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Indolamines (e.g., serotonin and melatonin) are tryptophan-derived class of neurotransmitters and neuromodulators that play crucial roles in mood regulation, sleep-wake cycles, and gastrointestinal functions. These biogenic amines exert their effects by binding to specific receptors in the central nervous system, influencing neuronal activity and signalling cascades. Indolamines are vital in maintaining homeostasis, and imbalances in their levels have been implicated in various neurological and psychiatric disorders. Hence, in the present study, we have investigated the nonlinear properties of indolamines under a continuous wave (CW) and pulsed laser excitation using the closed-aperture (CA) Z-scan technique. The CA Z-scan is a cost-effective and sensitive analytical tool for investigating nonlinear properties. It is observed that indolamines show negative refractive and positive absorptive nonlinearity under in vitro physiological conditions. The origin of nonlinearity is ascribed to the thermo-optical effect governed by the saturated atomic absorption and molecular orientation mechanisms under CW and pulsed laser excitation, respectively. The strength of nonlinearity is found to vary linearly with the concentration of indolamines. Overall, serotonin possesses stronger nonlinearity than melatonin. The maximum nonlinearity (refractive index (n 2) & absorption coefficient (β)) for melatonin under CW and pulsed laser excitations are (-1.266 × 10−12 m2W−1 and -1.883 × 10−17 m2W−1) & (8.046 × 10−8 mW−1 and 1.516 × 10−13 mW−1), respectively. Meanwhile, the maximum n 2 and β under pulsed laser excitation for serotonin are obtained as -3.195 × 10−17 m2W−1 and 6.149 × 10−12 mW−1, respectively. The outcome of the results may be utilized in understanding processes mediated by indolamines and designing therapeutic interventions. [Display omitted] • Nonlinear properties of indolamines are studied under CW and pulsed laser excitations. • Indolamines exhibit negative refractive and positive absorptive nonlinearity. • Origin of nonlinearity is ascribed to the thermo-optical effect. • Strength of nonlinearity varies linearly with the concentration of indolamines. [ABSTRACT FROM AUTHOR]

• Type 1 diabetes increased the levels of Ca+ and cAMP-dependent protein kinases. • These kinases activates/regulates indolamines in various areas of rat brain. • These changes results in impairment of retinal, renal, neuronal and heart. • Insulin or respective pharmacological suppressors reversed these effects. • Dual inhibition of both Ca+ and cAMP-dependent pathways may be useful in diabetes. From early to later stages of Type I Diabetes Mellitus (TIDM), signalling molecules including brain indolamines and protein kinases are altered significantly, and that has been implicated in the Metabolic Disorders (MD) as well as impairment of retinal, renal, neuronal and cardiovascular systems. Considerable attention has been focused to the effects of diabetes on these signalling systems. However, the exact pathophysiological mechanisms of these signals are not completely understood in TIDM, but it is likely that hyperglycemia, acidosis, and insulin resistance play significant roles. Insulin maintains normal glycemic levels and it acts by binding to its receptor, so that it activates the receptor's tyrosine kinase activity, resulting in phosphorylation of several substrates. Those substrates provide binding/interaction sites for signalling molecules, including serine/threonine kinases and indolamines. For more than two decades, our research has been focused on the mechanisms of protein kinases, CaM Kinase and Serotonin transporter mediated alterations of indolamines in TIDM. In this review, we have also discussed how discrete areas of brain respond to insulin or some of the pharmacological agents that triggers or restores these signalling molecules, and it may be useful for the treatment of specific region wise changes/disorders of diabetic brain. [ABSTRACT FROM AUTHOR]

