杏仁内侧核注射AVP和AVPMcAb对家兔ET性发热效应的影响

目的和方法：在大脑杏仁内侧核微量注射精氨酸加压素（ＡＶＰ）和精氨酸加压素单克隆抗体（ＡＶＰＭｃＡｂ）,观察其对家兔内毒素（ＥＴ）性发热效应以及视前区一下丘脑前部（ＰＯＡＨ）温敏神经元放电活动的影响。结果：①杏仁内侧核微量注射ＡＶＰ能明显抑制家兔ＥＴ性发热效应,注射ＡＶＰＭｃＡｂ能明显易化家兔ＥＴ性发热效应;②杏仁外侧核分别注射ＡＶＰ和ＡＶＰＭｃＡｂ则对家兔ＥＴ性发热效应无明显影响;③杏仁内侧核分别注射ＡＶＰ和ＡＶＰＭｃＡｂ后ＰＯＡＨ热敏神经元和冷敏神经元放电活动均无明显变化。结论：家兔杏仁内侧核也是ＡＶＰ抗热效应的一个重要的作用部位,杏仁内侧核注射ＡＶＰ的抗热作用途径与隔区注射ＡＶＰ的抗热途径可能不同     

Plasma growth hormone responses to microinfusion of noradrenergic agents into or electrical stimulation of the hypothalamus and amygdala in baboons

In nine baboons (Papio papio) guide cannulae and electrodes were stereotaxically implanted into the medial basal or lateral hypothalamus, the anterior hypothalamus or the dorsal amygdala. Plasma GH responses were measured after microinfusion (1 microliter) of the alpha2 adrenergic agonist, clonidine, or the beta adrenergic antagonist, propranolol, or electrical stimulation, in each of these sites. Clonidine, 100 nmol/microliter, infused into the medial basal or lateral hypothalamus elevated plasma GH levels by 5-30 ng/ml, 30-45 min post-infusion. Plasma GH responses to clonidine infused into the anterior hypothalamus or the dorsal amygdala were all less than 10 ng/ml. The prior, intravenous, administration of piperoxane, 1.0 mg/kg prevented GH responses to clonidine. Propranolol, 50 nmol/microliter, infused into the dorsal amygdala consistently increased plasma GH levels by 5-15 ng/ml. Electrical stimulation of the medial basal or lateral hypothalamus elevated plasma GH levels by 7-35 ng/ml, 15-45 min post stimulation. Electrical stimulation of anterior hypothalamus or dorsal amygdala did not alter plasma GH levels. The stimulation of alpha 2 adrenergic receptors in the medial basal or lateral hypothalamus of the baboons appears to facilitate GH release.     

Acute dopamine/norepinephrine reuptake inhibition increases brain and core temperature in rats.

The purpose of the present study was to examine the effects of an acute dose of the dual dopamine (DA) and norepinephrine (NE) reuptake inhibitor bupropion (Bup) on brain (T(brain)), body core (T(core)), and tail skin (T(tail)) temperature in freely moving rats and to simultaneously monitor the extracellular neurotransmitter concentrations in the preoptic area and anterior hypothalamus (PO/AH). A microdialysis probe was inserted in the PO/AH, and samples for NE, DA, and serotonin (5-HT) were collected every 20 min before and after the injection of 17 mg/kg of Bup, for a total sampling time of 180 min. T(core) was monitored using a biotelemetry system. T(brain) and T(tail), an index of heat loss response, were also measured. Both NE and DA levels in the PO/AH significantly increased after Bup injection compared with the baseline levels, reaching approximately 450 and 230%, respectively, 40 min after injection. There was no effect on 5-HT release. The neurotransmitter changes were accompanied by a significant decrease in T(tail) and an increase in both T(brain) and T(core) compared with the baseline levels. The present results demonstrate that inhibition of NE and DA reuptake suppresses heat loss mechanisms and elevates T(brain) and T(core) in freely moving rats.     

Thyrotropin-releasing hormone action in the preoptic/anterior hypothalamus decreases thermoregulatory set point in ground squirrels.

