Lateral hypothalamic dopaminergic neural activity in response to total parenteral nutrition.

Abstract

The lateral hypothalamic dopaminergic neurons dominate modulation of food intake. Changes in lateral hypothalamic synaptic dopaminergic release before and during total parenteral nutrition (TPN) and its components were measured in vivo with microdialysis probes. Rats had an intracerebral guide cannula and an internal jugular catheter placed. Ten days after recovery, rats were fasted for 24 hours. A 2 mm microdialysis probe was inserted into the lateral hypothalamus neurons via the guide cannula. Dopamine level was measured by high-performance liquid chromatography in three 60-minute baseline dialysis samples. TPN, glucose, fat, or amino acid was then infused via the internal jugular catheter, and dopamine level was measured in three more 60-minute dialysate samples. Single nutrients were infused for 24 hours, and dopamine was measured during the 3 hours after the infusions were stopped. Data were analyzed by paired t test (mean +/- standard error) and represented percentage change from baseline. Dopamine levels rose significantly (p < 0.05) and remained so during infusions in TPN (26% +/- 3%), glucose (26.5% +/- 4.6%), fat (36.2% +/- 6.7%), and amino acids (9.6% +/- 4.2%). After infusions were stopped, dopamine levels decreased to -35.4% +/- 1.5% in glucose but remained unchanged with fat and amino acids. Increase in lateral hypothalamic dopamine level occurs with TPN and its components, and changes persist temporarily after stopping the infusions, explaining in part the slow recovery of food intake after TPN is stopped.