Intra-paraventricular nucleus microinjection of D2 receptors antagonist, sulpiride, reduces food intake in 24 hours food-deprived rats

Dopamine plays an important role in modulating food intake in the central nervous system. Dopamine receptors are distributed within the hypothalamus with significant expression of D2 receptors in hypothalamic paraventricular nucleus (PVN). D2 receptors are involved in modulation of food intake. Therefore, they might have potential as a pharmacologic target in treatment of obesity. This study was conducted to find if microinjection of the D2 receptor antagonist sulpiride, into PVN can modulate food intake.

A guide cannula was stereotaxically implanted in PVN (coordinates: L:+0.4; DV:7 AP:-1.8 mm) of male Wistar rats weighing 220-250 g. Sulpiride (0.1, 0.3, 0.75, 1.5, and 3μg) or saline were injected into PVN after a 7 day recovery period. Food intake was then measured at one, two and three hours afterward. Moreover, effect of sulpiride (0.1 μg, intra-PVN) on spontaneous activity of animals was measured by Auto vision instrument.

Sulpiride at the doses of 0.1 μg (p < 0.001), 0.3 μg (p < 0.001), 0.75 μg (p < 0.01), and 3μg p < 0.05) significantly decreased food intake in a dose- and time-dependent manner. Sulpiride 0.1μg had no significant effect on the locomotor activity of animals.

Activation of D2 receptors of PVN increases food intake. Intra-PVN microinjection of sulpiride decreases food intake by blocking D2 receptors in this area.