Mecamylamine pretreatment counteracts cigarette smoke induced changes in hypothalamic catecholamine neuron systems and in anterior pituitary function

Venous plasma nicotine correlates of hormonal effects of tobacco smoking

The present study resolves some of the discrepancies in the literature by correlating the effects of tobacco smoking on hormone release with venous plasma nicotine levels. Cortisol, prolactin, and beta-endorphin concentrations were measured. Habitual male tobacco users smoked denicotinized (very low nicotine) and average nicotine cigarettes in the morning after overnight tobacco abstinence. Several venous blood samples were withdrawn before and during the smoking sessions for subsequent analyses. The increases in plasma nicotine correlated well with plasma cortisol and prolactin levels (correlation coefficients r=0.66 and 0.53, respectively, p<0.05). This study quantifies the well known increase in plasma cortisol and prolactin after nicotine postsmoking for about 1h with peak plasma levels up to 35 ng/ml. Contrary to most abused drugs which release dopamine and decrease prolactin, nicotine concentration correlated with increased prolactin release. Increases in maximal plasma beta-endorphin levels following tobacco smoking were barely statistically significant with insufficient data to obtain a correlation coefficient.

Study of the telomerase hTERT fraction, PCNA and CD34 expression on pituitary adenomas. Association with clinical and demographic characteristics

To determine the frequency of human telomerase reverse transcriptase (hTERT) catalytic fraction expression and its association with clinical and demographic characteristics of the patient, as well as with the expression of CD34 and proliferating cell nuclear antigen (PCNA) indexes on adenohypophyseal hormone tissues. A transverse study was realized with 49 cases of hypophyseal adenoma with analysis type cases and controls. The different adenohypophyseal hormones [prolactin (PRL), growth hormone (GH), follicle stimulating hormone, luteinizing hormone, thyroid gland stimulant hormone, adrenocorticotropic hormone (ACTH)], the catalytic fraction of the telomerase hTERT, the PCNA index and the CD34 density were determined by means of immunohistochemical techniques. The clinical, demographic and histopathological characteristics of the patients with and without hTERT expression were compared by means of Pearson's Chi-squared, Fisher's exact test and Mann-Whitney's U. Twenty-eight point six percent of the adenomas had positive expression for hTERT. The variables significantly correlated with hTERT's expression were younger age of presentation, diagnostic of adenoma producer, higher PCNA index, higher CD34 density, increased GH on serum and the expression on PRL tissue, GH and ACTH. Tobacco history had a negative association with hTERT's expression. The telomerase could be a marker of cellular proliferation associated with angiogenesis and hormonal activity. Evaluation of these variables could provide information about their biological behavior.

Cigarette smoking and the risk of goitre and thyroid nodules amongst parous women

OBJECTIVES

To clarify the mechanisms by which smoking is associated to toxic and nontoxic goitre and thyroid nodules.

DESIGN

Cohort study.

SETTING

Sweden.

SUBJECTS

A cohort of 874,507 parous women identified through the Medical Birth Registry, with smoking behaviour assessed through self-reported information at the first pre-natal visit, and follow-up between 1983 and 1997.

MAIN OUTCOME MEASURES

Hospital diagnoses of toxic and nontoxic goitre and thyroid nodules, identified by record-linkage with the national Inpatient Registry. Cox regression was employed to estimate the hazard ratio (HR) of smokers compared with nonsmokers and the corresponding 95% confidence limits (CL).

RESULTS

There was a significantly increased risk of goitre and nodules amongst smokers. The positive association was stronger for toxic (age adjusted HR = 1.94, CL = 1.74-2.16) than for nontoxic goitre and nodules (age-adjusted HR = 1.26; CL = 1.14-1.38). There was generally no clear risk trend with regard to amount smoked (below and above 10 cigarettes per day). Elevated body mass attenuated these associations, whilst being born in Swedish areas of endemic goitre enhanced the association with nontoxic goitre and nodules.

CONCLUSIONS

Smoking enhances the risk of thyroid goitre and nodules requiring hospital admission. Iodine deficiency and body weight are likely to be important modifiers of the risk of thyroid hyperplastic diseases amongst smokers.

