Behavioral addictive disorders (BADs) have become a significant societal challenge over time. The central feature of BADs is the loss of control over engaging in and continuing behaviors, even when facing negative consequences. The neurobiological underpinnings of BADs primarily involve impairments in the reward circuitry, encompassing the ventral tegmental area, nucleus accumbens in the ventral striatum, and prefrontal cortex. These brain regions form networks that communicate through neurotransmitter signaling, leading to neurobiological changes in individuals with behavioral addictions. While dopamine has long been associated with the reward process, recent research highlights the role of other key neurotransmitters like serotonin, glutamate, and endorphins in BADs' development. These neurotransmitters interact within the reward circuitry, creating potential targets for therapeutic intervention. This improved understanding of neurotransmitter systems provides a foundation for developing targeted treatments and helps clinicians select personalized therapeutic approaches. The neurobiological underpinnings of BADs primarily involve impairments in the reward circuitry, encompassing the ventral tegmental area, nucleus accumbens in the ventral striatum, and prefrontal cortex. These brain regions form networks that communicate through neurotransmitter signaling, leading to neurobiological changes in individuals with behavioral addictions. While dopamine has long been associated with the reward process, recent research highlights the role of other key neurotransmitters like serotonin, glutamate, and endorphins in BADs’ development. These neurotransmitters interact within the reward circuitry, creating potential targets for therapeutic intervention. It encompasses multiple brain regions, including the ventral tegmental area (VTA), nucleus accumbens (NAc)in the ventral striatum (VS), basal ganglia, prefrontal cortex (PFC), amygdala (AMY), and hippocampus. Among these regions, the mesolimbic dopamine pathway in the midbrain serves as the ultimate common pathway for reinforcement and reward triggered by physiological stimulation or addictive behaviors ( 9 ). In the development and maintenance of BADs, specific brain regions establish connectivity via neurotransmitter-mediated signaling, resulting in intricate individualized neurobiological changes. Furthermore, the heightened risk of BADs associated with levodopa is not solely attributed to its binding with D2 receptors but also to its inhibition of GABA release, a critical element ( 62 ). Some conflicting evidence exists regarding the effects of dopamine D2 receptor antagonists (such as haloperidol, olanzapine, etc.). While one study found ( 63 ) that haloperidol reduced the inclination of individuals with GD to place more aggressive bets after receiving a reward in a slot machine task, another study reported ( 64 ) that haloperidol heightened the rewarding effects and gambling desires reported by individuals with GD. The 5-HT1B receptors are other inhibitory receptors primarily located in the SNc, where their activation inhibits the release of neurotransmitters such as GABA, acetylcholine (ACh), and Glu, thereby modulating neural excitability and reward processing ( 115 – 118 ). Preclinical and clinical studies ( 119 – 121 ) have highlighted the role of the 5-HT1B receptors in managing depression and anxiety and their association with aggression and impulse control. Meta-chlorophenyl piperazine (mCPP) ( 122 , 123 ), a metabolite of trazodone, is a mixed agonist for 5-HT1 and 5-HT2 receptors, particularly 5-HT1B receptors. Previous studies ( 80 , 179 – 181 ) have found that gambling or gambling-like activities (i.e., horse racing, slot machines, etc.) can trigger the release of endorphins, particularly in the NAc and VTA, which are key regions in the brain’s reward circuitry. Simultaneously, the increased availability of MOR in the shell, caudate nucleus, and globus pallidus is associated with presynaptic DA synthesis capacity, implying that the release of endorphins not only directly augments DA release but also, through MOR activation, inhibits the inhibitory neurotransmitter GABA in the VTA, thereby facilitating DA release in the NAc ( 182 ). Glu projections contribute to changes in cognitive functioning, especially cognitive flexibility, which is essential for adapting to new situations and modifying behavior. These projections enable individuals to consciously resist impulses and form new associations between stimuli (e.g., gaming) and behavioral responses, linking them to unconditioned responses such as reward or punishment. Glu is a naturally occurring amino acid and a fundamental component of proteins. It is the most widely distributed excitatory neurotransmitter in the brain ( 220 ). Further, the involvement of norepinephrine transporter (NET) in BADs has also been reported. Atomoxetine, as a NET blocker, has been shown to improve decision-making in male and female rats in the rGT by increasing synaptic NE levels ( 262 ). NE interacts with other neurotransmitters, such as DA and Glu, to regulate reward sensitivity and cognitive control. NE modulates DA release in the NAc, influencing the reward system’s sensitivity to stimuli. Additionally, in adolescents with comorbid ADHD and IGD, treatment with atomoxetine for 12 weeks resulted in a significant reduction in impulsivity and severity of internet gaming addiction ( 77 ). Figure 1 Schematic representation of neurotransmitters crosstalk and regulation in behavioral addiction reward circuit. Dopamine, serotonin, endorphins, GABA, glutamate, norepinephrine, and other neurotransmitters collectively form a complex regulatory network in the reward circuitry of behavioral addictive disorders. These neurotransmitters interact and interfere with each other, influencing not only biological behaviors but also closely associated with the occurrence and development of addiction.

