Decreased activity of locus coeruleus neurons in the rat after DSP-4 treatment

The activity of noradrenergic neurons of the rat locus coeruleus was investigated at 10 and 50 days after the administration of DSP-4 (N-(2-chloroethyl)-N-ethyl-2-bromobenzyl-amine), a selective noradrenergic neurotoxin. The mean neuronal firing rate in control animals was 2.4 Hz. In contrast, DSP-4 animals had lower rates of 1.2 Hz at 10 days and 1.7 Hz at 50 days. Histological examinations revealed no morphological changes of locus coeruleus cell bodies at either the 10- or 50-day time points. These results suggest that DSP-4 can impair neuronal activity of the locus coeruleus without altering the structural appearance of locus coeruleus perikarya.     

Alteration of central alpha 2- and beta-adrenergic receptors in the rat after DSP-4, a selective noradrenergic neurotoxin

A peripheral injection of DSP-4 [N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine] produced a marked, selective, and lasting depletion of norepinephrine in certain regions of the rat central nervous system. This depletion at 10 days after injection was associated with regional alterations in some, but not all, adrenergic binding sites (receptors) as determined by in vitro [3H]prazosin (alpha 1), [3H]p-aminoclonidine (alpha 2), and [3H]dihydroalprenolol (beta) binding. The neocortical alpha 1-receptor was not changed. The alpha 2-receptor in several regions was altered as indicated by an increase in ligand affinity; additionally, the density of this receptor was slightly decreased in some regions. Depending on the region, the beta-receptor either increased in density or was unchanged. The increased density of this receptor in neocortex corresponded to an increased activity of isoproterenol-sensitive adenylate cyclase. These two changes were not affected by subchronic treatment with desipramine, a norepinephrine uptake inhibitor. The changes were, however, partially or completely reversed by subchronic administration of clenbuterol, a centrally-acting beta-receptor agonist. The dopaminergic receptor in various regions was unaltered as assessed by in vivo and/or in vitro binding of [3H]spiperone. The in vivo binding of this ligand also indicated that the serotoninergic receptor in frontal neocortex was unchanged. Assessment of adrenergic receptors in neocortex at 50 days after injection indicated only the above affinity change of the (presumably postsynaptic) alpha 2-receptor. The alpha 1-receptor remained unaltered. The density of the beta-receptor had normalized, as had the activity of isoproterenol-sensitive adenylate cyclase. Implicit in these findings is the following rank order of receptor sensitivity to chronic norepinephrine depletion: alpha 2 greater than beta greater than alpha 1. The use of DSP-4 has clear advantages over other methods of depleting central norepinephrine. This neurotoxin can be administered by intraperitoneal injection, the depletion of norepinephrine can be readily checked by absence of the post-decapitation reflex, and the changes in other neurotransmitter concentrations are relatively minor or nonexistent. The alteration of alpha 2- and beta-receptors, as a consequence of DSP-4 treatment, may form the basis of a new animal model of adrenergic receptor supersensitivity. Such a model may clarify the importance of these central receptors to physiological and behavioral processes.     

Long-lasting effects of the noradrenergic neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) on prevertebral sympathetic neurones in the rat

Following intraperitoneal administration of the neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) in rats, the irides and pieces of jejunum were treated by the glyoxylic acid method in order to reveal their adrenergic nerves. Seven days after the injection, the fluorescence of adrenergic nerves in the iris was partly restored and by 35 days was indistinguishable in density and brightness from controls. In contrast, even 118 days post-injection, the adrenergic component of Auerbach's plexus of the jejunum was still markedly affected by the DSP-4. The regeneration was incomplete, giving a patchy appearance, and less fluorescent than the controls. It is suggested that, when injected intraperitoneally, DSP-4 can have more potent effects than hitherto realised.     

The effect of sleep deprivation and recovery sleep on plasma corticosterone in the rat

The effect of 24-h sleep deprivation by forced locomotion on plasma corticosterone was investigated in the rat. Corticosterone was slightly elevated after 21.5 h sleep deprivation, but did not differ from controls after a 2.5-h recovery period. An acute 20-min forced locomotion period caused a marked rise in plasma corticosterone. It is concluded that stress is not a major factor contributing to the massive effects of sleep deprivation on sleep parameters.     

