Release of beta-endorphin immunoreactivity from brain by activation of a hypothalamic N-methyl-D-aspartate receptor.
Lateral ventricle-cisterna magna perfusion in the halothane-anesthetized rat was used as a model to study beta-endorphin release in the brain. Microinjection of N-methyl-D-aspartate into the arcuate nucleus of the hypothalamus released beta-endorphin immunoreactivity into perfusate and the release was blocked by systemic pretreatment with the N-methyl-D-aspartate antagonist dizocilpine (MK-801). N-methyl-D-aspartate microinjections did not increase beta-endorphin immunoreactivity in plasma, and pretreatment with dexamethasone did not prevent release of beta-endorphin immunoreactivity into perfusate, emphasizing that the released beta-endorphin immunoreactivity did not come from plasma. The non-N-methyl-D-aspartate glutamate receptor agonist alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid hydrobromide did not release beta-endorphin immunoreactivity. High-performance liquid chromatography characterization of perfusates collected after N-methyl-D-aspartate microinjection showed that a major part, but not all, of the beta-endorphin immunoreactivity co-eluted with authentic beta-endorphin. Microinjection of N-methyl-D-aspartate provoked an algogenic response in the anesthetized rat, and inhibited the motor and cardiovascular responses to tail immersion in 52.5 degrees C water. This block was reversed by pretreatment with MK-801, but not naloxone. Injection of alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid hydrobromide elicited the same behavioral response and blocked the nociceptive tail-dip reaction, but did not release beta-endorphin immunoreactivity.(ABSTRACT TRUNCATED AT 250 WORDS)
Bach
F W
FW
Anesthesiology Research Laboratory, University of California San Diego, La Jolla 92093-0818, USA.
Yaksh
T L
TL
D000818:Animals; D001921:Brain / Q000502:physiology; D002851:Chromatography, High Pressure Liquid; D002946:Cisterna Magna / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D007031:Hypothalamus / Q000502:physiology*; D007150:Immunohistochemistry; D008297:Male; D016202:N-Methylaspartate / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*; D013997:Time Factors; D001615:beta-Endorphin / Q000378:metabolism*
D016194:Receptors, N-Methyl-D-Aspartate; D001615:beta-Endorphin; D016202:N-Methylaspartate