Earlier work has shown that thyrotropin releasing hormone (TRH) produces dose-dependent decreases in body temperature (Tb) and metabolic rate when microinjected into the dorsal hippocampus (HPC) or preoptic/anterior hypothalamus (PO/AH) of awake ground squirrels. This study employed a behavioral paradigm to investigate the possibility that TRH-induced hypothermia is associated with a decrease in thermoregulatory set point. Six animals were successfully trained to press a bar for radiant heat escape and cool air reinforcement in order to obtain a cooler ambient temperature (Ta). During experimental testing, the animals were microinjected remotely with TRH (10-1000 ng/microliters) or a control solution (sterile saline or TRH-OH) into the PO/AH. The micro-injections were delivered via bilateral injection cannulae inserted through chronic bilateral cannula guides that had been stereotaxically implanted under pentobarbital anesthesia. Cumulative and time-integrated bar presses were obtained on a computer generated display. Tb, measured in the brain via a bead-type thermistor, and chamber Ta were recorded continuously. Following TRH administration, a significant increase in mean bar-press rate was observed during the period in which Tb was falling, when compared to a comparable time period just prior to the microinjection. These findings complement results obtained from four animals that were trained to press a bar for heat reinforcement in a cold (- 10 degrees C) environment. In this alternative behavioral paradigm, microinjection of TRH into the PO/AH or HPC induced a decrease in mean bar-press rate as Tb was falling. The results support the hypothesis that TRH-induced hypothermia in golden-mantled ground squirrels is achieved by lowering thermoregulatory set point.     

Effects of α2- and β-adrenoceptor agonists on growth hormone secretion following lesion of the noradrenergic system of the rat

The aim of the present investigation was to lesion the noradrenergic system and to measure the effect on growth hormone (GH) secretion following peripheral administration of ₂- and -adrenoceptor agonists. Direct injection of these agonists into the paraventricular nucleus of the hypothalamus (PVN) and its effect on GH secretion were also investigated. Systemic administration of N-2-chloroethyl-N-ethyl-2-bromobenzylamine (DSP₄, 60 mg/kg, injected i.p. 10 days prior to experimentation) significantly decreased the noradrenaline (NA) content of the hippocampus, frontal cortex and hypothalamus but had no effect on the dopamine (DA) or serotonin (5-HT) content of these areas. Bilateral injection of 6-hydroxydopamine (6-OHDA, 10 g/l, 14 days prior to experimentation) into the medial forebrain bundle (MFB) caused a greater reduction of NA and also decreased the DA and 5-HT content of the hypothalamus. Analysis of the PVN of the hypothalami of rats following 6-OHDA lesion of the MFB showed significantly decreased NA and 5-HT content. Neither DSP₄ treatment nor 6-OHDA lesion of the MFB affected the clonidine (250 g/kg, i.p.) induced stimulation of GH secretion. Injection of isoproterenol (1 mg/kg, i.p.) had varying effects on GH secretion. It stimulated GH release in control rats but not in DSP₄ or MFB lesioned rats. Direct injection of clonidine (0.1 g/l) into the PVN significantly stimulated GH secretion, whereas injection of isoproterenol (2.5 g/l) into the PVN did not affect GH levels when compared to controls. The results of the present study do not support the hypothesis that hypoactivity of the central noradrenergic system may be the cause of the blunted GH response to clonidine observed in depressed patients.     

Growth hormone responses to clonidine and GRF in spontaneously hypertensive rats: neuroendocrine evidence for an enhanced responsiveness of brain alpha 2-adrenoceptors in genetical hypertension

Clonidine induces growth hormone (GH) release in rat. According to previous investigations this effect is mediated by postsynaptic alpha 2-adrenoceptors in the hypothalamus exerting a stimulatory influence on the recently discovered GH releasing factor (GRF). In the present study it is demonstrated that spontaneously hypertensive rats (SHR) of the Wistar-Kyoto strain display enhanced GH responses to clonidine as compared to normotensive Wistar-Kyoto control rats. In contrast, the GH responses to GRF are similar in hypertensive and normotensive animals. These findings indicate that brain alpha 2-adrenoceptors are more responsive in SHR than in normotensive controls. Since the enhanced GH responses to clonidine were observed also in young, prehypertensive SHR they are probably not secondary to the elevated blood pressure. The possible importance of an altered alpha 2-adrenergic neurotransmission for the development of elevated blood pressure in SHR is discussed.     

