Release of 14C-norepinephrine into the lateral cerebroventricle of rats by exposure to a conditioned aversive stimulus.
Rats chronically implanted with push-pull cannulas were injected with a pulse of 14C-norepinephrine (NE) into the lateral cerebroventricle under a variety of pretreatment and behavioral conditions. Animals pretreated intraventricularly with 6-hydroxydopamine (Group A) or ascorbic acid vehicle (Group B) were subsequently perpised imder fpur conditions: (1) presentation of a novel, visual stimulus in a one-way avoidance chamber; (2) presentation of the light (CS) followed by shock; (3) training to a high level of avoidance behavior, after which the CS was presented in the absence of opportunity for an avoidance response and in the absence of shock; and (4) after forced extinction, followed by CS without opportunity to aboid and with out presentation of shock. Samples of perfusate from rats subjected to the four test conditions were analyzed by thin-layer chromatography for total 14C in a scintillation counter and for proportion of NE and normetanephrine (NM). During Tests 1 and 4 the 14C perfusion wash-out did not differ from control values for either Group A or B. During Test 2, total radioactivity as well as the proportions of NE and NM increased in the perfusate for both Groups A and B. Presenting the CS without shock (3) resulted in 14C and NE and NM for Group B (vehicle), but not for Group A (6-OHDA). To test for non-specific release unrelated to a brain catecholaminergic function, another group of rats was subjected to identical treatments with the exception that 14C-urea replaced 14C-NE as a pulse-label. In these animals Test 2 (shock) induced an increase in 14C in the perfusate, while Tests 1, 3 and 4 yielded wash-out curves essentially identical to controls.
D000818:Animals; D001362:Avoidance Learning / Q000502:physiology*; D002250:Carbon Radioisotopes; D002552:Cerebral Ventricles / Q000378:metabolism*; D003213:Conditioning, Psychological / Q000502:physiology*; D004597:Electroshock; D005108:Extinction, Psychological / Q000502:physiology; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D010775:Photic Stimulation; D051381:Rats; D014508:Urea / Q000378:metabolism
D002250:Carbon Radioisotopes; D014508:Urea; D009638:Norepinephrine