role in the motivational component of reward-motivated behavior. The anticipation of most types of rewards increases the level of dopamine in the brain, and Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. It is an amine synthesized by removing a carboxyl group through decarboxylation from a molecule of its precursor chemical, L-DOPA, which is synthesized in the brain and kidneys. Dopamine is Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. It is an amine synthesized by removing a carboxyl group through decarboxylation from a molecule of its precursor chemical, L-DOPA, which is synthesized in the brain and kidneys. Dopamine is also synthesized in plants and most animals. In the brain, dopamine functions as a neurotransmitter—a chemical released by neurons (nerve cells) to send signals to other nerve cells. The brain includes several distinct dopamine pathways, one of which plays a major role in the motivational component of reward-motivated behavior. The anticipation of most types of rewards increases the level of dopamine in the brain, and many addictive drugs increase dopamine release or block its reuptake into neurons following release. Other brain dopamine pathways are involved in motor control and in controlling the release of various hormones. These pathways and cell groups form a dopamine system which is neuromodulatory. In popular culture and media, dopamine is often portrayed as the main chemical of pleasure, but the current opinion in pharmacology is that dopamine instead confers motivational salience; in other words, dopamine signals the perceived motivational prominence (i.e., the desirability or aversiveness) of an outcome, which in The brain includes several distinct dopamine pathways, one of which plays a major role in the motivational component of reward-motivated behavior. The anticipation of most types of rewards increases the level of dopamine in the brain, and many addictive drugs increase dopamine release or block its reuptake into neurons following release. Other brain dopamine pathways are involved in motor control and in controlling the release of various hormones. These pathways and cell groups form a dopamine system which is neuromodulatory. D1 receptors are the most numerous dopamine receptors in the human nervous system; D2 receptors are next; D3, D4, and D5 receptors are present at significantly lower levels. === Storage, release, and reuptake === Inside the brain, dopamine functions as a neurotransmitter and neuromodulator, and is controlled by a set of mechanisms common to all monoamine neurotransmitters. After synthesis, dopamine is transported from the cytosol into secretory vesicles, including synaptic vesicles, small and large dense core vesicles by a solute carrier—a vesicular monoamine transporter, VMAT2. Dopamine is stored in these vesicles until it is ejected into the synaptic cleft. Once back in the cytosol, dopamine can either be broken down by a monoamine oxidase or repackaged into vesicles by VMAT2, making it available for future release. In the brain the level of extracellular dopamine is modulated by two mechanisms: phasic and tonic transmission. Phasic dopamine release, like most neurotransmitter release in the nervous system, is driven directly by action potentials in the dopamine-containing cells. Tonic dopamine transmission occurs when small amounts of dopamine are released without being preceded by presynaptic action potentials. Tonic transmission is regulated by a variety of factors, including the activity of other neurons and neurotransmitter reuptake. Together, these two pathways are collectively termed the mesocorticolimbic projection. The VTA also sends dopaminergic projections to the amygdala, cingulate gyrus, hippocampus, and olfactory bulb. Mesocorticolimbic neurons play a central role in reward and other aspects of motivation. Accumulating literature shows that dopamine also plays a crucial role in aversive learning through its effects on a number of brain regions. The posterior hypothalamus has dopamine neurons that project to the spinal cord, but their function is not well established. In human drug addicts, "wanting" becomes dissociated with "liking" as the desire to use an addictive drug increases, while the pleasure obtained from consuming it decreases due to drug tolerance. Within the brain, dopamine functions partly as a global reward signal. An initial dopamine response to a rewarding stimulus encodes information about the salience, value, and context of a reward. In the context of reward-related learning, dopamine also functions as a reward prediction error signal, that is, the degree to which This confluence of theory and data has led to a fertile interaction between neuroscientists and computer scientists interested in machine learning. Evidence from microelectrode recordings from the brains of animals shows that dopamine neurons in the ventral tegmental area (VTA) and substantia nigra are strongly activated by a wide variety of rewarding events. These reward-responsive dopamine neurons in the VTA and substantia nigra are crucial for reward-related cognition and serve as the central component of the reward system. The introduction of the first widely used antipsychotic, chlorpromazine (Thorazine), in the 1950s, led to the release of many patients with schizophrenia from institutions in the years that followed. By the 1970s researchers understood that these typical antipsychotics worked as antagonists on the D2 receptors. This realization led to the so-called dopamine hypothesis of schizophrenia, which postulates that schizophrenia is largely caused by hyperactivity of brain dopamine systems.

is called the reward pathway. In this pathway many neurotransmitters play a role in the activation of the reward sensation, including dopamine, serotonin Curiosity (from Latin cūriōsitās, from cūriōsus "careful, diligent, curious", akin to cura "care") can be a quality related to inquisitive thinking, such as exploration, investigation, and learning, evident in humans and other animals. It can also refer to something (an event, object, person, etc.) which can cause curiosity. When it is for an object it may be called a curio, and a collection of cu Th…