Sentence:  On the other hand , the temporary reduction in hypothalamic excitability through the injection of a <WSD>barbiturate</WSD> into the posterior hypothalamus causes a lessening in frequency and amplitude of cortical strychnine spikes until the hypothalamic excitability is restored . 
Meaning of the word marked with <WSD> tags:  organic compound having powerful soporific effect; overdose can be fatal