Peripheral involvement in nicotine-induced enhancement of ethanol intake

It is a well-known fact that a large percentage of alcoholics smoke, and in the experimental rat, intermittent nicotine administration enhances ethanol intake and ethanol preference in a free-choice situation between 6% (v/v) ethanol and water. The present study focuses on the possible involvement of central and/or peripheral nicotine acetylcholine receptors (nAChR) in nicotine-induced sensitization to dopamine-related behavioral effects of ethanol. Wistar rats drinking less than 60% of their total daily fluid from a 6% ethanol solution were used in the study. Nicotine, vehicle, mecamylamine, hexamethonium, mecamylamine+nicotine, and hexamethonium+nicotine were administered subchronically for 15 days. All groups, except the vehicle pre-treated group, markedly increased their ethanol preference to approximately 80%, as well as their ethanol intake. NMRI mice received the same treatments for 10 days, after which ethanol (2.5 g/kg, intraperitoneal (i.p.)) was given acutely and locomotor activity was recorded. Ethanol-induced locomotor stimulation was enhanced in most groups, as compared to the vehicle pre-treated group. Administration of quarternary autonomic drugs to ethanol high-preferring rats (hexamethonium, methscopolamine, sotalol and phentolamine) according to different acute and chronic treatment protocols indicated that the enhanced ethanol intake may involve increased ganglionic and/or peripheral muscarinic neurotransmission. Taken together, the above results indicate that peripheral mechanisms may be involved in the enhancement of dopamine-related behavioral effects of ethanol observed after subchronic intermittent treatment with nicotinic drugs.

The effects of nicotine on the immune system

Although considerable work has been done on the potential health effects of smoking, little is known about the contribution of nicotine to those effects. This paper presents an overview of the immune system, and a discussion of the existing literature on the effects of tobacco smoke and nicotine on immunity. Treatment with nicotine has been shown to influence all aspects of the immune system, including alterations in humoral and cellular immunity. In addition, preliminary data suggest that gender and genetic factors impact on the immunological effects of nicotine. Finally, the possible mechanisms that might mediate the effects of nicotine are discussed.

Cholinoceptor-mediated effects on glycerol output from human adipose tissue using in situ microdialysis

1. Possible cholinoceptor-mediated effects on lipolysis were investigated in vivo in human subcutaneous adipose tissue of non-obese, non-smoking, healthy subjects, by use of microdialysis. Cholinomimetic and sympathomimetic agents were added to the in going dialysate solvent. 2. Addition of nicotine to the perfusion solvent caused a concentration-dependent reversible increase in the levels of glycerol in the dialysate (lipolysis index). The opposite effect (also concentration-dependent and reversible) was caused by the addition of carbachol. The maximum effects were 100% stimulation and 50% inhibition, respectively, by nicotine and carbachol. Neither nicotine nor carbachol stimulated nutritive blood flow in adipose tissue (as measured with an ethanol escape technique). 3. The nicotine effect in situ was concentration-dependently counteracted by the nicotinic cholinoceptor antagonist, mecamylamine. Likewise, the carbachol effect was concentration-dependently counteracted by the muscarinic cholinoceptor antagonist, atropine. 4. When adipose tissue was pretreated with phentolamine plus propranolol in order to obtain a complete alpha and beta-adrenoceptor blockade, the subsequent addition of nicotine or carbachol still induced an increase and decrease in dialysate glycerol levels (lipolytic or antilipolytic effects), respectively. When adipose tissue was pretreated with mecamylamine or atropine, the subsequent addition of acetylcholine caused a reversible decrease and increase, respectively, of the dialysate glycerol levels. 5. Nicotine and carbachol had no effects on glycerol release from human isolated subcutaneous fat cells that were incubated in vivo. 6. In conclusion, the data demonstrate a dual effect of the cholinoceptor system on glycerol output inhuman adipose tissue: stimulation through nicotinic receptors and inhibition through muscarinic receptors. These effects, which are not observed in vitro, are independent of the adrenergic system and the local blood flow and seem not to be mediated by a direct action on the fat cell.

