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1Department of Physiology, Universidade Federal de São Paulo, Escola Paulista de Medicina, São Paulo, SP 04023-062; and 2Department of Physiology, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901, Brazil
Submitted 2 October 2002 ; accepted in final form 28 April 2003
The cardiovascular effects of substance P (SP) microinjections in the nucleus tractus solitarii (NTS) were evaluated in conscious rats. We chose this model because it is an effective way to access some of the cardiovascular effects of neurotransmitters in the NTS without the inconvenience of blunting pathways with anesthetic agents or removing forebrain projections by decerebration. The cardiovascular responses to SP injections were also evaluated after chronic nodose ganglionectomy. We found that, in conscious rats, SP microinjections into the NTS induced hypertension and tachycardia. Unilateral and bilateral SP injections into the NTS caused a slow increase in blood pressure and heart rate that peaked 1.55 min after injection and lasted for 2030 min. Nodose ganglionectomy increased the duration of the pressor and tachycardic effects of SP and enhanced the pressor response. These data show that SP in the NTS is involved in pressor pathways. The supersensitivity to SP seen after nodose ganglionectomy suggests that vagal afferent projections are involved in those pressor pathways activated by SP in the NTS.
blood pressure; heart rate; neurokinins; brain stem
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