Sulpiride increases and dopamine decreases intracranial temperature in rats when injected in the lateral hypothalamus: an animal model for the neuroleptic malignant syndrome?

Sulpiride in the perifornical lateral hypothalamus (pfLH) (4, 8 and 16 μg/ 0.5 μl) increased intracranial temperature (Tic). The hyperthermia started immediately after the injection, peaked 30 min later and lasted for more than 90 min. Sulpiride (12 μg) accelerated recovery from hypothermia in anesthetized animals. Forty-five min after sulpiride Tic raised 1.17±0.06°C. After a control injection the raise was only 0.5±0.13°C. Locally applied dopamine (DA) (5, 10 and 20 μg) 5 min before sulpiride (12 μg) attenuated sulpiride hyperthermia. The largest DA dose reduced Tic (−1.21°C) when administered alone. These findings suggest the existence of D2 receptors in the LH involved in thermoregulation. Chances are that D2 receptors in the human LH could be responsible for the neuroleptic malignant syndrome (NMS), and that sulpiride injections in the rat LH could be used as a model for the study of the pathogenesis of this syndrome.