Research has found that damage to the lateral hypothalamus (LH) in rats results in aphagia (decreased feeding). The stimulation of the LH stimulates eating, it is therefore suggested that the LH is the 'on' switch for feeding.
A more complex theory have been made, which involves a neurotransmitter in the LH, called Neuropeptide Y (NPY). When rats were injected with NPY, they began to feed immediately, even after satiation (Wickens (2000)) Within a few days of injecting NPY, the rats were obese (Stanley et al (1986)).
Damage to the ventromedial hypothalamus (VMH) caused rats to overeat, this ins a condition called hyperphalgia. Stimulation to the VMH inhibits feeding. Damage to a control of feeding causes increased feeding and body weight. It has been concluded that the VMH is the 'satiety centre' and stops feeding.
Damage to nerve fibers passing the VMH also damages other parts of the hypothalamus. The paraventricular nucleus (PVN) is believed to cause hyperphalgia (Gold (1973))
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