Melanin-concentrating hormone does not modulate serotonin release in primary cultures of fetal raphe nucleus neurons

Melanin-concentrating hormone (MCH) is a neuropeptide present in neurons located in the hypothalamus that densely innervate serotonergic cells in the dorsal raphe nucleus (DRN). MCH administration into the DRN induces a depressive-like effect through a serotonergic mechanism. To further understand the interaction between MCH and serotonin, we used primary cultured serotonergic neurons to evaluate the effect of MCH on serotonergic release and metabolism by HPLC-ED measurement of serotonin (5-HT) and 5-hydroxyindolacetic acid (5-HIAA) levels. We confirmed the presence of serotonergic neurons in the E14 rat rhombencephalon by immunohistochemistry and showed for the first time evidence of MCHergic fibers reaching the area. Cultures obtained from rhombencephalic tissue presented 2.2 ± 0.7% of serotonergic and 48.9 ± 5.4% of GABAergic neurons. Despite the low concentration of serotonergic neurons, we were able to measure basal cellular and extracellular levels of 5-HT and 5-HIAA without the addition of any serotonergic-enhancer drug. As expected, 5-HT release was calcium-dependent and induced by depolarization. 5-HT extracellular levels were significantly increased by incubation with serotonin reuptake inhibitors (citalopram and nortriptyline) and a monoamine-oxidase inhibitor (clorgyline), and were not significantly modified by a 5-HT1A autoreceptor agonist (8-OHDPAT). Even though serotonergic cells responded as expected to these pharmacological treatments, MCH did not induce significant modifications of 5-HT and 5-HIAA extracellular levels in the cultures. Despite this unexpected result, we consider that assessment of 5-HT and 5-HIAA levels in primary serotonergic cultures may be an adequate approach to study the effect of other drugs and modulators on serotonin release, uptake and turnover.

Neuropeptide glutamic acid-isoleucine (NEI)-induced paradoxical sleep in rats

Neuropeptideglutamic acid-isoleucine (NEI) as well as melanin concentrating hormone (MCH) is cleaved from the 165 amino acid protein, prepro-melanin concentrating hormone (prepro-MCH). Among many physiological roles of MCH, we demonstrated that intracerebroventricular (icv) injection of MCH induced increases in REM sleep episodes as well as in non REM sleep episodes. However, there are no studies on the effect of NEI on the sleep-wake cycle. As for the sites of action of MCH for induction of REM sleep, the ventrolateral periaqueductal gray (vlPAG) has been reported to be one of its site of action. Although MCH neurons contain NEI, GABA, MCH, and other neuropeptides, we do not know which transmitter(s) might induce REM sleep by acting on the vlPAG. Thus, we first examined the effect of icv injection of NEI on the sleep-wake cycle, and investigated how microinjection of either NEI, MCH, or GABA into the vlPAG affected REM sleep in rats. Icv injection of NEI (0.61μg/5μl: n=7) significantly increased the time spent in REM episodes compared to control (saline: 5μl; n=6). Microinjection of either NEI (61ng/0.2μl: n=7), MCH (100ng/0.2μl: n=6) or GABA (250mM/0.2μl: n=7) into the vlPAG significantly increased the time spent in REM episodes and the AUC. Precise hourly analysis of REM sleep also revealed that after those microinjections, NEI and MCH increased REM episodes at the latter phase, compared to GABA which increased REM episodes at the earlier phase. This result suggests that NEI and MCH may induce sustained REM sleep, while GABA may initiate REM sleep. In conclusion, our findings demonstrate that NEI, a cleaved peptide from the same precursor, prepro-MCH, as MCH, induce REM sleep at least in part through acting on the vlPAG.

Cuttlefish Ink Melanin Encapsulated in Nanolipid Bubbles and Applied Through a Micro-Needling Procedure Easily Stains White Hair Facilitating Photoepilation

BACKGROUND

Photothermolysis of unwanted hair depends on the presence of melanin in the hair follicle as the chromophore, but is not effective in patients with non-pigmented, melanin-sparse hair shafts and follicles. This split-scalp, double-blind study was to monitor the efficacy of melanin bound in nanosomes to inject exogenous melanin into the hair follicles thus potentiating successful photothermolysis.<br />

MATERIAL AND METHODS

Twelve patients, phototypes II-III, with white or very fair hair, were treated with a compound containing melanin encapsulated in nanosomes (Melaser^®) together with a fluorescent marker. Two equal 6 cm² areas were marked on each side of the occiput of the subjects. The compound was applied to a randomly selected experimental side on each patient (area A), and a saline solution applied in the same manner to the contralateral control side (area B). Penetration of the melanin into the hair follicle was assessed using optical and fluorescence microscopy. Also, condition of hair structure was checked in vivo after standard laser settings used for epilation.<br />

RESULTS

A slight transient erythema was observed in those areas where the compound was applied with some perifollicular edema. No such effects were noticed in those areas where saline solution was applied. No persistent complications such as scarring, hypo- or hyperpigmentation were observed in any of the experimental or control areas. Under fluorescence microscopy, the hair structures in the areas to which the compound had been applied showed a clear melanin deposit confirmed by the immunofluorescence intensity, which was highest at 2 hours after application. By optical microscopy, external melanin was deposited in hair follicles. Tests with standard settings for epilation were efficacious in damaging melanin-marked white hair.<br />

CONCLUSION

This study strongly suggests the safety and efficacy of the application of nanosomes encapsulating melanin for the introduction of melanin into hair follicles. Changes noticed in the hair structure compromising its viability indicated potential application of this external melanin marker for white hair photoepilation.<br /><br /> <em>J Drugs Dermatol</em>. 2016;15(5):615-625.

The median raphe nucleus participates in the depressive-like behavior induced by MCH: differences with the dorsal raphe nucleus

An emerging body of evidence involves the hypothalamic neuropeptide melanin-concentrating hormone (MCH) in the regulation of emotional states. We have reported a pro-depressive effect induced by MCH after its microinjection into the dorsal raphe nucleus (DR) evaluated in the forced swimming test (FST) in rats. Here we extended this study to the median raphe nucleus (MnR). Firstly, the presence of MCH-containing fibers in the rat MnR was analyzed by means of immunohistochemistry. Secondly, the behavioral effect induced by the microinjection of MCH into the MnR was assessed using the FST. Morphological results showed a large density of MCHergic fibers within the MnR. Behavioral results indicated that 100 ng of MCH (but not 50 ng) significantly increased the immobility time and decreased the swimming time, demonstrating a depressive-like effect. In contrast, climbing behavior was not significantly affected. Present findings revealed that the MnR neurons participate in the MCHergic control of affective-related behavioral responses. However, the behavioral patterns induced by MCH in the MnR and DR were different. This could be explained by anatomical and physiological differences between both nuclei.