延髓弧束核微量注射可乐宁对自发性高血压大鼠...

In order to study whether atrial natriuretic factor (ANF) is involved in the depressor effect of clonidine, microinjection of the latter into nucleus tractus solitarii (NTS) was carried out in anesthetized stroke-prone spontaneously hypertensive rats (SHRsp) and normotensive Wistar-Kyoto (WKY) rats. Each strain was randomly divided into three groups by injecting: (1) clonidine (1.0 microgram/0.2 microliter); (2) yohimbine (3.3 micrograms/0.2 microliter) followed by (1); (3) artificial cerebral spinal fluid (ACSF, 0.2 microliter) as control. A decrease of blood pressure and heart rate and a suppression of ANF release elicited by clonidine were significantly greater in SHRsp than in WKY rats. After blockade of alpha 2-receptor with yohimbine, the hypotensive effect of clonidine was blocked completely in WKY rats, but only partially in SHRsp, while the suppression effect on ANF release was eliminated in both strains. In addition, the decrease of plasma catecholamine produced by clonidine could also be blocked after yohimbine. The results suggest that ANF probably does not contribute to the depressor effect of centrally administered clonidine, while in SHRsp the decrease of plasma ANF might be a blood pressure-dependent compensatory response.     

Effects of ghrelin on growth hormone secretion in vivo in ruminants

Ghrelin, a novel endogenous growth hormone (GH) secretagogue, has been shown to exert very potent and specific GH-releasing activity in rats and humans. However, little is known about its GH-releasing activity and endocrine effects in domestic animals. To clarify the effect of ghrelin on GH secretion in vivo in ruminants, plasma GH responses to intra-arterial and intra-hypothalamic injections of rat ghrelin (rGhrelin) were examined in goats and cattle. The intra-arterial injection of 1 microg/kg BW of rGhrelin in ovariectomized goats failed to stimulate GH release, however, a dosage of 3 microg/kg BW significantly increased plasma GH concentrations (P<0.05). GH levels peaked at 15 min after the injection, then decreased to basal concentrations within 1 h after the injection. However, the secretory response to 3 microg/kg BW of rGhrelin was weaker than that of growth hormone-releasing hormone (GHRH) (0.25 microg/kg BW) (P<0.05). An infusion of 10 nmol of ghrelin into the medial basal hypothalamus (arcuate nucleus) significantly stimulated the release of GH in male calves (P<0.05). GH levels began to rise just after the infusions and peaked at 10 min, then decreased to the basal concentrations within 1 h after the injection. The present results show that ghrelin stimulates GH release in ruminants.     

Changes of body temperature and extracellular serotonin level in the preoptic area and anterior hypothalamus after thermal or serotonergic pharmacological stimulation of freely moving rats

Although many studies has been shown that serotonin (5-HT) in the preoptic area and anterior hypothalamus (PO/AH) is important for regulating body temperature (Tb), the exact role is not established yet due to conflicting results probably related to experimental techniques or conditions such as the use of anesthesia. The purpose of present study was to clarify the role of 5-HT in the PO/AH using the combined methods of telemetry, microdialysis and high performance liquid chromatography (HPLC), with a special emphasis on the regulation of Tb in freely moving rats. Firstly, we measured changes in Tb and levels of extracellular 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the PO/AH during cold (5 degrees C) and heat (35 degrees C) exposure. We also perfused fluoxetine (5-HT re-uptake inhibitor) and 8-hydroxy-2-(Di-n-propylamino)tetralin (8-OH-DPAT: 5-HT1A agonist) into the PO/AH. During both exposures, although Tb changed significantly, no significant changes were noted in extracellular levels of 5-HT and 5-HIAA in the PO/AH. In addition, although perfusion of fluoxetine or 8-OH-DPAT into the PO/AH increased or decreased extracellular 5-HT and 5-HIAA levels in the PO/AH respectively, but Tb did not change at all. Our results suggest that 5-HT in the PO/AH may not mediate acute changes in thermoregulation.     

