Responses to microinjections of d-tubocurarine into the hypothalamus of cats

Microinjections ofd-tubocurarine chloride (d-Tc) were made into the hypothalamus of cats through a stereotaxically implanted cannula-electrode to reproduce the effects of intraventricular doses (100–200 μg/kg) ofd-Tc. Single intrahypothalamic injections of 3–6 μg caused rise of blood pressure, stimulation of respiration and enhancement of knee jerk and produced tremor and jerks in most of the experiments. After a delay of 10–15 min the electrical activity of the injected site changed with the appearance of high voltage waves and spikes which were found to spread to other areas recorded. The effects of similarly low intraventricular doses were comparatively much less in incidence and intensity. Thus the hypothalamus appeared to be the site of origin ofd-Tc-induced autonomic and motor effects, and abnormal electrical activity. The effects of intrahypothalamic doses ofd-Tc were poorly counteracted by Prostigmin.