Noradrenergic alpha-2A receptor activation suppresses courtship vocalization in male Japanese quail.

Male Japanese quail produce high-frequency crow vocalizations to attract females during the breeding season. The nucleus of intercollicularis (ICo) is the midbrain vocal center in birds and electrical stimulation of the ICo produces calls that include crowing. Noradrenaline plays a significant role in sexual behavior but the contribution of noradrenaline in the control of courtship vocalizations in quail has not been well established. Using dose-dependent intracerebroventricular injection of clonidine, an α2-adrenergic receptor-specific agonist, crowing vocalization was immediately suppressed. At the same time as crow suppression by clonidine there was a reduction of immediate early gene, zenk mRNA, in the ICo; no zenk mRNA expression was detected in the dorsomedial division of the nucleus. Using histochemistry, we determined that the ICo receives noradrenergic innervation and expresses α2A-adrenergic receptor mRNA. Taken together, these data suggest that noradrenaline regulates courtship vocalization in quail, possibly via the alpha2A-adrenergic receptor expressed on ICo neurons.

Dopamine and noradrenaline modulation of goal-directed behaviour in prefrontal areas: Toward a division of labour?

The prefrontal cortex is considered to be at the core of goal-directed behaviours. Notably, the medial prefrontal cortex (mPFC) is known to play an important role in learning action-outcome associations, as well as in detecting changes in this contingency. Previous studies have also highlighted a specific engagement of the dopaminergic pathway innervating the mPFC in adapting to changes in action causality. While previous research on goal-directed actions has primarily focused on the mPFC region, recent findings have revealed a distinct and specific role of the ventral and lateral orbitofrontal cortex (vlOFC). Indeed, vlOFC is not necessary to learn about action-outcome associations but appears specifically involved when outcome identity is unexpectedly changed. Unlike the mPFC, the vlOFC does not receive a strong dopaminergic innervation. However, it receives a dense noradrenergic innervation which might indicate a crucial role for this neuromodulator. In addition, several lines of evidence highlight a role for noradrenaline in adapting to changes in the environment. We therefore propose that the vlOFC’s function in action control might be under the strong influence of the noradrenergic system. In the present paper, we review anatomical and functional evidence consistent with this proposal and suggest a direction for future studies that aims to shed light on the orbitofrontal mechanisms for flexible action control. Specifically, we suggest that dopaminergic modulation in the mPFC and noradrenergic modulation in the vlOFC may underlie distinct processes related to updating one’s actions.

Aging of Bone Marrow Microenvironment Promotes Myeloid Bias of Hematopoietic Progenitors and Is a Target in Age-Related Myeloproliferative Neoplasms

Background: BM HSC accumulate during aging but are functionally impaired; however, it remains debated whether this aging results from HSC-intrinsic and/or -extrinsic mechanisms. Myeloid malignancies are more frequent in the elderly, but whether the aged microenvironment predisposes to these malignancies is unclear. Myeloid-biased HSC and especially platelet-primed HSC expand in aged mice. However, both platelet-primed and unprimed old HSCs exhibit myeloid bias, possibly suggesting a microenvironmental participation. Moreover, some hallmarks of murine hematopoietic aging (like increased platelets) are present in premature aging (Hutchinson-Gilford progeria syndrome, HGPS) and are exacerbated in age-related myeloproliferative neoplasms (MPN), where we found that niche heterogeneity can influence disease progression (ASH abstract ID 113495). Given that aging increases myelopoiesis in physiology, HGPS and MPN (despite their heterogenous genetic background), we hypothesized that shared microenvironmental alterations influence HSC lineage bias during aging Results: HSCs, perisinusoidal megakaryocytes (Mk) and myelopoietic cytokines increase in the BM of HGPS mice, resembling normally aged mice. However, WT recipients of HGPS BM cells do not reproduce myeloid bias, indicating that premature aging affects hematopoiesis in HGPS in a non-HSC-autonomous manner. We have investigated niche contributions to lineage bias during physiological aging because HGPSmice do not tolerate myeloablation. Consistently with recent findings (Nat Med 2018;24:782-91) HSC niches decrease near bone (endosteal BM) and expand further from bone in aged mice, but we observed different vascular changes mainly consisting of halved endosteal transition zone vessels with associated Nes-GFP+ cells and 4-fold-increased non-endosteal capillaries with Nes-GFP+ cells. However, contrasting the afore mentioned study but in agreement with other reports, we found aging-related increase of BM noradrenergic innervation, which promotes megakaryopoiesis in WT mice, but not in mice lacking β2 and β3 adrenergic receptors (ARs). Yet, these receptors exhibit opposite effects on microenvironmental regulation of myelopoiesis. β2-AR-agonist promotes Mk differentiation from human CD34+ HSCs co-cultured with MS-5 cells or in WT (but not IL-6 KO) primary murine BM culture. Consequently, adult β2-AR KO mice exhibit decreased Mk-lineage cells, which correlated with reduced BM IL-6. In contrast, adult β3-AR KO mice exhibit increased mature Mk near sinusoids, which correlated with tripled Cxcl12 mRNA expression in non-endosteal BM. Mechanistically β3-AR regulates Cxcl12-dependent HSPC and megakaryocyte localization, nitric oxide (NO) production and expression of myelopoietic cytokines. In vitro, β3-AR-agonist-treated stromal cells decrease human and murine HSPC differentiation into Mk. This effect requires Nos1-dependent NO production, since Nos1-/- mice have high circulating platelets and β3-AR agonist specifically increases lymphoid-biased HSCs in primary BM cultures in a Nos1-dependent manner. Finally, Mk increased in β3-AR KO mice transplanted with MPN BM cells, whereas Mk decreased in MPN mice treated with β3-AR agonist. To test the clinical relevance of our findings, we measured plasma nitrates and myelopoietic cytokines in MPN patients (median age=62) chronically treated only with β3-AR agonist, who show improved myelofibrosis correlated by rescued nestin+ niches (Blood 2016;128:3108), which is consistent with previous results in mice (Nature 2014;512:78-81). We found inverse correlations between the concentration of nitrates and myelopoietic cytokines Conclusions: microenvironmental aging promotes myeloid bias through similar cytokines (e.g. IL1β, IL6) during premature or physiological aging. In the latter, HSC supporting niches decrease near bone but expand further from bone. Increased BM sympathetic noradrenergic innervation promotes β2-AR-IL-6-dependent myeloid bias. Reduction of endosteal niches decreases β3-AR-NO-dependent inhibition of myelopoietic cytokines. However, chronic treatment with β3-AR-agonist does not rejuvenate overall hematopoiesis but decreases exacerbated megakaryopoiesis in mice and humans with MPNs. Therefore, niche aging promotes myeloid bias and might represent a therapeutic target in age-related myeloproliferative disorders Disclosures No relevant conflicts of interest to declare.

