Localization of enkephalin‐like immunoreactivity in the cat carotid and aortic body chemoreceptors

Abstract

The purpose of this study was to determine if enkephalin-like immunoreactivity was present in the glomus cells of the carotid and aortic body peripheral arterial chemoreceptors. Cat carotid and aortic bodies were reacted with antisera to met- and leu-enkephalin using the indirect peroxidase-antiperoxidase immunocytochemical method of Sternberger (1979). Both the carotid and aortic bodies demonstrated clusters of immunoreactive cells for both met- and leu-enkephalin. Additionally, met-enkephalin-like immunoreactivity was observed in many of the dense-core vesicles of the glomus cells of the carotid body. The glomus cells of these chemoreceptors are known to contain catecholamines which may modulate chemoreceptor activity. The presence of opioid peptide-like substances co-existing with the glomus cell catecholamines, perhaps in the same vesicles, may have important implications for a trophic influence of these peptides on glomus cell chemoreceptor modulation.

Peripheral Chemoreceptors: Function and Plasticity of the Carotid Body

“…A variation in density has also been noted, with the highest density of 8 vesicles per um 2 , ascribed to the monkey (335). The vesicles contain various neurochemicals; primarily catecholamines (523) and chromogranin neuropeptides (336) but, presumably also, adenine nucleotides and Ca 2+ (914) giving the type I cell the appearance of adrenal medullary chromaffin cells, albeit that the dense core vesicles in the type I cell may, in most cases, only be up to half as large as their counterparts in the adrenal medulla (176, 319). The small size of the granules and the relative small mass of carotid body tissue, makes quantification of vesicular content difficult, but the use of insulated, carbon electrodes and amperometry with either enzymically dispersed, single, rabbit type I cells (849), or conglomerations of cells in a thin slice rat carotid body preparation (670) has revealed that type I cells from both species secrete catecholamine (presumed to be dopamine), with a single quantal charge of 44 to 46 pC.…”

Characterization of opioid receptors in the cat carotid body involved in chemosensory depression in vivo

“…[Metlenkephalin-like material is present in glomus (type 1) cells (Lundberg et al, 1979;Wharton et al, 1980) where it may be stored together with catecholamines (Hansen et al, 1982). Opioid receptors could be associated with one or more elements of the sensory receptor complex (e.g.…”

“…The cat carotid body contains both [Met] and [Leu]en-an effect that can be antagonized by relatively high kephalin-like material (Lundberg et al, 1979;Whar-doses of the opioid receptor antagonist naloxone ton et al, 1980;Hansen et al, 1982), and it has been (McQueen & Ribeiro, 1980;1981a;McQueen, 1981; shown that intracarotid injections or infusions of Pokorski & Lahiri, 1981 () The Macmillan Press Ltd 1986 There seem to be at least three types of opioid receptor, namely p, 6 and K (see Paterson et al, 1983), so which of these is involved in opioid-induced chemosensory depression? It is known that morphine, preferentially a n-receptor agonist, is not a very potent chemodepressant (McQueen & Ribeiro, 1980), and low doses of naloxone, which have a greater affinity for p-receptors than for the other types of opioid receptor (Paterson et al, 1983), are not very effective at antagonizing the chemodepressant action of [Met] or [Leu]enkephalin.…”

Changes in carotid body amine levels and effects of dopamine on respiration in rats treated neonatally with capsaicin

“…Further studies, possibly in conscious animals, are needed to determine how neonatal treatment with the neurotoxin capsaicin causes a reduction in respiratory responsiveness to peripheral chemoreceptor stimulation. It will also be interesting to investigate the extent to which central and/or peripheral effects of capsaicin influence the actions and interactions of polypeptides such as substance P and the enkephalins, which are present in the carotid body and can co-exist with monoamines (Hansen et al, 1982;Vamdell etal., 1982).…”