Bipolar Disorder and the Brain
Bipolar disorder is a condition where a person encounters varying periods of depression and mania. While research is still inconclusive to the cause of these swings, some research points that the altered production of key neurotransmitters—chemicals that allow the brain to communicate—affects mood.
There are two key areas of the brain affected by neurotransmitters: the cerebrum and the cerebellum. The cerebrum is the largest part of the brain that affects conscious thought, reasoning, and more, while the cerebellum is believed to regulate fear and pleasure responses.
Function of Neurotransmitters
Neurotransmitters, such as serotonin and dopamine, are chemicals produced in the brain that allow the brain to function by transmitting signals from one neuron to another across the junction between them called the synapse.
Problems with neurotransmitters, including low levels, can have a profound impact on mood, which is why common drugs prescribed to bipolar disorder patients involve altering the level of certain neurotransmitters.
Serotonin and Mood
Serotonin is an important neurotransmitter modulating mood, sleep, sexual, and some social behavior. Some researchers believe that faulty levels can cause depression.
Serotonin is released into the space between neurons—known as the synaptic cleft—involving transporters, which send out the serotonin and receptors on another cell that receive the serotonin. This exchange from the nerve terminal occurs when a nerve impulse courses through and transports serotonin to another cell like a chemical bolt of lightning.
Selective serotonin reuptake inhibitors, or SSRIs, are a common class of drugs prescribed to people with depression-like symptoms. They work by blocking certain serotonin transporters so the neurotransmitters do not get reabsorbed as quickly into the bloodstream and remain in the synaptic cleft. This allows for higher levels of serotonin to remain in the brain, which can elevate mood. However, the drugs can take some time to reach their desired effect.
Normal GABA Receptors
Gamma-aminobutyric acid (or GABA) is the main inhibitory neurotransmitter of the central nervous system. GABA and glutamate constitute nearly all the transmitters in the brain. A normal GABA receptor allows for GABA to bind with it, thus changing the shape of the channel that allows negatively-charged chloride ions (cl-) to enter the neuron. Without this smooth exchange, the neurons are more excitable, which researchers believe causes anxiety, one symptom of bipolar disorder.
GABA Receptors and Benzodiazepines
Benzodiazepines are a class of drug often prescribed for the short-term treatment of anxiety, insomnia, agitation, and other symptoms common in bipolar disorder. Benzodiazepines target one of three types of GABA receptors that prevent rapid mood change, such as panic.
When benzodiazepines bind with GABA receptors in a brain synapse, the effect of the GABA is more sustained, thus producing a calming, sedative effect.
Sodium-Potassium Pump and Your Brain
Each cell has an outer membrane that allows for the exchange of certain ions and molecules to help a cell perform its functions. In this membrane is a pump that allows for the exchange of potassium (k+) and sodium (Na+), two key elements in nervous cells for responding to stimuli and transmitting impulses.
This is an important function for bipolar disorder patients because the most commonly prescribed drug, lithium, affects these pumps. More is explained on the next slide.
The mood-stabilizing drug lithium is often prescribed for people with bipolar disorder because it can combat the effects of mania. It may do this by changing the activity of the sodium-potassium pump in nervous cells by slowing or stopping the transmission of sodium (Na+) and potassium (k+). It is speculated that lithium reduces the potential for a brain neuron to respond to neurotransmitters that contribute to the symptoms of mania.
Medications for Bipolar Disorder
While the chemistry behind bipolar disorder medications can seem tricky, there are several proven methods to help combat both the depression and mania associated with this lifelong condition.