[Features of behavioral reactions of chronically irradiated mice in the raised crosswise labyrinth with various genetically determined radiosensitivity and possibilities of their modification by the fungal biopolymer complex]

Structural elements of the central nervous system--neurons, along with the higher neuroendocrine structures and the hypothalamus centres, show high sensitivity to a chronic action of low doses of ionizing radiation (IR) in view of their extreme enrichment by phospholipids and intensive supply by oxygen, creating favorable conditions for the development of oxidizing stress. Stressful influences cause negative emotions in the behaviour of animals manifested as fear or uneasiness. The study represents the results of comparative research into the behavioral reactions characterized by uneasiness in the Balb/c and C57bl/6 mice exposed to a chronic irradiation at low doses. The chitin-melanin-glucan complex from fungi Fomes fomentarius (ChMG) was approved as an adaptive agent. It has been shown that under identical conditions, deposition levels of radionuclides 137Cs and 90Sr are raised in mice with IR hypersensitivity--line Balb/c, in comparison with less radio sensitive mice--line C57bl/6. Simultaneously, Balb/c mice were observed to exhibit the signs of a more anxious behaviour in the new environment. Chronic external and internal radiation exposure to rare ionizing radiation at low doses promotes strengthening of anxiety and phobic reactions in mice with IR hypersensitivity. The use of ChMG in animals neutralized the increase in anxiety and phobic reactions after a prolonged irradiation, thus indicating the presence in ChMG of the anxiolitic activity along with the above mentioned powerful radiosorbent, antioxidant, gene protective and immunomodulatory properties.

[Remote signaling of radiation damage to the extracellular space in mice with various levels of genetically determined radio sensitivity]

The search results of "bystander" signals are presented at different model of influence of IR on Balb/c and C57bl/6 mice, characterized by different levels of genetically determined sensitivity to IR influence. We used the following models of IR influence: 1) external gamma-quanta influence from small samples of nuclear fuel from the CNPP 4th power unit modified in the course of the accident in 1986, which are 99% connected with 137Cs, with the total dose of irradiation of about 5.0 Gy for 16 hours and accumulated dose of 0.290 Gy for 231 day of exposure, 2) internal intake of 137Cs with water for 40 days. It is shown that cells of different types (splenocytes, hepatocytes, bone marrow and astroglia cells) irrespective of a model of IR influence produce the factors, which failed to be identified in this research, raising the SSF levels in the DNA of non-irradiated cells. Under conditions of a single exposure to gamma-field external irradiation at a dose of about 5.0 Gy, the intensity of production of "bystander" signals is higher in the mice with the raised level of genetically determined sensitivity to RI (Balb/c). Under the same conditions of gamma-field exposure, induction of additional levels of SSF in the DNA of non-irradiated cells is detected for at least one month after IR exposure. Intraperitoneal injection of melanin in the melanin-glucan complex from fungus F. fomentarius before irradiation exposure promotes an essential decrease in the production of "bystander" signals, testifying in favor of the free radical nature of their certain part.

Microinjection of melanin concentrating hormone into the lateral preoptic area promotes non-REM sleep in the rat

The ventrolateral preoptic area (VLPO) has been recognized as one of the key structures responsible for the generation of non-REM (NREM) sleep. The melanin-concentrating hormone (MCH)-containing neurons, which are located in the lateral hypothalamus and incerto-hypothalamic area, project widely throughout the central nervous system and include projections to the VLPO. The MCH has been associated with the central regulation of feeding and energy homeostasis. In addition, recent findings strongly suggest that the MCHergic system promotes sleep. The aim of the present study was to determine if MCH generates sleep by regulating VLPO neuronal activity. To this purpose, we characterized the effect of unilateral and bilateral microinjections of MCH into the VLPO on sleep and wakefulness in the rat. Unilateral administration of MCH into the VLPO and adjacent dorsal preoptic area did not modify sleep. On the contrary, bilateral microinjections of MCH (100 ng) into these areas significantly increased light sleep (LS, 39.2±4.8 vs. 21.6±2.5 min, P<0.05) and total NREM sleep (142.4±23.2 vs. 86.5±10.5 min, P<0.05) compared to control (saline) microinjections. No effect was observed on REM sleep. We conclude that MCH administration into the VLPO and adjacent dorsal lateral preoptic area promotes the generation of NREM sleep.

The melanin-concentrating hormone (MCH) system modulates behaviors associated with psychiatric disorders

Deficits in sensorimotor gating measured by prepulse inhibition (PPI) of the startle have been known as characteristics of patients with schizophrenia and related neuropsychiatric disorders. PPI disruption is thought to rely on the activity of the mesocorticolimbic dopaminergic system and is inhibited by most antipsychotic drugs. These drugs however act also at the nigrostriatal dopaminergic pathway and exert adverse locomotor responses. Finding a way to inhibit the mesocorticolimbic- without affecting the nigrostriatal-dopaminergic pathway may thus be beneficial to antipsychotic therapies. The melanin-concentrating hormone (MCH) system has been shown to modulate dopamine-related responses. Its receptor (MCH1R) is expressed at high levels in the mesocorticolimbic and not in the nigrostriatal dopaminergic pathways. Interestingly a genomic linkage study revealed significant associations between schizophrenia and markers located in the MCH1R gene locus. We hypothesize that the MCH system can selectively modulate the behavior associated with the mesocorticolimbic dopamine pathway. Using mice, we found that central administration of MCH potentiates apomorphine-induced PPI deficits. Using congenic rat lines that differ in their responses to PPI, we found that the rats that are susceptible to apomorphine (APO-SUS rats) and exhibit PPI deficits display higher MCH mRNA expression in the lateral hypothalamic region and that blocking the MCH system reverses their PPI deficits. On the other hand, in mice and rats, activation or inactivation of the MCH system does not affect stereotyped behaviors, dopamine-related responses that depend on the activity of the nigrostriatal pathway. Furthermore MCH does not affect dizocilpine-induced PPI deficit, a glutamate related response. Thus, our data present the MCH system as a regulator of sensorimotor gating, and provide a new rationale to understand the etiologies of schizophrenia and related psychiatric disorders.

Chronic loss of melanin-concentrating hormone affects motivational aspects of feeding in the rat

Current epidemic obesity levels apply great medical and financial pressure to the strenuous economy of obesity-prone cultures, and neuropeptides involved in body weight regulation are regarded as attractive targets for a possible treatment of obesity in humans. The lateral hypothalamus and the nucleus accumbens shell (AcbSh) form a hypothalamic-limbic neuropeptide feeding circuit mediated by Melanin-Concentrating Hormone (MCH). MCH promotes feeding behavior via MCH receptor-1 (MCH1R) in the AcbSh, although this relationship has not been fully characterized. Given the AcbSh mediates reinforcing properties of food, we hypothesized that MCH modulates motivational aspects of feeding.

Here we show that chronic loss of the rat MCH-precursor Pmch decreased food intake predominantly via a reduction in meal size during rat development and reduced high-fat food-reinforced operant responding in adult rats. Moreover, acute AcbSh administration of Neuropeptide-GE and Neuropeptide-EI (NEI), both additional neuropeptides derived from Pmch, or chronic intracerebroventricular infusion of NEI, did not affect feeding behavior in adult pmch^+/+ or pmch^−/− rats. However, acute administration of MCH to the AcbSh of adult pmch^−/− rats elevated feeding behavior towards wild type levels. Finally, adult pmch^−/− rats showed increased ex vivo electrically evoked dopamine release and increased limbic dopamine transporter levels, indicating that chronic loss of Pmch in the rat affects the limbic dopamine system.

Our findings support the MCH-MCH1R system as an amplifier of consummatory behavior, confirming this system as a possible target for the treatment of obesity. We propose that MCH-mediated signaling in the AcbSh positively mediates motivational aspects of feeding behavior. Thereby it provides a crucial signal by which hypothalamic neural circuits control energy balance and guide limbic brain areas to enhance motivational or incentive-related aspects of food consumption.

