Isolating and characterizing three alternatively spliced mu opioid receptor variants: mMOR‐1A,mMOR‐1O,and mMOR‐1P

Extensive alternative pre‐mRNA splicing of the mu opioid receptor gene, OPRM1, has demonstrated an array of splice variants in mice, rats and humans. Three classes of splice variants have been identified: full‐length seven transmembrane (TM) domain variants with C‐terminal splicing, truncated 6TM variants and single TM variants. The current studies isolates and characterizes an additional three full‐length C‐terminal splice variants generated from the mouse OPRM1 gene: mMOR‐1A, mMOR‐1O, and mMOR‐1P. Using RT‐qPCR, we demonstrated differential expression of these variants' mRNAs among selected brain regions, supporting region‐specific alternative splicing. When expressed in Chinese Hamster Ovary cells, all the variants displayed high mu binding affinity and selectivity with subtle differences in the affinities toward some agonists. [³⁵S]γGTP binding assays revealed marked differences in agonist‐induced G protein activation in both potency and efficacy among the variants. Together with the previous studies of mu agonist‐induced phosphorylation and internalization in several carboxyl terminal splice variants, the current studies further suggest the existence of biased signaling of various agonists within each individual variant and/or among different variants. Synapse 68:144–152, 2014 . © 2013 Wiley Periodicals, Inc.     

Baroreflex failure as a late sequela of neck irradiation

Combined chemotherapy and radiotherapy increase long-term survival in patients with head and neck tumors. Late complications of treatment, however, are being recognized increasingly. Surgery or radiotherapy of the carotid sinuses or brain stem can evoke labile hypertension and orthostatic intolerance from acute or subacute baroreflex failure. Here we report cases in which chronic baroreflex failure appeared to develop as a late sequela of neck irradiation. Three patients referred for autonomic nervous system function testing had labile blood pressure and chronic orthostatic intolerance that developed years after neck irradiation for cancer. In each patient, heart rate remained constant during performance of the Valsalva maneuver, suggesting baroreflex-cardiovagal failure. All 3 patients had virtually zero baroreflex-cardiovagal gain, quantified by interbeat interval-systolic blood pressure relationships after intravenous phenylephrine or nitroglycerine. Ambulatory blood pressure monitoring revealed highly variable blood pressure, with sudden pressor and depressor episodes, a characteristic feature of baroreflex failure. Cardiovagal efferent function, assessed by power spectral analysis of heart rate variability during slow, deep respiration, was normal. Sympathetic noradrenergic efferent function, assessed by cold pressor testing and plasma catecholamine levels during supine rest and orthostasis, was also normal or increased. These findings indicated a primarily afferent lesion. Carotid ultrasonography revealed intimal thickening and atheromatous plaques in all 3 patients. We propose that labile hypertension and orthostatic intolerance can develop as a late sequela of neck irradiation, due to chronic carotid baroreflex failure, which in turn is due to radiation-induced accelerated development of carotid arteriosclerosis. Splinting of carotid sinus mechanoreceptors in rigidified arterial walls would impede detection of alterations in blood pressure and thereby disrupt baroreflex regulation of cardiovagal and sympathetic outflows.     

Effect of a modified, well-tolerated niacin regimen on serum total cholesterol, high density lipoprotein cholesterol and the cholesterol to high density lipoprotein ratio

One hundred one patients with coronary artery disease and pretreatment ratios of total cholesterol to high density lipoprotein (HDL) cholesterol greater than 4.0 were treated with niacin, commencing at low dosages (100 to 250 mg twice daily) and gradually increasing the dosage over 4 to 8 weeks to 1,000 mg twice daily. Dosage adjustments were made to minimize side effects. At a mean follow-up duration of 11 +/- 7 months, and a mean dosage of 1,415 +/- 698 mg/day, the group had a 13% reduction in total cholesterol, 31% increase in HDL and 32% decrease in the cholesterol to HDL ratio. A subgroup of 62 patients taking greater than 1,000 mg/day of niacin had an 18% reduction in total cholesterol, 32% increase in HDL and 36% improvement in the cholesterol to HDL ratio. A subgroup of 39 patients taking less than or equal to 1,000 mg/day of niacin had only a 5% reduction in total cholesterol, although a 29% increase in HDL and a 24% decrease in the cholesterol to HDL ratio were recorded. Side effects of niacin were reported in 38% of the patients, but led to discontinuation of therapy in only 4. Niacin can be administered in a fashion that is well tolerated, inexpensive and very effective in improving the cholesterol to HDL ratio.     

Classification of multiple morphine and enkephalin binding sites in the central nervous system.

