Olfactory associative conditioning in infant rats with brain stimulation as reward. I. Neurobehavioral consequences.
In Experiment 1, infant rats were implanted with a stimulating electrode in the medial forebrain bundle/lateral hypothalamus (MFB/LH) on postnatal day 12 (PN12). Four to 6 hours later, the pups underwent associative olfactory conditioning, with half of the pups trained with 30 temporal pairings of odor (5 s) and MFB/LH stimulation (200 Hz, 300 ms), and the other half trained with random presentations of odor and MFB/LH stimulation. On PN13, pups were tested for: (1) behavioral preference for the conditioned odor; (2) focal glomerular layer 2-DG uptake to the odor; or (3) mitral/tufted cell single-unit response pattern to the odor. Odor-MFB/LH pairings produced a relative behavioral preference, enhanced focal 2-DG uptake and a modified mitral/tufted cell response pattern to the conditioned odor. Random training resulted in none of these changes. In Experiment 2, PN12 pups were anesthetized with urethane and single-unit responses of mitral/tufted cells to MFB/LH stimulation were examined. MFB/LH stimulation produced a brief suppression of mitral/tufted cell activity followed either by a prolonged excitation (18/30 cells; 8-10 s duration) or a prolonged suppression (12/30 cells; 10-30 s). These results suggest that pairing olfactory nerve input with MFB/LH stimulation modifies subsequent behavioral and physiological responses to olfactory nerve input alone. Furthermore, the prolonged olfactory bulb response to MFB/LH stimulation may be critical in this modification.
Wilson
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Department of Psychology, University of Oklahoma, Norman 73019.
Sullivan
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D000818:Animals; D002490:Central Nervous System / Q000502:physiology*; D003214:Conditioning, Classical / Q000502:physiology*; D004558:Electric Stimulation; D005260:Female; D007026:Hypothalamic Area, Lateral / Q000502:physiology*; D008297:Male; D008474:Medial Forebrain Bundle / Q000502:physiology*; D009812:Odorants; D009833:Olfactory Pathways / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012201:Reward