Ibotenate lesion of the medial hypothalamus alters the salt intake and pressor responses to activation of the median preoptic nucleus in rats

We investigated the influence of ibotenic acid lesions of the medial hypothalamus (MH) on salt appetite and arterial blood pressure responses induced by angiotensinergic and adrenergic stimulation of the median preoptic nucleus (MnPO) of rats. Previous injection of the adrenergic agonists norepinephrine, clonidine, phenylephrine, and isoproterenol into the MnPO of sham MH-lesioned rats caused no change in the sodium intake induced by ANG II. ANG II injected into the MnPO of MH-lesioned rats increased sodium intake compared with sham-lesioned rats. Previous injection of clonidine and isoproterenol increased, whereas phenylephrine abolished the salt intake induced by ANG II into the MnPO of MH-lesioned rats. Previous injection of norepinephrine and clonidine into the MnPO of sham MH-lesioned rats caused no change in the mean arterial pressure (MAP) induced by ANG II. Under the same conditions, previous injection of phenylephrine increased, whereas isoproterenol reversed the increase in MAP induced by angiotensin II (ANG II). ANG II injected into the MnPO of MH-lesioned rats induce a decrease in MAP compared with sham-lesioned rats. Previous injection of phenylephrine or norepinephrine into the MnPO of MH-lesioned rats induced a negative MAP, whereas pretreatment with clonidine or isoproterenol increased the MAP produced by ANG II injected into the MnPO of sham- or MH-lesioned rats. These data show that ibotenic acid lesion of the MH increases the sodium intake and pressor responses induced by the concomitant angiotensinergic, α₂ and β adrenergic activation of the MnPO, whereas α₁ activation may have opposite effects. MH involvement in excitatory and inhibitory mechanisms related to sodium intake and MAP control is suggested.     

Effects of GABA-transaminase inhibitor Vigabatrin on thermoregulation in rats

Vigabatrin is a GABA derivative (gamma-vinyl GABA) which inhibits irreversibly the enzyme activity of GABA transaminase and thus increased indirectly brain GABA concentrations. We have used body temperature assay to examine the effects of Vigabatrin on thermoregulation in intact rats. In order to understand the mechanism of thermoregulatory action of Vigabatrin at cellular level, we have investigated its effect on individual warm-sensitive preoptic area/anterior hypothalamus (PO/AH) neurons in rat brain slice preparations. The results of the present study suggest that Vigabatrin produced dose-dependent hypothermia in rats and also increased temperature sensitivity of warm-sensitive PO/AH neurons.     

Thermoregulatory responses to preoptic-anterior hypothalamic heating and cooling in the bat,Eptesicus fuscus

Summary The central nervous control of temperature regulation in the bat, Eptesicus fuscus, was evaluated by heating the preoptic-anterior hypothalamus (PO/AH) of active, unanaesthetized bats. Because bats are metabolically very variable, change in body temperature was used as the criterion of change in heat balance in response to change in brain temperature and change in wing temperature as an indicator of vasomotor changes.Heating the preoptic-anterior hypothalamic area (PO/AH) of the bat Eptesicus fuscus caused an average increase in wing temperature due to vasodilation of 1.0° C and an average increase in body temperature of 0.4° C. Conversely, cooling the PO/AH led to an average decline in wing temperature due to vasoconstriction of 0.9° C and an average decline in body temperature of 0.4° C.Bats were heat-stressed to augment the responsiveness of the PO/AH. Heat-stress alone causes a rise in body temperature and wing temperature. Release from heat stress causes a fall in body temperature and a fall in wing temperature. When the PO/AH is heated following a period of high heat-stress, the body temperature continues to fall but wing temperature reverses its direction of change and rises. When bats are given a low heat-stress and simultaneous heating of the PO/AH, wing temperature rises in response to PO/AH temperature and the body temperature stabilizes. When the PO/AH is cooled in bats under high heat-stress, body temperature stabilizes and wing temperature falls. When bats are cold-stressed, body temperature and wing temperature fall regardless of heating of the PO/AH.These responses are related to the life habits of the bat.It is concluded that the PO/AH of the bat Eptesicus fuscus may be less thermally sensitive than the PO/AH in other vertebrates studied, and that other central nervous structures have acquired an increased thermoregulatory function.We thank Mrs. Ruth Chalmers for her excellent histological preparstions.This work was supported, in part, by National science Foundation grant GB 6303 and GB 13797.     