Nicotine and its major metabolite cotinine have different effects on aldosterone and prolactin serum levels in the normal male rat

Nicotine (0.01-1.0 mg/kg, i.p.) or cotinine (0.003-1.0 mg/kg, i.p.) treatment was administered to Sprague-Dawley male rats. The time-effect curves (5, 10, 30, 60 and 180 min) were analyzed. Nicotine dose-dependently increased blood aldosterone and corticosterone levels with a peak effect 10 min after the intraperitoneal injection. Nicotine treatment weakly decreased serum levels of aldosterone at 2 h, possibly as a consequence of nicotine metabolising to cotinine, resulting in higher serum levels of cotinine than nicotine. Cotinine dose-dependently reduced serum aldosterone levels, an effect which became more marked with time, leaving plasma corticosterone unchanged. Nicotine dose-dependently increased serum prolactin levels at 5 and 10 min following treatment, an effect which had diminished at 30 min. Cotinine dose-dependently reduced serum prolactin levels at 5 min followed by a dose-dependent increase at 10 min after which a dose-dependent reduction was again found after 30 min post treatment. In conclusion, acute nicotine and cotinine treatment produced opposite effects on aldosterone and prolactin serum levels. The prolonged effect of cotinine on aldosterone levels may be involved in changes in brain function, and may be connected to the development of withdrawal effects after stopping cigarette smoking. As reported by other investigators, nicotine produced enhanced plasma corticosterone levels while cotinine treatment was ineffective. Since cotinine induced marked changes in serum prolactin levels while leaving LH levels unchanged, it seems plausible that cotinine affects neuroendocrine regulation via mechanisms not primarily related to circulatory effects. Thus, an action at the median eminence--pituitary level seems likely.

Naltrexone treatment attenuates the inhibitory effect of nicotine treatment on serum LH in rats

The hypothesis that endogenous opioids might have a role in mediating the suppressive effects of nicotine on serum LH concentrations in rats was investigated. Naltrexone treatment prevented the inhibitory effect of high doses of nicotine on serum LH concentrations. Nicotine treatment also prevented the stimulatory effect of naltrexone on serum LH concentrations. These results suggest that the inhibitory effects of nicotine on serum LH concentrations involve an opioidergic component.

Effects of a postnatal exposure to cigarette smoke on hypothalamic catecholamine nerve terminal systems and on neuroendocrine function in the postnatal and adult male rat. Evidence for long-term modulation of anterior pituitary function

The purpose of this paper was to study the possible long-term effects of postnatal exposure to cigarette smoke. Male Sprague-Dawley rats were exposed to the smoke from 2 cigarettes (Kentucky reference IR-1 type) every morning from day 1 after birth for a period of 5, 10 or 20 days. The rats were decapitated 24 hours (5, 10 and 20 days of exposure), 1 week (20 days of exposure) or 7 months (20 days of exposure) after the last exposure. Using the Falck-Hillarp methodology in combination with quantitative histofluorimetry catecholamine levels and changes in catecholamine utilization (alpha MT-induced CA fluorescence disappearance) in discrete hypothalamic catecholamine nerve terminal systems were analysed. Serum prolactin, LH, TSH and corticosterone levels were determined by means of radioimmunoassay procedures. In the postnatal period serum LH levels were significantly increased 24 hours after a 10 and 20 day exposure to cigarette smoke. In adult life after a 20-day postnatal exposure to cigarette smoke a highly significant increase was observed in serum prolactin levels, which were unaltered by this exposure when measured in the postnatal period. Twenty-four hours following a 20-day postnatal exposure, catecholamine utilization was increased in the medial palisade zone of the median eminence and substantially reduced in the parvocellular and magnocellular parts of the paraventricular hypothalamic nucleus. One week and 7 months following a 20-day postnatal exposure to cigarette smoke no alterations were observed in catecholamine levels or utilization in various hypothalamic areas including the median eminence. All the above changes were observed in the presence of an unaltered development of body weight. The results indicate that marked but temporary increases in LH secretion occur 24 hours after a postnatal exposure to cigarette smoke, while increase in prolactin secretion only develop in adult life, when the maturational processes of the brain and/or the anterior pituitary gland are completed. Changes in catecholamine levels and utilization are found in discrete hypothalamic nerve terminal networks but do not play a major role in mediating the above changes in anterior pituitary function and are probably the result of a withdrawal phenomenon.

