Characterization of binding sites and effects of calcitonin gene-related peptide (CGRP) and CGRP 8-37 on regional blood flow in rabbit salivary glands

Salivary secretion effects of the antipsychotic drug olanzapine in an animal model

OBJECTIVE

Olanzapine, introduced as an alternative to clozapine in schizophrenia therapy, is thought to display a receptor affinity similar to that of clozapine. Antipsychotics are well-known xerogenic drugs. However, clozapine exerts both antagonistic and agonistic salivary effects ('clozapine-induced sialorrhea'), the latter probably via muscarinic M1 type of receptor. We hypothesise that olanzapine also has dual salivary effects.

MATERIAL AND METHODS

Effects of intravenous olanzapine were examined in rats, including those subjected to chronic preganglionic parasympathetic denervation (submandibular glands) or combined postganglionic parasympathetic and sympathetic denervation (parotid glands). Secretion was evoked reflexly, and by intravenous methacholine and the tachykinin substance P.

RESULTS

At 0.01-1 mg kg(-1), olanzapine dose dependently reduced secretion in response to methacholine or reflex stimulus but not that to substance P. At 10 mg kg(-1), olanzapine evoked a long-lasting secretion, independent of the autonomic innervation as well as of α- and β-adrenergic receptors and muscarinic receptors. The secretion was reduced, but not abolished, by a substance P receptor antagonist.

CONCLUSIONS

Like clozapine, olanzapine evoked secretion. The response to olanzapine was greater and, in contrast to clozapine, involved non-traditional gland receptors (such as substance P receptors). The findings imply that olanzapine plays an excitatory role via tachykinin receptors in humans.

Interaction of calcitonin gene-related peptide (CGRP), substance P (SP) and conventional autonomic agonists in rat submandibular salivary peroxidase release in vitro

Our previous immunohistochemical studies reveal that several neuropeptides, such as substance P and calcitonin gene-related peptide, innervate the major salivary glands of the mouse, rat and human. The aim of the study was to clarify their interactions by measuring their effects alone or with conventional autonomic agonists (carbachol, phenylephrine and isoproterenol) on peroxidase secretion of incubated submandibular gland slices. Calcitonin gene-related peptide evoked significant increase in peroxidase activity of the secretion only when used at 10(-5) M concentration, while substance P evoked significant, dose-dependent increase at much lower concentrations (10(-10) M). Adrenergic and cholinergic agonists enhanced peroxidase activity. Interestingly, substance P inhibited both phenylephrine and isoproterenol induced increase in peroxidase activity. Calcitonin gene-related peptide did not affect the inhibition caused by substance P. Our results demonstrate that in the salivary gland tissue substance P alone or in conjunction with adrenergic agonists result in opposing secretory responses with the doses used in vitro. Conversely, the response mediated by adrenergic receptors may be critically affected by simultaneous occupation of substance P receptors.

High-frequency color Doppler sonography of the submandibular gland: relationship between salivary secretion and blood flow

OBJECTIVE

The purpose of this study was to evaluate the changes of blood flow of the submandibular gland in comparison with salivary secretion after gustatory stimulation through use of color Doppler sonography.

STUDY DESIGN

High-frequency color Doppler sonography was performed on 30 healthy volunteers, aged 22 to 31 years. The prestimulation and poststimulation arterial blood flows were evaluated with color Doppler sonography and spectral analysis.

RESULTS

The means of prestimulation maximum and minimum velocities and pulsatility index of the submandibular gland were 6.35 +/- 2.57 cm/sec, 1.79 +/- 0.93 cm/sec, and 1.53 +/- 0.42, respectively. After the stimulation, the color signals and velocities increased and the pulsatility index decreased. There was a close correlation between the increase in minimum velocity and that of salivary secretion.

CONCLUSION

Color Doppler sonography is useful in analyzing changes in the blood flow of the submandibular gland caused by gustatory stimulation.

Immunohistochemical distribution of calcitonin gene-related peptide in nerve fibres of the anterior buccal gland of the rat

Calcitonin gene-related peptide immunoreactive (CGRP-IR) nerves in rat were studied as to their distribution and origin in anterior buccal glands, which are unique minor mucous salivary glands in the rat. A moderate number of CGRP-IR nerve fibres were located, mostly perivascularly and around intralobular ducts, but they were also found around acini. The latter fibres were mainly of sensory origin, as suggested by their disappearance after denervation of the ophthalmic and maxillary branches of the trigeminal nerve. On the contrary, CGRP-IR nerves around interlobular ducts and some of those in a perivascular location remained both after sensory denervation and after extirpation of the sympathetic superior cervical ganglion. Whether these fibres originate in dorsal root ganglia C3-C4 or represent parasympathetic fibres is not known. Based on the present data and the previous findings showing a regulatory role of CGRP both on blood and salivary flow, it is possible that CGRP in sensory, and possibly also in parasympathetic nerves, participates in the regulation of reflex blood flow and salivary secretion in the anterior buccal gland of the rat.

Calcitonin gene-related peptide (CGRP) and its effects on protein release in vitro in the developing submandibular gland of the rat

Indirect immunohistochemical methods were used to study presence and number of CGRP-immunoreactive (CGRP-IR) nerve fibers in the submandibular gland and ganglion cells of the superior cervical, submandibular and trigeminal ganglia of the developing rat. The effect of CGRP on peroxidase and total protein release was also studied in the developing postnatal submandibular glands of 1, 5, 12 and 30-day-old, as well as adult rats by in vitro methods. The possible costimulation of CGRP with SP, NKA or carbachol on 5-day-old and adult rats was also tested. The stimulatory effects of these compounds were compared to the basic release of peroxidase and total amount of proteins from submandibular gland fragments in incubation solution. CGRP-IR nerve fibers were found in relatively high number during post-natal development, mainly around blood vessels and ducts. Some CGRP-IR nerve fibers were also detected around acini. The number of these fibers was quite low and remained constant during the post-natal development. The number of CGRP-IR trigeminal ganglion cells was higher on the 5th and 12th post-natal day than later in development and in adult animals. At the same time, superior cervical- and submandibular ganglion cells were non-reactive for CGRP, suggesting trigeminal origin of CGRP-IR nerve fibers during the development in the submandibular gland. In the secretory studies, CGRP per se stimulated both peroxidase and total protein release in the submandibular gland most effectively on 5th and 12th post-natal days, while there was no clear secretory response in the adult glands. In the 5-day-old submandibular gland CGRP in combination with SP, NKA or carbachol clearly enhanced the total protein secretory response when compared with the release caused by these substances alone. However, in the adult submandibular gland, the combinations did not enhance total protein release more than any of the substances alone. Furthermore, it can be concluded that the presence of a more dense CGRP-IR innervation during the early postnatal period in the developing submandibular gland is accompanied with an increased responsiveness of the secretory elements to CGRP.