CB1 modulation of hormone secretion, neuronal activation and mRNA expression following extracellular volume expansion

Systematic review: pain, cognition, and cardioprotection-unpacking oxytocin's contributions in a sport context

Introduction

This systematic review investigates the interplay between oxytocin and exercise; in terms of analgesic, anti-inflammatory, pro-regenerative, and cardioprotective effects. Furthermore, by analyzing measurement methods, we aim to improve measurement validity and reliability.

Methods

Utilizing PRISMA, GRADE, and MECIR protocols, we examined five databases with a modified SPIDER search. Including studies on healthy participants, published within the last 20 years, based on keywords "oxytocin," "exercise" and "measurement," 690 studies were retrieved initially (455 unique records). After excluding studies of clinically identifiable diseases, and unpublished and reproduction-focused studies, 175 studies qualified for the narrative cross-thematic and structural analysis.

Results

The analysis resulted in five categories showing the reciprocal impact of oxytocin and exercise: Exercise (50), Physiology (63), Environment (27), Social Context (65), and Stress (49). Exercise-induced oxytocin could promote tissue regeneration, with 32 studies showing its analgesic and anti-inflammatory effects, while 14 studies discussed memory and cognition. Furthermore, empathy-associated OXTR rs53576 polymorphism might influence team sports performance. Since dietary habits and substance abuse can impact oxytocin secretion too, combining self-report tests and repeated salivary measurements may help achieve precision.

Discussion

Oxytocin's effect on fear extinction and social cognition might generate strategies for mental training, and technical, and tactical development in sports. Exercise-induced oxytocin can affect the amount of stress experienced by athletes, and their response to it. However, oxytocin levels could depend on the type of sport in means of contact level, exercise intensity, and duration. The influence of oxytocin on athletes' performance and recovery could have been exploited due to its short half-life. Examining oxytocin's complex interactions with exercise paves the way for future research and application in sports science, psychology, and medical disciplines.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=512184, identifier CRD42024512184.

Cannabinoid receptor type 1 activation causes a water diuresis by inducing an acute central diabetes insipidus in mice

Cannabis and synthetic cannabinoid consumption are increasing worldwide. Cannabis contains numerous phytocannabinoids that act on the G protein-coupled cannabinoid receptor type 1 (CB1R) and cannabinoid receptor type 2 expressed throughout the body, including the kidney. Essentially every organ, including the kidney, produces endocannabinoids, which are endogenous ligands to these receptors. Cannabinoids acutely increase urine output in rodents and humans, thus potentially influencing total body water and electrolyte homeostasis. As the kidney collecting duct (CD) regulates total body water, acid/base, and electrolyte balance through specific functions of principal cells (PCs) and intercalated cells (ICs), we examined the cell-specific immunolocalization of CB1R in the mouse CD. Antibodies against either the C-terminus or N-terminus of CB1R consistently labeled aquaporin 2 (AQP2)-negative cells in the cortical and medullary CD and thus presumably ICs. Given the well-established role of ICs in urinary acidification, we used a clearance approach in mice that were acid loaded with 280 mM NH4Cl for 7 days and nonacid-loaded mice treated with the cannabinoid receptor agonist WIN55,212-2 (WIN) or a vehicle control. Although WIN had no effect on urinary acidification, these WIN-treated mice had less apical + subapical AQP2 expression in PCs compared with controls and developed acute diabetes insipidus associated with the excretion of large volumes of dilute urine. Mice maximally concentrated their urine when WIN and 1-desamino-8-d-arginine vasopressin [desmopressin (DDAVP)] were coadministered, consistent with central rather than nephrogenic diabetes insipidus. Although ICs express CB1R, the physiological role of CB1R in this cell type remains to be determined.NEW & NOTEWORTHY The CB1R agonist WIN55,212-2 induces central diabetes insipidus in mice. This research integrates existing knowledge regarding the diuretic effects of cannabinoids and the influence of CB1R on vasopressin secretion while adding new mechanistic insights about total body water homeostasis. Our findings provide a deeper understanding about the potential clinical impact of cannabinoids on human physiology and may help identify targets for novel therapeutics to treat water and electrolyte disorders such as hyponatremia and volume overload.

