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Comments on Point:Counterpoint: Sympathetic activity does/does not influence cerebral blood flow. When noradrenergic restraint of cerebral blood flow makes homeostatic sense

Prakash ES

J Appl Physiol (1985), 2008 10;105(4):1373.
PMID: 18938648 DOI: 10.1152/japplphysiol.zdg-8199.pcpcomm.2008
Matched MeSH terms: Norepinephrine/metabolism
Serotonin Selective Reuptake Inhibitors (SSRIs) and Female Sexual Dysfunction (FSD): Hypothesis on its Association and Options of Treatment

Rappek NAM, Sidi H, Kumar J, Kamarazaman S, Das S, Masiran R, et al.

Curr Drug Targets, 2018;19(12):1352-1358.
PMID: 28025939 DOI: 10.2174/1389450117666161227142947

Sexual dysfunctions are commonly seen in women on selective serotonin reuptake inhibitors (SSRIs). The complexities of female sexual functioning are reflected through modulation of inter- playing factors like the neuropsychophysiological factors, inter-personal and relationship issue, psychiatric co-morbidities and physical disorder. The incidence of SSRIs-induced FSD is difficult to estimate because of the potential confounding effects of SSRIs, presence of polypharmacy, marital effect, socio-cultural factors and due to the design and assessment problems in majority of the studies. The exact mechanism of FSD-induced SSRIs is unknown. It has been postulated that although SSRIs may modulate other neurotransmitter system such as nitric oxide (NO), noradrenergic and dopamine in inducing FSD. In the present review, we highlight current evidence regarding potential mechanism of SSRIs in causing FSD, which include low sexual desire (low libido), arousal difficulties (lack of lubrication), and anorgasmia. The specific association of FSD to SSRI use, has not been ellucidated. The relationship is dose-dependent, and may vary among the groups with respect to mechanism of serotonin and dopamine reuptake, induction of release of prolactin from the pituitary gland, anticholinergic side-effects, inhibition of NO synthesis and emotional-memory circuit encryption for sexual experiences. Various interventional strategies exist regarding the treatment of SSRI-induced FSD and this includes tolerance, titration dosage, substitution to another antidepressant drug and psychotherapy. There is a need of better understanding of SSRIs-induced FSD for better treatment outcome.

Matched MeSH terms: Norepinephrine/metabolism
The debate over neurotransmitter interaction in aspartame usage

Choudhary AK, Lee YY

J Clin Neurosci, 2018 Oct;56:7-15.
PMID: 30318075 DOI: 10.1016/j.jocn.2018.06.043

Aspartame (NutraSweet®, Equal®) is a widely used artificial sweetener, has been reported to be accountable for neurological and behavioural disturbances in people. Upon ingestion, aspartame is hydrolyzed in gut and provides its metabolite; such as essential amino acid phenylalanine (Phy) (50%), aspartic acid (40%), and methanol (10%). Altered brain neurochemical compositions [such as dopamine (DA), norepinephrine (NE), and serotonin (5-HT)] have long been a concern and being involved in observed neurophysiological symptom (such as headaches, memory loss, mood changes, as well as depression) in aspartame consumers. Aspartames might act as chemical stressor through increasing plasma cortisol level. Aspartame consumption similarly altered gut microbiota. Taken together all this factors, we reviewed to search for convincing evidence, in what manner aspartame metabolites, stress hormones (cortisol), and gut dysbiosisis involved in altering brain neurochemical composition. We concluded that aspartame metabolite; mainly Phy and its interaction with neurotransmitter and aspartic acid by acting as excitatory neurotransmitter causes this pattern of impairments. Along with elevated cortisol and gut dysbiosis via interactions with different biogenic amine may also have additional impact to modulate neuronal signaling lead to neurobiological impairments. Hence ongoing research is instantly needed to understand the specific roles of aspartame metabolite, elevated cortisol, and gut dysbiosis with emerging neurophysiological symptom in aspartame consumers to improve healthy life in its consumers.

