Subtypes of guanine-nucleotide-binding regulatory proteins at the locus coeruleus involved in fentanyl-induced muscular rigidity in the rat

Previous results from our laboratory have established that the G_o subtype of guanine nucleotide (GTP)-binding regulatory proteins at the locus coeruleus (LC) may participate in the elicitation of muscular rigidity by fentanyl. The present study further examined the involvement of other subtypes of GTP-binding regulatory proteins at the LC in this process, using Sprague-Dawley rats anesthetized with ketamine (120 mg/kg, i.p., with 30 mg/kg/h i.v. infusion supplements) and under mechanical ventilation. Intravenous administration of fentanyl (100 µg/kg) induced a significant increase in electromyographic signals recorded from the sacrococcygeus dorsi lateralis muscle. Power spectral analysis revealed that this was accomplished by a decrease in the mean power frequency and an increase in the root mean square values of the signals. The above responses were appreciably antagonized by pretreating animals with bilateral microinjection into the LC of pertussis toxin (80 or 160 fmol), N-ethylmaleimide (16 pmol) or 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (100 or 200 fmol); but not by cholera toxin (120 or 240 fmol), forskolin (240 or 480 pmol) or N-ethylmaleimide at a higher dose (32 pmol). These results suggest that, in addition to G_o protein, fentanyl-induced muscular rigidity may also involve other pertussis toxin-sensitive GTP-binding regulatory proteins, possibly G_i and G_p subtypes, in the signal transduction processes following activation of -opioid receptors at the LC.     

Locus-control-region-coupled betaS Antilles- and alpha2-hemoglobin genes select for high alpha2-hemoglobin expression in adult transgenic mice

Two transgenic lines of mice were produced which contained the ^S _Antilles- and ₂-hemoglobin genes trandemly coupled to the micro locus control region (LCR). The LCR^S _Antilles2-hemoglobin transgenic mice expressed high levels of ₂-hemoglobin while ^S _Antilles-hemoglobin expression was virtually undetectable. Abundant ₂-hemoglobin protein was observed in the blood of transgenic mice, while ^S _Antilles-hemoglobin chains could not be detected. Transgenic red blood cells had substantially decreased sensitivity to osmotic lysis. Attempts to produce homozygotes containing the transgene were unsuccessful. The phenotype of these mice closely resembles that of -thalassemic mice. The LCR^S _Antilles2 transgenic mice demonstrate that if the LCR is coupled to the ^S _Antilles- and ₂-hemoglobin genes in tandem, only the distal ₂-hemoglobin gene is selected for expression to significant levels in adult mice. These results support a reciprocally competitive model for LCR-hemoglobin developmental switching.     

Majority of random cDNA clones correspond to single loci in the tomato genome

Summary The number of loci corresponding to each of 34 unique, random cDNA clones has been determined for the diploid plant species Lycopersicon esculentum (tomato) (2n=24). Fifty-three percent of the clones are homologous to loci represented only once in the tomato chromosomes. Thirty-two percent of the clones correspond to two genetically independent loci. The remaining clones belong to gene families represented by 3–5 loci. To determine the number of gene copies per locus, reconstruction experiments were performed on six of the single locus clones. The majority of these loci were estimated to contain only 1 or 2 copies of the gene. These results support the concept that the majority of structural genes in this diploid plant species are arranged in single loci and present in low copy number. Multigene families, such as those for the small subunit of ribulose bisphosphate carboxylase, chlorophyll a/b binding polypeptide and actin are exceptions to this rule.     

A light- and electron-microscopic study of mesencephalic neurons projecting to the ganglion of the nervus terminalis in the goldfish

Summary After application of various neuronal tracers (horseradish peroxidase, cobalt-chloride lysine, true blue) to the ganglion of the nervus terminalis a small number of neurons was retrogradely labeled in the mesencephalon. As revealed by combined horseradish peroxidase and catecholamine-fluorescence techniques these neurons are located in the isthmic area immediately rostral to, but not within the locus coeruleus. Cobalt-labeled axons of the mesencephalic neurons were traced individually in serial sections. Neurons projecting contralaterally cross in the horizontal commissure. Tracing of single fibers provided no evidence for axon collaterals within this pathway. Retrograde labeling reveals two different types of isthmic neurons afferent to the ganglion of the nervus terminalis: One smaller-sized type is located bilaterally and consists of four to six neurons; another type possessing many dendritic processes was consistently found as only one single cell located contralateral to the side of injection. The existence of two types of neurons was confirmed by their cytological differences: The small-sized type receives only sparse perisomatic input, while the large-sized type shows heavy somatic and dendritic, probably monoaminergic innervation.     

