Response of rat paraventricular neurones with central projections to suckling, haemorrhage or osmotic stimuli

In lactating, urethane-anaesthetized female rats extracellular recordings were made from paraventricular nucleus (PVN) neurones that were antidromically activated following electrical stimulation of the neurohypophysis, amygdala or nucleus tractus solitarius/vagal complex (NTS/VC). Of the PVN units, 98 projected to the neurohypophysis but none of these neurosecretory neurones were found to simultaneously project to extrahypothalamic areas. From the firing patterns and the response of these neurons to suckling, haemorrhage or osmotic stimuli both 'vasopressinergic' and 'oxytocinergic' neurones were identified. We found 43 PVN units to project to the NTS/VC and 22% of tested neurones were activated by osmotic or haemorrhage stimuli; no phasic activity was associated with this activation. The suckling stimulus failed to elicit any response from these units. Upon testing the PVN units that projected to the amygdala (n = 35), it was found that haemorrhage and suckling stimuli were without effect, while the osmotic stimulus activated one of 6 units tested. Thus, the extrahypothalamic PVN projections examined in this study were not associated with the suckling reflex response, although there is evidence for their limited involvement in neural response to osmotic or haemorrhage stimuli.     

Connections of neurons in the region of the nucleus tractus solitarius with the hypothalamic paraventricular nucleus: Their possible involvement in neural control of the cardiovascular system in rats

Extracellular recordings were made from 607 spontaneously firing neurons within the nucleus tractus solitarius (NTS) and its vicinity in urethane-anesthetized male rats. Following electrical stimulation of the hypothalamic paraventricular nucleus (PVN) area, 21% of the neurons were orthodromically excited, 6% were inhibited and 2.5% were antidromically activated. The antidromic spike latencies were 22-64 ms. Among those orthodromically responding neurons, 81 neurons were tested by pressure pulse stimulation of the isolated carotid sinus. The pressure stimulation produced excitation in 7 and inhibition in 13 neurons. Of the 8 tested neurons which were antidromically activated, one neuron was excited and another neuron inhibited by the pressure pulse stimulation. These results provide electrophysiological evidence for reciprocal connections between neurons in the NTS region and the PVN, and give support to the hypothesis that the PVN is involved in the neural control of the cardiovascular system.     

c-Fos expression in preoptic nuclei as a marker of sleep rebound in the rat

Thermoregulation is known to interfere with sleep, possibly due to a functional interaction at the level of the preoptic area (POA). Exposure to low ambient temperature ( T _a) induces sleep deprivation, which is followed by sleep rebound after a return to laboratory T _a. As two POA subregions, the ventrolateral preoptic nucleus (VLPO) and the median preoptic nucleus (MnPO), have been proposed to have a role in sleep-related processes, the expression of c-Fos and the phosphorylated form of the cAMP/Ca²⁺-responsive element-binding protein (P-CREB) was investigated in these nuclei during prolonged exposure to a T _a of −10 °C and in the early phase of the recovery period. Moreover, the dynamics of the sleep rebound during recovery were studied in a separate group of animals. The results show that c-Fos expression increased in both the VLPO and the MnPO during cold exposure, but not in a specific subregion within the VLPO cluster counting grid (VLPO T-cluster). During the recovery, concomitantly with a large rapid eye movement sleep (REMS) rebound and an increase in delta power during non-rapid eye movement sleep (NREMS), c-Fos expression was high in both the VLPO and the MnPO and, specifically, in the VLPO T-cluster. In both nuclei, P-CREB expression showed spontaneous variations in basal conditions. During cold exposure, an increase in expression was observed in the MnPO, but not in the VLPO, and a decrease was observed in both nuclei during recovery. Dissociation in the changes observed between c-Fos expression and P-CREB levels, which were apparently subject to state-related non-regulatory modulation, suggests that the sleep-related changes observed in c-Fos expression do not depend on a P-CREB-mediated pathway.     