Matched MeSH terms: Norepinephrine/metabolism
Effects of age on the glucoregulatory response following acute glucoprivation induced by 2-deoxyglucose (2DG) in the adrenal medulla of Sprague Dawley rats

Muda NA, Ramlan H, Damanhuri HA

Neuro Endocrinol. Lett., 2017 Jul;38(3):224-235.
PMID: 28759191

OBJECTIVES: Impairment in glucose homeostasis is one of the factors that may alter the feeding drive, hunger and satiety signals, which essential to maintain a sufficient level of energy for daily activities especially among the elderly. Adrenal medulla is one of the important organs that involves in glucose homeostasis through secretion of catecholamines. The catecholamines biosynthesis pathway utilizes various enzymes and protein kinases. The aims of this study are to investigate the effects of age on the biosynthetic pathway of catecholamines in adrenal medulla by determining the level of blood glucose and blood catecholamines, the gene and protein expression of biosynthetic catecholamine enzymes (TH, DBH and PNMT) as well as protein kinase substrates that involved in the phosphorylation of TH in 2DG-induced rats.
METHODS: Adrenal medulla from male Sprague Dawley rats at the age of 3-months (n=12) and 24-months (n=12) were further divided into two groups: 1) treatment group with 2DG to create glucoprivation condition and 2) the vehicle group which received normal saline as control.
RESULTS: The results showed that the level of glucose, adrenaline and noradrenaline were increased in response to acute glucoprivation conditions in both young and old rats. No age-related differences were found in the basal gene expression of the enzymes that involved in the catecholamines biosynthesis pathway. Interestingly the expressions of TH and DBH protein as well as the level of TH phosphorylation at Ser40, PKA, PKC and ERK1/2 substrates were higher in basal condition of the aged rats. However, contradicted findings were obtained in glucoprivic condition, which the protein expressions of DBH, pERK1/2 and substrates for pPKC were increased in young rats. Only substrate for pCDK was highly expressed in the old rats in the glucoprivic condition, while pPKC and pERK1/2 were decreased significantly. The results demonstrate that adrenal medulla of young and old rats are responsive to glucose deficit and capable to restore the blood glucose level by increasing the levels of blood catecholamines.
CONCLUSION: The present findings also suggest that, at least in rats, aging alters the protein expression of the biosynthetic catecholamine enzymes as well as protein kinase substrates that may attenuate the response to glucoprivation.

Matched MeSH terms: Norepinephrine/metabolism*
Anxiolytic- and antidepressant-like activities of a methanolic extract of Morinda citrifolia Linn. (noni) fruit in mice: Involvement of benzodiazepine-GABAAergic, serotonergic and adrenergic systems

Narasingam M, Vijeepallam K, Mohamed Z, Pandy V

Biomed Pharmacother, 2017 Dec;96:944-952.
PMID: 29217165 DOI: 10.1016/j.biopha.2017.11.148

This study presents anxiolytic- and antidepressant-like effects of a methanolic extract of Morinda citrifolia Linn. (noni) fruit (MMC) in well-established mouse models of anxiety and depression. The administration of MMC (1 g/kg, p.o.) and diazepam (1 mg/kg, i.p.) significantly attenuated anxiety-like behaviour in mice by increasing the percentage of time spent and number of entries in the open arms in the elevated plus maze (EPM), and significantly enhanced the exploration in the light box in the light/dark test (LDT). The pre-treatment with flumazenil (6 mg/kg, i.p.) or bicuculline (3 mg/kg, i.p.) or WAY 100635 (1 mg/kg, i.p.) antagonized the anxiolytic-like effect elicited by MMC (1 g/kg, p.o.). These results suggest the possible involvement of benzodiazepine-GABAAergic and serotonergic mechanisms in the anxiolytic-like effect of noni fruit. Meanwhile, in the antidepressant study, the administration of MMC (0.5 and 0.75 g/kg, p.o.) and desipramine (30 mg/kg, i.p.) significantly reduced the duration of immobility in the tail suspension test (TST). Furthermore, pre-treatment of mice with 4-chloro-DL-phenylalanine methyl ester hydrochloride (PCPA; 100 mg/kg, i.p., an inhibitor of serotonin synthesis) for four consecutive days or a single dose of WAY 100635 (1 mg/kg, i.p., 5HT1A receptor antagonist) or α-methyl-DL-tyrosine (AMPT; 100 mg/kg, i.p., an inhibitor of noradrenaline synthesis) significantly reversed the anti-immobility effect of MMC (0.5 g/kg, p.o.) in TST by indicating the specific involvement of the serotonergic and noradrenergic systems in the antidepressant-like effect of noni fruit. Taken together, these findings suggest that MMC has both anxiolytic- and antidepressant-like activities to be resorted as a valuable alternative therapy for comorbid anxiety and depressive conditions.

