STUDIES ON CHOLINERGIC FUNCTION AND MEMORY IN MICE (CHOLINOTOXINS, WORKING, REFERENCE MEMORY, RADIAL ARM MAZE)

Considerable evidence suggests that central cholinergic neurons participate in either acquisition, storage or retrieval of information. Experiments were designed to evaluate information processing in mice following either reversible or irreversible impairment in central cholinergic activity. The cholinergic receptor antagonists, atropine and methylatropine were used to reversibly inhibit cholinergic transmission. Irreversible impairment in central cholinergic function was achieved by central administration of the cholinergic-specific neurotoxins, N-ethyl-choline aziridinium (ECA) and N-ethyl-acetylcholine aziridinium (EACA).^ ECA and EACA appear to act by irreversible inhibition of high affinity choline uptake (proposed rate-limiting step in acetylcholine synthesis). Intraventricular administration of ECA or EACA produced persistent reduction in hippocampal choline acetyltransferase activity. Other neuronal systems and brain regions showed no evidence of toxicity.^ Mice treated with either ECA or EACA showed behavioral deficits associated with cholinergic dysfunction. Passive avoidance behavior was significantly impaired by cholinotoxin treatment. Radial arm maze performance was also significantly impaired in cholinotoxin-treated animals. Deficits in radial arm maze performance were transient, however, such that rapid and apparent complete behavioral recovery was seen during retention testing. The centrally active cholinergic receptor antagonist atropine also caused significant impairment in radial arm maze behavior, while equivalent doses of methylatropine were without effect.^ The relative effects of cholinotoxin and receptor antagonist treatment on short-term (working) memory and long-term (reference) memory in radial arm maze behavior were examined. Maze rotation studies indicated that there were at least two different response strategies which could result in accurate maze performance. One strategy involved the use of response algorithms and was considered to be a function of reference memory. Another strategy appeared to be primarily dependent on spatial working memory. However, all behavioral paradigms with multiple trails have reference memory requirements (i.e. information useful over all trials). Performance was similarly affected following either cholinotoxin or anticholinergic treatment, regardless of the response strategy utilized. In addition, rates of behavioral recovery following cholinotoxin treatment were similar between response groups. It was concluded that both cholinotoxin and anticholinergic treatment primarily resulted in impaired reference memory processes. ^

Galantamine: Effect on nicotinic receptor binding, acetylcholinesterase inhibition, and learning

Classical eyeblink conditioning is a well-characterized model paradigm that engages the septohippocampal cholinergic system. This form of associative learning is impaired in normal aging and severely disrupted in Alzheimer's disease (AD). Some nicotinic cholinergic receptor subtypes are lost in AD, making the use of nicotinic allosterically potentiating ligands a promising therapeutic strategy. The allosterically potentiating ligand galantamine (Gal) modulates nicotinic cholinergic receptors to increase acetylcholine release as well as acting as an acetylcholinesterase (AChE) inhibitor. Gal was tested in two preclinical experiments. In Experiment 1 with 16 young and 16 older rabbits, Gal (3.0 mg/kg) was administered for 15 days during conditioning, and the drug significantly improved learning, reduced AChE levels, and increased nicotinic receptor binding. In Experiment 2, 53 retired breeder rabbits were tested over a 15-wk period in four conditions. Groups of rabbits received 0.0 (vehicle), 1.0, or 3.0 mg/kg Gal for the entire 15-wk period or 3.0 mg/kg Gal for 15 days and vehicle for the remainder of the experiment. Fifteen daily conditioning sessions and subsequent retention and relearning assessments were spaced at 1-month intervals. The dose of 3.0 mg/kg Gal ameliorated learning deficits significantly during acquisition and retention in the group receiving 3.0 mg/kg Gal continuously. Nicotinic receptor binding was significantly increased in rabbits treated for 15 days with 3.0 mg/kg Gal, and all Gal-treated rabbits had lower levels of brain AChE. The efficacy of Gal in a learning paradigm severely impaired in AD is consistent with outcomes in clinical studies.

Cholinergic agonists stimulate secretion of soluble full-length amyloid precursor protein in neuroendocrine cells.

The Abeta peptide of Alzheimer disease is derived from the proteolytic processing of the amyloid precursor proteins (APP), which are considered type I transmembrane glycoproteins. Recently, however, soluble forms of full-length APP were also detected in several systems including chromaffin granules. In this report we used antisera specific for the cytoplasmic sequence of APP to show that primary bovine chromaffin cells secrete a soluble APP, termed solAPPcyt, of an apparent molecular mass of 130 kDa. This APP was oversecreted from Chinese hamster ovary cells transfected with a full-length APP cDNA indicating that solAPPcyt contained both the transmembrane and Abeta sequence. Deglycosylation of solAPPcyt showed that it contained both N- and O-linked sugars, suggesting that this APP was transported through the endoplasmic reticulum-Golgi pathway. Secretion of solAPPcyt from primary chromatin cells was temperature-, time-, and energy-dependent and was stimulated by cell depolarization in a Ca2+-dependent manner. Cholinergic receptor agonists, including acetylcholine, nicotine, or carbachol, stimulated the rapid secretion of solAPPcyt, a process that was inhibited by cholinergic antagonists. Stimulation of solAPPcyt secretion was paralleled by a stimulation of secretion in catecholamines and chromogranin A, indicating that secretion of solAPPcyt was mediated by chromaffin granule vesicles. Taken together, our results show that release of the potentially amyloidogenic solAPPcyt is an active cellular process mediated by both the constitutive and regulated pathways. solAPPcyt was also detected in human cerebrospinal fluid. Combined with the neuronal physiology of chromaffin cells, our data suggest that cholinergic agonists may stimulate the release of this APP in neuronal synapses where it may exert its biological functions. Moreover, vesicular or secreted solAPPcyt may serve as a soluble precursor of Abeta.

