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Tonic Suppression of the Mesolimbic Dopaminergic System by Enhanced Corticotropin-Releasing Factor Signaling Within the Bed Nucleus of the Stria Terminalis in Chronic Pain Model Rats.

ABSTRACT: Although dysfunction of the mesolimbic dopaminergic system has been implicated in chronic pain, the underlying mechanisms remain to be elucidated. We hypothesized that increased inhibitory inputs to the neuronal pathway from the dorsolateral bed nucleus of the stria terminalis (dlBNST) to the ventral tegmental area (VTA) during chronic pain may induce tonic suppression of the mesolimbic dopaminergic system. To test this hypothesis, male Sprague Dawley rats were subjected to spinal nerve ligation to induce neuropathic pain and then spontaneous IPSCs (sIPSCs) were measured in this neuronal pathway. Whole-cell patch-clamp electrophysiology of brain slices containing the dlBNST revealed that the frequency of sIPSCs significantly increased in VTA-projecting dlBNST neurons 4 weeks after surgery. Next, the role of corticotropin-releasing factor (CRF) signaling within the dlBNST in the increased sIPSCs was examined. CRF increased the frequency of sIPSCs in VTA-projecting dlBNST neurons in sham-operated controls, but not in chronic pain rats. By contrast, NBI27914, a CRF type 1 receptor antagonist, decreased the frequency of sIPSCs in VTA-projecting dlBNST neurons in the chronic pain rats, but not in the control animals. In addition, histological analyses revealed the increased expression of CRF mRNA in the dlBNST. Finally, bilateral injections of NBI27914 into the dlBNST of chronic pain rats activated mesolimbic dopaminergic neurons and induced conditioned place preference. Together, these results suggest that the mesolimbic dopaminergic system is tonically suppressed during chronic pain by enhanced CRF signaling within the dlBNST via increased inhibitory inputs to VTA-projecting dlBNST neurons.SIGNIFICANCE STATEMENT The comorbidity of chronic pain and depression has long been recognized. Although dysfunction of the mesolimbic dopaminergic system has been implicated in both chronic pain and depression, the underlying mechanisms remain to be elucidated. Here, we show that the inhibitory inputs to the neuronal pathway from the dorsolateral bed nucleus of the stria terminalis (dlBNST) to the ventral tegmental area increase during chronic pain. This neuroplastic change is mediated by enhanced corticotropin-releasing factor signaling within the dlBNST that leads to tonic suppression of the mesolimbic dopaminergic system, which may be involved in the depressive mood and anhedonia under the chronic pain condition.

SUBMITTER: Takahashi D

PROVIDER: S-EPMC6794933 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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Tonic Suppression of the Mesolimbic Dopaminergic System by Enhanced Corticotropin-Releasing Factor Signaling Within the Bed Nucleus of the Stria Terminalis in Chronic Pain Model Rats.

Takahashi Daiki D Asaoka Yuta Y Kimura Keisuke K Hara Ryuto R Arakaki Saya S Sakasai Keisuke K Suzuki Hiroe H Yamauchi Naoki N Nomura Hiroshi H Amano Taiju T Minami Masabumi M

The Journal of neuroscience : the official journal of the Society for Neuroscience 20190826 42

Although dysfunction of the mesolimbic dopaminergic system has been implicated in chronic pain, the underlying mechanisms remain to be elucidated. We hypothesized that increased inhibitory inputs to the neuronal pathway from the dorsolateral bed nucleus of the stria terminalis (dlBNST) to the ventral tegmental area (VTA) during chronic pain may induce tonic suppression of the mesolimbic dopaminergic system. To test this hypothesis, male Sprague Dawley rats were subjected to spinal nerve ligation ...[more]