Dissociation of hyperthermic and hyperglycemic effects of central prostaglandin F2 alpha.

We previously reported that intraventricular prostaglandins (PGs) produced hyperthermia and hyperglycemia in anesthetized rats. However, the relationship of them is little known. We examined the relationship between hyperthermia and hyperglycemia induced by intraventricular PGF2 alpha using curarized and adrenal demedullated rats. Iv curare completely prevented the PGF2 alpha-induced hyperthermia, but enhanced the hyperglycemic effect of PGF2 alpha. Adrenal demedullation completely prevented the hyperglycemia, but did not affect the hyperthermic effect of PGF2 alpha. To further assess the site of action concerned with PGF2 alpha-induced thermoregulation and glucoregulation in the central nervous system (CNS), we injected saline or PGF2 alpha into the preoptic area of the anterior hypothalamus (POA) in intact rats. After microinjection of PGF2 alpha into the POA, the rectal temperature rose, but the plasma glucose level did not increase significantly, as compared with saline-treated control rats. These results suggest that PGF2 alpha causes the central nervous system to produce hyperthermia via shivering, stimulated the somatic motor system, and to produce hyperglycemia by stimulating central sympathetic outflow to the adrenal medulla, but these operate independently under different neural regulation, and these sensitive sites are organically dissociated in the CNS.     

AAV-mediated leptin receptor installation improves energy balance and the reproductive status of obese female Koletsky rats

Leptin is a hormone secreted primarily by white adipocytes that regulates energy homeostasis and reproduction via CNS receptors. Koletsky (f/f) rats with a leptin receptor (OB-Rb) gene mutation are obese, diabetic and infertile. We employed recombinant adeno-associated viral (rAAV) vectors to transfer the human OB-Rb gene into the brains of female Koletsky rats to identify sites of leptin action in the brain. rAAV-OB-Rb was microinjected into the medial preoptic area (MPOA), the paraventricular nucleus (PVN), the ventromedial hypothalamus, the arcuate nucleus (ARC), or the dorsal vagal complex in the brainstem. Food intake and body weight were monitored bi-weekly for 55 days. Vaginal cytology was examined daily to assess estrous cyclicity. After sacrifice, uncoupling protein-1 (UCP-1) mRNA in brown adipose tissue and serum concentrations of leptin, insulin, glucose, estradiol and progesterone were measured. Expression of OB-Rb was documented by RT-PCR and site specificity of microinjection was verified by immunohistochemical detection of green fluorescent protein following a control microinjection of rAAV-GFP. OB-Rb installation in the ARC reduced food intake, however, energy expenditure, assessed by UCP-1 mRNA expression, was increased by OB-Rb installation in all sites except the PVN. When injected into the MPOA and ARC, rAAV-OB-Rb stimulated the reproductive axis as evidenced by normalization of estrous cycle length and increased luteinizing hormone releasing hormone concentrations in the hypothalamus. These studies show that long-term installation of a functional leptin receptor in the CNS is achievable using rAAV vectors and further show that leptin acts on specific sites in the brain to produce differential effects on food intake, energy expenditure and reproduction.     

家兔隔核中去甲肾上腺素对皮肤与内脏痛阈的影响

本工作以电刺激内脏大神经或耳尖部皮肤测定清醒家兔内脏痛阈或皮肤痛阈,以探讨隔核去甲肾上腺素在内脏镇痛和皮肤镇痛中的作用以及与中脑导水管周围灰质(PAG)中内阿片肽系统的关系。实验观察到,双侧隔核内微量注射α受体激动剂可乐宁(10μg/2μl)或α受体阻断剂酚妥拉明(10μg/2μl)对内脏痛阈无明显影响。注入β受体激动剂异丙肾上腺素(1μg/2μl)使内脏痛阐明显升高;而注入β受体阻断剂心得安(1Cμg/2μl)则内脏痛阈明显降低。隔核内注入酚妥拉明(10μg/2μl)或心得安(10μg/2μl)均可使皮肤痛阈明显提高。提示,隔核内NA通过β受体调制内脏痛;通过α受体和β受体调制皮肤痛。隔核内注入异丙肾上腺素(1μg/2μl)明显地镇内脏痛,此作用可被PAG内注射纳洛酮(1μg/2μl)或注射抗亮啡肽抗血清(1:20,000)所减弱;但可使PAG内亮啡肽样物质释放量增加。这提示,隔核内NA的镇内脏痛作用与PAG的内阿片肽系统有关;其中亮非肽在这一过程中具有重要作用。     