The antiestrogenic effect of cigarette smoking in women

Epidemiologic results indicate that women who smoke cigarettes are relatively estrogen-deficient. Smokers have an early natural menopause, a lowered risk of cancer of the endometrium, and an increased risk of some osteoporotic fractures. Moreover, women who smoke may have a reduced risk of uterine fibroids, endometriosis, hyperemesis gravidarum, and benign breast disease. Several possible mechanisms for these effects have been identified. Smoking does not appear to be clearly related to estradiol levels, at least in postmenopausal women, although levels of adrenal androgens are increased. Moreover, smoking appears to alter the metabolism of estradiol, leading to enhanced formation of the inactive catechol estrogens.

Effects of combined pre- and postnatal treatment with nicotine on hypothalamic catecholamine nerve terminal systems and neuroendocrine function in the 4-week old and adult male and female diestrous rat

Abstract Male and female Sprague-Dawley rats were treated with nicotine during the prenatal period and the first three postnatal weeks (the pregnant and lactating rats were given nicotine hydrogen (+) tartrate (165 mg/l) in the tap water). Catecholamine fluorescence was evaluated using quantitative histofluorometry on brain sections treated according to Falck-Hillarp methodology. In order to evaluate catecholamine utilization in discrete hypothalamic catecholamine nerve terminal networks, the alphaMT- (alpha-methyl-(+/-)-p-tyrosine methyl ester) induced catecholamine disappearance was studied 2 h following the tyrosine hydroxylase inhibition. The body weight was reduced in both the male and female rats from 3 weeks of age until 9 weeks of age following pre- and postnatal treatment with nicotine. Following one week of withdrawal from pre- and postnatal treatment with nicotine, an increased catecholamine utilization was observed in the medial and lateral palisade zones of the median eminence mainly in the female rat. In the female rat, reduced prolactin serum levels were found both in the presence and absence of alphaMT treatment as well as reduced luteinizing hormone concentration in the presence of alphaMT treatment. At 6 months of age indications of a maintained, weak activation of the catecholamine nerve terminal systems in the medial palisade zones of the median eminence were observed in male rats pre- and postnatally treated with nicotine. Furthermore, increased noradrenaline levels were found in the paraventricular hypothalamic nucleus. An increase in serum luteinizing hormone levels was also found in these rats. In the 7-month old diestrous rat, maintained marked increases in catecholamine utilization in the medial and lateral palisade zones of the median eminence were found following treatment with nicotine during the pre- and postnatal period. A significant reduction of nigral dopamine stores was also demonstrated. The serum levels of thyroid stimulating hormone, prolactin and luteinizing hormone were unchanged in these rats both in the presence and absence of tyrosine hydroxylase inhibition. Finally, pre- and postnatal treatment with nicotine did not alter [(3)H]nicotine binding (quantitative receptor autoradiography) in cortical, striatal and thalamic areas of the adult diestrous rat. The results demonstrate that pre- and postnatal treatment with nicotine in the drinking water produces permanent activations of the catecholamine nerve terminal networks of the external layer of the median eminence mainly in the female rat. These changes appear to be associated with reduced serum prolactin levels in the 4-week old female rat. Sex-specific changes occur in discrete noradrenaline nerve terminal systems. The observed changes may have functional consequences for neuroendocrine regulation and for the regulation of food and water intake as well as sex-specific responses to stress in the male versus the female rat. Nicotine-induced disturbances in brain cell replication and differentiation may underlie the permanent alteration found in discrete catecholamine neuron systems after pre- and postnatal exposure to this drug.