雷公藤甲素对DSP4致大鼠蓝斑NE能神经元丢失及海马NE能神经纤维溃变的影响

为了观察雷公藤甲素(T10)对DSP4致成年SD大鼠蓝斑去甲肾上腺素能(NE)神经元丢失及海马NE能神经纤维溃变的保护作用,将24只大鼠随机分为实验组(DSP4组)、治疗组(DSP4+T10组)、对照组(NS组)。DSP4组、DSP4+T10组动物在第1d、30d腹腔内注射DSP4(25μg/kg),NS组动物同时间腹腔内注射等容量生理盐水。DSP4+T10组动物第1d开始用T10[10μg/(kg.d)]灌胃持续45d,DSP4组、NS组动物用等容量生理盐水灌胃。45d后取材,用酪氨酸羟化酶(TH)多克隆抗体免疫组织化学染色显示蓝斑NE能神经元和海马NE能神经纤维,双盲法计数蓝斑去甲肾上腺素能神经元细胞数,HPIAS高清晰度彩色病理图像测量系统测定海马CA3区神经纤维阳性表达产物的平均灰度值。结果显示:NS组海马NE纤维长而连续;DSP4组海马NE纤维少,断裂现象多见,DSP4+T10组纤维的连续性较DSP4组好;DSP4组蓝斑NE阳性细胞数(505个±24个)明显低于NS组(1069个±49个)和DSP4+T10组(996个±63个)(P<0.05)。DSP4组海马NE阳性神经纤维平均灰度值为(141.89±2.17),明显高于NS组(134.32±2.29)和DSP4+T10组(136.59±3.25)(P<0.05)。以上实验结果提示:DSP4对大鼠蓝斑NE能神经元及海马NE能神经纤维有损伤,雷公藤甲素对其有保护作用。     

On the interactive role of central noradrenaline neurons and corticosterone in two-way active avoidance acquisition in the rat

The noradrenaline (NA) neurotoxin, DSP4, caused a marked impairment of two-way active avoidance acquisition. Pretreatment with desipramine, which inhibits the degeneration of NA neurons by DSP4, consistently blocked the avoidance deficit. Daily treatment with corticosterone (2 × 1 mg/kg, s.c.) also blocked the impaired acquisition of avoidance induced by DSP4 but failed to affect the increase in cortical β-noradrenergic receptors induced by DSP4. The present findings give further evidence for the important role interactions between the pituitary-adrenal axis and the locus coeruleus NA system play in aversive learning.     

Thymic stress in artificially reared and maternally reared rat pups

It is well documented that the hypothalamic-pituitary-adrenal (HPA) axis influences immunological responses to stress. Maternal factors have been shown to be necessary for appropriate modulation of the HPA axis in the developing rat. The purpose of this study was to determine whether artificially reared (AR) infant rat pups (a procedure whereby infant rats are gastrostomized and reared independently of maternal factors) have an altered function of the HPA axis in terms of thymocyte apoptosis (programmed cell death) and other indices of thymic stress. AR and maternally reared (MR) Long–Evans rat pups were randomized to control, fasted, stressed, and fasted+stressed treatment groups, as well as an unhandled, MR naive group that served as a baseline control. AR rat pups were significantly heavier than MR (p<0.001). AR rat pups had significantly lighter thymuses than did the MR pups (p<0.001) and fasted pups had significantly lighter thymuses than unfasted pups, regardless of whether they were in the AR or MR condition (p<0.005). AR pups had significantly lower thymic cell numbers and a greater percent of necrotic cells than did MR pups. There were no significant effects of rearing condition on the percent of apoptotic thymocytes. The thymocyte alterations observed in this study between the two rearing conditions suggest that AR reduces thymic weight and cell numbers, which may have consequences for the development of adult cellular immunity.     

水通道蛋白-4在大鼠甲状腺中的表达

目的:观察水通道蛋白-4(AQP4)在甲状腺滤泡细胞的表达和分布特点,为研究甲状腺内分泌及调节机制提供形态学基础。方法:利用免疫组织化学、免疫荧光组织化学和原位杂交组织化学技术,检测大鼠AQP4及其mRNA在甲状腺滤泡上皮细胞的表达。结果:免疫组织化学和免疫荧光组织化学显示,AQP4在甲状腺滤泡上皮细胞膜上有表达,而在上皮细胞基底面和管腔面表达更为明显;原位杂交组织化学显示AQP4 mRNA在上皮细胞中表达明显。结论:AQP4在甲状腺的表达和分布特点,提示其参与了甲状腺素的合成和分泌过程中渗透压的精细调节作用。     

Effect of encephalectomy on corticosterone content in the fetal rat adrenals

The functional state of the pituitary-adrenal system was studied after removal of the hypothalamus from rat fetuses (encephalectomy in utero). Hormonal activity of the adrenal glands was estimated by fluorometric determination of their corticosterone content. Removal of the hypothalamus in fetuses aged 18.5–19.5 days lowered the adrenal corticosterone level. Injection of a homogenate of the hypothalamus into the fetuses immediately after encephalectomy prevented this decrease. The results confirm the presence of a functional link between the hypothalamus and the pituitary-adrenal system in rat fetuses.Laboratory of Hormonal Regulation, Institute of Developmental Biology, Academy of Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR N. A. Kraevskii.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 81, No. 5, pp. 597–598, May, 1976.     

