Retinal dopamine

Melatonin is an important player in the regulation of many physiological functions within the body and in the retina. Melatonin synthesis in the retina primarily occurs during the night and its levels are low during the day. Retinal melatonin is primarily synthesized by the photoreceptors, but whether the synthesis occurs in the rods and/or cones is still unclear. Melatonin exerts its influence by binding to G protein-coupled receptors named melatonin receptor type 1 (MT1 ) and type 2 (MT2 ). MT1 and MT2 receptors activate a wide variety of signaling pathways and both receptors are present in the vertebrate photoreceptors where they may form MT1 /MT2 heteromers (MT1/2h )...

The retina has been considered a "window to the brain" and shares similar innervation by the dopaminergic system with the cortex in terms of an unequal distribution of D1 and D2 receptors. Here, we provide a comprehensive overview that Optical Coherence Tomography (OCT), a non-invasive imaging technique, which provides an "in vivo" representation of the retina, shows promise to be used as a surrogate marker of dopaminergic neuromodulation in cognition. Overall, most evidence supports reduced retinal thickness in individuals with dopaminergic dysregulation (e...

BACKGROUND: Acute retinal pigment epitheliitis (ARPE) is a rare, idiopathic and self-limiting disease. The article aims to present ARPE in a patient using D2 dopamine receptor agonists for the treatment of hyperprolactinemia. CASE PRESENTATION: A 28-year-old female during hyperprolactinaemia treatment suffered from a dyschromatopsia and a central visual field defect in the left eye. She noticed a deterioration of vision and discontinued the cabergoline administration...

The intricate functionality of the vertebrate retina relies on the interplay between neurotransmitter activity and calcium (Ca2+ ) dynamics, offering important insights into developmental processes, physiological functioning, and disease progression. Neurotransmitters orchestrate cellular processes to shape the behavior of the retina under diverse circumstances. Despite research to elucidate the roles of individual neurotransmitters in the visual system, there remains a gap in our understanding of the holistic integration of their interplay with Ca2+ dynamics in the broader context of neuronal development, health, and disease...

Basal electroretinogram (ERG) oscillations have shown predictive value for modifiable risk factors for type 2 diabetes. However, their origin remains unknown. Here, we seek to establish the pharmacological profile of the low delta-like (δ1) wave in the mouse because it shows light sensitivity in the form of a decreased peak frequency upon photopic exposure. Applying neuropharmacological drugs by intravitreal injection, we eliminated the δ1 wave using lidocaine or by blocking all chemical and electrical synapses...

Neurodegenerative diseases are an increasingly common group of diseases that occur late in life with a significant impact on personal, family, and economic life. Among these, Alzheimer's disease (AD) and Parkinson's disease (PD) are the major disorders that lead to mild to severe cognitive and physical impairment and dementia. Interestingly, those diseases may show onset of prodromal symptoms early after middle age. Commonly, the evaluation of these neurodegenerative diseases is based on the detection of biomarkers, where functional and structural magnetic resonance imaging (MRI) have shown a central role in revealing early or prodromal phases, although it can be expensive, time-consuming, and not always available...

BACKGROUND: Myopia, commonly known as near-sightedness, has emerged as a global epidemic, impacting almost one in three individuals across the world. The increasing prevalence of myopia during early childhood has heightened the risk of developing high myopia and related sight-threatening eye conditions in adulthood. This surge in myopia rates, occurring within a relatively stable genetic framework, underscores the profound influence of environmental and lifestyle factors on this condition...

PURPOSE: Members of the secretin/glucagon family have diverse roles in retinal physiological and pathological conditions. Out of them, glucagon has been associated with eye growth regulation and image defocus signaling in the eye, both processes central in myopia induction. On the other hand, dopamine is perhaps the most studied molecule in myopia and has been proposed as fundamental in myopia pathogenesis. However, glucagonergic activity in the mammalian retina and its possible link with dopaminergic signaling remain unknown...

BACKGROUND: Loss of substantia nigra dopaminergic cells and alpha-synuclein (α-syn)-rich intraneuronal deposits within the central nervous system are key hallmarks of Parkinson's disease (PD). Levodopa (L-DOPA) is the current gold-standard treatment for PD. This study aimed to evaluate in vivo retinal changes in a transgenic PD model of α-syn overexpression and the effect of acute levodopa (L-DOPA) treatment. METHODS: Anaesthetised 6-month-old mice expressing human A53T alpha-synuclein (HOM) and wildtype (WT) control littermates were intraperitoneally given 20 mg/kg L-DOPA (50 mg levodopa, 2...

BACKGROUND: Alcohol is the most widely consumed addictive substance around the world and have deleterious effect on the central nervous system. Alcohol consumption affect the balance of certain neurotransmitters like GABA, glutamate and dopamine. The retina provides an easy means of investigating dysfunctions of synaptic transmission in the brain. The purpose of this study is to assess the impact of alcohol consumption on retinal function using pattern electroretinogram (PERG) and flash electroretinogram (fERG)...

