Overexpression of corticotropin‐releasing factor in Barrington’s nucleus neurons by adeno‐associated viral transduction: effects on bladder function and behavior

Abstract

The stress-related neuropeptide, corticotropin-releasing factor (CRF), is prominent in neurons of the pontine micturition center, Barrington’s nucleus. These neurons co-innervate spinal preganglionic neurons that control the bladder and locus coeruleus (LC) neurons that provide norepinephrine innervation throughout the brain. Adeno-associated viral (AAV) vector-mediated transfer of CRF cDNA was used to increase CRF expression in Barrington’s nucleus neurons and investigate the impact of a gain of function in Barrington’s nucleus spinal and LC projections. AAV transfer of the reverse CRF cDNA sequence served as the control. Bladder urodynamics and behavior were assessed four weeks after vector injection into Barrington’s nucleus. Rats with bilateral injections of AAV-CRF cDNA into Barrington’s nucleus had immunohistochemical evidence of CRF overexpression in neurons and transport to the spinal cord and LC. The bladder: body weight ratio was greater and micturition pressure was less in these rats compared to controls, consistent with an inhibitory influence on bladder function. Other indices of urodynamic function were not altered. CRF innervation of the LC was increased in rats with bilateral Barrington’s nucleus injections of AAV-CRF cDNA and this was associated with increased burying behavior, an endpoint of LC activation by CRF. The results provide immunohistochemical evidence for viral vector-induced CRF overexpression in Barrington’s nucleus neurons and underscore the ability of AAV vector-mediated transfer to increase CRF function in selective circuits. The findings support an inhibitory influence of CRF in Barrington’s nucleus regulation of the bladder and an excitatory influence on the brain norepinephrine system that translates to behavioral activation.

Ascending mechanisms of stress integration: Implications for brainstem regulation of neuroendocrine and behavioral stress responses

“…Interestingly, the effects of stress on behavior may be mediated, in part, by CRH signaling in the LC. Although CRH input to the LC has been shown to arise from amygdalar and brainstem afferents (McCall et al, 2015; McFadden et al, 2012), the sensitivity of LC neurons to CRH is not static and is influenced by factors such as prior stress exposure (Curtis et al, 1999, 1995). …”

Evidence for the role of corticotropin-releasing factor in major depressive disorder

“…Another confounding factor appearing in several CRF overexpressing mouse lines is the hypercorticosteronism accompanied by a Cushing-like phenotype. In recent years, approaches applying viral expression systems (lenti- and adeno-associated viruses) have been used that provide means to overexpress CRF in a spatially more restricted manner allowing for more refined analyses of CRF actions in different brain nuclei (Flandreau et al, 2012; McFadden et al, 2012; Qi et al, 2014; Regev et al, 2011, 2012). Nevertheless, all approaches of CRF excess published until now are confounded by a substantial amount of ectopic expression.…”

A corticotropin-releasing factor receptor antagonist improves urodynamic dysfunction produced by social stress or partial bladder outlet obstruction in male rats

“…Surgery and injection of AAV vectors into Barrington's nucleus were as previously described (25). Rats were anesthetized with a mixture of isoflurane-in-air, positioned in a stereotaxic and surgically prepared for placement of a double-barrel glass micropipette into Barrington's nucleus.…”