CARDIOVASCULAR EFFECTS OF HYPERTONIC SODIUM CHLORIDE SOLUTIONS WHEN INJECTED INTO THE LIQUOR SPACE OF ANAESTHETIZED CATS

Abstract

1 In cats anaesthetized with chloralose, hyper- and hypotonic solutions were injected into the cisterna magna (in 0.5 ml) or into a lateral cerebral ventricle (in 0.2 to 0.3 ml), with aqueduct cannulated to prevent the injected solution from entering the subarachnoid space, and the effects on blood pressure and heart rate were examined. 2 Cisternal injections of hyper- and hypotonic solutions of NaCl (0.51 m and 0.05 m), glucose (1.03 m and 0.10 m), or sucrose (1.02 m and 0.10 m), as well as distilled water produced a rise in arterial blood pressure with tachycardias. Isotonic solutions of NaCl, glucose or sucrose were ineffective. 3 Ventricular injections of the hypertonic NaCl solution, also produced a pressor response with tachycardia as did an equally hypertonic solution of NaHC0₃ but the other solutions produced no circulatory effects when injected in this way. 4 The pressor responses and the tachycardias occurred after bilateral vagotomy and resulted from a sympathetic discharge which, on cisternal injection, originated from structures reached from the subarachnoid space, and on ventricular injection, from structures in the ventricular walls, probably in the hypothalamus. 5 The stimuli responsible for the discharge, were, on cisternal injection, the changes in osmolarity. and on ventricular injection, the sodium ions.