Lateral Hypothalamic Stimulation in Satiated Rats: The Rewarding Effects of Self-Induced Drinking

Abstract

Clearly the inactive phase cannot be explained by a general depression of the "ascending reticular system" because ECoG desynchronization (occurring either spontaneously or following stimulation of the reticular formation) was observed in cortex 1 cm or more from the site of depression. This inference is consistent with the finding of Bures et al. (18) that in the unanesthetized rat most reticular neurons only increased in rate during SD. (By contrast, the majority of medial thalamic neurons they studied showed only an inactive phase.) Neither synaptic fatigue (for example, transmitter depletion) nor delayed inhibition, caused by the high level of corticofugal discharge, adequately account for the inactive phase, because it was readily observed during cortical cooling without a preceding phase of hyperactivity. The mean rates of discharge attained during SD excitation exceeded those occurring either spontaneously or in response to stimulation of the reticular formation. However, some innervated neurons may be driven at comparable rates for many seconds by peripheral stimulation but return quickly to the control rate of discharge following such stimulation (19).Although reduction of corticothalamic discharge is associated with reduced activity of VP neurons, our experiments do not directly differentiate between reduced direct excitatory drive and reduced inhibition of tonically active inhibitory interneurons (disinhibition). Either mechanism would lead to reduced facilitation of VP neurons. However, because increased inhibition of tonic inhibition probably could not alone account for the very high level of discharge during the excitation phase we conclude that the dominant effect exerted by corticothalamic neurons is synaptic excitation. Therefore, the relatively small decrease in excitability that was observed during the early part of the inactive phase probably resulted from reduced synaptic facilitation. Our finding that depression of sigmoid gyrus and adjacent cortex leads to reduced VP neuron activity is consistent with anatomical evidence that this region of cortex projects to VP (17). The data imply that the response of VP neurons to reticular formation stimulation re-Clearly the inactive phase cannot be explained by a general depression of the "ascending reticular system" because ECoG desynchronization (occurring either spontaneously or following stimulation of the reticular formation) was observed in cortex 1 cm or more from the site of depression. This inference is consistent with the finding of Bures et al. (18) that in the unanesthetized rat most reticular neurons only increased in rate during SD. (By contrast, the majority of medial thalamic neurons they studied showed only an inactive phase.) Neither synaptic fatigue (for example, transmitter depletion) nor delayed inhibition, caused by the high level of corticofugal discharge, adequately account for the inactive phase, because it was readily observed during cortical cooling without a preceding phase of hyperactivity. The mean rates of discharge atta...

Lateral hypothalamic stimulation: Stimulus-bound eating and self-deprivation☆

“…On the other hand, if Spies' [16] assumption that rewarding stimulation produces a temporary food drive reduction ("transient satiety equivalent") is accepted then it is equally puzzling that animals eat when stimulated at the brain site. Attempts to resolve the paradox by noting that different stimulation durations are typically used to evoke eating and self-stimulation are not convincing as several investigators have demonstrated both phenomena with identical parameters [2,10]. Earlier work by Margules and Olds [9] and Hoebel and Teitelbaum [8] demonstrated that self-stimulation rates in the lateral hypothalamus are potentiated by food deprivation.…”

Neuroeconomics: How Neuroscience Can Inform Economics

“…Unlike more naturalistic rewards, EBS does not satiate. And electrical brain stimulation at specific sites often elicits behaviors such as eating, drinking (Mendelson 1967), or copulation (Caggiula and Hoebel 1966). Many abused drugs, such as cocaine, amphetamine, heroin, cannabis, and nicotine, lower the threshold at which animals will lever-press for EBS (Wise 1996).…”

Assessment of Safety and Outcome of Lateral Hypothalamic Deep Brain Stimulation for Obesity in a Small Series of Patients With Prader-Willi Syndrome

“… 10 This was supported by early experiments that contributed to our knowledge about mechanisms and circuits involved in these processes. Initial studies targeting the LHA in rodents 11 , 12 and felines 13 showed an increase in feeding, an effect partially attributed to the modulation of the medial forebrain bundle. 14 In contrast, recent experiments in rodents reported a reduction in weight gain following high-frequency stimulation.…”