ABSTRACT
In halothane-anesthetized rats, 283 caudal medullary neurons responsive to colorectal distension (CRD) were characterized using extracellular electrodes. Neurons inhibited by CRD (n = 82) were in the area dorsal to the lateral reticular nucleus (LRN). Most neurons excited by CRD (n = 130) were located within or immediately adjacent to the LRN, were excited by noxious heat and/or noxious pinch of at least half the body surface and were called bilateral nociceptive specific (bNS) neurons. bNS neurons had accelerating responses to graded CRD (threshold: 20 +/- 2 mmHg). Ten of twelve bNS neurons tested could be antidromically activated by electrical stimulation of the midline cerebellum. Other neurons excited by CRD (n = 71) had mixed responses to cutaneous stimuli and were generally located in the area dorsal to the LRN. Increases in blood pressure due to intravenous phenylephrine did not significantly alter the spontaneous activity of neurons excited by CRD, but altered spontaneous activity (12 excited, four inhibited) in all neurons tested which were inhibited by CRD. Decreases in blood pressure produced by intravenous nitroprusside produced a reciprocal response in most neurons inhibited by CRD and had a delayed onset (20-30 s after bolus administration) excitatory effect on 21 of 27 units excited by CRD. Combined with other studies, these data suggest a role for neurons within and adjacent to the LRN in the modulation of visceral nociception. They also implicate a role for the cerebellum in visceral nociceptive processing.
Subject(s)
Medulla Oblongata/physiology , Neurons/physiology , Pain/physiopathology , Skin/physiopathology , Viscera/physiopathology , Animals , Axons/physiology , Brain Mapping , Catheterization , Intestines/physiopathology , Male , Medulla Oblongata/drug effects , Medulla Oblongata/pathology , Neurons/drug effects , Pain/pathology , Physical Stimulation , Rats , Rats, Sprague-Dawley , Synaptic Transmission/physiology , Vasoconstrictor Agents/pharmacology , Vasodilator Agents/pharmacologyABSTRACT
Sleep apnea is a rare complicating factor of acromegaly associated with a high risk of perioperative airway compromise and unclear response to transsphenoidal resection of the underlying pituitary tumor. We reviewed four acromegalic patients with sleep apnea and documented postoperative objective and subjective improvement of their sleep disorders. The pathogenesis of this disorder and safe perioperative airway management are discussed.