[Correction of negative influence of long-term hypergastrinemia on gastric acid secretion]

We investigated the influence of long-term diminishing of gastric acid secretion in rats by H(+)-K(+)-ATPase omeprasole on the gastrin blood level and the basal gastric acid secretion. We performed an experimental analysis of possible prophylactic drugs of structural and functional changes in gastric mucosa evoked by hypergastrinemia. It was shown that following 28 days of omeprazole injections the blood gastrin level and the output of basal acid secretion increased by 189.3% and 173.9-283.7%, respectively. It was concluded that an augmentation of the output of basal acid secretion results from the development of parietal cells hyperplasia evoked by trophic action of gastrin. We also show here that agonists of nuclear peroxisome proliferator activator receptors pioglytasone and melanin effectively prevent the changes in gastric acid secretion as an index of morphological changes.

Role of melanin-concentrating hormone in the control of ethanol consumption: Region-specific effects revealed by expression and injection studies

The peptide melanin-concentrating hormone (MCH), produced mainly by cells in the lateral hypothalamus (LH), perifornical area (PF) and zona incerta (ZI), is suggested to have a role in the consumption of rewarding substances, such as ethanol, sucrose and palatable food. However, there is limited information on the specific brain sites where MCH acts to stimulate intake of these rewarding substances and on the feedback effects that their consumption has on the expression of endogenous MCH. The current study investigated MCH in relation to ethanol consumption, in Sprague-Dawley rats. In Experiment 1, chronic consumption of ethanol (from 0.70 to 2.7 g/kg/day) dose-dependently reduced MCH gene expression in the LH. In Experiments 2-4, the opposite effect was observed with acute oral ethanol, which stimulated MCH expression specifically in the LH but not the ZI. In Experiment 5, the effect of MCH injection in brain-cannulated rats on ethanol consumption was examined. Compared to saline, MCH injected in the paraventricular nucleus (PVN) and nucleus accumbens (NAc) selectively stimulated ethanol consumption without affecting food or water intake. In contrast, it reduced ethanol intake when administered into the LH, while having no effect in the ZI. These results demonstrate that voluntary, chronic consumption of ethanol leads to local negative feedback control of MCH expression in the LH. However, with a brief exposure, ethanol stimulates MCH-expressing neurons in this region, which through projections to the feeding-related PVN and reward-related NAc can promote further drinking behavior.

Chronic MCH infusion causes a decrease in energy expenditure and body temperature, and an increase in serum IGF-1 levels in mice

Melanin concentrating hormone (MCH) is an orexigenic peptide secreted from the lateral hypothalamus. Various observations suggest a role for MCH in energy expenditure in transgenic mice; however, the influence of MCH on energy expenditure and body temperature in WT mice was inadequately studied. Therefore, our first goal was to characterize the influence of chronic intracerebroventrical MCH infusion on energy homeostasis in mice. Our second goal was to explore the effect of MCH on the GH-insulin like growth factor 1 (IGF-1) axis in vivo. We have recently published that MCH directly increased GH-secretion from pituitary cells in vitro, suggesting that MCH may exert part of its effects on energy balance via direct pituitary hormone regulation. Mice were centrally infused with MCH for 14 days, resulting in a significant increase in food intake, body weight, fat mass and plasma IGF-1 levels, while decreasing body temperature and energy expenditure. Our data emphasize the role of MCH as a key regulator of energy homeostasis by means of appetite regulation, regulation of energy expenditure, and an integrator of energy balance with the neuroendocrine system regulating pituitary hormone secretion. They also support the notion that MCH may have a physiologic role in GH regulation that may, in turn, contribute to its effect on body weight.

[Experimental study of the neuroprotective properties of the melanin in embryos irradiated during antenatal development]

Daily introduction per os of the exogenous melanin in a doze of weight of 10 mg/kg pregnant female rats of line Wistar on a background continuous irradiations (dose rate of 2.6 mGy/h within 20 days of pregnancy) eliminated deficiency cognitive functions at posterity. On the basis of the received data it is concluded presence radioembryoprotective actions of melanin in the relation neuro embryotoxic effects of small dozes ionizing radiation. Taking into account small toxicity of melanin, the preparation can be perspective for practical application.

[Experimental study of the radioprotective action of melanin on the somatic development during irradiation in the antenatal period of ontogenesis]

Daily introduction per os of the exogenous melanin in a doze of weight of 10 mg/kg pregnant female rats Wistar eliminated the functional deficiency of somatic development revealed at posterity at chronic gamma-irradiation in a doze 1.00-1.25 Gy for all period of pregnancy. The irradiation or introduction melanin antenatal to a phase ontogenesis resulted in stimulation of the immune answer, which was determined at offspring on 3rd week after birth. On the basis of the received data it is concluded presence radioembryoprotective actions melanin in the relation embryotoxic effects of small dozes of ionizing radiation and its participation in regulation immunogenes.

A Randomized, Controlled, Double-Blind Study Evaluating Melanin-Encapsulated Liposomes as a Chromophore for Laser Hair Removal of Blond, White, and Gray Hair

INTRODUCTION

Laser hair removal of blond and white hair is a complicated task with often unsatisfactory results as a result of a lack of laser-absorbing chromophore. In the present study, we investigated if repetitive external application of liposomal melanin (Lipoxome; Dalton Medicare B.V., Zevenbergschen Hoek, The Netherlands) enables removal of blond/white and gray hair with a diode laser.

METHODS

Forty-two areas of blond, gray, or white facial and body hair of 16 patients were treated with a liposomal melanin spray (Lipoxome) and 3 cycles of 800 nm diode laser at intervals of 8 weeks (28-40 J/cm). A control group of 16 patients applied physiological saline spray before diode laser treatment. Hair regrowth was measured 8 weeks after each cycle and additionally 6 months after the last treatment by counting the number of terminal hairs compared with baseline pretreatment values. Complications and treatment outcomes were documented.

RESULTS

Mean regrowth in the liposomal melanin group was 83% after 3 treatment cycles. Six months after therapy, average terminal hair count compared with baseline pretreatment showed 14% reduction. Although significant difference was seen compared with the control group showing a 10% reduction of hair growth after 6 months (P < 0.05), the clinical outcome was disappointing.

CONCLUSIONS

Melanin-encapsulated liposomal spray in combination with diode laser treatment showed significant higher efficacy in the treatment of white and blond hair compared with a control group. However, the clinically observed hair reduction was so weak that additional effort as well as higher costs argues against the application of the tested formulation.

[Psychophysiological development of two generations of female rats chronically exposed to gamma-irradiation during pregnancy in the total dose of 1 Gy and its modification by melanin]

The purpose of the work was to study the embryotoxic action of chronic gamma-irradiation of pregnant female rats (F0) during the first 10 days of pregnancy in the total dose of 1 Gy (mean dose rate of 5.31 mGy/hour) on psychophysiological development of posterity of the first (F1) and the second (F2) generations and its modification by natural pigment melanin (peroral 10 mg/kg once per day during the irradiation). 54 pregnant female Wistar rats were the objects of research were their 180 descendants of the first generation and about 400 descendants of the second generation of maternal and of paternal lines. Psychophysiological development and its correction by melanin estimated on ability to learning with the test of training a conditioned avoidance reflex in the shuttle box. Precise negative action of gamma-irradiation in the aforesaid dose on psychophysiological development of posterity of the first generation is established. At rats of the second generation the inferiority is shown mainly at descendants of maternal line. Application of melanin of natural origin in most cases diminished negative consequences of the irradiation.

