Central nicotinic stimulation reduces vascular conductance in the gingiva in anesthetized rats

Tobacco-induced suppression of the vascular response to dental plaque

Cigarette smoking presents oral health professionals with a clinical and research conundrum: reduced periodontal vascular responsiveness to the oral biofilm accompanied by increased susceptibility to destructive periodontal diseases. This presents a significant problem, hampering diagnosis and complicating treatment planning. The aim of this review is to summarize contemporary hypotheses that help to explain mechanistically the phenomenon of a suppressed bleeding response to dysbiotic plaque in the periodontia of smokers. The influence of smoke exposure on angiogenesis, innate cell function, the production of inflammatory mediators including cytokines and proteases, tobacco-bacteria interactions, and potential genetic predisposition are discussed.

Pilocarpine-induced Salivation and Thirst in Conscious Rats

The muscarinic receptor agonist pilocarpine is widely used as a sialogogue. It has been well-established that it also induces water intake in animals. However, the mechanisms underlying the relationships between these events are unknown. To address this problem, we examined water intake and parotid salivary secretion in conscious rats. Intraperitoneally injected pilocarpine increased both water intake and salivary secretion. Intracerebroventricularly injected pilocarpine also induced water intake, but not salivary secretion. Intracerebroventricularly applied atropine, a muscarinic receptor antagonist, suppressed the water intake produced by pilocarpine applied intraperitoneally and intracerebroventricularly. However, it did not affect the salivary secretion induced by pilocarpine applied peripherally. We conclude that peripherally applied pilocarpine affects the parotid glands and the thirst center in the central nervous system, while it may induce salivary secretion mainly via peripheral responses, but water intake mainly via the central nervous system.

Effect of the use of snuff on the levels of interleukin-1 β and interleukin-8 in the gingival crevicular fluid of periodontitis patients

Background:

Use of smokeless tobacco in the form of moist snuff placed in the oral cavity is popular in rural India. The aim of the present cross-sectional study was to determine the effect of snuff on periodontitis by assessing interleukin (IL)-1 β and IL-8 levels in gingival crevicular fluid.

Materials and Methods:

A total of 60 subjects were selected for this study. 40 subjects presented with periodontitis, which included 20 snuff users (SP) and 20 nonsnuff users (NS). 20 periodontally healthy patients formed the controls (healthy control: HC). The clinical parameters recorded were gingival index (GI), plaque index, calculus index, bleeding on probing (BOP), probing depth (PD), recession (RC), and clinical attachment level (CAL). The IL-1 β and IL-8 levels were assessed through enzyme-linked immunosorbent assay (Quantikine^®). Analysis of variance (ANOVA), post-hoc Tukey's, Kruskal-Walli's ANOVA and Mann-Whitney test was used for comparison among groups and P > 0.05 was considered statistically significant.

Results:

No significant difference was seen in levels of IL-1 β and IL-8 between SP and NS groups (P = 0.16, 0.97). However, both the periodontitis groups (SP and NS) had increased IL-β levels when compared to HC group (P = 0.01, 0.001). The snuff users showed significant increase in GI, BOP, RC, and CAL when compared with NS (P = 0.002, 0.001, 0.012, 0.002) whereas NS group had significant increase in PD (P = 0.003).

Conclusion:

Within the limitations of this study, use of snuff does not affect the host inflammatory response associated with periodontitis and leads to RC and increased CAL due to local irritant effect.

Effect of central nicotinic activation on drinking behavior

Intracerebroventricular injections of angiotensin II (ANG) and nicotine activate the subfornical organ (SFO), an essential central nucleus for ANG-induced drinking. Nicotine has been, however, reported to induce little drinking behavior. To clarify this paradox, we investigated effects of nicotine and ANG on activity of SFO neurons and drinking behavior. In extracellular recordings many SFO neurons (57%) were excited by the both drugs. The nicotine-induced excitation was transient, whereas the ANG-induced was long-lasting. After intracerebroventricular injection of nicotine, the latency to drinking was dose-dependently shortened, but the drinking volumes were much smaller than those by ANG. These suggest that central nicotinic activation contributes to induction of drinking behavior while drinking volume is small because effects of nicotine on neurons are short-lasting.