Effects of withdrawal from chronic exposure to cigarette smoke on hypothalamic and preoptic catecholamine nerve terminal systems and on the secretion of pituitary hormones in the male rat

A 48 h but not a 72 h or 7 day withdrawal from chronic exposure to cigarette smoke was associated with increased noradrenaline levels (quantitative histofluorimetry) in the subependymal layer (SEL) of the median eminence, the anterior periventricular hypothalamic region (PV I) and the parvocellular part of the hypothalamic nucleus (PA FP) and an increased noradrenaline utilization (tyrosine hydroxylase inhibition by alpha MT) in the SEL and the PV I. Following a 48 h or 72 h but not a 7 day withdrawal from chronic exposure to cigarette smoke an increased catecholamine utilization was found in the medial palisade zone (MPZ) of the median eminence. Reduced serum prolactin, FSH and corticosterone levels were found following a 48 h withdrawal from chronic exposure to cigarette smoke. Following a 72 h withdrawal from chronic exposure to cigarette smoke a reduced concentration of serum prolactin was noted. Chronic exposure to cigarette smoke reduced serum TSH levels and lead to a tolerance development with regard to noradrenaline levels and utilization within the preoptic region with the exception of the periventricular preoptic region. The finding of special interest in the present study is the demonstration of a highly significant lowering of corticosterone serum levels despite maintained blood levels of ACTH as seen 48 h following withdrawal. It is suggested that this type of endocrine change may lead to changes in fear-motivated behaviour and contribute to behavioural withdrawal reactions. The maintained reductions of serum prolactin levels found after 48 h and 72 h of withdrawal from cigarette smoke exposure (cf. Andersson et al. 1985a) is discussed in terms of an increased catecholamine utilization in the medial palisade zone of the median eminance. This activation is suggested to be caused by the development of a prolactin receptor supersensitivity within the medium eminence. The present evidence indicates withdrawal effects mainly in the noradrenaline nerve terminals of the subependymal layer of the median eminence, the anterior periventricular hypothalamic region and the parvocellular part of the paraventricular hypothalamic nucleus which inter alia are involved in regulation of ACTH secretion (cf. Andersson et al. 1985a).

Studies of protective actions of nicotine on neuronal and vascular functions in the brain of rats: comparison between sympathetic noradrenergic and mesostriatal dopaminergic fiber systems, and the effect of a dopamine agonist

Neuroprotective and possible trophic actions of nicotine were studied in two types of experimental models: (1) one in which the meso-striatal dopamine system was subjected to partial hemitransection, and regional glucose utilization (using 2-[3H]deoxyglucose) and blood flow (using [14C]iodoantipyrine) were measured by computer-assisted quantitative autoradiography based on a double-isotope technique; and (2) another where the sympathetic cranial nervous system supplying the brain vasculature was subjected to decentralization, axotomy, and partial or complete ganglionectomy, and the neuronal survival and fiber regeneration were elucidated by fluorescence histochemistry of noradrenaline, tyrosine hydroxylase, and neuropeptide Y. Continuous nicotine infusion for 4 weeks failed to significantly affect the neuronal response to the surgical interference of the sympathetic noradrenergic system. The same nicotine treatment for 2 weeks significantly improved glucose utilization and blood flow in caudate-putamen on the side in which the meso-striatal dopamine system had been transected, thus eliminating the 16% side-to-side asymmetry in the metabolism caused by the axotomy. The dopamine agonist, EMD 23,448, was without significant effect on this asymmetry. The hemitransection produced marked reduction in metabolism and flow also in the ventro-lateral thalamus. In substantia nigra, glucose utilization was markedly elevated--perhaps as a consequence of a regenerative increase in protein synthesis--opposite to a considerable reduction in nigral blood flow. Little or no effect of the hemitransection was seen in hippocampus or nucleus accumbens. In neither of these four regions did nicotine (or EMD 23,448) have any overt influence on glucose metabolism or blood flow. It is concluded that nicotine, mainly through its protective action on the meso-striatal dopaminergic system, is able to improve striatal glucose utilization and associated blood flow, probably reflecting a tendency to amelioration of neurotransmission function of surviving terminals belonging to the nigro-striatal dopamine neurons.