Matched MeSH terms: Norepinephrine/metabolism
High-fructose feeding impacts on the adrenergic control of renal haemodynamics in the rat

Abdulla MH, Sattar MA, Johns EJ, Abdullah NA, Hye Khan MA, Rathore HA

Br J Nutr, 2012 Jan;107(2):218-28.
PMID: 21733307 DOI: 10.1017/S0007114511002716

The present study explored the hypothesis that a prolonged 8 weeks exposure to a high fructose intake suppresses adrenergic and angiotensin II (Ang II)-mediated vasoconstriction and is associated with a higher contribution of α1D-adrenoceptors. A total of thirty-two Sprague-Dawley rats received either 20 % fructose solution (FFR) or tap water (control, C) to drink ad libitum for 8 weeks. Metabolic and haemodynamic parameters were assessed weekly. The renal cortical vasoconstrictor responses to noradrenaline (NA), phenylephrine (PE), methoxamine (ME) and Ang II were determined in the presence and absence of BMY7378 (α1D-adrenoceptor antagonist). FFR had increased blood pressure, plasma levels of glucose, TAG and insulin. FFR expressed reduced renal vascular responses to adrenergic agonists and Ang II (NA: 50 %, PE: 50 %, ME, 65 %, Ang II: 54 %). Furthermore in the C group, the magnitude of the renal cortical vasoconstriction to all agonists was blunted in the presence of the low or high dose of BMY7378 (NA: 30 and 31 %, PE: 23 and 33 %, ME: 19 and 44 %, Ang II: 53 and 77 %), respectively, while in the FFR, vasoconstriction was enhanced to adrenergic agonists and reduced to Ang II (NA: 8 and 83 %, PE: 55 %, ME, 2 and 177 %, Ang II: 61 and 31 %). Chronic high fructose intake blunts vascular sensitivity to adrenergic agonists and Ang II. Moreover, blocking of the α1D-adrenoceptor subtype results in enhancement of renal vasoconstriction to adrenergic agonists, suggesting an inhibitory action of α1D-adrenoceptors in the FFR. α1D-Adrenoceptors buffer the AT1-receptor response in the renal vasculature of normal rats and fructose feeding suppressed this interaction.

Matched MeSH terms: Norepinephrine/metabolism
Neurophysiological symptoms and aspartame: What is the connection?

Choudhary AK, Lee YY

Nutr Neurosci, 2018 Jun;21(5):306-316.
PMID: 28198207 DOI: 10.1080/1028415X.2017.1288340

Aspartame (α-aspartyl-l-phenylalanine-o-methyl ester), an artificial sweetener, has been linked to behavioral and cognitive problems. Possible neurophysiological symptoms include learning problems, headache, seizure, migraines, irritable moods, anxiety, depression, and insomnia. The consumption of aspartame, unlike dietary protein, can elevate the levels of phenylalanine and aspartic acid in the brain. These compounds can inhibit the synthesis and release of neurotransmitters, dopamine, norepinephrine, and serotonin, which are known regulators of neurophysiological activity. Aspartame acts as a chemical stressor by elevating plasma cortisol levels and causing the production of excess free radicals. High cortisol levels and excess free radicals may increase the brains vulnerability to oxidative stress which may have adverse effects on neurobehavioral health. We reviewed studies linking neurophysiological symptoms to aspartame usage and conclude that aspartame may be responsible for adverse neurobehavioral health outcomes. Aspartame consumption needs to be approached with caution due to the possible effects on neurobehavioral health. Whether aspartame and its metabolites are safe for general consumption is still debatable due to a lack of consistent data. More research evaluating the neurobehavioral effects of aspartame are required.

Matched MeSH terms: Norepinephrine/metabolism