The effects on feeding of galanin and M40 when injected into the nucleus of the solitary tract, the lateral parabrachial nucleus, and the third ventricle

Several reports indicate that central injection of galanin stimulates feedi ng, and that there is macronutrient specificity in this response. In additi on, the galanin receptor antagonist, M40, reduces food intake when injected centrally. The nucleus of the solitary tract (NTS) and the lateral parabra chial nucleus (PBN) contain galanin receptors, and are involved in the cont rol of food intake. Hence, we sought to compare the feeding response to gal anin injection into these areas with that of third ventricle (3V) galanin i njection. The feeding response to injection of galanin was greatest for the 3V. Hindbrain injection of galanin stimulated food intake only at the begi nning of the dark period. NTS injection of M40 inhibited intake of a macron utrient diet in food-deprived rats, but was ineffective at reducing dark-on set feeding or deprivation-induced chow intake. 3V injection of M40 did not reduce deprivation-induced intake. PEN injection of galanin at dark onset had no effect in a group of fat-preferring rats. These results suggest that hindbrain galanin may contribute to feeding by inhibiting satiety, and tha t hypothalamic galanin receptors are involved with stimulation of intake. F urthermore, the absence of a consistent pattern of the stimulation of macro nutrient intake suggests that galanin may not be a significant effector of macronutrient selection during individual meals. (C) 1999 Elsevier Science Inc.