REMOVAL OF GABAERGIC INHIBITION IN THE MEDIODORSAL NUCLEUS OF THE RATTHALAMUS LEADS TO INCREASES IN HEART-RATE AND BLOOD-PRESSURE

The mediodorsal nucleus of the thalamus (MD) has connections with cent ral autonomic centers involved in cardiovascular control and undergoes severe degeneration in fatal familiar insomnia, a human disease chara cterized by progressive dysautonomia. Microinjections of the GABA(A) a ntagonist bicuculline methiodide (BMI) into the medial and central por tion of the MD lead to significant, dose-dependent increases in both h eart rate and blood pressure. Similar injections into surrounding regi ons elicited little to no change. The data suggest that the medial and central portion of the MD plays a role in central cardiovascular regu lation. Neurons of the MD may be under tonic GABAergic inhibition, and disruption of circuits at this level may underlie dysautonomia in man y neurological diseases. (C) 1998 Elsevier Science Ireland Ltd.