PMID: 31451580

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Project description:BACKGROUND:The bed nucleus of the stria terminalis (BNST) contains the highest density of corticotropin-releasing factor (CRF)-producing neurons in the brain. CRF-immunoreactive neurons show a female-biased sexual dimorphism in the dorsolateral BNST in the rat. Since CRF neurons cannot be immunostained clearly with available CRF antibodies in the mouse, we used a mouse line, in which modified yellow fluorescent protein (Venus) was inserted to the CRF gene, and the Neo cassette was removed, to examine the morphological characteristics of CRF neurons in the dorsolateral BNST. Developmental changes of CRF neurons were examined from postnatal stages to adulthood. Gonadectomy (GDX) was carried out in adult male and female mice to examine the effects of sex steroids on the number of CRF neurons in the dorsolateral BNST. METHODS:The number of Venus-expressing neurons, stained by immunofluorescence, was compared between male and female mice over the course of development. GDX was carried out in adult mice. Immunohistochemistry, in combination with Nissl staining, was carried out, and the effects of sex or gonadal steroids were examined by estimating the number of Venus-expressing neurons, as well as the total number of neurons or glial cells, in each BNST subnucleus, using a stereological method. RESULTS:Most Venus-expressing neurons co-expressed Crf mRNA in the dorsolateral BNST. They constitute a group of neurons without calbindin immunoreactivity, which makes a contrast to the principal nucleus of the BNST that is characterized by calbindin immunostaining. In the dorsolateral BNST, the number of Venus-expressing neurons increased across developmental stages until adulthood. Sexual difference in the number of Venus-expressing neurons was not evident by postnatal day 5. In adulthood, however, there was a significant female predominance in the number of Venus expressing neurons in two subnuclei of the dorsolateral BNST, i.e., the oval nucleus of the BNST (ovBNST) and the anterolateral BNST (alBNST). The number of Venus-expressing neurons was smaller significantly in ovariectomized females compared with proestrous females in either ovBNST or alBNST, and greater significantly in orchiectomized males compared with gonadally intact males in ovBNST. The total number of neurons was also greater significantly in females than in males in ovBNST and alBNST, but it was not affected by GDX. CONCLUSION:Venus-expressing CRF neurons showed female-biased sexual dimorphism in ovBNST and alBNST of the mouse. Expression of Venus in these subnuclei was controlled by gonadal steroids.

Project description:The peripartum period is accompanied by numerous physiological and behavioural adaptations organised by the maternal brain. These changes are essential for adequate expression of maternal behaviour, thereby ensuring proper development of the offspring. The corticotropin-releasing factor (CRF) plays a key role in a variety of behaviours accompanying stress, anxiety, and depression. There is also evidence that CRF contributes to maladaptations during the peripartum period. We investigated the effects of CRF in the bed nucleus of the stria terminalis (BNST) of lactating mice during maternal care and analysed locomotor activity and anxiety-like behaviour in the offspring. The BNST has been implicated in anxiety behaviour and regulation of the stress response. The effects of intra-BNST CRF administration were compared with those induced by the limited bedding (LB) procedure, a model that produces altered maternal behaviour. BALB/cJ dams were exposed to five infusions of CRF or saline into the BNST in the first weeks after birth while the LB dams were exposed to limited nesting material from postnatal days (P) 2-9. Maternal behaviour was recorded in intercalated days, from P1-9. Offspring anxiety-like behaviour was assessed during adulthood using the open-field, elevated plus-maze, and light/dark tests. Both intra-BNST CRF and LB exposure produced altered maternal care, represented by decreased arched-back nursing and increased frequency of exits from the nest. These changes in maternal care resulted in robust sex-based differences in the offspring's behavioural responses during adulthood. Females raised by CRF-infused dams exhibited increased anxiety-like behaviour, whereas males presented a significant decrease in anxiety. On the other hand, both males and females raised by dams exposed to LB showed higher locomotor activity. Our study demonstrates that maternal care is impaired by intra-BNST CRF administrations, and these maladaptations are similar to exposure to adverse early environments. These procedures, however, produce distinct phenotypes in mice during young adulthood and suggest sex-based differences in the susceptibility to poor maternal care.

Dataset Information

Tonic Suppression of the Mesolimbic Dopaminergic System by Enhanced Corticotropin-Releasing Factor Signaling Within the Bed Nucleus of the Stria Terminalis in Chronic Pain Model Rats.

Publications

Tonic Suppression of the Mesolimbic Dopaminergic System by Enhanced Corticotropin-Releasing Factor Signaling Within the Bed Nucleus of the Stria Terminalis in Chronic Pain Model Rats.

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