A knock-in allele of Hand2 expressing Dre recombinase.

HAND2 is a basic helix-loop-helix transcription factor with diverse functions during development. To facilitate the investigation of genetic and functional diversity among Hand2-expressing cells in the mouse, we have generated Hand2Dre, a knock-in allele expressing Dre recombinase. To avoid disrupting Hand2 function, the Dre cDNA is inserted at the 3' end of the Hand2 coding sequence following a viral 2A peptide. Hand2Dre homozygotes can therefore be used in complex crosses to increase the proportion of useful genotypes among offspring. Dre expression in mid-gestation Hand2Dre embryos is indistinguishable from wild-type Hand2 expression, and HandDre efficiently recombines rox target sites in vivo. In combination with existing Cre and Flp mouse lines, Hand2Dre will therefore extend the ability to perform genetic intersectional labeling, fate mapping, and functional manipulation of subpopulations of cells characterized by developmental expression of Hand2.

Locus coeruleus noradrenaline depletion and its differential impact on CO2-induced panic and hyperventilation in male and female mice.

CO2 exposure has been used to investigate the panicogenic response in patients with panic disorder. These patients are more sensitive to CO2, and more likely to experience the "false suffocation alarm" which triggers panic attacks. Imbalances in locus coeruleus noradrenergic (LC-NA) neurotransmission are responsible for psychiatric disorders, including panic disorder. These neurons are sensitive to changes in CO2/pH. Therefore, we investigated if LC-NA neurons are differentially activated after severe hypercapnia in mice. Further, we evaluated the participation of LC-NA neurons in ventilatory and panic-like escape responses induced by 20% CO2 in male and female wild type mice and two mouse models of altered LC-NA synthesis. Hypercapnia activates the LC-NA neurons, with males presenting a heightened level of activation. Mutant males lacking or with reduced LC-NA synthesis showed hypoventilation, while animals lacking LC noradrenaline present an increased metabolic rate compared to wild type in normocapnia. When exposed to CO2, males lacking LC noradrenaline showed a lower respiratory frequency compared to control animals. On the other hand, females lacking LC noradrenaline presented a higher tidal volume. Nevertheless, no change in ventilation was observed in either sex. CO2 evoked an active escape response. Mice lacking LC noradrenaline had a blunted jumping response and an increased freezing duration compared to the other groups. They also presented fewer racing episodes compared to wild type animals, but not different from mice with reduced LC noradrenaline. These findings suggest that LC-NA has an important role in ventilatory and panic-like escape responses elicited by CO2 exposure in mice.

Partial or Complete Loss of Norepinephrine Differentially Alters Contextual Fear and Catecholamine Release Dynamics in Hippocampal CA1.

Background: Contextual fear learning is heavily dependent on the hippocampus. Despite evidence that catecholamines contribute to contextual encoding and memory retrieval, the precise temporal dynamics of their release in the hippocampus during behavior is unknown. In addition, new animal models are required to probe the effects of altered catecholamine synthesis on release dynamics and contextual learning. Methods: We generated 2 new mouse models of altered locus coeruleus-norepinephrine (NE) synthesis and utilized them together with GRABNE and GRABDA sensors and in vivo fiber photometry to investigate NE and dopamine (DA) release dynamics in the dorsal hippocampal CA1 during contextual fear conditioning. Results: Aversive foot shock increased both NE and DA release in the dorsal CA1, while freezing behavior associated with recall of fear memory was accompanied by decreased release. Moreover, we found that freezing at the recent time point was sensitive to both partial and complete loss of locus coeruleus-NE synthesis throughout prenatal and postnatal development, similar to previous observations of mice with global loss of NE synthesis beginning postnatally. In contrast, freezing at the remote time point was compromised only by complete loss of locus coeruleus-NE synthesis beginning prenatally. Conclusions: Overall, these findings provide novel insights into the role of NE in contextual fear and the precise temporal dynamics of both NE and DA during freezing behavior and highlight complex relationships between genotype, sex, and NE signaling.

Measuring the impact of maternal critical care admission on short- and longer-term maternal and birth outcomes.

PURPOSE: Factors increasing the risk of maternal critical illness are rising in prevalence in maternity populations. Studies of general critical care populations highlight that severe illness is associated with longer-term physical and psychological morbidity. We aimed to compare short- and longer-term outcomes between women who required critical care admission during pregnancy/puerperium and those who did not. METHODS: This is a cohort study including all women delivering in Scottish hospitals between 01/01/2005 and 31/12/2018, using national healthcare databases. The primary exposure was intensive care unit (ICU) admission, while secondary exposures included high dependency unit admission. Outcomes included hospital readmission (1-year post-hospital discharge, 1-year mortality, psychiatric hospital admission, stillbirth, and neonatal critical care admission). Multivariable Cox and logistic regression were used to report hazard ratios (HR) and odds ratios (OR) of association between ICU admission and outcomes. RESULTS: Of 762,918 deliveries, 1449 (0.18%) women were admitted to ICU, most commonly due to post-partum hemorrhage (225, 15.5%) followed by eclampsia/pre-eclampsia (133, 9.2%). Over-half (53.8%) required mechanical ventilation. One-year hospital readmission was more frequent in women admitted to ICU compared with non-ICU populations [24.5% (n = 299) vs 8.9% (n = 68,029)]. This association persisted after confounder adjustment (HR 1.93, 95% confidence interval [CI] 1.33, 2.81, p < 0.001). Furthermore, maternal ICU admission was associated with increased 1-year mortality (HR 40.06, 95% CI 24.04, 66.76, p < 0.001), stillbirth (OR 12.31, 95% CI 7.95,19.08, p < 0.001) and neonatal critical care admission (OR 6.99, 95% CI 5.64,8.67, p < 0.001) after confounder adjustment. CONCLUSION: Critical care admission increases the risk of adverse short-term and long-term maternal, pregnancy and neonatal outcomes. Optimizing long-term post-partum care may benefit maternal critical illness survivors.