Cardiovascular effects of melanin-concentrating hormone

Melanin-concentrating hormone (MCH) is a cyclic 19-amino acid neuropeptide exclusively synthesized in the lateral hypothalamic area (LHA) and the zona incerta (ZI) that has been implicated in the regulation of energy balance. Despite what is known about the orexigenic effect of MCH, whether MCH has distinct cardiovascular and metabolic effects has yet to be determined. Thus, our goal here was to characterize the concurrent cardiovascular, metabolic, and behavioral responses of male rats to chronic intracerebroventricular (icv) infusion of MCH. Male Long-Evans rats were instrumented with telemetry transmitters for measurement of heart rate (HR) and housed in room calorimeters for assessment of food intake and oxygen consumption (VO(2)) at standard lab ambient temperature (23 degrees C) in order to examine physiological responses to chronic infusion of MCH (8 microg/d and 16 microg/d). Our findings provide the first evidence that chronic administration of MCH induces bradycardia and reduced mean arterial pressure, while it did not affect VO(2). A second experiment was performed in which the physiological responses to an acute icv infusion of MCH were observed. The results of experiment 2 indicate that MCH leads to a low HR that is maintained during the first 2 h post-infusion, the time period during which MCH acutely stimulated feeding. Collectively, these findings confirm that MCH may be an important modulator of sympathetic nervous system activity and thus may play a critical role in coordinating normal responses to negative energy balance.

Involvement of specific orexigenic neuropeptides in sweetener-induced overconsumption in rats

Palatability is one of the factors that regulates food and fluid intake and contributes to overconsumption in turn contributing to obesity. To elucidate the brain mechanisms of the palatability-induced ingestion, we explored the roles of six hypothalamic orexigenic neuropeptides, orexin, melanin-concentrating hormone (MCH), neuropeptide Y (NPY), agouti-related protein (AgRP), ghrelin and dynorphin, in the intake of a palatable solution, saccharin. Of the six peptides, intracerebroventricular (i.c.v.) administrations of orexin, MCH and NPY increased the intake of saccharin. Drinking of saccharin in turn elevated the mRNA levels of orexin and NPY, but not MCH. Pre-treatments of naloxone, an opioid antagonist, blocked the orexigenic effects of orexin and NPY. Specific gastric motor responses induced by central orexin-A and NPY are well known, however, MCH did not induce such responses. The i.c.v. administration of orexin-A facilitated gastric emptying. These results suggest that the overconsumption promoted by sweet and palatable tastes is attributed to the activation of orexigenic neuropeptides, such as orexin and NPY, and a downstream opioid system together with enhanced digestive functions.

Melanin-concentrating hormone-1 receptor modulates neuroendocrine, behavioral, and corticolimbic neurochemical stress responses in mice

Repeated exposure to stressful conditions is linked to the etiology of affective disorders. The melanin-concentrating hormone-1 receptor (MCHR1) may be a novel mechanism that is involved in the modulation of stress responses and affective states. The role of MCHR1 in neuroendocrine, behavioral, and neurochemical stress, and anxiety-related responses was examined by monitoring the effects of melanin-concentrating hormone (MCH) and the selective MCHR1 antagonist, GW3430, in inbred C57Bl/6NTac and MCHR1-knockout (KO) and wild-type (WT) mice. Intracerebroventricular injection of MCH increased plasma corticosterone, and produced anxiety-related responses in the elevated plus maze. The selective MCHR1 antagonist, GW3430, blocked the neuroendocrine and behavioral effects of MCH and produced anxiolytic-like effects by itself in animal models of anxiety. Moreover, KO mice had an anxiolytic-like phenotype in behavioral models of anxiety, and GW3430 had anxiolytic-like effects in WT, but not KO mice. Lastly, stressor-evoked acetylcholine release within the prefrontal cortex of inbred and WT mice, but not KO mice, was blocked by GW3430. We show that MCH elicits anxiety-like responses and that the effects of a selective MCHR1 antagonist and the phenotype of KO mice are consistent with anxiolytic-like action. Distinct behavioral, physiological, and neurochemical stress, and anxiety-related responses were selectively modulated by the MCHR1, and these actions may involve corticolimbic regulation of stress responsivity and anxiety.

Central administration of melanin-concentrating hormone increases alcohol and sucrose/quinine intake in rats

BACKGROUND

Alcohol is a caloric compound that can contribute to energy intake. Therefore, peptides that regulate energy balance likely modify the motivation to consume alcohol. Melanin-concentrating hormone (MCH) regulates energy homeostasis and has been implicated in other behaviors that impact alcohol consumption (i.e., anxiety, fluid balance, and reward). We tested the hypothesis that MCH would decrease the motivation to consume alcohol secondarily to reducing anxiety.

METHODS

Rats were trained to drink 10% ethanol or an isocaloric concentration of sucrose with use of a sucrose-fading technique. MCH (1, 5, or 10 microg) or its saline vehicle was administered into the third cerebral ventricle (i3vt), and intake of ethanol or sucrose and chow was assessed for 2 hr. Alcohol-naïve rats were evaluated in an elevated plus maze after i3vt MCH (10 microg), neuropeptide Y, or saline administration.

RESULTS

Contrary to the hypothesis, MCH dose-dependently increased alcohol intake: saline = 0.7 +/- 0.1 g/kg, 1 microg MCH = 1.0 +/- 0.1 g/kg, 5 microg MCH = 1.2 +/- 0.1 g/kg, and 10 microg MCH = 1.8 +/- 0.3 g/kg (p < 0.01), and this was true whether water was simultaneously available or not. MCH also significantly increased sucrose intake (saline = 1.0 +/- 0.3 g/kg, 10 mug MCH = 1.4 +/- 0.5 g/kg; p < 0.05). MCH had no effect on time spent in the open arms (54.3 +/- 11.5 sec) relative to saline (58.2 +/- 23.8 sec), whereas neuropeptide Y, a known anxiolytic, increased time spent on the open arms (119.2 +/- 22 sec, p < 0.05).

CONCLUSIONS

We conclude that MCH nonspecifically increases ingestive behavior. Furthermore, MCH had no apparent effect on anxiety. The ability of MCH to increase alcohol and/or sucrose intake may be explained by the effect of MCH on energy balance and/or reward processes.

Antiobesity effect of a melanin-concentrating hormone 1 receptor antagonist in diet-induced obese mice

Melanin-concentrating hormone (MCH) is a cyclic orexigenic peptide expressed in the lateral hypothalamus, which plays an important role in regulating energy balance. To elucidate the physiological role of MCH in obesity development, the present study examined the effect of a selective MCH1 receptor (MCH1R) antagonist in the diet-induced obesity mouse model. The MCH1R antagonist has high affinity and selectivity for MCH-1R and potently inhibits intracerebroventricularly injected MCH-induced food intake in Sprague Dawley rats. Chronic intracerebroventricular infusion of the MCH1R antagonist (7.5 microg/d) completely suppressed body weight gain in diet-induced obese mice during the treatment periods and significantly decreased cumulative food intake, by 14%. Carcass analysis showed that the MCH1R antagonist resulted in a selective decrease of body fat in the diet-induced obese mice. In addition, the MCH1R antagonist ameliorated the obesity-related hypercholesterolemia, hyperinsulinemia, hyperglycemia, and hyperleptinemia. These results indicate that MCH has a major role in the development of diet-induced obesity in mice and that a MCH1R antagonist might be a useful candidate as an antiobesity agent.

