Weeks 1-2

• Catecholamines are a class of neurotransmitters derived from tyrosine. There are three - dopamine, norepinephrine and epinephrine.
• There are two areas of Dopamine activating neurons in the midbrain - the Substantia Nigra and the Ventral Tegmental Area
• There are four dopaminergic pathways in the brainstem, 3 in the midbrain and 1 in the hypothalamus.

  1 - The mesolimbic pathway - the reward pathway - disorders are associated with addiction and anhedonia (a lack of pleasure).

  2 - The mesocortical pathway - plays a large role in cognitive function - dysfunction associated with schizophrenia.

  3 - The nigrostriatal pathway - involved in motor control and associated with parkinson’s disease.

  4 - The tuberoinfundibular pathway - prevents prolactin release - important for the treatment of psychosis.
• Norepinephrine neurons are located in locus coeruleus in the midbrain.
• Norepinephrine is involved in wakefulness, alertness, fight or flight, memory, stress and the sympathetic and parasympathetic nervous systems
• Serotonin is synthesised from tryptophan by a large congegation of neurons in the raphe nuclei in the brainstem. It has roles in mood and emotion; perception; reward; memory; attention; pain transmission; circadian rhythms; and feeding behaviour.
• Acetylcholine is used in 2 central cholinergic systems:

  1 - the basal forebrain complex comprised of the medial septal nuclei to provide cholinergic innervation of the hippocampus; and the basal nucleus of meynert to provide cholinergic innervation of the cortex and amygdala for learning, attention and memory.

  2 - The pontomesencephalotegmental complex which lies within the tegmentum on the border of the pons and midbrain. It projects basically everywhere with a wide array of functions but particularly involved in motor and sensory function; the sleep wake cycle; and general mental health.
• Glutamate is the main excitatory neurotransmitter and GABA is the main inhibitory neurotransmitter
• Glutamate is the main excitatory neurotransmitter and GABA is the main inhibitory neurotransmitter
• Glutamine is stored in astrocytes which enter the synapses, taken up by presynaptic neurons and converted into glutamate. Glial cell transporters mop up excess glutamate, transporting them back to the astrocyte for deactivation.
• Glutamate binds to three Ionotropic Receptors - NMDA, AMPA and Kainate-R. These receptors are involved in learning and memory formation in the hippocampus
• There are 2 classes of Metabotropic Receptors that glutamate binds to - they purely have secondary messenger effects (causing downstream effects) - they are mGluRI and mGluRII receptors.
• Alterations to the glutamate system may be involved in schizophrenia (glutamate excitotoxicity leading to glutamate hypofunction) and depression (from glutamate hyperfunction); cerebral ischemia; and in seizure generation.