The role of circulating catecholamines in the depletion of parotid acinar granules in conscious rats in the cold

Abstract

SUMMARYThe possibility that circulating catecholamines might affect parotid gland function during feeding (over a period of 80 min) and cold stress (2-4°C) was investigated in rats that had been fasted for 30 h. In the first set of experiments, in which the glands had been sympathectomized by removing both superior cervical ganglia 10-12 days previously, there was a substantial reduction in the density of acinar secretory granules (42 % compared with non-fed animals in the cold) and in the total glandular amylase activity (54 %). However, similar, or even greater, losses were recorded in rats subjected to additional bilateral adrenal medullectomy and pretreatment with atropine and aand ,/-adrenoceptor blockers. The losses were therefore attributed to activation of parasympathetic non-adrenergic, non-cholinergic mechanisms. In a second set of experiments, employing only morphometric assessment, the parasympathetic auriculotemporal nerve was cut on one side in addition to bilateral sympathectomy and, as a further precaution, the animal was atropinized. It was then found that there was a loss of 17 % of granules in the parasympathectomized plus sympathectomized gland, but not the contralateral gland, of non-fed cold-exposed rats compared with non-fed animals kept at room temperature. When rats were fed as well as exposed to cold the number of granules in parasympathectomized plus sympathectomized glands fell by 46 % compared with similar non-fed animals in the cold and by 55 % compared with those at room temperature. After adrenal medullectomy, cold exposure alone had no effect on the granular density of parasympathectomized plus sympathectomized glands but, when combined with feeding, granular loss amounted to 30 %. Pretreatment with a combination of

Depletion of vasoactive intestinal peptide and substance P in parotid glands of atropinized rats during reflex secretion

“…Sympathectomized glands with or without capsaicin pretreatment Before feeding, all animals were treated with atropine, phentolamine and propranolol. The adrenoceptor antagonists were used to prevent any influence of circulating catecholamines on the secretory cells (Asztely, Tobin & Ekstrom, 1996).…”

“…The adrenoceptor antagonists were used to prevent any influence of circulating catecholamines on the secretory cells (Asztely, Tobin & Ekstrom, 1996).…”

Non‐adrenergic, non‐cholinergic influences on parotid acinar degranulation in response to stimulation of the parasympathetic innervation in the anaesthetized rat

“…Thus the present results are consistent with the idea that parasympathetic NANC transmission of secretory impulses is important during such a normal condition as chewing food. Most likely, adrenergic, cholinergic and NANC mechanisms, possibly complemented by circulating catecholamines (Asztely, Tobin & Ekstrom, 1996b), act together to generate the most purposeful reflex response to food intake. In this situation, the equilibrium between peptide release and peptide replenishment does not seem to be upset (Asztely et al 1996 …”