Effect of lesions of forebrain circumventricular organs on c-fos expression in the central nervous system to plasma hypernatremia

Experiments were carried out on conscious adult male Wistar rats to investigate the effect of selective ablation of the subfornical organ (SFO), and/or the anteroventral third ventricular (AV3V) region on the induction of Fos in central structures in response to plasma hypernatremia. Fos induction, detected immunohistochemically, was used as a marker for neuronal activation. Intravenous infusions of hypertonic saline resulted in dense Fos-like immunoreactivity in several forebrain (paraventricular nucleus of the hypothalamus (PVH), supraoptic nucleus (SON), median preoptic nucleus (MnPO), medial preoptic nucleus, organum vasculosum of the laminae terminalis and SFO) and brainstem (nucleus of the solitary tract, ventrolateral medulla, and parabrachial nucleus) structures. Intravenous infusions of the hypertonic saline solution into animals with lesions of either the SFO, the AV3V or both resulted in a decreased number of Fos-like immunoreactive neurons in the MnPO, PVH and SON. In addition, the number of Fos-labeled neurons in the SON after lesions of both the SFO and the AV3V was significantly greater than that observed in isotonic saline infused controls. Finally, lesions of the forebrain circumventricular structures did not alter the Fos labeling in brainstem structures as a result of the infusion of the hypertonic solution. These data suggest that changes in plasma osmolality and/or concentration of sodium alter the activity of SON and brainstem neurons in the absence of afferent inputs from the SFO and AV3V.     

Projection of nucleus tractus solitarius units influenced by hepatoportal afferent signal to parabrachial nucleus

In urethan-chloralose anesthetized rats, units in the nucleus tractus solitarius (NTS) which antidromically responded to electrical stimulation of the parabrachial nucleus (PB) were investigated for their responses to hepatic-vagal afferent signals. Among 63 NTS units examined, 25 (40%) were excited, 17 (27%) inhibited and the remaining 21 (33%) unaffected by single shock electrical stimulation of the hepatic branch of the vagus nerve. Topical application of Na+ produced an increase in discharge rate of 9 units and a decrease in 5 units. Portal infusion of hypertonic saline produced an increase in discharge rate of 3 units and a decrease in 5 units. Furthermore, 3 units responded to both topical application of Na+ and portal infusion of hypertonic saline.     

Participation of the Prolactin-Releasing Peptide-Containing Neurones in Caudal Medulla in Conveying Haemorrhagic Stress-Induced Signals to the Paraventricular Nucleus of the Hypothalamus

The prolactin-releasing peptide (PrRP) has been proposed to be a co-transmitter or modulator of noradrenaline (NA) because it colocalises with NA in the A1 (in the ventrolateral reticular formation) and A2 (in the nucleus of the solitary tract; NTS) cell groups in the caudal medulla. The baroreceptor signals, originating from the great vessels, are transmitted primarily to the NTS, and then part of the signals is conveyed to the hypothalamic neuroendocrine neurones via the ascending NA neurones. The hypotensive haemorrhagic paradigm was employed to examine whether the PrRP-containing neurones in the caudal medulla participate in conveying signals to the hypothalamic neuroendocrine neurones. Among the caudal medullary A1 or A2 neurones, the majority of the PrRP-immunoreactive (-ir) neurones became c-Fos-ir at 2 h after hypotensive haemorrhage. Hypothalamic corticotrophin-releasing hormone-ir neurones and vasopressin-ir neurones became c-Fos positive in parallel with the activation of medullary PrRP-ir neurones. After delivery of retrograde tracer fluorogold (FG) to the paraventricular nucleus of the hypothalamus (PVN), part of the PrRP/FG double-labelled neurones in the A1 and A2 became c-Fos-ir after haemorrhage, demonstrating that PrRP-ir neurones participate in conveying the haemorrhagic stress-induced signals from the medulla to the PVN. PrRP and/or NA were microinjected directly to the PVN of conscious rats, and they presented a synergistic action on arginine vasopressin release, whereas an additive action was observed for adrenocorticotrophin release. These results suggest that the PrRP-containing NA neurones in the caudal medulla may relay the haemorrhagic stress-induced medullary inputs to the hypothalamic neuroendocrine neurones.     