Hypocretin-1/orexin-A activates subfornical organ neurons of rats

Central injection of hypocretins/orexins in rats induces water intake. As the subfornical organ (SFO) plays an important role in drinking behavior, hypocretins may excite SFO neurons. In this study, effects of hypocretins on SFO neurons were investigated electrophysiologically in slice preparations. In extracellular recordings, hypocretin-1 excited SFO neurons, but hypocretin-2 did not or it was little. After the block of synaptic inputs, the excitatory responses to hypocretin-1 remained, but some disappeared. In whole-cell patch-clamp recordings, hypocretin-1 reduced the frequencies of miniature inhibitory presynaptic currents with inward currents occasionally in SFO neurons, but hypocretin-2 did not. These results suggest that hypocretin-1 excites SFO neurons via the activation of hcrtR1 on premembranes and postmembranes.

Smoking and structural brain deficits: a volumetric MR investigation

Growing evidence from animal studies indicates brain-damaging properties of nicotine exposure. Investigations in humans found a wide range of functional cerebral effects of nicotine and cigarette smoking, but studies focusing on brain damage are sparse. In 22 smokers and 23 never-smokers possible differences of the cerebral structures were investigated using magnetic resonance imaging and voxel-based morphometry. Significantly smaller grey matter volume and lower grey matter density (P = 0.05, corrected) were observed in the frontal regions (anterior cingulate, prefrontal and orbitofrontal cortex), the occipital lobe and the temporal lobe including parahippocampal gyrus, in smokers than in never-smokers. Group differences of either grey matter volume or grey matter density were also found in the thalamus, cerebellum and substantia nigra, among other regions. Smokers did not show greater volumes than never-smokers in any cerebral region. Magnitude of lifetime exposure to tobacco smoke (pack-years) was inversely correlated with volume of frontal and temporal lobes and cerebellum (P = 0.001, uncorrected). The data indicate structural deficits of several cortical and subcortical regions in smokers relative to never-smokers. The topographic profile of the group differences show some similarities to brain networks known to mediate drug reinforcement, attention and working memory processing. The present findings may explain in part the frequently reported cognitive dysfunctions in chronic cigarette consumers.

Effects of cevimeline on salivation and thirst in conscious rats

OBJECTIVE

Intraperitoneal injection of a sialogogue, pilocarpine, at high concentrations induces salivation via peripheral pathways and thirst sensation via central pathways. In this study, we report that the effects of another sialagogue, cevimeline, on salivation and water intake in conscious rats differ from those of pilocarpine.

DESIGN

We investigated that effects of peripherally and centrally injected cevimeline on parotid saliva flow rate and water intake in conscious rats. The results were compared with those of pilocarpine.

RESULTS

The intraperitoneal injection of cevimeline induced salivation from the parotid gland, but not water intake. In contrast, the intracerebroventricular injection of cevimeline induced water intake without salivation. The concentration of cevimeline needed to induce salivation by intraperitoneal injection was several 10 times that of pilocarpine, but that needed to induce water intake by intracerebroventricular injection was over a 1000 times greater.

CONCLUSIONS

The finding that intraperitoneally injected cevimeline induces salivation without inducing water intake, suggests that the effects on the thirst center in the brain are weaker than those of pilocarpine.

Enamel matrix derivative versus guided tissue regeneration in the presence of nicotine: a histomorphometric study in dogs

AIM

The goal of this histometric study was to compare the healing process of dehiscence-type defects treated by enamel matrix derivative (EMD) or guided tissue regeneration (GTR) under the effect of nicotine in the dog model.

MATERIALS AND METHODS

Eight mongrel dogs were used. Buccal osseous dehiscences were surgically created on the mesial roots of the mandibular third and fourth pre-molars. The defects were exposed to plaque accumulation for 3 months. After this period, the defects were randomly assigned to one of the treatments: open flap debridement (OFD), EMD or GTR with a resorbable membrane. During 4 months, the dogs received subcutaneous administration of nicotine (2 mg/kg twice a day with a 12 h interval between the applications). After this period, the animals were killed and the blocks were processed. The histometric parameters evaluated included gingival recession, epithelial length, connective tissue adaptation, new cementum and new bone.

RESULTS

A superior length of new cementum was observed in the sites treated by EMD in comparison with OFD (p< or =0.05). No statistically significant differences were observed between GTR and the other groups.

CONCLUSIONS

In the presence of nicotine, EMD may promote more new cementum formation than OFD while GTR failed to provide a significant difference.