Enhanced in vivo release of substance P in the nucleus tractus solitarii during hypoxia in the rabbit: role of peripheral input.
In the adult, pentobarbitone-anaesthetized rabbit, the in vivo release of substance P-like immunoreactivity was measured in the nucleus tractus solitarii using microdialysis and radioimmunoassay. Increased 160 +/- 16%) extracellular concentrations of substance P-like immunoreactivity were observed during hypoxic provocations of 9% O2 in N2 which also resulted in an increase in phrenic nerve activity. In bilateral carotid sinus nerve-denervated animals no enhanced release of substance P was seen in response to hypoxic challenges (105 +/- 6%) and the phrenic nerve activity was not significantly affected. Perfusion of the nucleus tractus solitarii region with the dopamine agonist, apomorphine (10(-5) M) resulted in a significant decrease in the extracellular level of substance P. These results provide further evidence that substance P is involved in the mediation of the hypoxic drive inputs from the peripheral chemoreceptors. The interactions of apomorphine with substance P release might also suggest a presynaptic modulation of substance Pergic neurons by dopamine in the nucleus tractus solitarii.
Srinivasan
M
M
Nobel Institute for Neurophysiology, Karolinska Hospital, Stockholm, Sweden.
Goiny
M
M
Pantaleo
T
T
Lagercrantz
H
H
Brodin
E
E
Runold
M
M
Yamamoto
Y
Y
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D002346:Carotid Sinus / Q000502:physiology; D002628:Chemoreceptor Cells / Q000378:metabolism; D003956:Dialysis; D004298:Dopamine / Q000378:metabolism / Q000502:physiology; D000860:Hypoxia / Q000378:metabolism*; D008526:Medulla Oblongata / Q000187:drug effects / Q000378:metabolism*; D009475:Neurons, Afferent / Q000378:metabolism; D010525:Peripheral Nerves / Q000502:physiology*; D010791:Phrenic Nerve / Q000502:physiology; D011817:Rabbits; D011863:Radioimmunoassay; D013373:Substance P / Q000378:metabolism*
D013373:Substance P; D001058:Apomorphine; D004298:Dopamine