Example Phys Extra Credit

Serotonin is a neurotransmitter in the brain that is an important player in keeping emotions in balance. Irregular serotonin levels are thought to contribute to depression. Scientists have recently found an atypical method of serotonin release. Originally, it was thought that serotonin could only enter the cell through somatodendritic 5-HT1A autoreceptors. Studies conducted by Boris Milner et al., have shown that serotonin can enter the cell through simple diffusion across the plasma membrane. This discovery could alter the future of antidepressant drugs, such as Zoloft and Prozac.

Selective Serotonin Reuptake Inhibitors are a type of antidepressants that block the reuptake of serotonin. The result is a larger amount of extracellular serotonin is available. One of the negative aspects about Selective Serotonin Reuptake Inhibiters is that their effect is not immediate. Patients usually have to wait a couple of weeks before any effect is noticeable.

Part of the reason for the delay is this extra serotonin can prevent serotonin-detecting neurons from firing. This process is known as autoinhibition. For this reason, Selective Serotonin Reuptake Inhibitors may even decrease the amount of serotonin detected in the brain initially.

The serotonin chemicals that regulate autoinhibition were once thought to come from vesicles via exocytosis. Mlinar has discovered that the autoinhibition-related serotonin may instead come from diffusion across the cell membrane. These findings mean that the serotonergic system is not a collection of neurons acting alone, but an interdependent network of neurons (Milnar, 2015). The findings also suggest that the neurons use a collective “pool” of neurotransmitter, and that the rate of firing action potentials is controlled independently by a “nonexocytotic mechanism” (Milnar, 2015).

Mliner believes that a better understanding of this process may be able to increase the effectiveness of antidepressants, and the passive...