A selective attention deficit in the rat following induced dopamine receptor supersensitivity

In the blocking paradigm, prior training to one conditioned stimulus (CSA) blocks the ability to attend to a second conditioned stimulus (CSB) when the two form a compound (CSAB) in subsequent training. Blocking is an associative process by which animals learn to ignore CSB because it contains no new information regarding the reinforcing event. In Experiment 1, dopamine (DA) receptor supersensitivity was induced in rats by prolonged pretreatment with haloperidol. The animals with DA receptor supersensitivity failed to show blocking by responding equivalently to both elements of the CSAB compound. This effect was replicated in Experiment 2, which also tested for an arousal interpretation of disrupted blocking by introducing a novel stimulus following training. Supersensitive rats were no more responsive to this novel stimulus than were control animals, which supports a selective attention deficit interpretation of disrupted blocking with DA receptor supersensitivity. This attentional deficit resembles behavioral perseverations induced by DA agonists.     

Chronic ganglioside treatment counteracts the biochemical signs of dopamine receptor supersensitivity induced by chronic haloperidol treatment

Chronic ganglioside treatment (10 mg/kg, i.p.) using the molecular species with only one neuroaminic acid residue (GM1) given together with haloperidol (0.3 and 5 mg/kg, i.p.) once daily in male rats, counteracted the haloperidol-induced increase in the number of [³H]spiperone binding sites in striatal membranes when the low dosse of haloperidol, but not the high dose, was administered. The present results therefore indicate that chronic GM1 treatment can partially counteract the increase in the number of dopamine receptors having a high affinity for neuroleptics (D₂ type) induced by chronic haloperidol treatment in striatal membranes, and therefore may also partially counteract the development of neuroleptic-induced dopamine receptor supersensitivity.     

Changes in cytosolic calcium during cholinergic and adrenergic stimulation of the parotid salivary gland

Ca-selective microelectrodes were used to examine calcium transport during acetylcholine (ACh) and Epinephrine (Ep) stimulation of amylase secretion in the parotid gland. The cytosolic concentration of free ionized Ca2+ ( [Ca]i) determined in unstimulated cells was 0.44 +/- 0.04 microM. By measuring the induced changes in intracellular electrode potentials (ECa, EM) we were able to demonstrate that ACh at 10(-9), 10(-8), 10(-7), 10(-6), and 10(-5) M increased [Ca]i by 0.20 +/- 0.02, 0.61 +/- 0.04, 0.53 +/- 0.02, 0.30 +/- 0.05, and 0.14 +/- 0.03 microM. Similarly, Ep increased [Ca]i by 0.14 +/- 0.01, 0.42 +/- 0.06, 0.31 +/- 0.04, 0.15 +/- 0.03, and 0.05 +/- 0.04, respectively. Removal of extracellular Ca2+ significantly (P less than 0.001) altered the changes in ECa in response to ACh and Ep stimulation, thereby demonstrating that the induced increases in [Ca]i must be due to a transmembrane movement of Ca2+. Enzyme secretion was found to vary with the concentration of the stimulus used. Maximal secretion occurred during stimulation using 10(-7) M and 10(-8) M Ep with a suppression of release at supramaximal concentrations. The dose-response curve for ACh differed in that there were two concentrations of stimulus (2 X 10(-9) and 1 X 10(-6) M ACh) in which the greatest rate of secretion occurred. Concentrations of stimulus which increase [Ca]i between 0.86 +/- 0.06 microM and 0.74 +/- 0.05 appeared to produce optimal amylase secretion, indicating that salivary secretion in the mouse parotid is regulated within a narrow concentration range of cytosolic Ca2+.     

Non-specific secretory supersensitivity in rat parotid gland following neonatal sympathetic denervation

Newborn rats were surgically sympathectomized by extirpation of the left superior cervical ganglion. After 9 weeks the parotid glands of both sides were used for secretory studies. Isoprenaline, dopamine, and the dibutyryl analogue of cAMP (DBcAMP) caused an increase in amylase release, which was significantly higher in the denervated glands. Also carbamylcholine was more effective in the denervated gland; the concentration-response curve was shifted to the left, and the maximal output of amylase was increased. Neonatal sympathetic denervation induces supersensitivity for both adrenergic and cholinergic agonists as well as for DBcAMP. This may be due to compensatory mechanisms involving both up-regulation of receptors as well as amplification of the intracellular mediation.     