Melanin-concentrating hormone enhances sucrose intake

Melanin-concentrating hormone (MCH) is known to be an important regulator for feeding and energy balance. MCH was recently reported to stimulate water intake independent of food intake. The purpose of the present study is to examine the dipsogenic response of MCH with special emphasis on sweetened beverages, the preference for which is well documented in diabetic animals. Our results showed that intracerebroventricular injection of MCH acutely increased food as well as water intake. Human (h)MCH and salmon (s)MCH increased water intake independent of food intake, which was not suppressed by angiotensin antagonists. hMCH and sMCH significantly increased both sucrose solution and food intake; on the other hand, agouti-related protein (AgRP) stimulated food but not sucrose intake when provided simultaneously. MCH-treated rats significantly increased the ingestion of sucrose and glucose solution, but not of saccharin, indicating that MCH-induced dipsogenic response is more related to caloric content than sweet taste per se. Significant correlation was observed between the sucrose intake and the mRNA expression of MCH and MCHR1 in normal rats. These results indicate that MCH may be an important regulator of sugar intake in normal as well as in obese diabetic animals.

The role of previous exposure in the appetitive and consummatory effects of orexigenic neuropeptides

The ingestion of foods is comprised of two distinct phases of behavior: appetitive and consummatory. While most food intake paradigms include both phases, the intraoral intake test emphasizes the stereotyped consummatory-phase by infusing a liquid food directly into the oral cavity. Several hypothalamic peptides have been shown to increase intake of chow in standard food intake paradigms and the current experiments sought to test whether these peptides would increase food intake in the intraoral intake paradigm. NPY, melanin-concentrating hormone (MCH) and orexin-A were infused into the third ventricle (i3vt) in a counterbalanced latin-square design just prior to rats getting 0.1M sucrose solution infused via indwelling intraoral catheters and compared it to intake on bottle tests with access to the same sucrose solution. On the first day, each peptide increased intraoral intake relative to saline in the between-subjects comparison. Moreover, intake of sucrose following i3vt saline increased as a function of training. By the final day of the experiment, rats receiving saline consumed as much sucrose as rats receiving NPY, MCH, or orexin-A. This finding was conceptually replicated in the second experiment in which rats drank sucrose freely from a bottle on the home cage. A third experiment directly assessed the role of previous exposure in the sucrose intake induced by NPY. Those results confirm that repeated exposure to sucrose increases baseline intake and attenuates the hyperphagic effect of NPY. These results are consistent with two conclusions: (1) NPY, MCH, and orexin-A increase both appetitive and consummatory-phase ingestive behaviors on initial exposures; (2) repeated training interacts with the effects of these orexigenic peptides.

Intracerebroventricular melanin-concentrating hormone stimulates food intake in sheep

Melanin-concentrating hormone (MCH) stimulates feeding when injected intracerebroventricularly (ICV) in rats. At present it is not clear whether the function of MCH is similar in ruminants, which are species with a continuous delivery of nutrients. Therefore the current investigation sought to determine the role of MCH in sheep. In the first experiment, six, castrate male sheep were satiated and received one of four treatments [saline, 0.1, or 1.0 nmol/kg MCH, and NPY (0.1 nmol/kg)] injected ICV over 30s, then infused ICV for 6 h ( approximately 500 microl/h). Food intake was measured for 2 h before and at 2, 4, 6, 8, 12 and 24 h. In this experiment, feed intake was increased (P<or=0.05) in NPY treated sheep only. In the second experiment, the same sheep were fed to satiety and then randomized to receive one of six treatments [saline and either 0.1, 1.0 or 5.0 nmol/kg MCH, 0.1 nmol/kg NPY, or MCH+NPY (0.1 nmol/kg)] injected ICV over 30 s. Food intake was measured for 2 h before and at 2, 4, 6, 8, 12, and 24 h after ICV injection. All doses of MCH as well as NPY resulted in greater (P<or=0.05) food intake than saline. In order to determine whether MCH expression was regulated by fasting, brains from fed and 3-day fasted sheep were fixed in situ, sectioned in the coronal plane, and subjected to dual-label immunohistochemistry using Fos as a marker for neuronal activity. Nutritional state (fed or fasted) did not alter Fos expression in MCH neurons. Finally, using real time PCR, MCH mRNA was unchanged by fasting. In this study we found bolus ICV MCH to be a potent stimulus to food intake in sheep, but MCH was not regulated by fasting.

Characterization of MCH-mediated obesity in mice

Melanin-concentrating hormone (MCH) is a cyclic orexigenic peptide expressed in the lateral hypothalamus. Recently, we demonstrated that chronic intracerebroventricular infusion of MCH induced obesity accompanied by sustained hyperphagia in mice. Here, we analyzed the mechanism of MCH-induced obesity by comparing animals fed ad libitum with pair-fed and control animals. Chronic infusion of MCH significantly increased food intake, body weight, white adipose tissue (WAT) mass, and liver mass in ad libitum-fed mice on a moderately high-fat diet. In addition, a significant increase in lipogenic activity was observed in the WAT of the ad libitum-fed group. Although body weight gain was marginal in the pair-fed group, MCH infusion clearly enhanced the lipogenic activity in liver and WAT. Plasma leptin levels were also increased in the pair-fed group. Furthermore, MCH infusion significantly reduced rectal temperatures in the pair-fed group. In support of these findings, mRNA expression of uncoupling protein-1, acyl-CoA oxidase, and carnitine palmitoyltransferase I, which are key molecules involved in thermogenesis and fatty acid oxidation, were reduced in the brown adipose tissue (BAT) of the pair-fed group, suggesting that MCH infusion might reduce BAT functions. We conclude that the activation of MCH neuronal pathways stimulated adiposity, in part resulting from increased lipogenesis in liver and WAT and reduced energy expenditure in BAT. These findings confirm that modulation of energy homeostasis by MCH may play a critical role in the development of obesity.

Intraventricular melanin-concentrating hormone stimulates water intake independent of food intake

The lateral hypothalamus (LH) has a critical role in the control of feeding and drinking. Melanin-concentrating hormone (MCH) is an orexigenic peptidergic neurotransmitter produced primarily in the LH, and agouti-related protein (AgRP) is an orexigenic peptidergic neurotransmitter produced exclusively in the arcuate (ARC), an area that innervates the LH. We assessed drinking and eating after third ventricular (i3vt) administration of MCH and AgRP. MCH (2.5, 5, and 10 micro g i3vt) significantly increased food as well as water intake over 4 h when administered during either the light or the dark portion of the day-night cycle. When MCH (5 micro g) was administered to rats with access to water but no food, they drank significantly more water than when given the vehicle. AgRP (7 micro g i3vt), on the other hand, increased water intake but only in proportion to food intake during the dark and the light, and water intake was not increased after i3vt AgRP in the absence of food. Hence, in contrast to AgRP, MCH elicits increased water intake independent of food intake. These results are consistent with historical data linking activity of the LH with water as well as food intake.

Protection of tea melanin on hydrazine-induced liver injury

The protective activity of melanin derived from tea (MDFT) was studied using hydrazine as a DNA-reactive chemical agent. Intra-peritoneal administration of MDFT at the doses of 5 or 20 mg/kg dose-dependently prevented liver toxicity induced by hydrazine in rats. It normalized rises in serum alanine transferase activity and a decrease in the glutathione level in the liver. It also reduced the hepatic malondialdehyde concentration. Monitoring the intensity of chemiluminescence showed that MDFT could prevent the production of free radicals that are generated owing to metabolic transformation of hydrazine. It also prevented the formation 8-hydroxy-deoxyguanosine (8-OH-dG) DNA adducts. The results obtained in vivo and in vitro suggest that MDFT confers marked protection of the liver against hydrazine-induced oxidative toxicity.

