Effective defense against natural threats in the environment is essential for the survival of individual animals. Thus, instinctive behavioral responses accompanied by fear have evolved to protect ...individuals from predators and from opponents of the same species (dominant conspecifics). While it has been suggested that all perceived environmental threats trigger the same set of innately determined defensive responses, we tested the alternate hypothesis that different stimuli may evoke differentiable behaviors supported by distinct neural circuitry. The results of behavioral, neuronal immediate early gene activation, lesion, and neuroanatomical experiments indicate that the hypothalamus is necessary for full expression of defensive behavioral responses in a subordinate conspecific, that lesions of the dorsal premammillary nucleus drastically reduce behavioral measures of fear in these animals, and that essentially separate hypothalamic circuitry supports defensive responses to a predator or a dominant conspecific. It is now clear that differentiable neural circuitry underlies defensive responses to fear conditioning associated with painful stimuli, predators, and dominant conspecifics and that the hypothalamus is an essential component of the circuitry for the latter two stimuli.
The endocannabinoid (eCB) system is a potential target for the treatment of symptoms of post-traumatic stress disorder (PTSD). Similar to clinical PTSD, approximately 25–30% of rats that undergo cued ...fear conditioning exhibit impaired extinction learning. In addition to extinction-resistant fear, these “weak extinction” (WE) rats show persistent anxiety-like behaviors. The goal of the present study was to test the hypothesis that behavioural differences between WE animals and those presenting normal extinction patterns (strong extinction; SE) could be mediated by the eCB system. Rats undergoing fear conditioning/extinction and fear recall sessions were initially segregated in weak and strong-extinction groups. Two weeks later, animals underwent a fear recall session followed by a novelty-suppressed feeding (NSF) test. In acute experiments, WE rats were injected with either the fatty acid amide hydrolase (FAAH) inhibitor URB597 or the CB1 agonist WIN55,212-2 1 h prior to long-term recall and NSF testing. SE animals were injected with the inverse CB1 receptor agonist AM251. In chronic experiments, WE and SE rats were given daily injections of URB597 or AM251 between short and long-term recall sessions. We found that acute administration of WIN55,212-2 but not URB597 reduced anxiety-like behaviour in WE rats. In contrast, AM251 was anxiogenic in SE animals. Neither treatment was effective in altering freezing expression during fear recall. The chronic administration of AM251 to SE or URB597 to WE did not alter fear or anxiety-like behaviour or changed the expression of FAAH and CB1. Together, these results suggest that systemic manipulations of the eCB system may alter anxiety-like behaviour but not the behavioural expression of an extinction-resistant associative fear memory.
•25-30% of rats exhibit impaired extinction learning and long-term anxiety following fear conditioning.•Acute injections of endocannabinoid agonists reduced anxiety-type behaviour in these animals.•In animals presenting normal extinction and anxiety-type responses, inverse agonists of CB1 were anxiogenic.•Neither of these drugs affected fear-type responses.•The chronic administration of drugs that modulate the endocannabinoid system did not alter behavioral responses.
Breast cancer is the second most common diagnosed type of cancer in women. Chronic neuropathic pain after mastectomy occurs frequently and is a serious health problem. In our previous single-center, ...prospective, randomized controlled clinical study, we demonstrated that the combination of serratus anterior plane block (SAM) and pectoral nerve block type I (PECS I) with general anesthesia reduced acute postoperative pain. The present report describes a prospective follow-up study of this published study to investigate the development of chronic neuropathic pain 12 months after mastectomy by comparing the use of general anesthesia alone and general anesthesia with SAM + PECS I. Additionally, the use of analgesic medication, quality of life, depressive symptoms, and possible correlations between plasma levels of interleukin (IL)-1 beta, IL-6, and IL-10 collected before and 24 h after surgery as predictors of pain and depression were evaluated. The results showed that the use of SAM + PECS I with general anesthesia reduced numbness, hypoesthesia to touch, the incidence of patients with chronic pain in other body regions and depressive symptoms, however, did not significantly reduce the incidence of chronic neuropathic pain after mastectomy. Additionally, there was no difference in the consumption of analgesic medication and quality of life. Furthermore, no correlation was observed between IL-1 beta, IL-6, and IL-10 levels and pain and depression. The combination of general anesthesia with SAM + PECS I reduced the occurrence of specific neuropathic pain descriptors and depressive symptoms. These results could promote the use of SAM + PECS I blocks for the prevention of specific neuropathic pain symptoms after mastectomy.Registration of clinical trial: The Research Ethics Board of the Hospital Sirio-Libanes/Brazil approved the study (CAAE 48721715.0.0000.5461). This study is registered at Registro Brasileiro de Ensaios Clinicos (ReBEC), and ClinicalTrials.gov, Identifier: NCT02647385.
