Food Intake Is Inversely Correlated with Central Nervous System Histamine Receptor (H1) Concentrations in Male Sprague-Dawley Rats Fed Normal, Low Protein, Low Energy or Poor Quality Protein Diets

The reported studies were designed to examine relationships between whole-brain histamine receptors (H 1 ) and food intake in male Sprague-Dawley rats. Three different experiments were conducted. In each experiment, control rats were fed normal protein (25 g casein/100 g food) and normal metabolizable energy (16.21 kJ /100 g food) diets. Feeding low protein diets (1 g casein/100 g food) elevated central H 1 receptor concentrations (P < 0.0027) and reduced voluntary food intake (P < 0.007) compared with normal diets. Feeding low energy diets lowered H 1 receptor concentrations (P < 0.0089) and increased voluntary food intake (P < 0.0012). Low quality protein diets also affected the central nervous histaminergic system. Whole-brain H 1 receptor concentrations were significantly higher for rats fed low quality protein (25 g gelatin/100 g food) compared with rats fed casein (P < 0.0001). Rats fed medium quality protein (25 g wheat gluten/100 g food) or low quality protein ate significantly less food (P < 0.0001). In all experiments, dietary manipulation affected central histamine receptors. Elevated concentrations of H 1 receptors were associated with a decrease in food intake whereas lowered concentrations of H 1 receptors were associated with an increase in food intake (P < 0.001). The results of these experiments support the hypothesis that central histamine H 1 receptor concentrations in male rats are inversely correlated with voluntary food intake and affected by dietary composition. .