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Neurotransmitter
A chemical messenger produced and stored in neurons. It is released into the synaptic gap by the presynaptic neuron and helps transmit signals between neurons by binding to receptors on the postsynaptic neuron.
Agonist
A substance that enhances or mimics the action of a neurotransmitter. It binds to the same receptors, amplifying the neurotransmitter’s effects.
Antagonist
A substance that inhibits the action of a neurotransmitter. It blocks or reduces neurotransmitter activity by binding to the receptors, dampening or stopping the signal.
Nicotine acts as an agonist for acetylcholine by stimulating its receptors. This activation increases neural signaling in the brain, leading to heightened focus, faster reaction times, and a sense of alertness or wakefulness.
Neurotransmission involves both electrical and chemical mechanisms.
Neurons are the fundamental units of the nervous system, consisting of three main parts:
Neurotransmitter Interaction: The activity of neurotransmitters can be modulated by various chemicals:
Remember, Agonists and antagonists influence the strength or suppression of these signals.
Glutamate is an excitatory neurotransmitter, like pressing the "gas pedal" in a car. It increases brain activity, making the brain more alert and responsive. Higher glutamate levels make the brain more excitable, while lower levels slow things down.
GABA (gamma-aminobutyric acid) is an inhibitory neurotransmitter, like pressing the "brake pedal" in a car. It decreases brain activity, calming and relaxing the brain. Higher GABA levels promote calmness, while lower levels can lead to anxiety or overstimulation.
Aim: to see whether acetylcholine (ACh) aids spatial memory, and it can be slowed down by scopolamine, since scopolamine is an antagonist for acetylcholine.
Method: injected with scopolamine or a saline (placebo) and completed a virtual maze. Participants came back 3-4 weeks later and got injected with the solution they did not receive in the first round and repeated the using randomized double blind crossover design.
Sample: 20 men with average age of 28
Results: Scopolamine led the participants to make more errors in the maze than people who received the placebo, and it reduced activity in the hippocampal area
Conclusion: Scopolamine reduced activity in the hippocampal area, demonstrates a correlation between ACh and spatial memory.
Aim: To investigate how serotonin influences moral decision-making and prosocial behavior.
Participants: 30 healthy volunteers.
Method: Experimental, repeated measures design with double-blind and counterbalanced conditions.
Procedure: Participants were administered either a dose of citalopram (an SSRI) or a placebo. They were presented with moral dilemmas modeled on the "trolley problem":
Results: In personal scenarios, participants under citalopram were less likely to choose harm, reflecting increased prosocial tendencies. Impersonal decisions were unaffected.
Conclusion: Serotonin enhances prosocial behavior by reducing the acceptability of causing direct harm to others.
Aim: To assess the effect of dopamine-producing neuron transplants on Parkinson’s disease symptoms.
Participants: 40 patients with severe Parkinson’s disease, aged 34–75.
Method: Experimental, independent measures design.
Procedure: The experimental group received transplants of dopamine-producing neurons into the putamen, a brain region affected by Parkinson’s. The control group underwent sham surgery. PET scans and clinical observations assessed brain changes and symptom improvement over a year.
Results: Younger participants in the transplant group showed significant symptom reduction (28%), linked to increased dopamine production in the putamen.
Conclusion: Dopamine is critical in managing Parkinson’s symptoms, especially in younger patients.
Aim: To investigate the neural basis of romantic love and its association with dopamine activity.
Participants: 17 individuals "intensely in love" (mean age: 21; mean duration: 7 months).
Method: Experimental, repeated measures design using fMRI scans.
Procedure: Participants viewed images of their romantic partner and neutral acquaintances in alternating sequences while undergoing fMRI scans. Brain activity patterns were compared.
Results: Photos of romantic partners triggered increased activation in dopamine-rich brain regions linked to reward and motivation.
Conclusion: Romantic love is associated with dopamine activity, reinforcing its role in reward processing.
Neurotransmitter Systems: Neurotransmitters do not operate in isolation. They interact with one another, influencing and modulating each other’s effects.
Serotonin might affect dopamine pathways, making it difficult to pinpoint the exact role of a single neurotransmitter in complex behaviors like decision-making or aggression.
Brain Regions: The effects of neurotransmitters also depend on where they act in the brain.
Dopamine’s role in the prefrontal cortex may influence decision-making, while in the striatum, it is more closely linked to reward and habit formation.
Artificial Conditions: Many studies artificially manipulate neurotransmitter levels (e.g., through drugs or dietary controls). While laboratory research helps establish causal links, its ecological validity is low and does not fully replicate the complexity of natural neurotransmission.
Real-world factors such as stress, social interactions, or genetic predispositions often play a role on behavioral effects.
Social and Cognitive Factors: Behaviors influenced by neurotransmitters, such as aggression or prosocial acts, are also shaped by life experiences, cultural norms, and situational contexts.
Serotonin may lower aggression, but a person’s upbringing or immediate environment could override this biological tendency.
Consent and Risks: In human studies, ensuring informed consent and minimizing risks is paramount, especially when the research involves vulnerable populations, such as those with mental health disorders.
