI rats and significantly correlated with the escape latency in the LH test. Conclusion These findings suggest that the aberrant VP neuronal activity due to environmental deprivation early in life leads to pessimistic associative and implicit learning. Modulating VP neuronal activity could be a novel therapeutic and preventive strategy for the patients with this specific pathophysiology.

Introduction: The diagnosis of cancer-related neuropathic pain is often difficult for non-pain medicine specialists. We examined whether a Japanese version of a neuropathic pain screening questionnaire (Japan-Q), which was developed for chronic pain, is appropriate for screening cancer-related neuropathic pain. Methods: Our palliative care team screened 104 patients from May 2014 to December 2015 and compared total points of the Japan-Q with diagnosis of the type of cancer pain by specialized pain clinicians. Validity was evaluated using a receiver operating characteristic (ROC) curve. Results: The area under the ROC curve in terms of the total score, sensitivity, and specificity for the Japan Q was 0.82, which indicated a moderate level of diagnostic accuracy. A cut-off value of 3 points was shown to be best (sensitivity: 79%, specificity: 82%). When a cut-off value of 9 points was used as the diagnostic criterion for neuropathic pain, there was greatly reduced sensitivity (sensitivity: 40%, specificity: 97%). Conclusion: Although the Japan-Q shows moderate diagnostic accuracy related to cancer pain, the cut-off value for this tool is lower than that for chronic pain. Cancer-related neuropathic pain should be suspected with a total score of 3 or more in the Japan-Q.