The role of "the law of initial value" and the levels of the central nervous system in the spatial interactions of blood pressure reflexes.

In experiments carried out on cats it has been found that various anaesthesia (chloralose, pentobarbital or urethan, given in doses of 50 mg/kg, 45 mg/kg and 800 mg/kg, respectively) did not influence the parameters of regression lines describing the spatial interactions of depressor reflexes of somatic and visceral origin. The individual differences showed a correlation with the "mean basal blood pressure" only. There was a linear relationship between the "mean basal blood pressure" and the X-axis intercepts of the regression lines. The size of the latters determined the extent of the facilitatory zone. No differences could be demonstrated between spatial interactions of depressor reflexes evoked by stimulation of somatic or visceral afferents. It seems that the depressor reflex-mechanism operates identically, independently of the input level. The interactions of pressor reflexes were shown to be of the additive type in the case of chloralose or pentobarbital anaesthesia, while of the facilitatory type under urethan anaesthesia. The distribution of spatial interactions of pressor reflexes observed in spinal cats was similar to that observed in animals anaesthetized with chloralose or pentobarbital. The role or various levels of the central nervous system in the organization of spatial interactions of blood pressure reflexes is discussed.