Effects of agouti-related protein, orexin and melanin-concentrating hormone on oxygen consumption in mice

Neuropeptides in the hypothalamus play a pivotal role in the regulation of energy balance. Agouti-related protein (AGRP), orexin and melanin-concentrating hormone (MCH) have been identified in the hypothalamus as orexigenic peptides. This study was undertaken to investigate the effects of AGRP, orexin and MCH on oxygen consumption. Oxygen consumption was determined by an O2/CO2 metabolism measuring system at 22 degrees C. Mice were kept unrestrained in the chamber without food or water during the light cycle, and the oxygen consumption was measured for 2 h after intra-cerebroventricular (ICV) administration. ICV administered AGRP (1 nmol/mouse) significantly decreased oxygen consumption compared to ACSF-treated controls. Orexin (1 nmol/mouse) significantly increased oxygen consumption, while MCH (1 nmol/mouse) had no significant effect compared to ACSF-treated controls. These results suggest that AGRP, orexin and MCH might have different effects on energy expenditure, thereby regulating appetite and body weight.

Acute and chronic administration of melanin-concentrating hormone enhances food intake and body weight in Wistar and Sprague-Dawley rats

AIM

Although melanin-concentrating hormone (MCH) is believed to be an important regulator of feeding behavior, both its acute and chronic effects on food intake as well as its interaction with other brain peptides involved in the control of appetite remain unclear. Therefore, the acute effects of MCH on food intake and the chronic effect of MCH on food intake and the gene expression of various hypothalamic peptides involved in the control of appetite were studied in rats.

METHODS AND RESULTS

Either the acute or the continuous intraventricular infusion of MCH for 12 days stimulated feeding in both Wistar or Sprague-Dawley rats. Removal of the hypothalamus at the end of the chronic infusion studies allowed measurement of the expression of mRNAs encoding for MCH, neuropeptide Y (NPY), orexin, agouti gene-related peptide, cocaine and amphetamine-related transcript and neurotensin-neuropeptides involved in the control of appetite. Chronic intraventricular infusion of MCH activated only NPY mRNA synthesis in Sprague-Dawley rats. The increase in food intake in response to MCH in Sprague-Dawley rats did not appear to be due to the release of NPY since combination studies demonstrated consistently additive effects of the two peptides on food intake at maximum or near maximum doses.

CONCLUSIONS

These results strongly suggest that MCH is an orexigenic peptide involved in the control of both short- and long term food intake in satiated rats and further indicate that the MCH pathway is a possible target for the control of food intake and obesity.

Synthetic neuromelanin is toxic to dopaminergic cell cultures

In the present study, primary cultures of mesencephalic dopaminergic cells were exposed to synthetic dopamine neuromelanin (NM) for 48 hrs at concentrations of 0, 1, 10, 20, 50 and 100 microg NM/ml medium. Differently prepared synthetic NM with or without incorporated iron and NM oxidatively damaged by hydrogen peroxide were used. All NMs affected cellular structures e.g. as swelling of neural processes, rounding of cells, and occasional inclusion of neuromelanin particles. Cell numbers were uniformly and dose dependently reduced. Exposure to MPP(+) and ferric iron led to cytotoxic changes which could be further aggravated by oxidatively damaged NM, suggesting cytotoxicity of soluble compounds of NM in predamaged neurons.

The effect of leptin on luteinizing hormone release is exerted in the zona incerta and mediated by melanin-concentrating hormone

The adipose hormone, leptin, not only restrains appetite, but also influences energy expenditure. One such influence is to promote sexual maturation and fertility. The neuromodulatory circuits that mediate this effect are not well known but the present study suggests that one mediator could be melanin-concentrating hormone (MCH). We show that the long-form receptor (Ob-Rb) is expressed in the zona incerta of the rat and that administration of leptin (both 0.5 microg and 1.0 microg/side) into this area of ovariectomized, oestrogen-primed rats stimulated the release of luteinizing hormone (LH) within 1 h, the effect enduring for a further 1 h. Injections of leptin into the arcuate nucleus induced a smaller, transient rise in LH while injections into the paraventricular and ventromedial nuclei were without effect. MCH neurones are present in the zona incerta and administration of this hormone into the medial preoptic area (mPOA) stimulates LH release, therefore we investigated the possibility that MCH might mediate this effect of leptin. An injection of MCH antiserum into mPOA prevented the rise in LH normally induced by leptin injected into the zona incerta. In addition, melanocortin receptor antagonists ([D-Arg8]ACTH(4-10) and [Ala6]ACTH(4-10)), previously shown to inhibit the stimulatory effect of MCH on LH release, also inhibited the effect of leptin. We propose that one route by which leptin may promote reproductive activity is by enhancing MCH release from fibres within the mPOA. Speculative mechanisms for the action of MCH include the following possibilities: MCH may be acting on the specific MCH receptor which in turn interacts with a melanocortin or melanocortin-like receptor; MCH may bind directly to one of the melanocortin receptors; or melanocortin antagonists may interact with the MCH receptor.

Intracerebroventricular injection of mammalian motilin, melanin-concentrating hormone or galanin does not stimulate food intake in neonatal chicks

1. Several neural peptides are known to stimulate feeding behaviour in mammalian species. The aim of this study was to elucidate whether central injection of mammalian motilin, melanin-concentrating hormone (MCH) or galanin stimulates feeding in the neonatal chick. 2. None of the peptides applied here enhanced the food intake of the chick. 3. It is suggested that motilin, MCH and galanin, at least those of mammalian origin, may not regulate feeding in neonatal chicks, when administered to the central nervous system.

Cellular migration into neural retina following implantation of melanin granules in the subretinal space

BACKGROUND

In some retinal diseases and following transplantation of retinal pigment epithelium (RPE), melanin granules are liberated to the subretinal space. Our aim was to investigate the cellular response to implanted extracellular melanin.

METHODS

After pars plana vitrectomy, 17 albino rabbits received a suspension of melanin granules in the subretinal space. Postoperative examination included ophthalmoscopy, color fundus photography, histology using monoclonal antibodies identifying RPE cells (AE1/3), macrophages (RAM 11), B-lymphocytes (CD20) and T-lymphocytes (CD45), and electron microscopy. The follow-up time was 2 weeks, 4 weeks and 6 months.

RESULTS

On fundus photographs, the layer of melanin showed focal attenuation with lighter areas at 6 months. Melanin granules were phagocytosed by RPE cells and macrophages at 2 weeks, as identified by monoclonal antibodies. In areas where an abundance of melanin was present, multilayers of macrophages were seen associated with considerable photoreceptor damage. Pigment-laden cells invaded the neural retina. The cellular infiltration of the retina was focal, and when it involved the outer nuclear layer the photoreceptor damage was severe. Electron microscopy demonstrated the presence of melanosomes intracellularly in Müller glia. The process of phagocytosis and removal of melanin granules from the subretinal space was slow and not completed at 6 months.

CONCLUSION

Our experiments show that implantation of melanin granules in the subretinal space of albino rabbits may induce a considerable phagocytic cellular response featuring the host's RPE, macrophages and glial cells. The migration of pigment-laden cells into the neural retina was associated with focal photoreceptor damage.

