| Abstract No.: | B-G2182 |
| Country: | Canada |
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| Title: | DISCHARGE PROPERTIES OF LATERAL HYPOTHALAMUS NEURONS IN RELATION TO REWARDING AND AVERSIVE CONDITIONED AND UNCONDITIONED STIMULI |
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| Authors/Affiliations: | 1 Christopher Cordova*; 1 Barbara Jones;
1 Montreal Neurological Institute, McGill University, Montreal, QC, Canada.
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| Content: | Objectives: The lateral hypothalamus (LH) has been implicated in diverse regulatory functions, including feeding, reward learning, stress and behavioral arousal. To address the functional selectivity of neuronal responses in the LH, discharge properties of neurons were characterized in response to rewarding and aversive conditioned and unconditioned stimuli.
Materials and Methods: Rats were trained to differentially respond to two conditioned auditory tones (CS), which predicted either the instrumental delivery of a sweet sucrose solution or a bitter quinine solution (US), obtained by licking a straw and avoided by delaying or withholding a licking response. Single units were subsequently recorded using glass micropipettes in association with EEG and EMG during the performance of the discrimination task, and some cells were juxtacellularly labeled with Neurobiotin (Nb) following recording for histological confirmation.
Results: EEG and EMG activities were altered during and after the CS periods, reflecting an increase in cortical activation (decreased delta, 1-4 Hz and increased gamma, 30 – 60 Hz, power) and muscle tone or movement in response to the CS and US. Of 18 recorded cells, 7 exhibited a significant task-related modulation of firing rate. One group of cells (n=3) showed a modulation of discharge that was dependent on the valence of the CS and US as rewarding or aversive. Another group of cells (n=4) showed a task-related modulation that was independent of the valence of the CS and US as rewarding or aversive.
Conclusion: Although some neurons in the LH respond selectively to rewarding or aversive stimuli, many respond in a valence-independent manner. The latter activity pattern can be characterized as discharge in association with the generalized arousal of a motivated behavioral response. This pattern is consistent with arousal related functions of the LH neurons, including the Orexin/ Hypocretin neurons, whose contribution is essential for the maintenance of the waking state.
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