1. Widely Found and Studied Neurotransmitters  Glutamate – has excitatory functions  4 Ascending activating systems are very important  Cholinergic System uses acetylcholine  Adrenergic system uses noradrenalin  Dopaminergic system (actually 2 systems) use dopamine  Serotonergic system uses 5-Ht or serotonin  GABA or gamma-amino butyric acid – has inhibitory functions

2. Acetylcholine  Activate two types of receptors:  Nicotinic receptors– also stimulated by nicotine and inactivated or blocked by curare  Muscarinic receptors– stimulated by muscurine and blocked by atropine and scopolamine – use second messenger

3. Monoamines  Dopamine – up to 6 types of receptors  Tyrosine forms L-dopa  L-dopa synthesized to form dopamine  Norepinephrine – created by synthesis of dopamine  Epinephrine – created from Norepinephrine  Serotonin (5-Ht) – synthesized from tryptophan

4. Peptides  Many types of neuropeptides; two have been extensively studied  Sustance P – constriction and dilation of blood vessels  Opioid types –  Endorphins  enkephalins

5. How Drugs Work in the Brain  They work at the level of the synapse  Agonists  Antagonists

6. Possible Drug Actions at the Synapse  increase or decrease the synthesis or production of neurotransmitters  increase or decrease the ability of the cell to store the chemical in vesicles  increase or decrease the amount of transmitter released by vesicles into the synapse  it can increase the number and length of time a receptor is open by increasing or decreasing the production of enzymes that break down the neurotransmitter  block or enhance the reuptake and reuse of the neurotransmitter  Altering the actions of second messegers