Ventricular, paraventricular and circumventricular structures involved in peptide-induced satiety

Cholecystokinin, bombesin or gastrin (2 microliter of 50 ng/microliter) was injected stereotaxically into the paraventricular nucleus of the hypothalamus, the arcuate/ventromedial area, the subfornical organ, the area postrema and the cerebral aqueduct of Sprague-Dawley rats and the effects of these injections on food and water intake were studied. While the injection of cholecystokinin reduced food intake when it was injected into both hypothalamic loci, food and water intake were most severely affected by the injection of this peptide into the cerebral aqueduct. Bombesin reduced food intake after its injection into all areas except the subfornical organ and reliable reductions in water intake were seen after injection of this peptide into all areas except the paraventricular nucleus. Minor reductions in food intake were seen following gastrin injection into the paraventricular nucleus while increased water consumption was observed after this peptide was injected into the paraventricular nucleus and cerebral aqueduct. In a second study 6-hydroxydopamine injections (2 microliter of 8 micrograms/microliter were made into the five areas studied 10 days before animals were injected with 100 micrograms/kg of cholecystokinin (i.p.). All 6-hydroxydopamine-injected animals reduced their food and water intake in response to the cholecystokinin challenge as did intact controls. These results indicate that while the changes in food and water intake produced by the central injection of cholecystokinin, bombesin or gastrin may involve central catecholamine systems, those occurring after its systemic administration do not. Therefore, if the release of gastrointestinal peptides during natural feeding is part of a homeostatic mechanism regulating hunger and satiety, this mechanism may operate without directly involving central catecholamine systems.     

Alpha 2-adrenoceptor agonists stimulate growth hormone secretion but have no acute effects on plasma cortisol under basal conditions

Ten normal male subjects were administered clonidine (0.1 and 0.2 mg) or a highly-selective alpha 2-adrenoceptor agonist S 3341 (1 and 2 mg) on separate occasions in a double-blind randomised placebo-controlled study; blood samples were obtained for measurement of serum GH and plasma cortisol via an indwelling venous cannula for 4 h after each drug administration. Both clonidine and S 3341 were equally effective at lowering supine, and particularly standing BP; both also caused mild sedation, although this was slightly less marked for S 3341. High doses of both clonidine and S 3341 significantly increased serum GH (peak increment after clonidine: 18.8 +/- 5.5 mU/l (mean +/- SEM); peak increment after S 3341: 21.1 +/- 4.8 mU/l). Neither drug affected plasma cortisol. It is concluded that GH release may be stimulated by alpha 2-adrenoceptor agonism. As S 3341 has slightly less central activity than clonidine at the doses employed, but is at least equally potent at stimulating GH release, it is probable that the alpha 2-adrenoceptor stimulation of GH release occurs outside the blood-brain barrier. The pituitary-adrenal axis appears resistant to manipulation of alpha 2-adrenoceptors under basal conditions.     

Paraventricular noradrenergic systems participate in angiotensin II-induced drinking

The present study was designed to examine the role of noradrenergic systems in the hypothalamic paraventricular nucleus (PVN) in the drinking response induced by microinjection of angiotensin II (ANG II) into the subfornical organ (SFO) in the awake rat. Intracerebral microdialysis techniques were utilized to quantify the extracellular concentration of noradrenaline (NA) in the region of the PVN. Injections of ANG II (10⁻⁶ M, 0.2 μl) into the SFO significantly increased NA release in the PVN area. The increase in the NA concentration caused by the ANG II injection was significantly attenuated by water ingestion. In urethane-anesthetized rats, injections of ANG II into the SFO elicited an elevation in mean arterial pressure (MAP). On the other hand, intravenous injections of the -agonist metaraminol (5 μg) slightly decreased the release of NA in the PVN area that accompanied an elevation in MAP. These results show that the noradrenergic system in the PVN area may be involved in the dipsogenic response induced by ANG II acting at the SFO.