Motor cortex stimulation (MCS) is a neurosurgical technique used to treat patients with refractory neuropathic pain syndromes. MCS activates the periaqueductal gray (PAG) matter, which is one of the ...major centers of the descending pain inhibitory system. However, the neurochemical mechanisms in the PAG that underlie the analgesic effect of MCS have not yet been described. The main goal of this study was to investigate the neurochemical mechanisms involved in the analgesic effect induced by MCS in neuropathic pain. Specifically, we investigated the release of γ-aminobutyric acid (GABA), glycine, and glutamate in the PAG and performed pharmacological antagonism experiments to validate of our findings.
Male Wistar rats with surgically induced chronic constriction of the sciatic nerve, along with sham-operated rats and naive rats, were implanted with both unilateral transdural electrodes in the motor cortex and a microdialysis guide cannula in the PAG and subjected to MCS. The MCS was delivered in single 15-minute sessions. Neurotransmitter release was evaluated in the PAG before, during, and after MCS. Quantification of the neurotransmitters GABA, glycine, and glutamate was performed using a high-performance liquid chromatography system. The mechanical nociceptive threshold was evaluated initially, on the 14th day following the surgery, and during the MCS. In another group of neuropathic rats, once the analgesic effect after MCS was confirmed by the mechanical nociceptive test, rats were microinjected with saline or a glycine antagonist (strychnine), a GABA antagonist (bicuculline), or a combination of glycine and GABA antagonists (strychnine+bicuculline) and reevaluated for the mechanical nociceptive threshold during MCS.
MCS reversed the hyperalgesia induced by peripheral neuropathy in the rats with chronic sciatic nerve constriction and induced a significant increase in the glycine and GABA levels in the PAG in comparison with the naive and sham-treated rats. The glutamate levels remained stable under all conditions. The antagonism of glycine, GABA, and the combination of glycine and GABA reversed the MCS-induced analgesia.
These results suggest that the neurotransmitters glycine and GABA released in the PAG may be involved in the analgesia induced by cortical stimulation in animals with neuropathic pain. Further investigation of the mechanisms involved in MCS-induced analgesia may contribute to clinical improvements for the treatment of persistent neuropathic pain syndromes.
Surgery is the first-line treatment for early, localized, or operable breast cancer. Regional anesthesia during mastectomy may offer the prevention of postoperative pain. One potential protocol is ...the combination of serratus anterior plane block (SAM block) with pectoral nerve block I (PECS I), but the results and potential benefits are limited. Our study compared general anesthesia with or without SAM block + PECS I during radical mastectomy with axillary node dissection and breast reconstruction using evaluations of pain, opioid consumption, side effects and serum levels of interleukin (IL)-1beta, IL-6 and IL-10. This is a prospective, randomized controlled trial. Fifty patients were randomized to general anesthesia only or general anesthesia associated with SAM block + PECS I (25 per group). The association of SAM block + PECS I with general anesthesia reduced intraoperative fentanyl consumption, morphine use and visual analog pain scale scores in the post-anesthetic care unit (PACU) and at 24 h after surgery. In addition, the anesthetic protocol decreased side effects and sedation 24 h after surgery compared to patients who underwent general anesthesia only. IL-6 levels increased after the surgery compared to baseline levels in both groups, and no differences in IL-10 and IL-1 beta levels were observed. Our protocol improved the outcomes of mastectomy, which highlight the importance of improving mastectomy protocols and focusing on the benefits of regional anesthesia.
Post-traumatic stress disorder (PTSD) is an often debilitating disease with a lifetime prevalence rate between 5⁻8%. In war veterans, these numbers are even higher, reaching approximately 10% to 25%. ...Although most patients benefit from the use of medications and psychotherapy, approximately 20% to 30% do not have an adequate response to conventional treatments. Neuromodulation strategies have been investigated for various psychiatric disorders with promising results, and may represent an important treatment option for individuals with difficult-to-treat forms of PTSD. We review the relevant neurocircuitry and preclinical stimulation studies in models of fear and anxiety, as well as clinical data on the use of transcranial direct current stimulation (tDCS), repetitive transcranial magnetic stimulation (rTMS), and deep brain stimulation (DBS) for the treatment of PTSD.
Oxytocin has been administered to patients with autism spectrum disorder (ASD) in order to improve social skills, communication, and manage repetitive behaviors in the context of research trials. The ...majority of the studies focus on acute administration; thus, the effectiveness and potential side effects of chronic administration remain unknown. The main goal of this case report is to highlight the importance of the safety parameters for the chronic use of intranasal oxytocin administration. In a single case conducted in our outpatient clinic, one adolescent (15 years old) received intranasal oxytocin (24 IU) twice per day, in accordance with the recommended doses for this age group that varies from 8 - 25 IU twice per day. After three weeks of treatment, the patient presented with gynecomastia. While it is not certain that the gynecomastia was oxytocin-induced, this case highlights the importance of developing optimal regimens for chronic oxytocin administration, with a particular focus on safety parameters.
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