The Region of Medial Forebrain Bundle is Involved in Tonic Maintenance of Arterial Pressure and Heart Rate

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Abstract
The role of the medial forebrain bundle (MFB) in central regulation of cardiovascular system was studied in freely moving rats. Injection of lidocaine into the ventral, but not other portions of the MFB, produced transient (approximately ten minutes) pressor and tachycardic responses. These responses resulted from an increase in sympathetic tone, since they were abolished by ganglionic blockade. The pressure response was attenuated by alpha-adrenoceptor blockade and both pressor and tachycardic responses were diminished by beta-adrenoceptor blockade. Electrolytic lesion of the same site caused long lasting pressor and tachycardic responses. Injection into the MFB of the excitatory amino acids, kainate (KA) and N-methyl-D,L-aspartate (NMDA) produced pressor and tachycardic responses accompanied by behavioral excitation, whereas no effects were produced by L-glutamate. The cardiovascular responses induced by KA and NMDA were abolished by ganglionic blockade. These results suggest that a selective region of MFB contains fibers of passage and/or cell bodies, with receptor specificity for excitatory amino acids, that are capable of influencing sympathetic sympathetic control of arterial pressure.