Synergies from a distance: Inspirations from the struggles of Dr James M Krueger

In this article for Dr Krueger's Festschrift, I trace how his early career influenced many aspects in the fields of sleep, neuroimmunology, and the microbiome. Mostly, however, I trace how his career and interests intertwined with those of Abba J. Kastin and mine and how he exerted a profound influence on the direction of our studies. Dr. Krueger, while developing his career as a sleep researcher, encountered resistance to his work that required two major paradigm shifts: 1) that bacterial products could affect sleep and 2) that small peptides can cross the blood-brain barrier (BBB) in sufficient amounts to affect brain functioning. Dr Kastin had also shown that small peptides administered peripherally could affect brain function and postulated that this was because they could cross the BBB. Our efforts to determine whether peptides could or could not cross the BBB were bolstered by Dr Krueger's exemplary struggles.