Endogenous opioids, circadian rhythms, nutrient deprivation, eating and drinking

Area of Science:

• Neuroscience
• Endocrinology
• Behavioral Biology

Background:

• Endogenous opioids like beta-endorphin (b-END) and dynorphin (DYN) are implicated in regulating physiological processes.
• Circadian rhythms govern daily patterns of essential behaviors such as eating and drinking.
• The specific roles of b-END and DYN in the diurnal regulation of feeding and drinking remain to be fully elucidated.

Purpose of the Study:

• To investigate the involvement of immunoreactive (ir) beta-endorphin (b-END) and dynorphin (DYN) in the regulation of eating and drinking patterns in rats.
• To examine the influence of food and water deprivation on brain and pituitary levels of ir-b-END and ir-DYN.
• To assess the impact of arcuate nucleus lesions on the circadian rhythmicity of eating and drinking.

Main Methods:

• Measurement of immunoreactive beta-endorphin (ir-b-END) and dynorphin (ir-DYN) in rat brain and pituitary tissues.
• Experimental manipulation involving food and water deprivation.
• Assessment of eating and drinking behaviors in rats with arcuate nucleus lesions.

Main Results:

• Circadian variations in ir-DYN levels were observed, with higher concentrations in the hypothalamus and lower concentrations in the pituitary at night.
• Water deprivation, particularly, led to increased hypothalamic ir-DYN during the day and decreased pituitary ir-DYN.
• Arcuate nucleus lesions, which depleted both ir-b-END and ir-DYN, did not alter total daily food or water intake but significantly modified the circadian rhythmicity of these behaviors.

Conclusions:

• The findings support the conclusion that beta-endorphin (b-END) and dynorphin (DYN) play a significant role in maintaining the day-night patterns of eating and drinking.
• These neuropeptides are integral components of the neural circuitry regulating circadian rhythms of ingestive behaviors.
• Modulation of hypothalamic and pituitary opioid levels by deprivation states affects feeding and drinking patterns.