ENDOCANNABINOID SYSTEM IN THE PARAVENTRICULAR NUCLEUS OF THE HYPOTHALAMUS MODULATES AUTONOMIC AND CARDIOVASCULAR CHANGES BUT NOT VASOPRESSIN RESPONSE IN A RAT HEMORRHAGIC SHOCK MODEL

ABSTRACT

We evaluated the participation of the endocannabinoid system in the paraventricular nucleus of the hypothalamus (PVN) on the cardiovascular, autonomic, and plasma vasopressin (AVP) responses evoked by hemorrhagic shock in rats. For this, the PVN was bilaterally treated with either vehicle, the selective cannabinoid receptor type 1 antagonist AM251, the selective fatty acid amide hydrolase amide enzyme inhibitor URB597, the selective monoacylglycerol-lipase enzyme inhibitor JZL184, or the selective transient receptor potential vanilloid type 1 antagonist capsazepine. We evaluated changes on arterial pressure, heart rate, tail skin temperature (ST), and plasma AVP responses induced by bleeding, which started 10 min after PVN treatment. We observed that bilateral microinjection of AM251 into the PVN reduced the hypotension during the hemorrhage and prevented the return of blood pressure to baseline values in the posthemorrhagic period. Inhibition of local 2-arachidonoylglycerol metabolism by PVN treatment with JZL184 induced similar effects in relation to those observed in AM251-treated animals. Inhibition of local anandamide metabolism via PVN treatment with URB597 decreased the depressor effect and ST drop induced by the hemorrhagic stimulus. Bilateral microinjection of capsazepine mitigated the fall in blood pressure and ST. None of the PVN treatments altered the increased plasma concentration of AVP and tachycardia induced by hemorrhage. Taken together, present results suggest that endocannabinoid neurotransmission within the PVN plays a prominent role in cardiovascular and autonomic, but not neuroendocrine, responses evoked by hemorrhage.

The type-1 cannabinoid receptor modulates the hydroelectrolytic balance independently of the energy homeostasis during salt load

Hydroelectrolytic imbalances, such as saline load (SL), trigger behavioral and neuroendocrine responses, such as thirst, hypophagia, vasopressin (AVP) and oxytocin (OT) release and hypothalamus–pituitary–adrenal (HPA) axis activation. To investigate the participation of the type-1 cannabinoid receptor (CB1R) in these homeostatic mechanisms,male adult Wistar rats were subjected to SL (0.3MNaCl) for four days. SL induced not only increases in the water intake and plasma levels of AVP, OT and corticosterone, as previously described, but also increases in CB1R expression in the lamina terminalis, which integrates sensory afferents, aswell as in the hypothalamus, the main integrative and effector area controlling hydroelectrolytic homeostasis. A more detailed analysis revealed that CB1R-positive terminals are in close apposition with not only axons but also dendrites and secretory granules of magnocellular neurons, particularly vasopressinergic cells. In satiated and euhydrated animals, the intracerebroventricular administration of the CB1R selective agonist ACEA (0.1 μg/5 μL) promoted hyperphagia, but this treatment did not reverse the hyperosmolality-induced hypophagia in the SL group. Furthermore, ACEA pretreatment potentiated water intake in the SL animals during rehydration as well as enhanced the corticosterone release and prevented the increase in AVP and OT secretion induced by SL. The same parameters were not changed by ACEA in the animals whose daily food intake was matched to that of the SL group (Pair-Fed). These data indicate that CB1Rs modulate the hydroelectrolytic balance independently of the food intake during sustained hyperosmolality and hypovolemia.

