GENDER AFFECTS RATS CENTRAL-NERVOUS-SYSTEM HISTAMINERGIC RESPONSES TODIETARY MANIPULATION

The histaminergic system (histamine and its H-1-receptor) of the centr al nervous system has been implicated in control of food intake. The r eported studies were designed to examine the effects of food restricti on and very low (1%) protein diets on central nervous system H-1-recep tors in male and female rats. In a series of experiments, groups of ra ts were freely fed a 25% protein diet, a 1% protein diet, or fed the 2 5% protein diet at 4 g/100 g body weight for 14-20 d. When freely fed 25% protein diets, females had higher whole-brain H-1-receptor binding than males on d 1 (female 122.36 +/- 4.53 and male 65.78 +/- 3.82 pmo l/g protein; P < 0.001). Changing diets affected central H-1-receptor binding in both males and females (P < 0.003). When rats were fed both restricted levels of food and 1% protein diets, the receptor binding of males increased by d 5 whereas that of females decreased by d 5 (P < 0.001). When fed 1% protein diets, females had decreased H-1-recepto r binding (98.4 +/- 2.38 pmol/g protein) and that in males increased t o 119.81 +/- 5.09 pmol/g protein. After 15 d, females had eaten signif icantly more food than males: females 166 +/- 4.9 g, males 124 +/- 1.9 g (P < 0.0007). Males had a significantly greater weight loss than fe males: males -28.8 +/- 2.6 g, females -17.08 +/- 0.97 g (P < 0.0007). When fed restricted diets, females had decreased H-1-receptor binding (93.81 +/- 5.58 pmol/g) whereas binding in males increased to 111.27 /- 8.55 pmol/g. preliminary saturation binding studies indicated that restricted food intake lowered receptor density (females consuming 25% protein: 715 +/- 30 pmol/g protein; female restricted: 467 +/- 28 pmo l/g protein, P < 0.05), while 1% protein increased receptor sensitivit y, i.e., lowered K-D (males consuming 25% protein: 15.3 +/- 1.8 nmol; males fed low protein: 2.8 +/- 0.27 nmol). This study suggests that di etary manipulation affects central H-1-receptor binding in a gender-sp ecific manner, thereby modulating central histaminergic activity durin g food or protein deficit.