Drugs online research references
Digestion. 1990;46 Suppl 2:112-24.
Carbachol-induced down-regulation of receptors for pancreatic secretagogues.
Vinayek R, Murakami M, Sharp C, Jensen RT, Gardner JD.
Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Md.
Pancreatic acini possess a high affinity class of cholinergic receptors and a low affinity class of cholinergic receptors. Carbachol occupation of high affinity cholinergic receptors produces a reduction in binding of [3H]N-methylscopolamine. First incubating acini with carbachol caused a complete loss of high affinity cholinergic receptors with no change in the number or affinity of low affinity cholinergic receptors. Carbachol occupation of low affinity cholinergic receptors appears to produce a reduction in binding of 125I-CCK-8 and 125I-[Tyr4]bombesin. Acini possess two classes of CCK receptors. One class has a high affinity for CCK-8; the other class has a low affinity for CCK-8. First incubating acini with carbachol caused a 60% decrease in the number of high affinity CCK receptors with no change in the number of low affinity receptors or the affinities of either class of receptors for CCK-8. Acini possess a single class of bombesin receptors and first incubating acini with carbachol caused a 40% decrease in the number of bombesin receptors with no change in their affinity for bombesin.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2175722&dopt=Abstract
J Biol Chem. 1995 Mar 31;270(13):7213-8.
Transcriptional down-regulation of m2 muscarinic receptor gene expression in human embryonic lung (HEL 299) cells by protein kinase C.
Rousell J, Haddad EB, Mak JC, Barnes PJ.
Department of Thoracic Medicine, National Heart and Lung Institute, London, United Kingdom.
m2 muscarinic receptor gene expression was investigated following stimulation of protein kinase C (PKC) with the phorbol ester 4 beta-phorbol dibutyrate (PDBu) in HEL 299 cells. PDBu (100 nM) caused a time-dependent decrease in the steady-state levels of m2 receptor mRNA and in specific [3H]N-methyl-scopolamine binding. Preincubation with the PKC inhibitor GF-109203X inhibited the reduction in M2 receptor and mRNA levels induced by PDBu, confirming the involvement of PKC. Chronic PDBu treatment also caused desensitization of the receptor as forskolin-stimulated cAMP accumulation, inhibited by carbachol in control cells, was lost upon treatment with PDBu for 24 h. Co-incubation with PDBu and the protein synthesis inhibitor cycloheximide, inhibited PDBu-mediated reduction of m2 receptor mRNA, indicating new protein synthesis is required for down-regulation. Half-life studies using the transcriptional inhibitor actinomycin D suggested that the stability of the m2 receptor mRNA was not altered by PDBu treatment (t1/2 = 2 h). Nuclear run-on assays showed a 50% reduction in the rate of m2 receptor gene transcription after treatment with PDBu for 12 h. In conclusion we have provided evidence for heterologous regulation of m2 receptor gene expression through changes in gene transcription resulting in uncoupling of M2 receptors. Furthermore, the synthesis of an unidentified factor is required for the down-regulation process.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7706260&dopt=Abstract
Pharmacol Biochem Behav. 1975 Nov-Dec;3(6):1037-42.
Effects of scopolamine and D-amphetamine on one-way, shuttle and inhibitory avoidance: a diallel analysis in mice.
Anisman H.
The effects of scopolamine (2.0 mg/kg) and d-amphetamine (3.0 mg/kg) on one-way, shuttle and inhibitory avoidance performance were evaluated in 3 strains of mice (A/J, DBA/2J and C57BL/6J) and their 6 reciprocal F1 hybrids. In the saline condition, intermediate inheritance was observed in the inhibitory task, complete dominance for superior avoidance in the one-way task, and hybrid superiority in the shuttle situation. Administration of d-amphetamine disrupted inhibitory performance in all strains. In the shuttle task no amphetamine effect was observed in C57BL/6J mice, while improvement was seen in A/J and DBA/2J mice, as well as in all the hybrid corsses. No drug effect was seen in the one-way task. As with d-amphetamine, scopolamine disrupged performance in the inhibitory task among the inbreds, but had negligible effects in the hybrids. In the shuttle task, only the A/J mice exhibited improved performance, while a small decline in response rate was seen in one-way avoidance. Results were interpreted in terms of tha role of scopolamine and d-amphetamine in modifying non-associative factors involved in avoidance, and the interaction between associative and non-associative factors in modulating avoidance response rate.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1223892&dopt=Abstract
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