Adrenocortical response to stress in fasted and unfasted artificially reared 12-day-old rat pups

Recent studies have compared artificially reared (AR) rats with dam-reared rats on behavioral outcomes but, despite the fact that they are deprived of their mothers during the stress hyporesponsive period (SHRP), little is known about the effects of AR on the development of the stress response. In this study, the corticosterone (CORT) response to a stressor (saline injection ip) on postnatal Day 12 was assessed in rat pups that had been either dam-reared (DR) or artificially reared since Day 5. In the preceding 24 hr, half the pups in the DR group were maternally deprived (DEP). To control for the food deprivation consequent to maternal deprivation in these groups, half the pups in the AR groups also underwent 24-hr food deprivation (DEP). In the nondeprived condition AR pups did not differ from DR pups on untreated CORT levels or on levels at 1-hr poststress (i.e., all rats demonstrated low levels of CORT characteristic of the SHRP). In contrast, both maternally deprived DR pups and food-deprived AR pups exhibited increased untreated CORT levels as well as a significant increase at 30-min poststress, but CORT elevations were lower in the AR groups than in the DR groups. Thus, long-term maternal deprivation through artificial rearing in rats does not affect the reduced CORT levels and reduced CORT responsiveness associated with the SHRP; however, if animals are food deprived, then all show increased basal CORT levels and a greater CORT response to stress, although this response is lower in AR groups than in DR groups. These results suggest that rat pups artificially reared with adequate nutrition will still exhibit the SHRP.     

Shock predictability and gastric secretion in the chronic gastric fistula rat

In Experiment 1 rats exposed to unpredictable grid shock demonstrated a significant decrease in gastric secretion and total acid output as compared to rats exposed to predictable shock and rats exposed only to the tone stimulus. In Experiment 2 rats were immobilized in restraint cages. Restraint plus predictable shock and restraint plus unpredictable shock resulted in a significant decrease in stomach acid output as compared to restrained no-shock controls. These results do not support a gastric hypersecretion hypothesis for studies which have reported the development of stomach ulcers by using unpredictable shock stress.     

Sexual motivation in the female rat after testosterone treatment

The effect of testosterone propionate (TP) on sexual motivation in the ovariectomized female rat was studied. The urge to seek sexual contact was measured in terms of location in the male vicinity in an open field, the amount of aversive stimulus (crossing of an electric grid) the animal was willing to take to seek contact with a sexually active male and the preference in a run and choice situation for a sexually active male versus a female. It was a consistent finding in the three different methods used that TP 1 mg/kg induced a significant increase in the willingness of ovariectomized rats to seek contact with a sexually active male. A sexually active male was more incentive than a castrated male or a female. The effect of TP was dose-dependent and the maximal response occurred after 2–4 days.     

水通道蛋白4在大鼠脑垂体中的表达

目的：研究水通道蛋白4(AQP4)及其mRNA在脑垂体中的表达,探讨其在脑垂体激素分泌过程中的作用。方法：应用免疫组织化学和原位杂交技术,观察成年Wistar大鼠脑垂体中AQP4及其mRNA的正常分布。结果：AQP4及其mRNA在成年大鼠神经垂体的垂体细胞上表达呈阳性,分布在毛细血管窦周围的垂体细胞表达尤为强烈。腺垂体的所有细胞均有AQP4的表达,胞质中AQP4 mRNA表达呈阳性。中间叶所有细胞AQP4及其mRNA的表达呈弱阳性,其中滤泡星形细胞表达较内分泌细胞强烈。结论：AQP4广泛分布于脑垂体的各种组织细胞表面,可能在垂体激素的正常分泌过程中起重要的调节作用。     

Shock-stress,gastric secretion and habituation in the chronic gastric fistula rat

Unrestrained rats exposed to shock-stress showed an abrupt reduction in both the volume and acidity of gastric secretions, followed by a rapid poststress recovery. The gastric response pattern did not distinguish between rats receiving avoidable or unavoidable shock. Marked habituation of the acid inhibition response occurred within 4 stress sessions.     

