Role of the central muscarinic receptor of prostaglandin I2 in cardiovascular function in rat

Gut-Brain Axis in Gastric Mucosal Damage and Protection

Abstract: Background

The gut-brain axis plays a potential role in numerous physiological and pathological conditions. Several substances link stomach with central nervous system. In particular, hypothalamo-pituitary-adrenocortical axis, thyrotropin-releasing factor-containing nerve fibers and capsaicin-sensitive nerves are principal mediators of the harmful and protective central nervous system-mediated effects on gastric mucosa. Also, existing evidence indicates that nitric oxide, prostaglandins and calcitonin gene-related peptide play a role as final effectors of gastric protection.

Methods

We undertook a structured search of bibliographic databases for peer-reviewed research literature with the aim of focusing on the role of gut-brain axis in gastric damage and protection. In particular, we examined manuscripts dealing with the role of steroids, thyrotropin-releasing hormone, prostaglandins, melatonin, hydrogen sulfide and peptides influencing food intake (i.e. leptin, cholecystokinin, peptide YY, central glucagon–like peptide-1, and ghrelin). Also, the role of GABAergic and glutamatergic pathways in gastric mucosal protection have been examined.

Results

We found and reviewed 61 peer-reviewed papers dealing with the major aspects related to the role of gut brain axis in gastric mucosal damage and protection.

Conclusions

A dense neuronal network links stomach with central nervous system and a number of neurotransmitters and peptides functionally and anatomically related to central nervous system play a major role in contributing to gastric mucosal integrity.

Exploiting the mechanisms underlying the connection between brain and gut may lead to a better understanding of the pathophysiology of gastric mucosal injury and to an improvement in the prevention and, eventually, management of gastric damage.

Lipid mediators in plasma of autism spectrum disorders

Background

Inflammation is increasingly recognized as being of both physiological and pathological importance in the immature brain. Cerebellar pathology occurs in autism, as a neurodevelopmental disorder with genetic and environmental origins. The genesis of this disorder is still not understood but inflammation in utero or early in childhood is an environmental risk factor.

Methods

Prostaglandin E2 (PGE2), cysteinyl leukotriene as two important lipid mediators together with 8 isoprostane as marker of oxidative stress were measured using ELISA in plasma of 20 male autistic patients compared to 19 age and gender matching control participants.

Results

PGE2, leukotrienes and isoprostanes recorded significantly elevated levels in autistics compared to controls. Role of these measured parameters in inflammation and autoimmunity as two etiological factors in autism were discussed in details.

Conclusion

Receiver Operating Characteristic (ROC) curve analysis shows satisfactory values of area under the curve (AUC) which could reflect the high degree of specificity and sensitivity of the altered PGE2, leukotrienes and isoprostanes as predictive biomarkers in autistic patients from Saudi Arabia.

Muscarinic effects and foetal cardiovascular and hormonal responses in utero

Introduction. Cholinergic mechanisms play an important role in the control of hormonal and vascular regulation. However, in utero development of cholinergic regulation in the foetal hormonal systems is not clearly understood.This study investigated foetal hormonal and cardiovascular responses following application of the muscarinic antagonist atropine.

Materials and methods. Chronically prepared near-term ovine foetuses (control and experimental: n=5, each group) were used.After 4—5 days’ surgical recovery, conscious ewes and their foetuses were tested in vivo.

Results. In response to intravenous atropine, foetal systolic, diastolic, and mean arterial pressure, as well as heart rate, increased immediately. Inhibition of muscarinic systems in the circulation caused a reduction of plasma angiotensin II levels, while angiotensin I in the circulation remained unchanged in the foetus. In addition, foetal plasma aldosterone levels were significantly increased following blockade of the cholinergic receptor, while other hormones, including arginine vasopressin, adrenocorticotrophic hormone, and atrial natriuretic peptide, were not changed in foetal blood under the same condition.