Chronic Cocaine Treatment Decreases Levels of the G Protein Subunits Giα and Goα in Discrete Regions of Rat Brain

A possible role for G proteins in contributing to the chronic actions of cocaine was investigated in three rat brain regions known to exhibit electrophysiological responses to chronic cocaine: the ventral tegmental area, nucleus accumbens, and locus coeruleus. It was found that chronic, but not acute, treatment of rats with cocaine produced a small (approximately 15%), but statistically significant, decrease in levels of pertussis toxin-mediated ADP-ribosylation of Gi alpha and Go alpha in each of these three brain regions. The decreased ADP-ribosylation levels of the G protein subunits were shown to be associated with 20-30% decreases in levels of their immunoreactivity. In contrast, chronic cocaine had no effect on levels of G protein ADP-ribosylation or immunoreactivity in other brain regions studied for comparison. Chronic cocaine also had no effect on levels of Gs alpha or G beta immunoreactivity in the ventral tegmental area and nucleus accumbens. Specific decreases in Gi alpha and Go alpha levels observed in response to chronic cocaine in the ventral tegmental area, nucleus accumbens, and locus coeruleus are consistent with the known electrophysiological actions of chronic cocaine on these neurons, raising the possibility that regulation of G proteins represents part of the biochemical changes that underlie chronic cocaine action in these brain regions.     

Ontogeny of Tyrosine Hydroxylase Concentration in Locus Coeruleus of Newborn Rats: Long-Term Effects of RU24722

The ontogenetic variations of tyrosine hydroxylase (TH) have been studied in locus coeruleus of developing rats. During the first 2 weeks after birth, a large increase in TH content (6.04-23.99 TH units) in the noradrenergic structure was observed, followed by a period of progressive increase of the protein concentration (42 TH units in adult rats). The expression of TH was studied in the same ontogenetic period after treatment by RU24722 (20 mg/kg, i.p.). The long-term increase in TH concentration produced by the drug was found to follow ontogenetic variations. It becomes significant around the middle of the second week after birth and gradually increases until the 24th day of postnatal development, indicating a maturation of the mechanisms involved in the inducing effect.     

Normal pharmacological and morphometric parameters in the noradrenergic hyperinnervated mutant mouse, “tottering”

Summary Pharmacological and anatomical analyses of central monoaminergic and cholinergic neurons were performed in the tottering mouse, an autosomal recessive neurologic gene mutation that results in an overproduction of axons of the locus coeruleus and an increase in norepinephrine content in specific terminal fields. Except for the previously reported increase in norepinephrine content, all pharmacological parameters measured, including tyrosine hydroxylase activity, norepinephrine turnover, serotonin content, and choline acetyltransferase activity, in targets hyperinnervated by the locus coeruleus were normal. Immunocytochemical staining for tyrosine hydroxylase demonstrated the pronounced hyperinnervation in the tottering brain, whereas both serotonin and choline acetyltransferase immunostaining were similar between tottering and wild type. The volume of 3 target areas that are hyperinnervated by the locus coeruleus in the tottering mouse, the hippocampus, cerebellum, and cochlear nuclei, were normal. In addition, neuronal number and somal size in the locus coeruleus were found to be unchanged in the mutant genotype. These data demonstrate several features of the effects of the tottering gene: 1) compensatory changes in several adrenergic pharmacological parameters do not occur in response to the hyperinnervation of targets by locus coeruleus axons; 2) neither direct effects of the tottering gene on, nor compensatory changes in, the extent of cholinergic or serotonergic innervation of several targets of the locus coeruleus appear to occur; and 3) the lack of changes in size of the targets of the locus coeruleus suggest that the hyperinnervation in the tottering mouse is due to a direct genetic alteration of axonal growth by the locus coeruleus neurons, rather than to selective shrinkage of targets in the presence of normal terminal arbors.     

