Differential patterns of sympathetic responses to selective stimulation of nucleus tractus solitarius purinergic receptor subtypes

1, Studies are described that indicate that stimulation of different purinergic receptor subtypes (A(1), A(2A) and P2X) located in the sub-postremal nucleus tractus solitarius (NTS) evokes qualitatively and quantitatively different regional haemodynamic and efferent sympathetic responses. 2. Stimulation of A(2A) receptors evoked the most diverse pattern of regional sympathetic responses: preganglionic adrenal nerve activity (pre-ASNA) was increased, lumbar sympathetic nerve activity (LSNA) did not change, while renal (RSNA) and post-ganglionic adrenal (post-ASNA) sympathetic nerve activity was decreased. Stimulation of Al receptors evoked qualitatively uniform, although quantitatively different, sympathoactivation: up arrow pre-ASNA > up arrow RSNA > up arrow LSNA, Stimulation of P2X receptors evoked qualitatively uniform, although quantitatively different, sympathoinhibition: down arrow RSNA = down arrow post-ASNA > down arrow LSNA = down arrow pre-ASNA. 3, These qualitatively and quantitatively different patterns of regional sympathetic responses strongly suggest that purinergic receptor subtypes may be specifically located and differentially expressed on NTS neurons/neural terminals that control different sympathetic outputs. Different NTS purinoceptors may contribute to patterned autonomic responses observed in specific physiological or pathological situations.