RESUMO
Nucleus accumbens is proposed as one of the centers in the neural circuitry involved in the regulation of feeding and drinking behaviour in rats. Injection of dopamine and angiotensin-II into this nucleus has been documented to affect water and food intake in rats. Reports on the effect of intracerebral injection of catecholamines on feeding and drinking behaviour in animal models are conflicting. Therefore, in the present study the effect of adrenaline and noradrenaline injected into nucleus accumbens on food and water intake in rats was assessed. 24 h basal food and water intakes were recorded in Wistar rats and were found to be 12.3 +/- 0.46 g and 21.7 +/- 1.03 ml respectively. Stainless steel cannulae were implanted stereotaxically into the nucleus accumbens. Four different doses (0.1 microgram, 0.5 microgram, 1 microgram, and 2 micrograms) of adrenaline and noradrenaline were injected into the nucleus accumbens through the implanted cannulae in different group of animals and their 24 h food and water intakes were recorded following these injections. No change in food and water intake was observed following the administration of different doses of adrenaline. A significant increase in 24 h water intake reaching a maximum of 28.88 +/- 1.45 ml at 1 microgram dose, without change in food intake was observed following administration of different doses of noradrenaline. The noradrenaline-facilitated water intake was blocked when noradrenaline was injected following injection of phentolamine, an alpha-receptor blocker. The bilateral lesions of nucleus accumbens resulted in a significant and sustained inhibition of water intake (16.61 +/- 0.67 ml) without change in food intake. These observations suggest that noradrenaline facilitates water intake without affecting food intake when injected into the nucleus accumbens in rats and the dipsogenic effect of noradrenaline is mediated by alpha-receptors. Adrenaline does not affect these ingestive behaviours when injected into the nucleus accumbens in rats.