Arvid Carlsson, a Swedish pharmacologist whose research on chemical signals in the brain resulted in a leading treatment for Parkinson’s disease and earned him a Nobel Prize, died on June 29. He was 95.

The Sahlgrenska Academy at the University of Gothenburg in Sweden, where Dr. Carlsson had served on the faculty since 1959, announced the death but did not say where or how he died. In recent years, he lived in Gothenburg and kept a summer home in the nearby town of Onsala.

Carlsson shared the 2000 Nobel Prize in physiology or medicine with Paul Greengard and Eric Kandel, scientists who independently studied the molecular underpinnings of the brain, in particular the ways neural signals affect memory, mood and movement.

Their research helped resolve a debate over whether signals in the brain were transmitted mainly through electricity, as was previously believed, or through chemicals known as neurotransmitters.

Beginning in the 1950s, Carlsson focused primarily on dopamine, which most of his contemporaries believed was an unimportant precursor to norepinephrine — a neurotransmitter that plays a crucial role in regulating a person’s heart rate and alertness.

Through experiments that began in the United States at the National Institutes of Health and continued in Sweden, Carlsson showed that dopamine was a neurotransmitter in its own right. Concentrated in a region of the brain known as the basal ganglia, it affects a person’s ability to wave their arms, run across a stage or otherwise move their body.

“Dopamine is involved in everything that happens in our brain, all the important functions,” he said in a 2016 podcast with the Sahlgrenska Academy. “If you look at the number of citations dealing with dopamine, over the decades, it was going up all the time, dramatically, and finally it was so high that the Nobel assembly couldn’t avoid me.”

In one major study, Carlsson administered an antipsychotic drug to rabbits, reducing dopamine levels in their brains. The rabbits were all but crippled, and displayed similar symptoms to those of a Parkinson’s patient.

Carlsson went on to find that their symptoms could be treated using an amino acid known as L-dopa or levodopa, which increased dopamine levels in their brains. He later described the discovery as “one of the most astounding experiences in my scientific career,” adding that he and his colleagues “felt as though we had come across something like a ‘Rosetta Stone,’ which would provide the key to the chemical language of the brain.”

Within a decade, through the efforts of biochemists including Oleh Hornykiewicz, L-dopa became the standard treatment for Parkinson’s, helping reduce tremors, stiffness and slowness of movement. (After the 2000 Nobel Prize was announced, more than 250 neuroscientists signed a letter to the award committee declaring that Hornykiewicz also deserved the honor.)

“Parkinson’s used to be a disease of which people would die a horrible death, often by suffocation,” Nobel committee chairman Ralf Patterson said after Carlsson received the medical prize. Through L-dopa, he continued, millions of people had their symptoms under control. “That’s almost a magical thing.”

Carlsson also was cited by the Nobel committee for contributing “strongly” to the development of a popular new class of antidepressants, selective serotonin reuptake inhibitors (SSRIs). In effect, the drugs increase the concentration of serotonin, another neurotransmitter that fascinated Carlsson.

According to the medical historian Edward Shorter, Carlsson “developed the first SSRI” while working as a consultant for the Swedish pharmaceutical company Astra, now AstraZeneca. The drug was ultimately withdrawn from the market over clinical concerns, much to Carlsson’s disappointment, but was credited with paving the way for Prozac, one of the world’s most commonly prescribed medications.

The third of four children, Arvid Carlsson was born in Uppsala, Sweden, on Jan. 25, 1923. The family moved to the university town of Lund after his father, a historian, was offered a teaching post; his mother focused on raising the children, but later became a noted scholar of women’s legal status in the Middle Ages.

In part to separate himself from his humanities-oriented family, Carlsson decided to study medicine and pharmacology, and enrolled at the University of Lund two years after the outbreak of World War II.

He had just begun his clinical training when, in the spring of 1944, about 30,000 prisoners from Nazi concentration camps were transported to Sweden. Carlsson was part of a group of physicians and medical students who treated them for tuberculosis and malnutrition.

“Most shocking was their mental status,” he wrote in a biographical sketch for the Nobel Prize. “They behaved like wild animals, obviously suffering from severe anguish and suspiciousness and trusting nobody.”

After Carlsson completed his doctoral thesis in 1951, a scholarly committee told him its subject — calcium metabolism — wasn’t particularly pharmacological, let alone interesting.

Searching for a new research specialty, he asked Sune Bergstrom, a University of Lund researcher who later received a Nobel Prize, if he could recommend anyone working at a “chemically oriented” pharmacology lab.

The request led him to the National Heart Institute (now the National Heart, Lung and Blood Institute), where he worked under Bernard Brodie, a boxer turned biochemist, and began the research that brought him the Nobel.

Carlsson married Ulla-Lisa Christoffersson in 1945, and they had five children. His daughter, Maria Carlsson, eventually worked as his laboratory manager. “Without her commitment,” Carlsson told Sahlgrenska Academy on his 90th birthday, “I would have been an ordinary pensioner today.”