Encephalon 4: Chronic and Acute Pains

Pains, both chronic and acute, are among the factors that impair quality of life. Pain has always been a crucial problem to find an effective solution at the clinic level due to it being the most common complaint of patients. Pain is not only a simple pathophysiological process. It also has attentional, cognitive, and emotional aspects. However, the traditional pharmaceutical approaches mainly ignore the complexity of the pain process (Bushnell et al., 2013).

The studies on animal models show that activity of the parabrachial nucleus (PB) in the pons immensely increased in a pain state. This finding suggests the potential roles of PB on pain. PB is known as a station relaying sensory information to forebrain structures. PB harbors mainly excitatory Glutamatergic neurons and a few inhibitory GABAergic interneurons.

The evidence shows that PB received the inhibitory GABAergic inputs through forebrain structures and mainly from the amygdala. Further studies revealed that activation of GABAergic amygdala neurons projecting to lateral PB suppresses and inhibits acute pain. Also, findings show that chronic pain suppressed the efficacy of this amygdalo-parabrachial pathway (Raver et al., 2020). Apart from PB’s prominent role in pain processing, it also plays a key role in fluid homeostasis, cardiovascular function, satiety/appetite, and sleep/arousal.

This novel amygdalo-parabrachial pathway mediating pain is not only limited to planning novel therapies for pain. Also, effective therapeutical alternatives can emerge for the other processes that are relevant to this pathway.