Neuroendocrine actions of nicotine and of exposure to cigarette smoke: medical implications

Over many years a large number of studies have demonstrated that nicotine and exposure to cigarette smoke produce marked neuroendocrine changes in animals and in man. The initial effects of nicotine are characterized by a marked hypersecretion of ACTH, vasopressin, beta-endorphin, prolactin and LH. Many of these very acute stimulatory effects of nicotine rapidly disappear, probably due to a desensitization of the central nicotinic cholinergic receptors involved. Instead, upon acute intermittent treatment with nicotine or exposure to cigarette smoke, an inhibition of prolactin, LH and TSH secretion occurs, which is associated with maintained hypersecretion of corticosterone. These effects are probably mediated via activation of central cholinergic receptors of the ganglionic type. Evidence indicates that the inhibitory effects of nicotine on LH and prolactin secretion are produced via an activation by these nicotinic receptors of the tubero-infundibular dopamine neurons, releasing dopamine as a prolactin inhibitory factor. Dopamine inhibits LHRH release via an axonic interaction involving D1-like dopamine receptors in the median eminence. It therefore seems possible that the reduced fertility found in heavy smokers may be counteracted by D1 receptor antagonists. The symptoms associated with glucocorticoid hypersecretion induced by nicotine is discussed considering not only the peripheral side effects but also permanent deficits in hippocampal glucocorticoid receptors and loss of hippocampal neurons. In view of the important influence of hormones on immune functions, it seems likely that smoking will cause disturbances in immune responsiveness. Finally, the nicotine-induced alterations of neuroendocrine function, especially in the pituitary-adrenal axis and in vasopressin release, may also lead to behavioural consequences in smokers, especially in the withdrawal phase.

Neuroregulatory effects of nicotine

The impact of nicotine on the central nervous system is, in an important sense, neuroregulatory, with cascading effects on physiological and biochemical function as well as on behavioral activity. Accordingly, the neurotransmitter and neuroendocrine effects of nicotine constitute a critical part of its biological action, which includes reinforcing as well as pathophysiological consequences. This review focuses on nicotine's effects on cholinergic and non-cholinergic nicotine receptors and on the responses of catecholamines, monoamines, hypophyseal hormones, and cortisol. The contribution of critical variables, such as timing and duration of neuroregulator release and the patterns that make up the total response, is still largely unknown, particularly with regard to the effects of environmental context, history of nicotine use, and mode of administration. The evidence suggests that by altering the bioavailability of the above-listed neuroregulators, nicotine serves as a pharmacological "coping response", providing immediate though temporary improvement in affect or performance in response to environmental demands. Much of what is known to date is based on studies involving the administration of agonists and antagonists under different environmental conditions. Newer technological approaches such as autoradiography and positron emission tomography show potential for determining the neuroregulatory patterns involved and specifying nicotine's locus of action relevant to its behavioral and physiological effects.

The effect of an acute nicotine infusion on the local cerebral glucose utilization of the awake rat

The effect of acute infusion of nicotine on local cerebral glucose utilization (LCGU) was studied in discrete regions of the central nervous system of the rat by means of the quantitative autoradiographic 2-deoxy-D-[1-14C]glucose method described by Sokoloff et al. Nicotine was administered in 3 dosages: 0.5 microgram/kg/min, 1.58 micrograms/kg/min and 5 micrograms/kg/min. The resulting plasma concentrations of nicotine were 10/39/114 ng/ml plasma. During the experiment, blood pressure, heart rate, body temperature, hematocrit, acid-base status and plasma glucose concentration showed no--or minor--changes. Nicotine significantly increased LCGU in a dose-dependent manner in the following 9 of 45 examined structures: substantia nigra (compact part), superior colliculus (superficial grey layer), interpeduncular nucleus and cingulate cortex (P less than 0.01); lateral geniculate body, optic chiasm, anteroventral and anteromedial nucleus of thalamus and mamillary body (P less than 0.05). For most of these structures with increased LCGU, other groups have reported a high regional receptor binding of nicotine (exception: mamillary body and optic chiasm). It is concluded that nicotine has distinct effects on the functional activity of localized brain areas.