Effects of Dehydroepiandrosterone Sulfate on the Conversion of Corticosterone into 11-Dehydrocorticosterone in Stress: A Regulatory Scheme

In male rats, repeated but not single exposures to stress increased the conversion of corticosterone (CS) to 11-dehydrocorticosterone (11-DHCS), particularly on the background of administration of dehydroepiandrosterone sulfate (DHEAS). Naltrexone given 20 min before DHEAS at a dose of 0.1 mg/kg, at which it selectively blocks μ opioid receptors, prevented this effect of DHEAS, which is evidence that it is mediated by μ opioid receptors. This action of DHEAS involved endogenous ACTH and was thus mediated by central regulatory mechanisms. Our results, along with published data, lead to the first proposed scheme for the physiological regulation of the interconversion of CS and 11-DHCS in conditions of repeated stress with the involvement of DHEAS and μ opioid receptors. Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 94, No. 8, pp. 945–951, August, 2008.     

Ontogeny of urine preference and its relationship to NH4Cl preference and sodium hunger in suckling rat pups

We chart the postnatal ontogeny of urine preference in the suckling rat. Twelve-day-old sucklings, when offered urine, NH4Cl, or NaCl, ingest more urine and NH4Cl than NaCl. When rendered sodium hungry by ivc renin or by sodium depletion, these sucklings prefer urine and NH4Cl to NaCl, dilute urine, or an NaCl and KCl mineral mix equimolar to urine; however, by 18 days of age, urine and NH4Cl are no longer preferred to NaCl. Hence, urine preference in the suckling may be specific and preparatory for the variety of purposes urine preference serves in the adult rat, and it might guide the pup to urinary sodium in the nest. Since preference for urine and NH4Cl covary during postnatal development, the high preference for NH4Cl in midterm sucklings might be because its ammonium flavor is similar to urine.     

Effect of microelectrophoretically applied corticosterone on raphe neurones in the rat

The effect of microelectrophoretic application of corticosterone (CS) on single neurones of raphe nuclei (RN) were investigated in rats under urethane anaesthesia. Ejecting currents generally ranged from 5 to 40 nA. CS produced an excitatory effect in 61% and no effect in 39% of the neurones. None of the 54 neurones studied was inhibited by CS. These quite homogeneous data support the hypothesis that RN are involved in the regulation of most of the nervous functions in which glucocorticoid hormones have been implicated.     

Cyclic AMP and adenyl cyclase in the developing rat brain

The level of endogenous cyclic AMP in the rat brain in vivo began to increase markedly between the third and sixth days after birth, as did the ability of norepinephrine to stimulate the formation of cyclic AMP in brain tissue in vitro. Adenyl cyclase activity in broken cell preparations, when measure in the absence of sodium fluoride, increased with age up to a point, but began to decline between the fifth and ninth days postpartum. Activity continued to increase when measured in the presence of fluoride, suggesting that the apparent stimulatory effect of this ion may in fact be the reversal of an inhibitory influence which is absent or almost absent at birth. Cyclase activity at all ages was restricted to particulate matter, whereas apparent phosphodiesterase activity was present in particulate as well as soluble fractions. The catabolic system for cyclic AMP developed in a similar manner in both fractions. Theophylline produced the same degree of inhibition of this system at all ages.     

Enhancement of lipid peroxidation in the rat hypothalamus after short-term emotional stress

P. K. Anokhin Institute of Normal Physiology, Academy of Medical Sciences, Moscow. Department of Biophysics, N. I. Pirogov Second Moscow State Medical Institute. (Presented by Academician of the Academy of Medical Sciences K. V. Sudakov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 113, No. 5, pp. 486–488, May, 1992.     

Pavlovian conditioning of corticotropin-releasing factor-induced increase of blood pressure and corticosterone secretion in the rat

Corticotropin-releasing factor (CRF) is clearly involved in the central regulation of the pituitary-adrenal axis and, moreover, of autonomic nervous system functions. Enhanced sympathetic activity with subsequent increases in blood pressure and heart rate and attenuation of the baroreceptor reflex results from the intracerebroventricular (i.c.v.) administration of CRF. Additionally, the peptide has a variety of potent effects on behavioural responses in animals similar to those observed after an experimentally evoked stress. It was therefore of obvious interest to examine whether CRF is a possible mediator of the learning processes associated with physiological stress reaction patterns. This report clearly demonstrates a classical conditioning of the endocrine (i.e. corticosterone secretion) and haemodynamic (i.e. blood pressure) sequelae following central CRF application and thus indicates that this mechanism is of physiological significance for learned stress responses.