Feeding following intraventricular injection of CA++, MG++ or pentobarbital in pigs

The effects on food intake, of injections into the lateral ventricle of Ca++, Mg++ or equimolar mixtures of the 2 ions have been studied in pigs. The chloride salts were made up in normal saline which together with 1.35 percent NaC1 was used as a control injection. Dosages of 12.5 mumoles, 25 mumoles, or 50 mumoles either Ca++ or Mg++ elicited increased food intake in the 30 min following the injection and there was a predominantly linear feeding response to increasing concentration of the two ions. Ca++ was more effective in eliciting increased food intake than Mg++. Equimolar mixtures of Ca++ and Mg++ of 6.5 + 6.5 mumoles, 12.5 + 12.5 mumoles or 25 + 25 mumoles also increased food intake linearly and the mixture of ions was more effective than equivalent concentrations of Ca++ or Mg++ alone. No antagonism between Ca++ and Mg++ was seen with respect to food intake. Intraventricular injections of 16 mumoles of sodium pentobarbital also elicited increased food intake in the 30 min following injection. It is suggested that the ions and the barbiturate probably act by deression of periventricular neurons, particularly in the medial hypothalamus which is adjacent to the third ventricle.