Role of paraventricular hypothalamic dopaminergic D1 receptors in food intake regulation of food-deprived rats.

Dopaminergic neurons play an important role on central regulatory mechanisms of feeding behavior. Dopamine receptors are distributed within the hypothalamus and densely localized in the paraventricular hypothalamic nucleus (PVN). From these ideas we postulated that PVN D1 receptors may play a role in regulating the food intake behavioral process. In this paper, we considered the effects of SKF38393, a D1 receptor agonist, and the D1 receptor antagonist (SCH23390), on food intake of conscious rats deprived of food for 24h. Our findings revealed that intraparaventricular injections of SKF383993 (0.3-5µg) stimulated food intake behavior in a dose dependent manner. This stimulatory effect of SKF3833 persisted over 2h of the monitoring period. The PVN injections of D1 receptor antagonist were associated with dose-dependent inhibition of food intake. SCH23390 (0.01µg) was also administered 5min before intraparaventricular injection of SKF3833. The results showed that SCH23390 suppressed stimulated food intake induced by SKF38393 (1.2µg). In conclusion, endogenous dopamine impact PVN D1 receptors and may be a factor in regulating the food intake behavioral process.

Comparison of Effects of Light Anesthetics, Diethyl Ether and Carbon Dioxide, on Hypothalamic Paraventricular Nucleus D1 and D2 Dopamine Receptors- and Glucosensitive Neurons-Induced Food Intake in Fasted Conscious Rats.

INTRODUCTION: Carbon Dioxide (CO2) and diethyl ether are used as light anesthetics. However, experimental data about their side effects are scarce. In addition, in all our previous works on regulatory mechanisms of hypothalamus during food intake, including the effect of Paraventricular Nucleus (PVN) D1 and D2 dopamine receptors and glucosensitive neurons, the drug injections were performed under brief diethyl ether anesthesia. In the current study, we tested the hypothesis which postulates that CO2 and diethyl ether as light anesthetic agents affect the stimulatory effect of PVN dopamine receptors and glucosensitive neurons in feeding behavior. METHODS: Male Wistar rats were implanted with guide cannula directed to their PVN. Glucose (0.8 µg), SKF38393 (D1 agonist, 0.5 µg), quinpirole (D2 agonist, 0.3 µg) and saline (0.3 µL) were microinjected into the PVN and food intake was measured over 1 hour. RESULTS: Our results showed that CO2 but not diethyl ether decreased food intake compared to intact animals. The PVN injections of glucose, SKF38393, and quinpirole increased food intake under brief diethyl ether anesthesia. In contrast, the PVN microinjected glucose-induced and dopamine receptor agonists-induced food intake were inhibited under light CO2 anesthesia. CONCLUSION: Our results suggest that brief exposure to CO2 and diethyl ether as light anesthetic agents may affect PVN glucosensing neurons-induced and dopamine receptors-induced food intake in fasted rats.