蓝斑核Orexin-A对肥胖抵抗大鼠自发活动的影响及机制研究

目的:探讨蓝斑核(LC)orexin-A对肥胖抵抗(OR)大鼠自发活动的影响及机制并进一步探究LC的orexin调控是否与肥胖抵抗相关。方法:雄性SD大鼠和选择性培育的OR大鼠,一侧蓝斑核置管,缓慢均匀注射0.5μL药物(orexin-A或人工合成脑脊液),用大鼠自发活动检测装置SPA箱红外线活动传感器测定测大鼠自发活动(SPA),间接测热法测定其能量消耗,定量磁共振身体组成分析器检测大鼠脂体重和瘦体重。大鼠肥胖程度用体脂百分比表示。结果:与SD大鼠相比,OR大鼠的总体重,脂体重和去脂体重显著降低(P0.05)。OR大鼠肥胖程度明显小于SD大鼠(P0.05)。OR大鼠在3月龄是主要表现为水平活动,6月龄时垂直活动增加,故OR大鼠随年龄增长活动量显著增多(P0.05)。OR大鼠注射orexin A增加SPA的作用比SD大鼠更强,其主要原因是OR大鼠水平活动时间明显高于垂直活动时间。与SD大鼠相比,OR大鼠SPA水平高、体重轻,日间能量消耗和SD大鼠无明显差异,夜间活动消耗更多能量。在OR大鼠的LC注射orexin-A后,两组高剂量orexin-A可显著增加SPA(P0.05),并呈现剂量依赖性。对于SD大鼠,只有最高剂量的OXA才能引起SPA显著高于对照组(P0.05)。最高剂量的两组orexin-A注射后,OR大鼠SPA改变比SD大鼠更显著(250 pmol:P0.05;500 pmol:P0.05)。结论:蓝斑核(LC)orexin-A对肥胖大鼠自发活动有重要影响,其orexin调控与肥胖抵抗相关。     

Role of Neuronal Signal Input in the Down-Regulation of Central Noradrenergic Receptor Function by Antidepressant Drugs

Rats with unilateral lesions of the locus coeruleus were used to study the role of norepinephrine (NE) signal input in the down-regulation by antidepressants of the noradrenergic cyclic AMP-generating system in the cortex. Chronic administration of both desipramine (blockade of NE reuptake) and iprindole (no blockade of NE reuptake) reduced the cyclic AMP response to NE on the nonlesioned side, but had little or no effect on the lesioned side. The results indicate that NE signal input and thus the formation of the NE-receptor complex are prerequisites for inducing noradrenergic subsensitivity.     

Impact of acute and chronic stressor experiences on heart atrial and brain natriuretic peptides in response to a subsequent stressor

The impact of stressful events on processes related to cardiovascular functioning might vary with previous stressor experiences, just as such sensitization effects have been detected with respect to several neurochemical and hormonal processes. The present investigation assessed the impact of a psychosocial stressor on factors directly or indirectly related to cardiovascular functioning among CD-1 mice that had previously experienced an acute or chronic stressor regimen. These factors included plasma variations of atrial and brain natriuretic peptides (ANP and BNP, respectively), inflammatory cytokines in plasma, mRNA expression of natriuretic peptides and inflammatory cytokines in the ventricles, and norepinephrine (NA) levels and utilization within the locus coeruleus, a brain region implicated in cardiac functioning. A social stressor (exposure to a dominant mouse) increased NE levels and utilization within the locus coeruleus, plasma corticosterone, cytokine and ANP levels. Among mice initially exposed to an acute stressor (restraint), NE utilization, ventricular ANP mRNA expression, and plasma interleukin-6 (IL-6) concentrations were markedly increased by the subsequent social stressor. In chronically stressed mice some of the effects of the social stressor were dampened, including changes of plasma corticosterone, locus coeruleus NE utilization, as well as plasma and ventricular IL-6 mRNA expression. Conversely, plasma ANP was markedly enhanced by the combined stressor events as was ventricular BNP and IL-1β mRNA expression. It seems that stressors may profoundly influence (sensitize or desensitize) on factors that could influence cardiovascular functioning. It remains to be determined whether these actions would be translated as pathophysiological outcomes.