Comparison of diagnostic tests in myasthenia gravis

Results of 3 tests, intravenous edrophonium chloride, EMG, and acetylcholine receptor antibody testing, were compared in patients with generalised and ocular myasthenia gravis. None of the 3 tests was positive in any patient with a diagnosis other than myasthenia. However, equivocal results were obtained with edrophonium and EMG testing in some patients with myasthenia gravis and in patients with other diseases. It is concluded from this survey that antibody and edrophonium testing were equally efficient in detecting generalised myasthenia gravis. Edrophonium testing was superior in ocular myasthenia gravis. Although the yields from each test varied, all 3 tests were needed for the evaluation of some myasthenia gravis patients as each test may provide additional information.

Clinical phenotype and the lack of mutations in the CHRNG, CHRND, and CHRNA1 genes in two Indian families with Escobar syndrome

The objective of this study was to report the clinical phenotype and genetic analysis of two Indian families with Escobar syndrome (ES). The diagnosis of ES in both families was made on the basis of published clinical features. Blood samples were collected from members of both families and used in genomic DNA isolation. The entire coding regions and intron-exon junctions of the ES gene CHRNG (cholinergic receptor, nicotinic, gamma), and two other related genes, CHRND and CHRNA1, were amplified and sequenced to search for mutations in both families. Both families show a typical form of ES. Sequencing of the entire coding regions including the intron-exon junctions of the three genes did not yield any mutations in these families. In conclusion, it is possible that the mutations in these genes are located in the promoter or deep intronic regions that we failed to identify or the ES in these families is caused by mutations in a different gene. The lack of mutations in CHRNG has also been reported in several families, suggesting the possibility of at least one more gene for this syndrome. Clin Dysmorphol 22:54-58 (C) 2013 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.

Damage of the medial preoptic area impairs peripheral pilocarpine-induced salivary secretion

The existence of neural connections between the medial preoptic area (MPOA) and the salivary glands and the increase in salivation by thermal or electrical stimulation of the MPOA have suggested an important role of MPOA in the control of salivary gland function. Although direct cholinergic activation of the salivary glands induces salivation, recent studies have suggested that salivation produced by i.p. pilocarpine may also depend on the activation of central mechanisms. Therefore, in the present study, we investigated the effects of bilateral electrolytic lesions of the MPOA on the salivation induced by i.p. pilocarpine. Adult male Holtzman rats (n = 11-12/group) with bilateral sham or electrolytic lesions of the MPOA were used. One, five, and fifteen days after the brain surgery, under ketamine anesthesia, the salivation was induced by i.p. pilocarpine (1 mg/kg of body weight), and saliva was collected using preweighted small cotton balls inserted into the animal's mouth. Pilocarpine-induced salivation was reduced 1 and 5 days after MPOA lesion (341 +/- 41 and 310 +/- 35 mg/7 min, respectively, vs. sham lesions 428 +/- 32 and 495 +/- 36 mg/7 min, respectively), but it was fully recovered at the 15th day post-lesion (561 +/- 49 vs. sham lesion: 618 27 mg/7 min). Lesions of the MPOA did not affect baseline non-stimulated salivary secretion. The results confirm the importance of MPOA in the control of salivation and suggest that its integrity is necessary for the full sialogogue effect of pilocarpine. However, alternative mechanisms probably involving other central nuclei can replace MPOA function in chronically lesioned rats allowing the complete recovery of the effects of pilocarpine. (c) 2006 Published by Elsevier B.V.

Role of the medial septal area on pilocarpine-induced salivary secretion and water intake

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Pressor, dipsogenic, natriuretic and kaliuretic responses to central carbachol in rats with lesion of the medial septal area

In the present study we investigated the effect of electrolytic lesion of the medial septal area (MSA) on the dipsogenic, natriuretic, kaliuretic and pressor responses elicited by intracerebroventricular (i.c.v.) injection of the cholinergic agonist carbachol. Freely moving rats with sham or MSA lesion (1-7 days and 14-18 days) and a stainless steel cannula implanted into the lateral ventricle were studied. In sham rats, i.c.v. injection of carbachol (7.5 nmol) produced an increase in water intake (10.2 ± 1.5 ml/h), mean arterial pressure (MAP) (35 ± 5 mmHg) and urinary Na+ and K+ excretion (551 ± 83 and 170 ± 17 μEq 120 min, resp.). The pressor (18 ± 3 and 14 ± 4 mmHg, resp.) and natriuretic responses (178 ± 58 and 172 ± 38 μEq 120 min) produced by i.c.v. carbachol in acute or chronic MSA-lesioned rats were reduced. No change was observed in urinary K+ excretion and a reduced water intake (5 ± 1.3 ml/h) was observed only in acute MSA-lesioned rats. These results suggest that the MSA plays an important role for the pressor and natriuretic responses induced by central cholinergic activation in rats. A small influence of this structure on water intake may also be suggested. © 1991.

