Biology subjects

Herbison, A.

Publications and source records attributed to Herbison, A..

3 recordsLinked to original sources

bioRxiv2024

Ultradian rhythms of CRHPVN neuron activity, behaviour and stress hormone secretion

The stress axis is always active, even in the absence of any threat. This manifests as hourly pulses of corticosteroid stress hormone secretion over the day. Corticotropin-releasing hormone neurons in the paraventricular nucleus of the hypothalamus (CRHPVN) control both the neuroendocrine stress axis as well as stress-associated behaviours. However, it is currently unclear how the resting activity of these neurons is coordinated with both spontaneous behaviour and ultradian pulses of corticosteroid secretion. To investigate this, we performed fiber photometry recordings of CRHPVN neuron activity in Crh-Ires-Cre mice and a newly generated line of Crh-Ires-Cre rats. In both mice and rats, CRHPVN neurons displayed an ultradian rhythm of activity with reoccurring upstates of activity approximately once per hour over the 24-hour day. Upstates in activity were coordinated with increases in animal activity/arousal. Chemogenetic activation of CRHPVN neurons was also sufficient to induce behavioural arousal. In rats, increases in CRH neural activity preceded some pulses of corticosteroid secretion but not others. Thus, while CRHPVN neurons display an ultradian rhythm of activity over the 24-hour day that is coordinated with behavioural arousal, the relationship between CRHPVN activity and pulses of corticosteroid secretion is not one-to-one. Significance StatementUltradian rhythms are present in many biological systems, however, the underlying neural mechanisms responsible for generating these rhythms is unclear. Corticotropin-releasing hormone (CRH) neurons control corticosteroid levels in the body as well as arousal and behaviour. Here we show that CRH neurons exhibit a pronounced ultradian rhythm in neural activity over the 24-hour day. CRH neural activity was highly correlated with, and predictive of, behavioral arousal. However, CRH neural activity was not as well correlated with pulses of corticosteroid secretion. Together, these data revel the patterns of CRH neuron activity over the 24-hour day and their relationship with behaviour and stress hormone secretion.

neuroscience↗

bioRxiv2024

The GnRH pulse generator activity in mouse models of polycystic ovary syndrome

One in ten women in their reproductive age suffer from polycystic ovary syndrome (PCOS) that, alongside subfertility and hyperandrogenism, typically presents with increased luteinizing hormone (LH) pulsatility. As such, it is suspected that the arcuate kisspeptin (ARNKISS) neurons that represent the GnRH pulse generator are dysfunctional in PCOS. We used here in vivo GCaMP fiber photometry and other approaches to examine the behavior of the GnRH pulse generator in two mouse models of PCOS. We began with the peripubertal androgen (PPA) mouse model of PCOS but found that it had a reduction in the frequency of ARNKISS neuron synchronization events (SEs) that drive LH pulses. Examining the prenatal androgen (PNA) model of PCOS, we observed highly variable patterns of pulse generator activity with no significant differences detected in ARNKISS neuron SEs, pulsatile LH secretion, or serum testosterone, estradiol, and progesterone concentrations. However, an unsupervised machine learning approach identified that the ARNKISS neurons of acyclic PNA mice continued to exhibit cyclical patterns of activity similar to that of normal mice. The frequency of ARNKISS neuron SEs was significantly increased in algorithm-identified "diestrous stage" PNA mice compared to controls. In addition, ARNKISS neurons exhibited reduced feedback suppression to progesterone in PNA mice and their pituitary gonadotrophs were also less sensitive to GnRH. These observations demonstrate the importance of understanding GnRH pulse generator activity in mouse models of PCOS. The existence of cyclical GnRH pulse generator activity in the acyclic PNA mouse indicates the presence of a complex phenotype with deficits at multiple levels of the hypothalamo-pituitary-gonadal axis.

neuroscience↗

bioRxiv2018

PACAP neurons in the ventral premammillary nucleus regulate reproductive function in the female mouse

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuromodulator implicated in anxiety, metabolism and reproductive behavior. PACAP global knockout mice have decreased fertility and PACAP modulates LH release. However, its source and role at the hypothalamic level remain unknown. We demonstrate that PACAP-expressing neurons of the ventral premamillary nucleus of the hypothalamus (PMVPACAP) project to, and make direct contact with, kisspeptin neurons in the arcuate and AVPV/PeN nuclei and a subset of these neurons respond to PACAP exposure. Targeted deletion of PACAP from the PMV through stereotaxic virally mediated cre- injection or genetic cross to LepR-i-cre mice with PACAPfl/fl mice led to delayed puberty onset and impaired reproductive function in female, but not male, mice. We propose a new, sex-specific role for PACAP-expressing neurons in the PMV in the relay of nutritional state information to regulate GnRH release by modulating the activity of kisspeptin neurons, thereby regulating reproduction.

neuroscience↗