Academic anaesthesiology: a global perspective on training, support, and future development of early career researchers.

As anaesthesiologists face increasing clinical demands and a limited and competitive funding environment for academic work, the sustainability of academic anaesthesiologists has never been more tenuous. Yet, the speciality needs academic anaesthesiologists in many roles, extending beyond routine clinical duties. Anaesthesiologist educators, researchers, and administrators are required not only to train future generations but also to lead innovation and expansion of anaesthesiology and related specialities, all to improve patient care. This group of early career researchers with geographically distinct training and practice backgrounds aim to highlight the diversity in clinical and academic training and career development pathways for anaesthesiologists globally. Although multiple routes to success exist, one common thread is the need for consistent support of strong mentors and sponsors. Moreover, to address inequitable opportunities, we emphasise the need for diversity and inclusivity through global collaboration and exchange that aims to improve access to research training and participation. We are optimistic that by focusing on these fundamental principles, we can help build a more resilient and sustainable future for academic anaesthesiologists around the world.

Ryanodine receptor leak triggers fiber Ca2+ redistribution to preserve force and elevate basal metabolism in skeletal muscle.

Muscle contraction depends on tightly regulated Ca2+ release. Aberrant Ca2+ leak through ryanodine receptor 1 (RyR1) on the sarcoplasmic reticulum (SR) membrane can lead to heatstroke and malignant hyperthermia (MH) susceptibility, as well as severe myopathy. However, the mechanism by which Ca2+ leak drives these pathologies is unknown. Here, we investigate the effects of four mouse genotypes with increasingly severe RyR1 leak in skeletal muscle fibers. We find that RyR1 Ca2+ leak initiates a cascade of events that cause precise redistribution of Ca2+ among the SR, cytoplasm, and mitochondria through altering the Ca2+ permeability of the transverse tubular system membrane. This redistribution of Ca2+ allows mice with moderate RyR1 leak to maintain normal function; however, severe RyR1 leak with RYR1 mutations reduces the capacity to generate force. Our results reveal the mechanism underlying force preservation, increased ATP metabolism, and susceptibility to MH in individuals with gain-of-function RYR1 mutations.

Transient Receptor Potential Cation Channels and Calcium Dyshomeostasis in a Mouse Model Relevant to Malignant Hyperthermia.

BACKGROUND: Until recently, the mechanism for the malignant hyperthermia crisis has been attributed solely to sustained massive Ca release from the sarcoplasmic reticulum on exposure to triggering agents. This study tested the hypothesis that transient receptor potential cation (TRPC) channels are important contributors to the Ca dyshomeostasis in a mouse model relevant to malignant hyperthermia. METHODS: This study examined the mechanisms responsible for Ca dyshomeostasis in RYR1-p.G2435R mouse muscles and muscle cells using calcium and sodium ion selective microelectrodes, manganese quench of Fura2 fluorescence, and Western blots. RESULTS: RYR1-p.G2435R mouse muscle cells have chronically elevated intracellular resting calcium and sodium and rate of manganese quench (homozygous greater than heterozygous) compared with wild-type muscles. After exposure to 1-oleoyl-2-acetyl-sn-glycerol, a TRPC3/6 activator, increases in intracellular resting calcium/sodium were significantly greater in RYR1-p.G2435R muscles (from 153 ± 11 nM/10 ± 0.5 mM to 304 ± 45 nM/14.2 ± 0.7 mM in heterozygotes P < 0.001] and from 251 ± 25 nM/13.9 ± 0.5 mM to 534 ± 64 nM/20.9 ± 1.5 mM in homozygotes [P < 0.001] compared with 123 ± 3 nM/8 ± 0.1 mM to 196 ± 27 nM/9.4 ± 0.7 mM in wild type). These increases were inhibited both by simply removing extracellular Ca and by exposure to either a nonspecific (gadolinium) or a newly available, more specific pharmacologic agent (SAR7334) to block TRPC6- and TRPC3-mediated cation influx into cells. Furthermore, local pretreatment with SAR7334 partially decreased the elevation of intracellular resting calcium that is seen in RYR1-p.G2435R muscles during exposure to halothane. Western blot analysis showed that expression of TRPC3 and TRPC6 were significantly increased in RYR1-p.G2435R muscles in a gene-dose-dependent manner, supporting their being a primary molecular basis for increased sarcolemmal cation influx. CONCLUSIONS: Muscle cells in knock-in mice expressing the RYR1-p.G2435R mutation are hypersensitive to TRPC3/6 activators. This hypersensitivity can be negated with pharmacologic agents that block TRPC3/6 activity. This reinforces the working hypothesis that transient receptor potential cation channels play a critical role in causing intracellular calcium and sodium overload in malignant hyperthermia-susceptible muscle, both at rest and during the malignant hyperthermia crisis.

The progesterone metabolite allopregnanolone potentiates GABA(A) receptor-mediated inhibition of 5-HT neuronal activity.

The dorsal raphe nucleus (DRN) is the origin of much of the 5-HT innervation of the forebrain. The activity of DRN 5-HT neurons is regulated by a number of receptors including GABA(A) and 5-HT(1A) inhibitory receptors and by excitatory alpha(1)-adrenoceptors. Using in vitro electrophysiological recording we investigated the action of progesterone and its metabolite, allopregnanolone on receptor-mediated responses of DRN 5-HT neurons. Neither allopregnanolone nor progesterone affected the alpha(1)-adrenoceptor agonist-induced firing. Allopregnanolone also had no effect on the inhibitory response to 5-HT. However, allopregnanolone significantly potentiated the inhibitory responses to GABA(A) receptor agonists. Progesterone did not enhance GABA(A) receptor-meditated inhibitory responses. Thus, the neuroactive metabolite of progesterone, allopregnanolone, has the ability to cause potentiation of GABA(A)-mediated inhibition of DRN 5-HT neurons. This effect on 5-HT neurotransmission may have relevance for mood disorders commonly associated with reproductive hormone events, such as premenstrual dysphoric disorder and postpartum depression.