Psychiatric medications can help correct imbalances in the neurotransmitters that affect mood and behavior. Selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine (Prozac), fit into the serotonin neuroreceptors on neuron dendrites. This blocks serotonin from entering the neuron and keeps it active for longer periods of time in the synaptic gaps between transmitting and receiving neurons. Serotonin (5-Hydroxytryptamine) is a calming neurotransmitter that is manufactured in nerve cells from the amino acid tryptophan. Turkey is one good source of tryptophan, which may help explain why people often feel relaxed and sleepy after Thanksgiving dinner.