Fig. 7. Changes in ventral aortic blood pressure (P_VA) and heart frequency (fH) arising from sequential injections of glutamate, vehicle (NaCl) and N-methyl-L-aspartate (NMDA) receptor antagonist MK-801 at 1.0 mm rostral of obex and 0.3 mm lateral to the midline. The arrows indicate the time of injection, and the numbers (in mm) indicate the depth of the injections. Note the rapid and the marked bradycardia. Also observe the absence of responses to NaCl and the preciseness of the MK-801 blockade. Injection volume ranged between 40 nl and 100 nl.