Atropine, a muscarinic cholinergic receptor antagonist increases serotonin, but not dopamine levels in discrete brain regions of mice

We investigated the effects of atropine, a muscarinic acetylcholine (ACh) receptor antagonist, on the level of serotonin in discrete brain regions, the nucleus raphe dorsalis (NRD), nucleus caudatus putamen (NCP), cerebral cortex and the cerebellum. Biogenic amines were assayed employing HPLC electrochemistry in these regions 30 min following different doses of atropine (5, 10, 25mg/kg; i.p.), and at various time points (15, 30, 60, 120 min) after 25mg/kg of the drug. The cholinergic receptor antagonist caused a dose-dependent alteration in the level of serotonin in NRD, but the increase was not dose-dependent for other regions studied. The metabolite of serotonin, 5-hydroxyindoleacetic acid was unaffected. Atropine did not affect the levels of dopamine or its metabolites dihydroxyphenyl acetic acid and homovanillic acid. The present study suggests significant effect of this antimuscarinic agent on the synthesis of serotonin in the central serotoninergic pathways, which may have clinical relevance.     

Perivascular nerves in the rat submandibular salivary gland.

Perivascular nerves in the rat submandibular salivary gland have been studied using a variety of histochemical procedures coupled with electron microscopy. Two principal nerve types, adrenergic and cholinergic, appear to predominate and are localized principally around arterioles. Venules are rarely innervated. The possibility that a non-adrenergic non-cholinergic nerve population might influence blood flow is discussed critically in the light of anatomical and physiological findings.     

Calcium ion uptake induced by cholinergic and α-adrenergic stimulation in isolated cells of rat salivary glands

Summary Adrenaline (10^–5 M) and carbamylcholine (10^–4 M) stimulate⁴⁵Ca²⁺ uptake into isolated cells of rat submandibular gland and parotid glands. In the presence of the -adrenoreceptor blocking agent phentolamine, adrenaline stimulation of⁴⁵Ca²⁺ uptake is abolished. The -adrenergic stimulant isoproterenol has no effect on⁴⁵Ca²⁺ uptake. Carbamylcholine induced⁴⁵Ca²⁺ uptake is inhibited by atropine. The Ca²⁺ ionophore A23187 stimulates⁴⁵Ca²⁺ uptake, whereas dibutyryl cyclic adenosine 3,5-monophosphate and dibutyryl cyclic guanosine 3,5-monophosphate have no effect on⁴⁵Ca²⁺ uptake.A graphical analysis of the⁴⁵Ca²⁺ uptake curves reveals at least two phases: a fast phase and a slow phase, both of which are stimulated by adrenaline and carbamylcholine.The⁴⁵Ca-exchangeable pool size is increased by adrenaline and carbamylcholine in both the fast and the slow phases.These results suggest that -adrenergic and cholinergic agonists act by increasing the rate of Ca²⁺ transfer into the cells of the parotid and submandibular salivary glands most probably through an increase of the cell membrane permeability for Ca²⁺.Supported by Swiss National Science Foundation Grant No. 3.298.074     

Regeneration of submandibular salivary gland autografted in the rat tongue

Autologous SMG fragments were implanted in tongues of male rats which were sacrificed 15–20 min, 24 hr, 72 hr, 1 week, or 8 weeks after implantation. The tongues were excised, fixed, and processed for light and electron microscopy. In addition, some rats were injected with [³H]-thymidine 1 hr before sacrifice and the labeling indices (L.I.) of the salivary epithelial and interstitial cells were calculated. Twenty-four hours after implantation, SMG autografts showed massive central necrosis with some acini and ducts surviving at the periphery of the lobules. There was marked infiltration of the autografts with neutrophils and macrophages. Also the basal laminae surrounding the necrotic acini and ducts remained intact. The morphology of the autografts after 72 hr was similar to that after 24 hr except that there was additional necrosis and acini and ducts could no longer be identified in the autografts. By 1 week after implantation, the autografts showed lobular morphogenesis, ductal branching, and revascularization. At this time, the regenerating salivary epithelium appeared undifferentiated with no evidence of secretory granules. The L.I. of interstitial and ductlike structures showed significant increases over control values at 1 week after implantation, and then declined toward control levels by 3 weeks after implantation. By 8 weeks after implantation, there was evidence of acinar and striated ductal cytodifferentiation in two autografts. The results emphasize the potential of SMG autografts to regenerate subsequent to severe tissue necrosis.     

