Blood Pressure Responses to Electrical Stimulation of Peripheral Nerves and their Modification by Nembutal

Blood pressure changes, evoked by stimulation of peripheral nerves, decline if the frequency of stimulation passes beyond the optimal range. Instability of a response develops progressively and is ascribed to the increasing influence of inhibitory components in a given circuit.2. Unstable reactions can be converted into sustained responses by two methods: a by intermittent stimulation, which prevents the inhibitory effects to summate to their threshold value; and b by application of barbiturate, which produces selective block of inhibitory transmission.3. With graded doses of nembutal, a double reversal of the blood pressure response to sciatic stimulation can be produced. This phenomenon is interpreted on the basis of the complex composition of the nerve, which sends fibres to autonomic centres in the hypothalamus and the medulla.