Conclusions. The results suggest that foetal automatic systems, not those hormonal factors tested, play a major role in cholinergic mechanisms mediating cardiovascular control. Furthermore, the data provide new information on how muscarinic inhibition affects renin-angiotensin system and adrenal cortex functions. Key words: aldosterone, angiotensin-converting enzyme, autonomic regulation, foetus

Differential effects of cyclooxygenase inhibitors on haloperidol-induced catalepsy

Prostaglandins (PGs) might play a role as putative transmitters or as modulators in the central nervous system (CNS). In the present study, haloperidol (1 mg/kg i.p.)-treated mice showed significant cataleptic behaviour. Naproxen, a nonselective cyclooxygenase (COX) inhibitor, dose-dependently (5 and 10 mg/kg) antagonized the haloperidol-induced catalepsy in mice. Nimesulide, a preferential COX inhibitor, also dose-dependently reduced the cataleptic score in haloperidol treated animals at the first and second hour but not at the third and fourth hour of haloperidol treatment. Rofecoxib, a selective COX-2 inhibitor, did not show any effect on haloperidol-induced catalepsy. The major findings of the present study suggest that PGs might play a significant role in haloperidol-induced catalepsy. The findings of the present study further suggested that COX-1 derived rather than COX-2 derived PGs might play a potential role in haloperidol-induced catalepsy. In conclusions COX inhibitors can be screened as potential drug candidates for the treatment of neuroleptic-induced extrapyramidal side effects (EPS).

Iloprost, a stable analogue of PGI2, potentiates the hyperthermic effect of PGE2 in rats

Centrally mediated effects of iloprost, a stable analogue of PGI2, on rectal temperature have been investigated in conscious rats. ICV administration of iloprost (100-1,000 ng, ICV) produced a dose-dependent, monophasic hyperthermic response that was not inhibited by indomethacin. When injected into the preoptic anterior hypothalamic (POAH) region, iloprost (2-50 ng/POAH) induced a biphasic increase in rectal temperature. While the first phase was inhibited by AH 6809, an E1-type prostaglandin (EP1) receptor antagonist, the second phase was abolished by indomethacin pretreatment. Iloprost was found not to alter rectal temperature when injected into the ventromedial hypothalamic area. Administration of iloprost into the POAH in a dose that had no effect on rectal temperature significantly potentiated the hyperthermic effect of PGE2 (50 ng, ICV). These findings suggest that the pyrogenic effect of iloprost is partly mediated by EP1 receptors located on the POAH. Regarding the similarities of iloprost and PGI2, it is further proposed that endogenous PGI2 might act to modulate hyperthermic effect of PGE2 released during arachidonic acid- or endogenous pyrogen-induced fever.

The effect of neurotransmitters on cataleptic behavior induced by PG D2 in rats

The effects of several neurotransmitters on prostaglandin (PG) D2-induced cataleptic behavior in rats were investigated by the high bar test. Intracerebroventricular administration of PG D2 elicited cataleptic behavior in a dose-dependent manner without producing a marked change in spontaneous motor activity. The incidences of cataleptic behavior were 20% and 100% at doses of 2 nmol and 50 nmol of PG D2, respectively. Intraperitoneal pretreatment with L-DOPA (100 mg/kg), apomorphine (1 mg/kg), amantadine (0.2 mg/kg), atropine (0.5 mg/kg) or p-chlorophenylalanine (300 mg/kg) significantly decreased the cataleptic behavior induced by 50 nmol of PG D2. Conversely, simultaneous treatment with 5-hydroxy-L-tryptophan (30 mg/kg), 5-methoxy-N,N-dimethyltryptamine (5 mg/kg), imipramine (20 mg/kg) or clomipramine (10 mg/kg) markedly increased the cataleptic behavior induced by 2 nmol of PG D2. Propranolol (10 mg/kg) and phenoxybenzamine (10 mg/kg) did not affect the induction of cataleptic behavior by either 2 nmol or 50 nmol of PG D2. These results suggest that PG D2 might be involved in inducing cataleptic behavior by modulating serotonergic, cholinergic and dopaminergic systems.