Reaction of the rat submandibular salivary gland to injury to the contralateral gland

After burns of resection of the submandibular salivary gland the intact contralateral gland in rats responds by increased proliferative activity. The number of mitoses reached a maximum 72 h after injury in the case of burns and 48 h after resection. Burns of the salivary gland cause lasting but weak compensatory hypertrophy of the contralateral gland. Hypertrophy of the gland is accompanied by an increase in size of the cells and nuclei, the area of which rises by 10 and 17% respectively. Resection of the salivary gland causes an increase in weight of the intact gland only in the early period of observation; by the 30th and 45th days after the operation the weight of the experimental glands was not significantly different from the control. Differences in compensatory growth of the intact glands observed after two types of injury of the contralateral gland evidently depend on the quantity of tissue breakdown products and the duration of their presence in the body.Department of Biology and General Genetics, Moscow Medical Stomatological Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR A. P. Avtsyn.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 9, pp. 1108–1110, September, 1976.     

Muscarinic cholinergic receptor binding in rat mast cells

Specific [³H]-QNB binding was present in isolated, purified, intact rat mast cells and in crude membrane preparations. The binding is saturable, time- and temperature-dependent. Cholinergic agents inhibit selectively the binding: atropine is the most effective of the antagonists while oxotremorine is the most potent of the muscarinic agonists. It is concluded that rat mast cells are provided with muscarinic cholinergic receptors.     

Effect of cold stress on cholinergic receptors in the rat adrenal gland

The effects of cold exposure on cholinergic binding sites in the rat adrenal gland were assessed by examining the binding of [125I]alpha-bungarotoxin (BTX), a nicotonic receptor antagonist and [3H]quinuclidinyl benzilate (QNB), a muscarinic receptor antagonist, to adrenal tissue homogenates. Cold exposure resulted in significant alterations in both nicotinic and muscarinic binding. Exposure to cold for 4 and 7 days resulted in a significant decrease in QNB binding. Scatchard analysis indicates that this alteration is due to a decrease in binding sites (Bmax) rather than a change in ligand affinity (Kd). In contrast, chronic cold exposure produced a significant increase in BTX binding sites. These results indicate that adrenal cholinergic receptors are altered in reciprocal fashion by chronic cold exposure, and that this change may represent a key event in the sympathoadrenal system's adaptive response to chronic cold stress.     

Innervation of the rat harderian gland by adrenergic and cholinergic nerve fibres

The innervation of the rat Harderian gland was studied using histochemical methods for catecholamines and acetylcholinesterase (AChE). Selective denervations were performed to investigate the neural connections of this gland with various ganglia. Light microscopically the AChE-positive nerves seemed to run as thick bundles in the intertubular connective tissue. These bundles sent finer branches around the acini. The blood vessels, localized in the connective tissue septa, were surrounded by a dense plexus of AChE-containing fibres. By electron microscopy, the AChE-positive fibres were seen to terminate near the myoepithelial cells surrounding secretory cells. These fibres were also observed in contact with the blood vessels and occasionally close to the secretory cells. Fluorescent adrenergic nerves surrounded the blood vessels. Some fibres were also observed in the interlobular tissue. All the AChE-containing nerves degenerated after cutting the zygomatic nerve. On the other hand, removal of the ciliary ganglion or the superior cervical ganglion, or stereotactic coagulation of the ophthalmic nerve did not affect these nerves. The fluorescent adrenergic fibres disappeared following both removal of the superior cervical ganglion and coagulation of the ophthalmic nerve. These fibres were intact after removal of the ciliary ganglion.     

Vasoactive intestinal peptide evoked secretion of fluid and protein from rat salivary glands and the development of supersensitivity

Vasoactive intestinal peptide (VIP) injected intravenously was found to induce a flow of saliva from both the parotid and the submaxillary gland in the rat. The secretion was slow in onset. The amount of saliva secreted from the parotid gland was less than that from the submaxillary gland. Parotid saliva was very viscous. VIP-evoked parotid saliva was more protein rich than both submaxillary saliva and saliva secreted in response to other sialagogue drugs including the beta-adrenergic receptor agonist isoprenaline. The effect of VIP was direct; it occurred after removal of the adrenals, after degeneration of intraglandular nerves and in the presence of autonomic blockers. A supersensitivity to VIP was demonstrable. In the parotid and the submaxillary glands the secretory response to VIP was enlarged following parasympathetic denervation and decentralization, respectively, while after sympathetic denervation supersensitivity was only found to develop in the submaxillary gland.     

