Nucleus Accumbens Core
Encyclopedia
The nucleus accumbens core is a structure that, together with the nucleus accumbens shell
, makes up the entire nucleus accumbens
. The nucleus accumbens is an important area of the brain related to motor function, reward, and emotionality.
Location: The core of the nucleus accumbens (NAc) is part of basal ganglia, which plays a role in controlling things from voluntary motor function to emotions.
Cell types: The core of the NAc is made up mainly of medium spiny neurons. The neurons in the core, as compared to the neurons in the shell, have an increased density of dendritic spines, branch segments, and terminal segments. From the core, the neurons project to other sub-cortical areas such as the globus pallidus and the substantia nigra. GABA is one of the main neurotranasmitters in the NAc, and GABA receptors are also abundant.
Function: The NAc core is involved in sensory motor integration, reward, the regulation of goal-directed behavior, and emotional cues.
A recent study conducted by Ambroggi et al. at the University of California found that selective inactivation of the core, and not the shell, lead to a decreased response to rewarding cues in rats, suggesting the core is involved in regulating goal-directed behavior. Inactivation of the core via GABA agonists also shows an effect on the magnitude of response to food rewards.
Inactivation studies have also demonstrated that the core plays a similar role in natural and drug reward situations, indicating the core as an essential, and possibly final neuronal pathway for influencing the magnitude of behavior related to responding to both drug and food stimuli. The core essentially facilitates reward-related stimuli in affecting response magnitude.
Hormones:
Dopamine: The role of dopaminergic projections in the NAc core is still uncertain. However, it is clear that levels of extracellular dopamine increase in response to a drug stimulus, particularly, stimuli related to drugs of abuse like cocaine, morphine, and amphetamines. Recent studies have shown that repeated exposure to these drug stimuli makes the dopaminergic projection response more sensitive.
Glutamate: Studies have shown that local blockades of NMDA receptors (glutamate receptors) in the core had a negative effect on spatial learning, but did not have an effect in the NAc shell. Another study demonstrated that both NMDA and AMPA (both glutamate receptors) play important roles in regulating instrumental learning.
Serotonin (5-HT): Compared to the serotonin axons in the shell, the serotonin axons in the core are significantly thinner and less varicose. Cross-sectional diameters of these axons in the core are smaller than those of the shell, (0.3 vs. 0.7 micron). Serotonin axon terminals found in the core had fewer large dense core vesicles than those in the shell.
Nucleus Accumbens Shell
The nucleus accumbens shell is a structure that, together with the nucleus accumbens core, makes up the entire nucleus accumbens. The nucleus accumbens is an important area of the brain related to motor function, reward, and emotionality....
, makes up the entire nucleus accumbens
Nucleus accumbens
The nucleus accumbens , also known as the accumbens nucleus or as the nucleus accumbens septi , is a collection of neurons and forms the main part of the ventral striatum...
. The nucleus accumbens is an important area of the brain related to motor function, reward, and emotionality.
Location: The core of the nucleus accumbens (NAc) is part of basal ganglia, which plays a role in controlling things from voluntary motor function to emotions.
Cell types: The core of the NAc is made up mainly of medium spiny neurons. The neurons in the core, as compared to the neurons in the shell, have an increased density of dendritic spines, branch segments, and terminal segments. From the core, the neurons project to other sub-cortical areas such as the globus pallidus and the substantia nigra. GABA is one of the main neurotranasmitters in the NAc, and GABA receptors are also abundant.
Function: The NAc core is involved in sensory motor integration, reward, the regulation of goal-directed behavior, and emotional cues.
A recent study conducted by Ambroggi et al. at the University of California found that selective inactivation of the core, and not the shell, lead to a decreased response to rewarding cues in rats, suggesting the core is involved in regulating goal-directed behavior. Inactivation of the core via GABA agonists also shows an effect on the magnitude of response to food rewards.
Inactivation studies have also demonstrated that the core plays a similar role in natural and drug reward situations, indicating the core as an essential, and possibly final neuronal pathway for influencing the magnitude of behavior related to responding to both drug and food stimuli. The core essentially facilitates reward-related stimuli in affecting response magnitude.
Hormones:
Dopamine: The role of dopaminergic projections in the NAc core is still uncertain. However, it is clear that levels of extracellular dopamine increase in response to a drug stimulus, particularly, stimuli related to drugs of abuse like cocaine, morphine, and amphetamines. Recent studies have shown that repeated exposure to these drug stimuli makes the dopaminergic projection response more sensitive.
Glutamate: Studies have shown that local blockades of NMDA receptors (glutamate receptors) in the core had a negative effect on spatial learning, but did not have an effect in the NAc shell. Another study demonstrated that both NMDA and AMPA (both glutamate receptors) play important roles in regulating instrumental learning.
Serotonin (5-HT): Compared to the serotonin axons in the shell, the serotonin axons in the core are significantly thinner and less varicose. Cross-sectional diameters of these axons in the core are smaller than those of the shell, (0.3 vs. 0.7 micron). Serotonin axon terminals found in the core had fewer large dense core vesicles than those in the shell.