Muscimol injection into the lateral hypothalamus inhibits the hypotension and bradycardia caused by somato-visceral nociception

This study investigated whether the lateral hypothalamus (LH) contributes to the depressor response evoked by somato-visceral nociception. Lidocaine (2%; 0.1, 0.3 or 1.0 μl) or muscimol (0.34 nmol; 0.5 μl) was microinjected into the rostral LH of halothane-anesthetized rats bilaterally and somato-visceral nociception was induced 2 min later by injecting 5% acetic acid (0.5 ml) intraperitoneally. Lidocaine and muscimol inhibited the hypotension and bradycardia caused by somato-visceral nociception significantly without affecting cardiovascular function in normotensive animals.