Intracerebroventricular administration of melanin-concentrating hormone suppresses pulsatile luteinizing hormone release in the female rat

Melanin-concentrating hormone (MCH) has been reported to be involved in the regulation of feeding behaviour in rats and mice. Because many neuropeptides that influence ingestive behaviour also regulate reproductive function, the present study was designed to determine if central administration of MCH changes pulsatile secretion of luteinizing hormone (LH) in the rats. Wistar-Imamichi strain female rats were ovariectomized and implanted with oestradiol to produce a moderate inhibitory feedback effect on LH release. The effects of i. c.v. injections of MCH on LH release were examined in freely moving animals. Blood samples were collected every 6 min for 3 h through an indwelling cannula. After 1 h of sampling, MCH (0.1, 1 or 10 microg/animal) or vehicle (saline) was injected into the third cerebroventricle. Because MCH is also reported to affect the hypothalamo-pituitary-adrenal (HPA) axis, which in turn, can influence reproductive function, plasma corticosterone concentrations were determined in the same animals at 30-min intervals during the first and last hours and every 12 min during the second hour of the 3-h sampling period. When expressed as per cent changes, mean plasma LH concentrations after MCH administration were significantly lower in the animals injected with all doses of the peptide compared with vehicle-treated animals; LH pulse frequency was significantly lowered by 1 microg of MCH. Per cent changes in mean plasma corticosterone levels were not significantly affected by MCH administration. These results in oestradiol-treated ovariectomized rats indicate that central MCH is capable of inhibiting pulsatile LH secretion. We have previously shown that 48-h fasting suppresses pulsatile LH release in the presence of oestrogen. Take together, these results raise the possibility that MCH could play a role in mediating the suppression of LH secretion during periods of reduced nutrition.

Melanin-concentrating hormone, melanocortin receptors and regulation of luteinizing hormone release

Melanin-concentrating hormone (MCH) is a neuropeptide, identified by its ability to either mimic or antagonize the melanin-dispersing action of alpha-melanocyte stimulating hormone (alphaMSH) on skin melanophores. MCH and alphaMSH also have antagonistic actions in the brain affecting feeding behaviour, aggression, anxiety, arousal and reproductive function through the release of luteinizing hormone (LH). It is not clear, however, how they exert their opposite effects in the central nervous system (CNS). One possibility is that they act via a common receptor. In this study we have examined the effect of a number of MC receptor antagonists, with relative selectivity for the MC3, 4 and 5 subtypes, on the actions of MCH on LH release. We confirmed that bilateral administration of MCH (100 and 200 ng/side) into the medial preoptic area of oestrogen-primed (oestradiol benzoate 5 microgram) ovariectomized anaesthetized rats, stimulated the release of LH. This effect was blocked by the concomitant administration into the medial preoptic area of the MC4/5 antagonist ([D-Arg8]ACTH(4-10) and the MC3/5 antagonist ([Ala6]ACTH(4-10)-both at 500 ng/side-but not by the MC3/4 antagonist, SHU9119 (200 ng/side). Furthermore, the MC3 agonist [Nle3]-gamma2 MSH failed to affect LH release. These results indicate that the MC3 and MC4 receptors are not involved in mediating the action of MCH but are consistent with an action via the MC5 subtype. Preputial glands, which express MC5 receptors, were also stimulated by MCH which is in keeping with this idea. In HEK293 cells transfected with the MC5 receptor MCH increased the production of IP3. However, it was much less potent than alphaMSH and unlike alphaMSH, had no effect on the production of cAMP. MCH (10-10 to 10-5 M) also failed to displace I125NDP-MSH from cells transfected with MC5 receptors indicating that it was not acting as a competitive antagonist and its binding site was distinct from that of alphaMSH. Thus while MCH may function as an agonist at the MC5 receptor, its stimulation of LH release is more likely to be mediated via a specific MCH receptor that has common properties with the MC5 receptor.

Melanin-concentrating hormone (MCH) modifies memory retention in rats

The purpose of the present study was to evaluate the possible effect of melanin-concentrating hormone (MCH) on learning and memory by using the one-trial step-down inhibitory avoidance test in rats. The peptide was infused into hippocampus, amygdala, and entorhinal cortex. MCH caused retrograde facilitation when given at 0 or 4 h post-training into hippocampus, but only at 0 h into amygdala. From these results, it seems that MCH modulates memory early after training by acting on both the amygdala and hippocampus and, 4 h after training, on the hippocampus.

Response to novelty after i.c.v. injection of melanin-concentrating hormone (MCH) in rats

Some behavioral response of rats to spatial novelty after i.c.v. administration of melanin-concentrating hormone (MCH) were evaluated. To this purpose, an open-field test was used, as well as an elevated plus-maze to study the possible anxiolytic effect of this peptide. In the open field, the frequency of exploratory components (locomotion and rearing) increased after MCH administration in comparison to controls. Moreover, in the plus-maze, MCH increased the number of entries into the open arms as well as the time spent on them, whereas no changes in the number of entries onto the closed arms were found. The data indicate that MCH exerts an anxiolytic effect, and suggests a physiological role for this.

Functional interactions between melanin-concentrating hormone, neuropeptide Y, and anorectic neuropeptides in the rat hypothalamus

A growing body of evidence indicates that a number of peptides expressed in the mammalian hypothalamus are involved in the regulation of food intake and energy balance. Among these, melanin-concentrating hormone (MCH) and neuropeptide Y (NPY) are potent appetite stimulants, whereas alpha-melanocyte-stimulating hormone (alpha-MSH), neurotensin, and glucagon-like peptide (GLP)-1(7-36) amide have appetite-suppressing properties. However, the functional interactions between pathways involving these neuropeptides remain incompletely understood. In the current study, we describe the functional interactions between orexigenic (appetite-stimulating: MCH and NPY) and anorectic (appetite-suppressing: alpha-MSH, neurotensin, and GLP-1) peptides after intracerebroventricular (i.c.v.) administration in the rat. The i.c.v. administration of GLP-1 completely prevents the orexigenic effects of both MCH and NPY. However, i.c.v. administration of alpha-MSH prevents only the orexigenic effect of MCH, as we have previously shown, but does not prevent the effect of NPY on food intake. Similarly, i.c.v. administration of neurotensin prevents only the orexigenic effect of MCH, but does not prevent the appetite-stimulating effect of NPY. Thus, our study suggests that the functional interactions between these neuropeptides are specific, although the underlying mechanisms are as yet unexplored.

Topical liposome targeting of dyes, melanins, genes, and proteins selectively to hair follicles

For therapeutic and cosmetic modification of hair, we have developed a hair-follicle-selective macromolecule and small molecule targeting system with topical application of phosphatidylcholine-based liposomes. Liposome-entrapped melanins, proteins, genes, and small-molecules have been selectively targeted to the hair follicle and hair shafts of mice. Liposomal delivery of these molecules is time dependent. Negligible amounts of delivered molecules enter the dermis, epidermis, or bloodstream thereby demonstrating selective follicle delivery. Naked molecules are trapped in the stratum corneum and are unable to enter the follicle. The potential of the hair-follicle liposome delivery system for therapeutic use for hair disease as well as for cosmesis has been demonstrated in 3-dimensional histoculture of hair-growing skin and mouse in vivo models. Topical liposome selective delivery to hair follicles has demonstrated the ability to color hair with melanin, the delivery of the active lac-Z gene to hair matrix cells and delivery of proteins as well. Liposome-targeting of molecules to hair follicles has also been achieved in human scalp in histoculture. Liposomes thus have high potential in selective hair follicle targeting of large and small molecules, including genes, opening the field of gene therapy and other molecular therapy of the hair process to restore hair growth, physiologically restore or alter hair pigment, and to prevent or accelerate hair loss.