Locus coeruleus noradrenergic innervation of the amygdala facilitates alerting-induced constriction of the rat tail artery

The amygdala, innervated by the noradrenergic locus coeruleus, processes salient environmental events. α2-adrenoceptor-stimulating drugs (clonidine-like agents) suppress the behavioral and physiological components of the response to salient events. Activation of sympathetic outflow to the cutaneous vascular bed is part of the physiological response to salience-mediated activation of the amygdala. We have determined whether acute systemic and intra-amygdala administration of clonidine, and chronic immunotoxin-mediated destruction of the noradrenergic innervation of the amygdala, impairs salience-related vasoconstrictor episodes in the tail artery of conscious freely moving Sprague-Dawley rats. After acute intraperitoneal injection of clonidine (10, 50, and 100 μg/kg), there was a dose-related decrease in the reduction in tail blood flow elicited by alerting stimuli, an effect prevented by prior administration of the α2-adrenergic blocking drug idazoxan (1 mg/kg ip or 75 nmol bilateral intra-amygdala). A dose-related decrease in alerting-induced tail artery vasoconstriction was also observed after bilateral intra-amygdala injection of clonidine (5, 10, and 20 nmol in 200 nl), an effect substantially prevented by prior bilateral intra-amygdala injection of idazoxan. Intra-amygdala injection of idazoxan by itself did not alter tail artery vasoconstriction elicited by alerting stimuli. Intra-amygdala injection of saporin coupled to antibodies to dopamine-β-hydroxylase (immunotoxin) destroyed the noradrenergic innervation of the amygdala and the parent noradrenergic neurons in the locus coeruleus. The reduction in tail blood flow elicited by standardized alerting stimuli was substantially reduced in immunotoxin-treated rats. Thus, inhibiting the release of noradrenaline within the amygdala reduces activation of the sympathetic outflow to the vascular beds elicited by salient events.

The Noradrenergic Innervation and Steroidogenic Activity of Porcine Cystic Ovaries

The aim of the present study was to investigate the distribution and density of noradrenergic nerve fibres (NNFs), content of catecholamines (CATs) and steroids in the cystic ovaries of gilts receiving DXM from middle luteal phase. Cystic status of ovaries was induced by i.m. DXM injections on days 7-21 of the estrous cycle. During the same time, gilts in the control group received saline. The ovaries were collected on predicted day 11 of the second studied estrous cycle. The cystic ovaries were supplied by more numerous NNFs than the control gonads. Moreover after DXM injections, the content of CATs and progesterone and androstendione (A4) in the cystic wall were elevated, while the levels of A4, testosterone and estradiol-17β in the cystic fluid were lowered. Our results show that in the porcine cystic ovaries, induced by DXM injections from middle phase of estrous cycle, increased the density of NNFs and level of CATs, and that it was accompanied by changes in the content of steroids. Moreover, this study is a further confirmation that the morphological and functional changes of cystic ovaries are partly dependent on phase of the estrous cycle in which the induction of the ovarian cysts was initiated.