The association between pupillary responses to repeated stimuli and adult refractive error has been previously demonstrated. This study evaluated whether this association exists in children and if it varies by season. Fifty children aged 8-17 years (average: 11.55 ± 2.75 years, 31 females) with refractive error between + 1.51 and - 5.69 diopters (non-cycloplegic) participated (n = 27 in summer, and n = 23 in winter). The RAPDx pupilometer measured pupil sizes while stimuli oscillated between colored light and dark at 0...

Neuromodulation in the retina is crucial for effective processing of retinal signal at different levels of illuminance. Intrinsically photosensitive retinal ganglion cells (ipRGCs), the neurons that drive non-image forming visual functions, express a variety of neuromodulatory receptors that tune intrinsic excitability as well as synaptic inputs. Past research has examined actions of neuromodulators on light responsiveness of ipRGCs, but less is known about how neuromodulation affects synaptic currents in ipRGCs...

A new study shows that retinal ganglion cell neurons can optimize local oxygen and nutrient availability at a key developmental timepoint in a surprising manner: by generating a temporally restricted burst of dopamine that patterns their dedicated vasculature.

Whereas excitation and inhibition of neurons are well understood, it is clear that neuromodulatory influences on neurons and their synapses play a major role in shaping neural activity in the brain. Memory and learning, emotional and other complex behaviors, as well as cognitive disorders have all been related to neuromodulatory mechanisms. A number of neuroactive substances including monoamines such as dopamine and neuropeptides have been shown to act as neuromodulators, but other substances thought to play very different roles in the body and brain act as neuromodulators, such as retinoic acid...

Myopia, a common ophthalmic disorder, places a high economic burden on individuals and society. Genetic and environmental factors influence myopia progression; however, the underlying mechanisms remain unelucidated. This paper reviews recent advances in circadian rhythm, intrinsically photosensitive retinal ganglion cells (ipRGCs), and dopamine (DA) signalling in myopia and proposes the hypothesis of a circadian rhythm brain retinal circuit in myopia progression. The search of relevant English articles was conducted in the PubMed databases until June 2023...

Parkinson's disease (PD) is caused due to degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc) which leads to the depletion of dopamine in the body. The lack of dopamine is mainly due to aggregation of misfolded α-synuclein which causes motor impairment in PD. Dopamine is also required for normal retinal function and the light-dark vision cycle. Misfolded α-synuclein present in inner retinal layers causes vision-associated problems in PD patients. Hence, individuals with PD also experience structural and functional changes in the retina...

Dopamine is a key neurotransmitter in the signaling cascade controlling ocular refractive development, but the exact role and site of action of dopamine D1 receptors (D1Rs) involved in myopia remains unclear. Here, we determine whether retinal D1Rs exclusively mediate the effects of endogenous dopamine and systemically delivered D1R agonist or antagonist in the mouse form deprivation myopia (FDM) model. Male C57BL/6 mice subjected to unilateral FDM or unobstructed vision were divided into four groups: one non-injected and three groups that received intraperitoneal injections of either a vehicle, D1R agonist SKF38393 (18 and 59 nmol/g) or D1R antagonist SCH39166 (0...

OBJECTIVE: Progressive supranuclear palsy (PSP) involves a variety of visual symptoms that are thought to be partly caused by structural abnormalities of the retina. However, the relationship between retinal structural changes, disease severity, and intracranial alterations remains unknown. We investigated distinct retinal thinning patterns and their relationship with clinical severity and intracranial alteration in a PSP cohort. METHODS: We enrolled 19 patients with PSP (38 eyes) and 20 age-matched healthy controls (40 eyes)...

High myopia is a leading cause of blindness worldwide with increasing prevalence. Retina percepts visual information and triggers myopia development, but the underlying etiology is not fully understood because of cellular heterogeneity. In this study, single-cell RNA sequencing analysis was performed on retinas of mouse highly myopic and control eyes to dissect the involvement of each cell type during high myopia progression. For highly myopic photoreceptors, Hk2 inhibition underlying metabolic remodeling from aerobic glycolysis toward oxidative phosphorylation and excessive oxidative stress was identified...

This study aimed to investigate the changes in retinal neurotransmitters and the role of the dopamine D2 receptor (D2R) pathway in regulating the myopic refractive state. Tricolor guinea pigs were randomly divided into two groups: the normal control group (NC) and the form-deprivation myopia group (FDM). Animals in the FDM group had their right eye covered with a balloon for 4 weeks. These two groups were further divided into two subgroups based on intravitreal injection with D2R antagonist sulpiride once a week for 3 weeks (NC, NC-Sul, FDM, and FDM-Sul groups)...