Type 1 cannabinoid receptor modulates water deprivation-induced homeostatic responses

The present study investigated the type 1 cannabinoid receptor (CB1R) as a potential candidate to mediate the homeostatic responses triggered by 24 h of water deprivation, which constitutes primarily a hydroelectrolytic challenge and also significantly impacts energy homeostasis. The present results demonstrated for the first time that CB1R mRNA expression is increased in the hypothalamus of water-deprived (WD) rats. Furthermore, the administration of ACEA, a CB1R selective agonist, potentiated WD-induced dipsogenic effect, whereas AM251, a CB1R antagonist, attenuated not only water but also salt intake in response to WD. In parallel with the modulation of thirst and salt appetite, we confirmed that CB1Rs are essential for the development of appropriated neuroendocrine responses. Although the administration of ACEA or AM251 did not produce any effects on WD-induced arginine vasopressin (AVP) secretion, oxytocin (OXT) plasma concentrations were significantly decreased in WD rats treated with ACEA. At the genomic level, ACEA significantly decreased AVP and OXT mRNA expression in the hypothalamus of WD rats, whereas AM251 potentiated both basal and WD-induced stimulatory effects on the transcription of AVP and OXT genes. In addition, we showed that water deprivation alone upregulated proopiomelanocortin, Agouti-related peptide, melanin-concentrating hormone, and orexin A mRNA levels in the hypothalamus, and that CB1Rs regulate main central peptidergic pathways controlling food intake, being that most of these effects were also significantly influenced by the hydration status. In conclusion, the present study demonstrated that CB1Rs participate in the homeostatic responses regulating fluid balance and energy homeostasis during water deprivation.

Endocannabinoid Regulation of Neuroendocrine Systems

The hypothalamus is a part of the brain that is critical for sustaining life through its homeostatic control and integrative regulation of the autonomic nervous system and neuroendocrine systems. Neuroendocrine function in mammals is mediated mainly through the control of pituitary hormone secretion by diverse neuroendocrine cell groups in the hypothalamus. Cannabinoid receptors are expressed throughout the hypothalamus, and endocannabinoids have been found to exert pronounced regulatory effects on neuroendocrine function via modulation of the outputs of several neuroendocrine systems. Here, we review the physiological regulation of neuroendocrine function by endocannabinoids, focusing on the role of endocannabinoids in the neuroendocrine regulation of the stress response, food intake, fluid homeostasis, and reproductive function. Cannabis sativa (marijuana) has a long history of recreational and/or medicinal use dating back to ancient times. It was used as an analgesic, anesthetic, and antianxiety herb as early as 2600 B.C. The hedonic, anxiolytic, and mood-elevating properties of cannabis have also been cited in ancient records from different cultures. However, it was not until 1964 that the psychoactive constituent of cannabis, Δ(9)-tetrahydrocannabinol, was isolated and its chemical structure determined (Gaoni & Mechoulam, 1964).

Prenatal ethanol increases ethanol intake throughout adolescence, alters ethanol-mediated aversive learning, and affects μ but not δ or κ opioid receptor mRNA expression

Animal models of prenatal ethanol exposure (PEE) have indicated a facilitatory effect of PEE on adolescent ethanol intake, but few studies have assessed the effects of moderate PEE throughout adolescence. The mechanisms underlying this facilitatory effect remain largely unknown. In the present study, we analysed ethanol intake in male and female Wistar rats with or without PEE (2.0 g/kg, gestational days 17-20) from postnatal days 37 to 62. The results revealed greater ethanol consumption in PEE rats than in controls, which persisted throughout adolescence. By the end of testing, ethanol ingestion in PEE rats was nearly 6.0 g/kg. PEE was associated with insensitivity to ethanol-induced aversion. PEE and control rats were further analysed for levels of μ, δ and κ opioid receptor mRNA in the infralimbic cortex, nucleus accumbens shell, and ventral tegmental area. Similar levels of mRNA were observed across most areas and opioid receptors, but μ receptor mRNA in the ventral tegmental area was significantly increased by PEE. Unlike previous studies that assessed the effects of PEE on ethanol intake close to birth, or in only a few sessions during adolescence, the present study observed a facilitatory effect of PEE that lasted throughout adolescence. PEE was associated with insensitivity to the aversive effect of ethanol, and increased levels of μ opioid receptor transcripts. PEE is a prominent vulnerability factor that probably favors the engagement of adolescents in risky trajectories of ethanol use.