Doença pulmonar obstrutiva crônica

Chronic obstructive pulmonary disease (COPD) is an extremely common disorder that all primary care physicians should be able to manage. In this review we will define the entities incorporated in COPD and will present various aspects of the diagnoses and treatment. We could not cover every aspect of this broad topic even providing a detailed review of those areas but some facets of therapy like smoking cessation, drug therapy, oxygen therapy, nutrition, and respiratory rehabilitation will be described.

Functional evidence that the central renin-angiotensin system plays a role in the pressor response induced by central injection of carbachol

We investigated the effects of losartan, an AT 1-receptor blocker, and ramipril, a converting enzyme inhibitor, on the pressor response induced by angiotensin II (ANG II) and carbachol (a cholinergic receptor agonist). Male Holtzman rats (250-300 g) with a stainless steel cannula implanted into the lateral ventricle (LV) were used. The injection of losartan (50 nmol/l μl) into the LV blocked the pressor response induced by ANG II (12 ng/l μl) and carbachol (2 nmol/l μl). After injection of ANG II and carbachol into the LV, mean arterial pressure (MAP) increased to 31 ± 1 and 28 ± 2 mmHg, respectively. Previous injection of losartan abolished the increase in MAP induced by ANG II and carbachol into the LV (2 ± 1 and 5 ± 2 mmHg, respectively). The injection of ramipril (12 ng/l μl) prior to carbachol blocked the pressor effect of carbachol to 7 ± 3 mmHg. These results suggest an interaction between central cholinergic pathways and the angiotensinergic system in the regulation of arterial blood pressure.

Doença pulmonar obstrutiva crônica

In this review the definition of COPD is presented and the epidemiology and risk factors for disease development are briefly discussed. Characteristics clinical features, pulmonary functions indices, radiologics signs and arterial blood gases alterations are presented and discussed. Classification of disease severity and components of COPD management are also described.

Consumo de drogas psicoactivas por adolescentes escolares de Assis, SP

To quantify psychoactive drug use and investigate use-related variables among students of Assis, Brazil, a questionnaire was administered to collect sociodemographic data and identify the pattern of non-medical use of psychoactive drugs in 20% of public and private school students. The largest consumption indexes for lifetime use were seen for alcohol (68.9%) and tobacco (22.7%). Drugs most often used were: solvents (10.0%); marijuana (6.6%); benzodiazepines (3.8%); amphetamines (2.6%); cocaine (1.6%); and anticholinergics (1.0%).

Doença pulmonar obstrutiva crônica

The chronic obstructive lung disease is reviewed with emphasys on its epidemiology and risk factors. The diagnosis, clinical aspects pulmonary, functional alterations and laboratorial findings are discussed. The treatment is also reviewed, based on the actual consensus, considering the following classes of approaches: bronchodilators, inhaled β-agonists, corticoids, methilxanthines, prolonged domiciliar-orygen therapy.

Activation of central aα-adrenoceptors mediates salivary gland vasoconstriction

Objective: Peripheral treatment with the cholinergic agonist pilocarpine increases salivary gland blood flow and induces intense salivation that is reduced by the central injection of moxonidine (aα-adrenoceptors/ imidazoline agonist). In the present study, we investigated the effects of the intracerebroventricular (i.c.v.) injection of pilocarpine alone or combined with moxonidine also injected i.c.v. On submandibular/sublingual gland (SSG) vascular resistance. In addition, the effects of these treatments on arterial pressure, heart rate and on mesenteric and hindlimb vascular resistance were also tested. Design: Male Holtzman rats with stainless steel cannula implanted into lateral ventricle and anaesthetized with urethane + α-chloralose were used. Results: Pilocarpine (500 nmol/1 μl) injected i.c.v. Reduced SSG vascular resistance and increased arterial pressure, heart rate and mesenteric vascular resistance. Contrary to pilocarpine alone, the combination of moxonidine (20 nmol/1 μl) and pilocarpine injected i.c.v. Increased SSG vascular resistance, an effect abolished by the pre-treatment with the α2-adrenoceptor antagonist yohimbine (320 nmol/2 μl). The increase in arterial pressure, heart rate and mesenteric resistance was not modified by the combination of moxonidine and pilocarpine i.c.v. Conclusion: These results suggest that the activation of central α2- adrenoceptors may oppose to the effects of central cholinergic receptor activation in the SSG vascular resistance. © 2012 Elsevier Ltd. All rights reserved.