ABSTRACT
The lateral septum (LS) is a forebrain structure that has been implicated in a wide range of behavioral and physiological responses to stress. However, the specific populations of neurons in the LS that mediate stress responses remain incompletely understood. Here, we show that neurons in the dorsal lateral septum (LSd) that express the somatostatin gene (hereafter, LSd Sst neurons) are activated by diverse stressors. Retrograde tracing from LSd Sst neurons revealed that these neurons are directly innervated by neurons in the locus coeruleus (LC), the primary source of norepinephrine well-known to mediate diverse stress-related functions in the brain. Consistently, we found that norepinephrine increased excitatory synaptic transmission onto LSd Sst neurons, suggesting the functional connectivity between LSd Sst neurons and LC noradrenergic neurons. However, optogenetic stimulation of LSd Sst neurons did not affect stress-related behaviors or autonomic functions, likely owing to the functional heterogeneity within this population. Together, our findings show that LSd Sst neurons are activated by diverse stressors and suggest that norepinephrine released from the LC may modulate the activity of LSd Sst neurons under stressful circumstances.
ABSTRACT
PURPOSE: A laparoscopic colectomy in colorectal-cancer patients is usually associated with a high risk of postoperative nausea and vomiting (PONV). The purpose of this study is to evaluate the efficacy of injection of long-acting 5-hydroxytryptamine type 3 (5-HT3) receptor antagonist for the reduction of PONV in patients with colorectal cancer. METHODS: A total of 48 patients scheduled to undergo a laparoscopic colectomy for colorectal cancer were randomized in a double-blinded fashion. Patients were randomly allocated to 1 of 2 groups and assigned to receive either 0.3 mg of ramosetron intravenously (group A, n = 25) or 2 mL of normal saline (placebo) (group B, n = 22) immediately after the operation. The incidence of PONV, the nausea severity scale score, the visual analogue scale (VAS) score for pain, the total amount of patient-controlled analgesia used, the recovery of bowel function, and morbidities were assessed at 1 hour and at 24, 48, and 72 hours after surgery. RESULTS: The baseline and the operative characteristics were similar between the groups (P > 0.05). The number of cases without PONV (complete response) was higher for group A (ramosetron) than group B (normal saline): 24 hours after surgery, 92.0% (23 of 25) for group A versus 54.5% (12 of 22) for group B; 48 hours after surgery, 92% (23 of 25) for group A versus 81.8% (18 of 22) for group B (both P < 0.05). No serious adverse events occurred. CONCLUSION: Postoperative ramosetron injection is effective for the prevention of PONV after a laparoscopic colectomy in colorectal-cancer patients.