Biology subjects

Lacoste, B.

Publications and source records attributed to Lacoste, B..

4 recordsLinked to original sources

bioRxiv2023

Astroglial Hmgb1 regulates postnatal astrocyte morphogenesis and cerebrovascular maturation.

Astrocytes are intimately linked with brain vessels, a relationship that is critical for neuronal health and function. However, astroglial factors driving these physical and functional associations during postnatal brain development have yet to be identified. We characterized structural and transcriptional changes in mouse cortical astrocytes and microvessels during the first two postnatal weeks and found that high-mobility group box 1 (Hmgb1), normally upregulated with injury and involved in adult cerebrovascular repair, was highly expressed in astrocytes at birth and then decreased rapidly. Astrocyte-selective ablation of Hmgb1 at birth affected astrocyte morphology and endfoot placement, altered distribution of endfoot proteins connexin43 and aquaporin-4, induced transcriptional changes in astrocytes related to cytoskeleton remodeling, and profoundly disrupted endothelial ultrastructure. While lack of astroglial Hmgb1 did not affect the blood-brain barrier or angiogenesis postnatally, it impaired neurovascular coupling and behavior in adult mice. These findings identify astroglial Hmgb1 as a key player in postnatal gliovascular maturation.

developmental biology↗

bioRxiv2023

Cyclical control of female rejection behavior by progesterone receptor expressing neurons of the anterior ventromedial hypothalamus

Internal state-dependent behavioral responses, such as the switch between rejection and acceptance of sexual advances depending on a females reproductive capacity, are fundamental to maintain social interactions and wellbeing. Here we characterize a dedicated circuit for the cyclical control of rejection behavior in the mouse, located in the anterior ventrolateral ventromedial hypothalamus (aVMHvl). In vivo recordings reveal that progesterone receptor expressing neurons of the aVMHvl (aVMHvlPr+) are active during rejection but silent when females accept the male. Moreover, we show that aVMHvlPr+ neurons receive reduced excitatory to inhibitory synaptic input balance during the receptive phase of the reproductive cycle. Finally, optogenetic activation of aVMHvlPr+ neurons in receptive females is sufficient to increase rejection behavior, disrupting the probability of copulation, without affecting other male-directed interactions. This population of aVMHvlPr+ neurons is thus a key neural substrate controlling female sexual behavior, providing an additional barrier to mating when fertilization is not possible.

neuroscience↗

bioRxiv2022

Sex-specific acute cerebrovascular response to photothrombotic stroke in mice requires rho-kinase

With high energy consumption and low energy storage, the brain is highly reliant on continuous cerebral blood flow (CBF) that delivers substrates to maintain proper function, which is compromised after a stroke. The current study explores the overlapping roles played by two important modulators of cerebrovascular tone, rho-kinase (ROCK) and endogenous sex hormones, in the acute CBF responses to a photothrombotic (PT) model of ischemic stroke in ROCK2+/- mice and wild-type (WT) littermates. To remove endogenous hormones, male mice were gonadectomized and female mice were ovariectomized, whereas control ("intact") animals received a sham surgery prior to stroke induction. Intact WT males showed a delayed drop in CBF compared to intact WT females, where maximal CBF drop was observed 48 hours following stroke. Gonadectomy in males did not alter this response, however ovariectomy in females produced a "male-like" response. Intact ROCK2+/- males also showed such phenotypic response, which was not altered by gonadectomy. Alternatively, intact ROCK2+/- females showed a striking difference in CBF values compared to intact WT females, where they displayed higher CBF values immediately post-stroke and also showed a maximal CBF drop 48 hours post-stroke, which was not altered by ovariectomy. Overall, there is a marked sex difference in acute CBF responses to PT stroke, which appears to be mediated by endogenous female sex hormones and ROCK2. This study reveals important sex-differences and the involvement of ROCK2 in acute CBF responses to PT stroke in mice. Significance StatementThere are very few mechanistic investigations on disparities between sexes in post-stroke CBF outcome. Rho-kinase, an important regulator of vascular tone, has only been explored in males in terms of its modulation of CBF following stroke. Both rho-kinase and endogenous female sex hormones have a converging role on the regulation of endothelial nitric oxide synthase (eNOS), an important modulator of vascular tone. Rho-kinase is thought to elicit its neuroprotective effects against ischemic stroke through eNOS, however this has never been investigated in both sexes. Elucidating the cellular and molecular bases of sex differences in cerebrovascular pathophysiology is vital for understanding the origins of stroke outcomes, and for designing novel therapeutic strategies to promote functional recovery in both women and men.

physiology↗

bioRxiv2022

A galanin-positive population of lumbar spinal cord neurons modulates sexual behavior and arousal

During sex, male arousal increases to the ejaculatory threshold, allowing genital sensory input to trigger ejaculation. While copulation and sexual arousal are thought to be centrally regulated by the brain, ejaculation is considered a reflex controlled by a spinal circuit. In this framework, the spinal cord is assumed to be strongly inhibited by descending input from the brain until the ejaculatory threshold, playing no role in the regulation of copulatory behavior. However, this remains untested. Here, we mapped the spinal circuit controlling the bulbospongiosus muscle, which is involved in sperm expulsion in mice. Our findings reveal that bulbospongiosus muscle-motor neurons receive input from galanin-expressing interneurons. This galanin-positive population receives genital input and, while its stimulation leads to bulbospongiosus muscle activity, the evoked muscle-potentials are dependent on spinalization, the males internal state and decrease with repeated stimulation. Moreover, ablation of galanin neurons affected the latency to ejaculate and altered the copulatory pattern. These results suggest an unexpected role of spinal circuits in the control of copulation and arousal, in addition to its established role in ejaculation.

neuroscience↗