Emotion. Health. Disease

Author: Esther Sternberg (USA), translated by Meng Zhiping and others
Translator: Quan Ruojian, Meng Zhiping
Country:
Publisher:
Publishing Date: 2002-09-01
Features: Reintegrate body and mind
At first, only a few scientists believed that the nervous and immune systems could communicate with each other. They studied this issue as if playing the same puzzle from different angles. Each person proposed their own questions with different motivations, but no one realized that they were all working in related fields of the same thing. Neuroanatomists found it hard to believe the prevailing idea that immune organs were isolated in the body and had no connection with the nervous system. So, these scientists began to search for anatomical evidence to prove that immune organs were innervated.
Endocrinologists, on the other hand, had long accepted the view that scattered glands throughout the body could coordinate synchronously. Therefore, they found it easy to believe that various glands in different regions could communicate through soluble molecules in the bloodstream, known as hormones. So, why couldn’t molecules released by immune cells, like hormones, affect distant organs and cells?
Subsequently, immunologists began to test the effects of chemical substances from the nervous system on immune cells. Others studied animals highly susceptible to inflammatory and infectious diseases. They noticed that the differences in disease susceptibility could not always be fully explained by differences in the animals' immune systems. Some began to search for other possible factors, while others accidentally stumbled upon this very factor.
At the same time, in the 1970s and 1980s, another group of scientists stood in stark contrast to those holding completely different biological views. They questioned how the higher functions of the brain affected the immune system and diseases from a psychological and emotional perspective. However, no one worked in a completely vacuum. The exploration of how the nervous and immune systems communicate was entirely based on the scientific achievements of the previous 50 years, which had discovered the functions of the brain and the body's stress response.
At the base of the brain, there is a gland situated in its own small bony seat within the skull, hanging like a cherry on a stalk. This bony seat reminded anatomists of a Turkish saddle, which they named the "turkey saddle" (sella turcica). This gland is the pituitary gland, with a size and density similar to an olive, appearing as if part of the brain and part of general tissue. It is located very close to the upper part of the nose.
When you cut this gland and observe it under a microscope, you will find it consists of two parts: the posterior lobe, made up of long nerve cell processes, with cell bodies located above the brain and processes extending through the pituitary stalk into the gland. The anterior lobe hangs in a network of blood vessels. The different layouts of the two parts of the gland imply different functions, though their functions are not immediately apparent from this layout alone.
If you only had eyes and a set of anatomical tools, how could you know what such a structure does? One way to understand its function is to link anatomical abnormalities found in post-mortem examinations with the loss of functions in living individuals. In the 19th century, doctors performed autopsies on recently deceased patients to do just this.
In the early 20th century, Sir Harvey Cushing, a British doctor, observed a disease pattern in a group of patients with extreme obesity. These patients were not generally overweight; their upper and lower limbs were slender. Fat accumulated in their necks, resembling the hump of a water buffalo. They also exhibited other strange symptoms: shiny, thin skin with spider-like subcutaneous blood vessels. Many patients showed signs of depression: they cried, had difficulty sleeping, felt lethargic, and could not engage in daily activities. They often felt they had not accomplished anything worthwhile. Some blamed themselves for their incompetence and even took their own lives.
Autopsies revealed that in each case, the pituitary gland was swollen and had a tumor. However, knowing that the pituitary gland was swollen along with these symptoms did not fully explain the situation. How could one gland produce such emotional symptoms, or even whether it could produce them at all. To find the answer, a completely different set of techniques was needed. These techniques involved extracting the contents of the swollen pituitary gland, separating the complex mixture into simpler components, and then testing the function of each component.
In general, the various chemical analysis methods used in such research belong to the fields of biochemistry and endocrinology, which developed in the mid-20th century. These studies later revealed that the swollen pituitary glands, due to tumors, produced large amounts of adrenocorticotropic hormone (ACTH). This hormone was named as such because its function is to stimulate the outer layer (cortex) of another endocrine gland, the adrenal gland. The adrenal gland is not in the brain but located in the lower abdomen, sitting atop the kidneys like a hat. Almost all the clinical features of Cushing's syndrome can be explained as the result of excessive hormone production by these pituitary tumors.
It was precisely in these extreme cases that scientists understood this cascade of hormonal activity, which later prompted endocrinologists to look for and discover similar, though weaker, hormonal response patterns in patients with depression. Once we knew that the extreme sadness and anxiety in Cushing's syndrome were related to excessive cortisol and ACTH, we could simply measure their concentrations in depressed patients.
Such research led scientists to discover that in certain types of depression, the concentrations of hormones like cortisol and ACTH were indeed very high. Further studies showed that the hormone relay from the pituitary to the adrenal gland had not ended but had just begun. Later, scientists began to ask which part of the brain and what hormones controlled this response in the human body. It was then discovered that this cascade reaction was initiated by the hypothalamus, a part of the brain located above the pituitary gland. First, a hormone called corticotropin-releasing hormone (CRH) is released into the blood vessels surrounding the pituitary gland. This hormone is named as such because it stimulates the pituitary cells to release its hormone, ACTH, in sequence. The latter hormone is named because it promotes the enlargement of the adrenal cortex and the release of their hormones, corticosteroids.
These two glands, located half a body length apart, are connected not by anatomical structure but by hormones. Once any of the numerous stressors pull the trigger, this cascade reaction is triggered, and hormones are released in the same sequence into the bloodstream.
When we understand this series of reactions, an unavoidable question arises: if a tumor producing excessive ACTH and cortisol can trigger a series of typical symptoms, then can other diseases that cause the release of these hormones also lead to similar, though less severe, symptoms?
On a steep hillside near University Street in Montreal's downtown area, stands an Italian-style red-brick building at a corner of a crossroads opposite the main gate of McGill University. Looking back up the hill from this corner, you can see a stone bridge spanning University Street, connecting the Royal Victoria Hospital and the Montreal Neurological Institute. It was here that neurosurgeon Wilder Penfield and his colleagues completed their work mapping the functions of the brain.
If you look up to the green awning under the window on the third floor of the corner building, your gaze will settle on the ornate stone arch above the street door. There, carved into a piece of gray stone within the red bricks, is the unmistakable molecular structure of a steroid hormone. That is the home of Hans Selye, the Austrian-born Canadian doctor and physiologist whose theory of stress caused a stir in the scientific community in the 1950s. It was also Selye who introduced the term "stress" into many languages, popularizing the concept and gaining worldwide recognition.