Detailed competitive displacement curves of 3H-labeled [D-Ala2,Met5]enkephalinamide, [D-Ala2,D-Leu5]enkephalin, and dihydromorphine by a series of opiates and enkephalins are biphasic, suggesting multiple sites. After treatment of tissue with naloxazone, the displacement of the three 3H-labeled ligands by all opiates and enkephalins tested becomes monophasic, losing the high-affinity displacement seen with low concentrations of both opiates and enkephalins. Coupled with Scatchard analysis of saturation experiments, these findings suggest a common site that binds both opiates and enkephalins equally well and with highest affinity (Kd values, less than 1 nM). Termed the mu 1 site, it corresponds to the previously described high-affinity site and appears to be the site responsible for analgesia under normal circumstances. The low-affinity binding of [3H]dihydromorphine (Kd, 3 nM) remaining after naloxazone treatment differs dramatically from low-affinity [D-Ala2,D-Leu5]-[3H]enkephalin binding (Kd, 5 nM). The mu 2 site, corresponding to the low-affinity [3H]dihydromorphine receptor sites, binds morphine (Ki, 10 nM) and dihydromorphine (Kd, 3 nM) far better than [D-Ala2,D-Leu5]enkephalin (Ki, 50 nM). Low-affinity [D-Ala2,D-Leu5]-[3H]enkephalin receptor sites bind [D-Ala2,D-Leu5]enkephalin (Ki, 5-8 nM) more potently than morphine (Ki, 71 nM) and correspond to the previously established delta receptor.     

Differential sensitivities of mouse strains to morphine and [Dmt1]DALDA analgesia

[Dmt(1)]DALDA (H-Dmt-D-Arg-Phe-Lys-NH(2)), is a highly potent and selective mu-opioid agonist. Nevertheless, systemic [Dmt(1)]DALDA retained its analgesic actions in MOR-1 knockout animals and CXBK mice despite the inactivity of morphine in these mice. [Dmt(1)]DALDA was 6-fold less potent in C57BL/6J mice than in CD-1 mice, whereas morphine potency did not differ between the two strains. Thus, [Dmt(1)]DALDA is a highly selective mu-opioid analgesic with significant pharmacological differences with the prototypic mu-opioid morphine.     

Anatomical and functional correlation of the endomorphins with mu opioid receptor splice variants

The present study characterizes the relationship between the endogenous mu opioid peptides endomorphin-1 (EM-1) and endomorphin-2 (EM-2) and several splice variants of the cloned mu opioid receptor (MOR-1) encoded by the mu opioid receptor gene (Oprm). Confocal laser microscopy revealed that fibers containing EM-2-like immunoreactivity (-LI) were distributed in close apposition to fibers showing MOR-1-LI (exon 4-LI) and to MOR-1C-LI (exons 7/8/9-LI) in the superficial laminae of the lumbar spinal cord. We also observed colocalization of EM-2-LI and MOR-1-LI in a few fibers of lamina II, and colocalization of EM-2-LI and MOR-1C-LI in laminae I-II, and V-VI. To assess the functional relevance of the MOR-1 variants in endomorphin analgesia, we examined the effects of antisense treatments that targeted individual exons within the Oprm1 gene on EM-1 and EM-2 analgesia in the tail flick test. This antisense mapping study implied mu opioid receptor mechanisms for the endomorphins are distinct from those of morphine or morphine-6beta-glucuronide (M6G).     

The influence of intra-abdominal electrophoresis and enteral sorption on the immune indices in children with peri-appendicular abscess

Comparative characteristic of application of different methods of intratissue electrophoresis and their influence on immune indexes in children with perioappendicular abscess was presented. Application of complex treatment with usage of intraabdominal electrophoresis and enterosorption had guaranteed an effective correction of systemic and local immune disorders, the peritoneal macrophages activation, improvement of cytokines cooperation of cells in the immune answer.     

Effects of serial lesions of telencephalic components of the visual system in pigeons

A serial-lesion technique was used to investigate interactions in visual processing between telencephalic components of the pigeon visual system. Pigeons were trained to discriminate pairs of stimuli that differed in color, intensity or pattern. After mastering the discrimination tasks, they were assigned to one of three groups. The first group (WI-EII) received lesions of the visual Wulst and were retested. After the discrimination tasks were again mastered, a second set of lesions was made, this time in the ectostriatum. The birds were tested once again after the second surgery. The second group (EI-WII), underwent the same sequence of events except that the order of the lesions was reversed. In the third group (E + W), lesions of both the visual Wulst and ectostriatum were made in a single operation, followed by retesting. The performance after the first lesion of the subjects in each of the two-stage lesion groups was typical of performance after such lesions; i.e. the birds with visual-Wulst lesions showed little or no impairment on any of the tasks, whereas the pigeons with ectostriatum lesions showed considerable deficits in intensity and pattern discrimination, which diminished after prolonged retraining. In contrast, the pigeons in the one-stage group (E + W) showed profound deficits that appeared to be permanent. The performance after the second operation of the WI-EII group was the same as that of pigeons with lesions of ectostriatum alone; i.e. destruction of ectostriatum first or second resulted in the same duration of impairment. The performance of the EI-WII group after its visual Wulst lesion, however, was similar to that observed in the E + W group. The results are interpreted as a reflection of parallel processing within the avian visual system; i.e. the presence of an intact tectofugal pathway may mask the effects of thalamofugal pathway interruption.