Abstract: Sex differences and gonadal hormone influences are well known for diverse aspects of forebrain amine and indolamine neurotransmitter systems, the cognitive and affective functions they govern and their malfunction in mental illness. This study explored whether hormone regulation/dysregulation of these systems could be related to gonadal steroid effects on catechol-O-methyltransferase and monoamine oxidase which are principal enzymatic controllers of forebrain dopamine, serotonin and norepinephrine levels. Driven by male over female differences in cortical enzyme activities, by male-specific associations between monoamine oxidase and catechol-O-methyltransferase gene polymorphisms and cognitive and dysfunction in disease and by male-specific consequences of gene knockouts in mice, the question of hormone sensitivity was addressed here using a male rat model where prefrontal dopamine levels and related behaviors are also known to be affected. Specifically, quantitative O-methylation and oxidative deamination assays were used to compare the activities of catechol-O-methyltransferase''s soluble and membrane-bound isoforms and of monoamine oxidase''s A and B isoforms in the pregenual medial prefrontal cortex and dorsal striatum of male rats that were sham operated, gonadectomized or gonadectomized and supplemented with testosterone propionate or with estradiol for 28 days. These studies revealed significant effects of hormone replacement but not gonadectomy on the soluble but not the membrane-bound isorfom of catechol-O-methyltransferase in both striatum and cortex. A significant, cortex-specific testosterone—but not estradiol—attenuated effect (increase) of gonadectomy on monoamine oxidase''s A but not B isoform was also observed. Although none of these actions suggest potential roles in the reguation/dysregulation of prefrontal dopamine, the suppressive effects of testosterone on cortical monoamine oxidase-A that were observed could have bearing on the increased incidence of cognitive deficits and symptoms of depression and anxiety that are repeatedly observed in males in conditions of hypogonadalism related to aging, other biological factors or in prostate cancer where androgen deprivation is used as a neoadjuvant treatment. [Copyright &y& Elsevier]

Abstract: Hyperglycemia and ketoacidosis are the two most serious factors in acute metabolic complications of both type 1 and type 2 diabetes. Dysfunction of the central nervous system is a well-documented complication of diabetes. We and others have previously reported that acute or chronic diabetes in animal''s results in altered brain neurotransmitter levels. In this study, we investigated the effects of acute (7 days) glucose-induced hyperglycemia and sodium acetoacetate (NaAcAc) or ammonium chloride (NH4Cl) induced acidosis on the level of indolamines (5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA)) as well as PKC-α expression/activity in discrete areas of rat brain. Glucose-induced (500mg/kg, bw) hyperglycemic (∼249mg%) rats showed significant (p <0.05) increase in 5-HT levels in mid brain (MB), pons medulla (PM) and cerebellum (CB), respectively. 5-HIAA level increased in hippocampus (HC) (p <0.05) as compared to control. The rats treated with sodium acetoacetate (NaAcAc) for 7 days (60mg/kg, bw) showed significant decrease (p <0.05) of 5-HT level in hypothalamus (HT). Whereas, the 5-HIAA level increased in MB (p <0.05). Similarly, the PKC-α expression as well as the enzyme activity showed significant increase in HC, MB, PM and CB under glucose-induced hyperglycemia and that changes correlated the changes of indolamines, suggesting that the hyperglycemia may be the major metabolic disorder in diabetic complications. [Copyright &y& Elsevier]

A specific capillary electrophoresis–time-of-flight mass spectrometry (CE–TOFMS) method for the determination of serotonin (5HT) and its precursors tryptophan (Trp) and 5-hydroxytryptophan (5HTP) in human platelet rich plasma is described. The analytes were removed from the plasma samples and preconcentrated by solid phase extraction (SPE) on mixed mode cation-exchange sorbents. The SPE recoveries were 71.6 ± 3.1 for 5HT, 91.0 ± 2.8 for Trp, and 95.3 ± 5.9% for 5HTP. Deuterated analogues of 5HT and Trp were used as internal standards for quantitation purposes. Submicromolar detection limits were obtained for standard mixtures of all compounds and their deuterated isotopes, except 5HTP, which had detection limits in the low micromolar range. The potential usefulness of this method in the clinical setting was demonstrated by analyzing plasma extracts from healthy volunteers as well as from pathological samples. While 5HTP was not present in any of the analyzed samples, the levels of 5HT and Trp in both normal and pathological plasma were determined. [Copyright &y& Elsevier]