Topical liposome delivery of molecules to hair follicles in mice

The hair cycle consisting of growing and resting phases, is subject to widespread disease such as androgenic alopecia or loss of pigment which are in need of effective, targeted therapeutics. In order to develop a hair-follicle delivery system we demonstrate here that phosphatidylcholine liposomes entrapping either the fluorescent dye calcein or the pigment melanin can deliver these molecules into the hair follicle and hair shafts of mice when applied topically. Liposomal delivery of these molecules is time dependent. Negligible amounts of delivered molecules enter the dermis, epidermis or blood stream thereby demonstrating the enrichment of follicle delivery. Naked calcein and melanin are trapped in the stratum corneum and are unable to enter the follicle. The potential of the hair-follicle liposome delivery system for therapeutic use for hair disease is discussed.

alpha-Melanocyte-stimulating hormone (alpha-MSH) and melanin-concentrating hormone (MCH) modify monoaminergic levels in the preoptic area of the rat

The effect of perfusion of melanin-concentrating hormone (MCH) or alpha-melanocyte-stimulating hormone (alpha-MSH) (100 ng/microliter) in the ventromedial nucleus (VMN) or medial preoptic area (MPOA) on monoaminergic levels of female rats was measured using microdialysis and HPLC-electrochemical detection. In the MPOA, alpha-MSH raised 5-HIAA concentration, whereas MCH reduced both 5-HT and 5-HIAA. Neither peptide had any effect in the VMN. The opposite effects of the peptides on the serotonergic system might be responsible for their antagonistic or opposite actions previously reported on several CNS functions. Dopamine may mediate the similar effects of the two peptides, because alpha-MSH inhibits dopaminergic release in the MPOA (but not VMN) and MCH tends to follow the same pattern.

Melanin-concentrating hormone (MCH) antagonizes the effects of alpha-MSH and neuropeptide E-I on grooming and locomotor activities in the rat

The intraventricular (i.c.v.) administration of the neuropeptide melanocyte stimulating hormone (alpha-MSH) is known to elicit a series of behaviors in the rat which include excessive grooming and other motor activities. In bony fish, the pigmentary effects of alpha-MSH can be antagonized by the neuropeptide melanin-concentrating hormone (MCH). We therefore examined whether MCH or its sister peptide neuro-peptide E-I (NEI), derived from the same precursor molecule, would modulate the effect of alpha-MSH on grooming and motor activity in the rat, or perhaps elicit some responses of their own. Rats were injected i.c.v. with either artificial cerebrospinal fluid, alpha-MSH, MCH, NEI, or with two peptides together, and behavioral responses were monitored over the next 65 min. The i.c.v. injection of 1 microgram MSH significantly enhanced grooming behavior. NEI at the same dose increased grooming, rearing, and locomotor activities. MCH alone had no behavioral effects but it annulled the behavioral responses induced by either alpha-MSH or NEI. alpha-MSH also antagonized the locomotor and rearing behavior induced by NEI. The physiological significance of these observations is discussed.

A role for melanin-concentrating hormone in the central regulation of feeding behaviour

The hypothalamus plays a central role in the integrated regulation of energy homeostasis and body weight, and a number of hypothalamic neuropeptides, such as neuropeptide Y (ref. 1), galanin, CRH (ref. 3) and GLP-1 (ref. 4), have been implicated in the mediation of these effects. To discover new hypothalmic peptides involved in the regulation of body weight, we used differential display polymerase chain reaction to identify messenger RNAs that are differentially expressed in the hypothalamus of ob/+ compared with ob/ob C57B1/6J mice. We show here that one mRNA that is overexpressed in the hypothalamus of ob/ob mice encodes the neuropeptide melanin-concentrating hormone (MCH). Fasting further increased expression of MCH mRNA in both normal and obese animals. Neurons containing MCH are located in the zona incerta and in the lateral hypothalamus. These areas are involved in regulation of ingestive behaviour, but the role of MCH in mammalian physiology is unknown. To determine whether MCH is involved in the regulation of feeding, we injected MCH into the lateral ventricles of rats and found that their food consumption increased. These findings suggest that MCH participates in the hypothalamic regulation of body weight.

Behavioral effects of alpha-MSH and MCH after central administration in the female rat

The behavioral effects of alpha-MSH, MCH, and alpha-MSH + MCH were investigated in the ventromedial nucleus (VMN) and medial preoptic area (MPOA) (bilateral, 100 ng in 0.5 microliter). Infusion of alpha-MSH into the VMN increased aggressive behavior; in the MPOA it reduced exploration and increased anxiety. In both areas it stimulated sexual behavior. MCH also stimulated sexual behavior in the MPOA and VMN and had an anxiogenic effect in the MPOA. The effect of alpha-MSH on aggression and exploration was antagonized by MCH. When given together, the two peptides were mutually antagonistic on anxiety. This study indicates that MCH has central nervous system effects and may be a partial alpha-MSH agonist.

[Effect of enomelanin on lipid peroxidation and the glutathione system in rat lung tissue exposed to NO2]

Effect of preliminary intraperitoneal injection on the state of the glutathione system and lipid peroxidation intensity in the lungs of rats subjected to NO2 has been studient. This compound is shown to decrease significantly all lipid peroxidation processes and to inhibit completely glutathion oxidation. These effects are supposed to be a result not only of antioxidant properties of enomelanin, but also of its ability to promote a decrease in the activity of glutathione-depending enzymes subjected to NO2.

Influence of salmon melanin concentrating hormone on vasopressin analogue (dDAVP) activity and sodium transport in frog skin

Salmon melanin-concentrating hormone (sMCH) is a peptide known to regulate skin pigmentation both in fish and tetrapod (frog and lizard). To evaluate the influence of sMCH on ionic transport in frog skin, standard voltage-clamp technique for the measurement of transepithelial short-circuit current (ISC) reflecting net sodium transport was used. It was found that sMCH alone applied at concentrations of 0.5; 5 or 10 mumol/l failed to influence ISC. The application of 5 mumol/l of sMCH, however, inhibited ISC across the skin stimulated by a synthetic analogue of vasopressin (dDAVP), whereas no influence on natriferic effect of 1 mumol/l forskolin by the studied peptide was observed. The results indicate that cAMP was presumably not involved in the mediation of sMCH action in frog skin. We assume that the interaction of sMCH with the basolateral membrane could lead either (1) to changes of membrane structure including organization of its lipid surrounding or (2) to modification of AVP/dDAVP receptor activity and binding capacity. The nature of these interactions and change(s) in cell membrane and signal(s) which trigger processes responsible for the inhibitory effect of sMCH on dDAVP-stimulated frog skin sodium transport remains to be elucidated.

[Activity of the antioxidant system of rat liver in benzidine poisoning and administration of enomelanin]

It has been shown that benzidine administered in vivo attenuates the protective effect of the antioxidant system manifested as a reduction of the total antioxidant activity of rat liver cytosol and decreasing activities of superoxide dismutase and catalase. Enomelanin promotes the reconstitution of the superoxide dismutase activity. The data obtained suggest that the toxic effect of benzidine may be due to disturbances in the antioxidant protective mechanisms of liver cells responsible for the control over the free radical processes occurring in those cells.