RT info:eu-repo/semantics/article
T1 Synthesis and Release of Catecholamines by the Cat Carotid Body in Vitro: Effects of Hypoxic Stimulation
A1 Rigual Bonastre, Ricardo Jaime
A1 González, E.
A1 González, Constancio
A1 Fidone, Salvatore
K1 Neurofisiología
AB The role of catecholamines (CAs) in cat carotid body chemoreception has been controversial. On the basis of pharmacological experiments,it would appear that endogenous dopamine (DA) may act either as an inhibitory or excitatory transmitter. Neurochemicalstudies on the effects of natural stimulation on the release of carotid body CAs in the cat have also been inconclusive. In the presentstudy, we have characterized the synthesis and release of CAs in the in vitro cat carotid body preparation in response to different levelsof hypoxic stimulation and have correlated these measures with the chemosensory activity of the carotid sinus nerve. The synthesis of[3H]DA and [3H]norepinephrine was linear for at least 4 h in carotid bodies incubated with their natural precursor [~H]tyrosine. Synthesisof both [3H]CAs plateaued when the [3H]tyrosine concentration in the media reached 40 uM, which is a concentration similar tothat found in cat plasma. Exposure of the animals to an atmosphere of 10% 02 in N~ for 3 h prior to removal and incubation of the carotidbodies with [3H]tyrosine resulted in an approximately 100% increase in the rate of [3H]DA synthesis but no change in [3H]norepinephrinesynthesis. This selective increase in [3H]DA synthesis was not detected when [3H]dihydroxyphenylalanine was used as precursor.Carotid bodies first incubated with [3H]tyrosine and later superfused with solutions equilibrated with different gas mixtures (0100% 0 2 in N2) exhibited an increase in [3H]DA release and carotid sinus nerve discharge which were inversely related to the oxygenconcentration. This relationship was strongest for the weaker stimuli (between 50% and 20% O 2 in N2), where both nerve activity and[3H]DA release increased almost in parallel. With lower oxygen concentrations (10% O 2 and 0% 02 equilibrated solutions), the increasein the release of [3H]DA was proportionally greater than the increase in carotid sinus nerve discharge. Our results demonstratethat hypoxic stimulation increases both the rate of synthesis and release of DA in the cat carotid body. Although the precise role of DAin this chemoreceptor organ is presently unknown, our findings suggest that this biogenic amine plays a direct role in generating orcontrolling the electrical activity in the carotid sinus nerve.INTRODUCTIONThe mammalian carotid body is an arterial chemoreceptororgan activated by low paO2, low pH andhigh p~CO2 (ref. 21). Structurally, the receptor complexis formed by clusters of two types of cells, thetype I and type II cells; the clusters lie within a supportingconnective tissue matrix containing a densecapillary net24, 41. Sensory fibers of the carotid sinusnerve (CSN) penetrate these cell clusters to end insynaptic apposition with type I cells, which are consideredto be preneural (receptor) elements. Twoperennial issues pertaining to arterial chemoreception,concern first, whether the type 1 cells are in fact
PB Elsevier
SN 0006-8993
YR 1986
FD 1986
LK http://uvadoc.uva.es/handle/10324/6844
UL http://uvadoc.uva.es/handle/10324/6844
LA eng
NO Brain Research, 1986, vol. 374, p.101-109
NO Producción Científica
DS UVaDOC
RD 26-dic-2024