Neurotransmitter Release and Receptors

Neurotransmitter Release, Receptors, and Effects

• Neurotransmitters are released through exocytosis upon an action potential.
• Unbound neurotransmitters are cleared from the synapse through endocytosis or transporters.
• Metabolism or recycling of neurotransmitters occurs in the presynaptic terminal.
• The synaptic cleft contains neurotransmitters that bind to receptors in the postsynaptic density.
• Mutations in genes encoding postsynaptic density proteins have been linked to disorders such as schizophrenia, autism, and learning disabilities.
• Neuropharmacology studies receptor systems, including ionotropic receptors (ligand-gated ion channels) and metabotropic receptors (connected to G proteins).
• Ionotropic receptors are composed of subunits with an orthosteric site for neurotransmitter binding.
• Metabotropic receptors are connected to G proteins and can activate ion channels or second messenger systems.
• Neurotransmitters are synthesized in the presynaptic terminal and transported to the synaptic cleft.
• Reuptake transporters or endocytosis clear neurotransmitters from the synapse, while enzymes metabolize them in the presynaptic terminal.
• Ion channels are responsible for allowing ions in/out of neurons, and their activation is dependent on neurotransmitter binding.
• Synaptic integration involves the interaction of multiple neurotransmitters with ionotropic and metabotropic receptors, producing different effects on the cell.

Receptor Pharmacology and Effects

• Non-endogenous drugs can alter neurotransmitter communication, either by binding to receptors and having an effect on the neuron (agonists) or by blocking endogenous ligands (antagonists).
• Neurotransmitter binding can produce excitatory or inhibitory effects, and binding to metabotropic glutamate receptors can trigger neuroplasticity, leading to increased connectivity and learning.
• The complexity of the system lies in the infinite combination of ways neurotransmitters can interact with receptors, and different types of receptors and neurotransmitters can have different effects on the cell. The brain is highly plastic and capable of learning and adapting.

Neuronal Plasticity, Stroke, and Drugs

• Neurons can change in size based on experience, and synapses can increase or decrease in strength based on experience.
• Stroke occurs due to a blood clot in the brain, leading to neuronal death and loss of function.
• Agonists bind to receptors and have the same effect as neurotransmitters, while antagonists block neurotransmitters.
• Psychoactive drugs can affect neurotransmitter levels, and toxic levels of neurotransmitters can lead to respiratory failure or inhibition of vital systems.

Animal Models in Neuroscience

• Eric Kandel studied neuroscience using sea slugs, while squids and manatees have also been studied for their nervous systems.
• Comparative societies study the way animals learn, and Pavlovian conditioning has been studied in manatees.
• Tetanus occurs due to excessive excitation of neurons, and GABA agonists can inhibit vital systems.
• A learning conference focused on comparative