Christine Wiebe, MA; Sue Carter, PhD; Seymour Reichlin, MD, PhD


July 11, 2017

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Sue Carter, PhD, is an internationally recognized expert in behavioral neuroendocrinology and the first person to identify the physiologic mechanisms of monogamy in pairs.[1]

Seymour Reichlin, MD, PhD, is a pioneer in the field of neuroendocrinology, and an expert on hormones involved in human reproduction.

Their careers have crossed paths several times over the years, including the era when sex researchers Masters and Johnson were breaking new ground, and both of them count Nobel laureates among their colleagues and friends. But they had never met in person until Dr Reichlin approached Dr Carter at the recent annual meeting of the Endocrine Society.

She had just delivered a popular presentation on oxytocin, a hormone that has been central to her research, and she was hurrying over to the Medscape studio to videotape a synopsis. She was "delighted" to meet the man whose distinguished career had intersected her own, so she invited him to walk along to her next appointment so they could catch up.

By the time they arrived at the studio, Dr Carter was convinced that this "historic" exchange should be recorded, and she convinced Dr Reichlin to join her in front of the camera.

"Should I call you Seymour?" she asked as they got their microphones adjusted.

"Call me Si," he replied (like the first part of "science").

Dr Carter began by asking him to name the most important aspect of his life's work —the thing that made him most proud.

"I know this is a cliché," he replied with a smile, "but the thing I am most proud of is the large number of students and fellows that have worked with me and what they have accomplished."

Dr Carter nodded in agreement. "Yes," she said, "the ones that I know about started fields —not the field, but many fields. These are not ordinary people."

Thinking back, Dr Reichlin recalled the research climate in his early career.

"I was working in a very novel field at the time," he said. "There was almost nothing known about neuroendocrinology in the United States." He traveled to London to work with Geoffrey Harris on studies examining how the brain controls the thyroid gland.

When he returned, he set up a laboratory and started publishing prolifically. In 1963, with 32 citations already to his name, he wrote a seminal paper for the New England Journal of Medicine that summarized the emerging field of neuroendocrinology.[2]

"It was that article that brought the field to the attention of the medical community," Dr Reichlin recalled. "I started getting these wonderful young people to come work with me because of the excitement of a new field."

Back then, Dr Carter noted, "we thought the pituitary gland was essentially a freestanding system, and the brain was separate."

So, how did the pituitary know what to do?

"The first really good research on that came from reproduction," Dr Reichlin explained, "because many species of animals —sheep and goats, particularly —are seasonal breeders. They come into reproductive heat and the capacity to ovulate when there is a change in the ratio of light to dark."

As the researchers soon learned, light was an environmental trigger on the brain, which then signaled the pituitary to stimulate the hormones that mediate reproduction.

"Now it all seems so easy," Dr Reichlin said with a chuckle.

What initially stumped researchers was how the pituitary gland —which has no nerves —could react to the nervous system. They postulated that the answer lay with the blood vessels supplied from the brain to the pituitary.

"That meant there must be chemical mediators," Dr Reichlin said. "That is what the whole field of neuroendocrinology is about."

Giants Among Giants

If his British colleague Dr Harris had not died so young, Dr Reichlin asserted, he would have won a Nobel Prize for his work. Instead, it went to Roger Guillemin and Andrew Schally in 1977.

The mention of those names provoked another memory for Dr Carter. "I met Roger Guillemin at the Salk Institute a few years ago," she recalled. She engaged in a discussion with him about the language origin of "oxytocin," which he argued should have been spelled "ocytocin."

"I said, 'Here is a great chance to get a publication, Dr Guillemin! You have got that Nobel Prize. Would you not like to publish this?'" Although he demurred, he did call people at the Oxford English Dictionary, she said, asking them to correct the spelling.

"They said, 'No, it is in common use. It is O-X-Y,'" Dr Carter said, sharing the story with great amusement. "'Oxy-gen' means 'acid- generating.' 'Oxytocin' technically means 'acid birth.' Most people think it means 'swift birth.' Wrong ; it was a mistake! Is that not amazing?"

The Science of Childbirth and Lactation

The two researchers not only shared historical memories, but also found common ground in their body of work.

"Let's talk about lactation," Dr Carter said, her colleague nodding. "You can explain both oxytocin and prolactin for us, because these are very critical to human evolution."

"The main milk-promoting hormone is prolactin, which is secreted during the nursing episode," Dr Reichlin began. "It stimulates milk production by the breast.

"Also, it is one of two hormones —oxytocin is the other —that has a bonding effect on the infant/mother relationship. A woman who nurses her baby gets a big psychological boost from prolactin, as well as from oxytocin, which is really quite interesting."

He then recalled the origins of this current understanding.

"Going back thousands of years," Dr Reichlin explained, "farmers have known that when a calf or a baby goat or a baby sheep starts to nurse, milk does not appear at the nipple until an appreciable time has passed —as much as a minute. Then, milk suddenly appears in the nipple, and the baby can start to take the milk. That reflex has been called the 'let-down reflex.'"

Oxytocin then stimulates the contraction of the lobules that contain the milk, he continued, and the milk appears in the nipple.

"Without oxytocin, you do not get let-down," he said. "And without let-down, the breasts can be filled with milk, but the baby cannot get at it."

Dr Carter nodded, adding that another colleague once said , "Prolactin sets the table, and oxytocin serves the meal."

Dr Reichlin nodded, smiling. "If you think about it —how this complicated system has evolved in mammals —it is just mind-boggling."

Follow Christine Wiebe on Twitter: @CWiebeMedscape

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