3-DIMENSIONAL ANATOMIC RELATIONSHIP OF SEROTONERGIC AND MUSCARINIC RECEPTOR-BINDING IN THE PONTINE RETICULAR-FORMATION OF THE HUMAN INFANT BRAIN-STEM

Cholinergic and serotonergic neurons of the rostral pontine reticular formation have been implicated by animal studies in the modulation of sleep and waking, To define better the spatial relationships between m uscarinic and serotonergic receptor binding in the rostral human brain stem, we used 3-dimensional computer reconstructions of serial autorad iographs generated with radioligands to muscarinic and serotonergic re ceptors. Receptor binding was assessed in a series of 9 human infants, and 3-dimensional reconstructions were performed in a representative infant at 53 postconceptional weeks. The computer reconstructions demo nstrated a 3-dimensional distinct pattern in the rostral pontine retic ular formation, with high (H-3)lysergic acid diethylamide binding to s erotonin receptors in the median raphe nucleus flanked by paramedian b ands of high (3H)quinuclidinyl benzilate binding to muscarinic choline rgic receptors in the medial nucleus pontis oralis. Based upon compari sons to animal data, we suggest that the muscarinic-serotonergic patte rn of receptor binding in the rostral pontine reticular formation repr esents part of the neurochemical organization of the circuitry involve d in the modulation of rapid eye movement (REM) sleep in humans.