The endocannabinoid system and the neuroendocrine control of hydromineral balance

Endocannabinoids (ECBs) are ubiquitous lipophilic agents, and this characteristic is consistent with the wide range of homeostatic functions attributed to the ECB system. There is an increasing number of studies showing that the ECB system affects neurotransmission within the hypothalamic neurohypophyseal system. We provide an overview of the primary roles of ECBs in the modulation of neuroendocrine function and, specifically, in the control of hydromineral homeostasis. Accordingly, the general aspects of ECB-mediated signalling, as well as the specific contributions of the central component of the ECB system to the integration of behavioural and endocrine responses that control body fluid homeostasis, are discussed.

Oxytocin in the central amygdaloid nucleus modulates the neuroendocrine responses induced by hypertonic volume expansion in the rat

The present study investigated the involvement of the oxytocinergic neurones that project into the central amygdala (CeA) in the control of electrolyte excretion and hormone secretion in unanaesthetised rats subjected to acute hypertonic blood volume expansion (BVE; 0.3 M NaCl, 2 ml/100 g of body weight over 1 min). Oxytocin and vasopressin mRNA expression in the paraventricular (Pa) and supraoptic nucleus (SON) of the hypothalamus were also determined using the real time-polymerase chain reaction and in situ hybridisation. Male Wistar rats with unilaterally implanted stainless steel cannulas in the CeA were used. Oxytocin (1 μg/0.2 μl), vasotocin, an oxytocin antagonist (1 μg/0.2 μl) or vehicle was injected into the CeA 20 min before the BVE. In rats treated with vehicle in the CeA, hypertonic BVE increased urinary volume, sodium excretion, plasma oxytocin (OT), vasopressin (AVP) and atrial natriuretic peptide (ANP) levels and also increased the expression of OT and AVP mRNA in the Pa and SON. In rats pre-treated with OT in the CeA, previously to the hypertonic BVE, there were further significant increases in plasma AVP, OT and ANP levels, urinary sodium and urine output, as well as in gene expression (AVP and OT mRNA) in the Pa and SON compared to BVE alone. Vasotocin reduced sodium, urine output and ANP levels, although no changes were observed in plasma AVP and OT levels or in the expression of the AVP and OT genes in both hypothalamic nuclei. The results of the present study suggest that oxytocin in the CeA exerts a facilitatory role in the maintenance of hydroelectrolyte balance in response to changes in extracellular volume and osmolality.

Glucocorticoids disrupt neuroendocrine and behavioral responses during lactation

The influence of glucocorticoids on the neuroendocrine system and behavior of lactating rats is not well known. To evaluate the effects of glucocorticoids on the neuroendocrine system and maternal and aggressive behavior, lactating female rats were treated with dexamethasone or vehicle for 2 h before experiments. Blood samples were collected 15 min after the beginning of suckling to evaluate hormonal changes. To evaluate the maternal behavior of lactating rats, eight pups were placed in their home cages on the side opposite the location of the previous nest, and the resulting behavior of the lactating rat was filmed for 30 min. Aggressive behavior was evaluated by placing a male rat (intruder) in the home cage. Dexamethasone treatment reduced oxytocin and prolactin secretion during lactation and reduced pup weight gain. Relative to control treatment, dexamethasone treatment also adversely affected a variety of maternal behaviors; it increased the latency to build a new nest, decreased the number of pups gathered to the nest, increased the latency to retrieve the first pup, and decreased the percentage of time spent in the arched-nursing position. Dexamethasone treatment, compared with control, also reduced aggressive behavior, as evidenced by an increase in the latency to the first attack, a reduction in the number of front and side attacks, and a decrease in lateral threat and biting. Taken together, our results suggest dexamethasone treatment in lactating rats disrupts prolactin and oxytocin secretion, and this is followed by an attenuation of maternal and aggressive behavior.