Intraglandular transport of 125I-glandular kallikrein in the rat submandibular salivary gland

The transport of radiolabeled rat submandibular gland kallikrein was studied after local administration to the resting and activated rat submandibular gland. The iodinated kallikrein was electrophoretically, immunologically, and biologically indistinguishable from the intact enzyme. After intraductal and intraglandular application the radioactivity in venous effluent was quantitated and characterized. As judged by gel-filtration ¹²⁵I-kallikrein in venous effluent eluted at a position similar to that seen when the iodinated enzyme was mixed with plasma, but earlier than the elution of ¹²⁵I-kallikrein in buffer. In plasma, therefore, glandular kallikrein is probably bound to macromolecules. The radioactive fractions in venous effluent did not contain free iodine. Maximum concentration of ¹²⁵I-kallikrein in venous effluent of resting glands was repeatedly reached about 20 min after intraductal administration. Moreover, the ductal epithelium represented the main permeation barrier since after intraglandular application the maximum venous ¹²⁵I-kallikrein concentration was reached almost immediately. In activated gland (parasympathetic and sympathetic nerve stimulation), the venous ¹²⁵I-kallikrein concentration was inversely related to glandular blood flow. We conclude that kallikrein present in the duct lumen or in the interstitium is able to reach the circulation, thereby making possible the local generation of plasma-kinins.     

Immunohistochemical expression of epidermal growth factor receptor in salivary gland tumours

Summary Immunohistochemical localization of epidermal growth factor receptor (EGFR) in normal salivary glands and tumours (108 cases) was studied using a monoclonal antibody. In the normal salivary glands, EGFR was occasionally detected in ductal segments of intercalated, striated, and excretory ducts, but not in acinar cells. The frequency of positive EGFR staining in salivary gland tumours was not high: pleomorphic adenoma, 33.8%; mucoepidermoid tumour, 25.0%; adenolymphoma, 44.4%; and sialoadenocarcinoma, 66.6%. Pleomorphic adenomas showed positive staining for EGFR on the luminal side of luminal cells and in squamous metaplastic cells of tumour tissue. Some modified myoepithelial cells were also reactive whereas outer spindle tumour cells were unstained. Adenolymphomas regularly exhibited positive EGFR staining in the cell membrane; mucoepidermoid carcinoma displayed positive staining in cell membranes in epidermoid tumour cells and cytoplasmic staining in mucous-secreting tumour cells. Sialocarcinomas revealed cell membrane staining and whole cytoplasmic staining for EGFR. The immunohistochemical localization of EGFR could be classified into two types, one the cell membrane-positive type found in epithelial tumour cells, and the second the cytoplasmic positive type seen in normal ductal cells, the luminal tumour cells of pleomorphic adenomas and mucous-secreting tumour cells.     

Localization of prostate-specific antigen-like immunoreactivity in human salivary gland and salivary gland tumors

Immunoreactivity of prostate-specific antigen (PSA), a kallikrein-like enzyme present in the seminal plasma, was demonstrated by indirect immunoperoxidase staining using a PSA antiserum in the apical cytoplasm along the luminal border of small-sized duct epithelial cells of the major salivary (parotid and submandibular) gland of both sexes (56/56, 100%). No PSA-like immunoreactivity was seen in large-sized duct epithelial cells and acinar cells. Minor salivary gland ducts were negative. When inflammatory and atrophic changes were observed, ductal expression of PSA-like immunoreactivity was decreased (12/37, 32%) and the site of intracellular localization often became diffusely cytoplasmic. The immunoreactivity was absorbed by human seminal plasma. Immunoreactivities of prostatic acid phosphatase and sex hormone receptors were undetectable in the salivary gland. Twenty-nine (34%) of 86 salivary gland tumors with ductal differentiation were immunoreactive for PSA mainly in the cytoplasm. A PSA monoclonal antibody ER-PR8 detected immunoreactivity in the prostate but not in the salivary glands or their tumors. Prostate-specific antigen-like immunoreactivity in small-sized (intercalated) duct epithelial cells of the major salivary gland and their tumors may be due to cross-reactivity of the antiserum with kallikrein-like substances.     

The histopathological observation of the salivary gland in hamsters with streptozotocin induced diabetes

It has been reported that the natural defence mechanisms against bacterial infection decreases in diabetic patients. Saliva and salivary gland have an important role to keep healthy condition in oral cavity. Thus, it is possible that saliva from diabetic subject may influence to a development of dental caries. The purpose of this study is to examine the histopathological changes and excretory function of the salivary glands of hamsters with streptozotocin (SZ) induced diabetes. Male hamsters were provided in this experiment at 8 weeks after a single i.p. injection with a dose of SZ (65 mg/kg b. wt.). The flow rate of saliva was determined by stimulation with pilocarpine (8 mg/kg b. wt.). Three major salivary glands and pancreas were obtained from these animals. No difference between diabetic and non-diabetic animals in the flow rate of saliva and wet weight of submandibular and sublingual gland was observed. Pathological finding of salivary gland was not observed in both of the 2 groups of animals but the wet weight of the parotid gland of diabetic hamsters was heavier than that of the non-diabetic hamsters. Moreover, an enlargement of some acinus cells was observed only in the parotid gland of diabetic hamsters.