Direct effects of endogenous pyrogen on medullary temperature-responsive neurons in rabbits.
The effect of endogenous pyrogen (E.P.) injected directly into the tissue near the recording site were examined on the activities of the medullary temperature-responsive (TR) neurons in rabbits anesthetized with urethane. Endogenous pyrogen prepared from rabbit's whole blood was administered by a fine glass cannula (100-200 micrometer in diameter) in a fluid volume of 1 to 4 microliter. The cannula was fixed to the manipulator in parallel with a microelectrode and their tips were less than 0.05 mm apart. In rabbits with the intact preoptic/anterior hypothalamic (PO/AH) region, 4 warm-responsive neurons out of 7 were inhibited and 6 cold-responsive neuron out of 7 were excited by the direct administration of the E.P. In rabbits with lesions of the PO/AH, 5 warm-responsive neurons out of 9 were inhibited and 6 cold-responsive neurons out of 8 were facilitated by E.P. Antipyretics administered locally after the E.P. antagonized the pyretic effect, causing a return of the discharge of TR neuron to the control rate within 2.4 +/- 1.2 (mean +/- S.D.) min. The medullary TR neuron itself has the ability to respond to the E.P. and contributes to the development of fever.
D000818:Animals; D001831:Body Temperature; D004177:Dipyrone / Q000494:pharmacology; D007032:Hypothalamus, Anterior / Q000473:pathology / Q000502:physiology; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D011301:Preoptic Area / Q000473:pathology / Q000502:physiology; D011749:Pyrogens / Q000502:physiology*; D011817:Rabbits
D011749:Pyrogens; D004177:Dipyrone