MICROINJECTION OF S-NITROSOCYSTEINE INTO THE NUCLEUS-TRACTUS-SOLITARII OF CONSCIOUS RATS DECREASES ARTERIAL-PRESSURE BUT L-GLUTAMATE DOES NOT

Unilateral microinjection of L-glutamate into the nucleus tractus solitarii of conscious rats increased arterial pressure and caused bradycardia while microinjection of S-nitrosocysteine into the same site of these animals caused hypotension and bradycardia. The responses to S-nitrosocysteine were blocked by prior microinjection of methylene blue into the nucleus tractus solitarii. The bradycardia and fall in arterial pressure induced by S-nitrosocysteine resemble more the cardiovascular changes in response to activation of baroreceptor afferents than the bradycardia and increase in arterial pressure induced by microinjection of L-glutamate into the nucleus tractus solitarii of conscious rats.