Neuronal expression of fos protein in the forebrain of diabetic rats

We sought to identify the areas that have altered neuronal activity within the hypothalamus of diabetic rats by mapping neuronal expression of c-fos protein (Fos) and Fos-related antigens. After a standard PAP immunocytochemical protocol, Fos-like immunoreactivity was observed in the paraventricular nucleus (PVN), supraoptic nucleus (SON), median preoptic area (MnPO), anterior hypothalamus (AH) and posterior hypothalamus (PH) of control (vehicle; n=6) and diabetic rats (Sprague-Dawley rats injected with STZ 65 mg/kg/ip 4 weeks prior to the experiment; n=6). Blood glucose levels were significantly elevated in the diabetic group (370+/-8 mg/dl) compared to control group (104+/-3 mg/dl). Diabetic rats had a significantly higher number of Fos-positive cells in PVN (2.5x), SON (7x) and MnPO (2x) compared to the control rats. However, diabetic rats had significantly fewer Fos-positive cells in the AH (0.3x) and no difference was observed in the PH between the diabetic and control rats. Despite the elevated number of Fos-positive cells in the diabetic rats, dehydration (water withdrawal for 24 h) or hypertonic challenge (1.5 ml of 0.1 M NaCl i.p. injection) produced a further increase in the number of Fos-positive cells in the PVN, SON and MnPO. Dehydration did not alter the number of Fos-positive cells in the AH or PH, but hypertonic challenge produced a significant increase in the Fos-positive cells in both the AH and PH of diabetic rats. This study demonstrates that: (1) there is increased basal neuronal activity in the PVN, SON and MnPO, a decrease in neuronal activity in the AH and no change in neuronal activity in the PH as indicated by Fos staining in diabetic rats; and (2) dehydration or hypertonic challenge produces a further increase in the number of Fos-positive cells in the PVN, SON, and MnPO which is comparable to control rats. These data support the conclusion that vasopressin producing neurons in the PVN and SON and autonomic areas within the lamina terminalis and hypothalamus are activated during diabetes and may contribute to the elevated levels of vasopressin and autonomic dysfunction during diabetes.     

Bidirectional cardiovascular connections between ventrolateral medulla and nucleus of the solitary tract

Single-unit recording experiments were done in chloralose-anesthetized, paralyzed and artificially ventilated cats to identify neurons in ventrolateral medulla (VLM) that send efferent axons directly to the region of the nucleus of the solitary tract (NTS) and receive cardiovascular afferent inputs from the carotid sinus (CSN) and aortic depressor (ADN) nerves and the NTS. Units in VLM were identified by antidromic excitation to stimulation of functionally and histologically verified sites in the NTS complex. Antidromic potentials were recorded from 34 units in VLM. Units responded with a mean antidromic latency of 4.37 +/- 0.32 ms corresponding to a mean conduction velocity of 0.93 +/- 0.07 m/s. Of these 34 units, 18 were excited orthodromically by stimulation of the CSN and/or ADN. Furthermore, 10 of the 18 units responding to stimulation of the buffer nerves were also orthodromically excited by stimulation of NTS. An additional 76 units were identified in VLM that only responded orthodromically to stimulation of NTS with a mean latency of 9.75 +/- 2.93 ms, of which 33 also responded orthodromically to stimulation of the buffer nerves. These data provide electrophysiological evidence of a bidirectional connection between neurons in VLM that receive and integrate peripheral cardiovascular afferent inputs and send efferent axons directly back to the region of NTS. These results suggest that neurons in the VLM may be part of a medullary feedback reflex loop through which afferent information from cardiovascular receptors exerts an influence on NTS neurons involved in the control of the circulation.     

Cytoarchitectonic Analysis of Fos-immunoreactivity in Brainstem Neurones Following Visceral Stimuli in Conscious Rats

Visceral inputs to the brain make their initial synapses within the nucleus of the solitary tract (NTS), where information is relayed to other brain regions. These inputs relate to markedly different physiological functions and provide a tool for investigating the topography of visceral processing in brainstem nuclei. Therefore, Fos immunoreactivity was used to determine whether a gastric stimulus affects neurones within different or similar parts of the NTS, ventrolateral medulla (VLM) and parabrachial nucleus (PBN), compared to a baroreceptive stimulus. The contribution of catecholaminergic neurones in these areas was studied by combining Fos and tyrosine hydroxylase (TH) immunoreactivity. Conscious male rats received either cholecystokinin (CCK) intraperitoneally to activate gastrointestinal afferents, or were made hypertensive by intravenous infusion of phenylephrine (PE) to activate baroreceptors. Tissue sections were processed immunocytochemically for Fos and/or TH. Phenylephrine infusion and CCK injection elicited Fos expression in distinct and in overlapping regions of the NTS and the VLM. Cholecystokinin injections increased the number of Fos-immunoreactive neurones in the area postrema (AP) and throughout the rostral-caudal extent of the NTS, including commissural neurones and the medial subnuclei. Some reactive neurones in NTS were also positive for TH, but most were not, and most of the TH-positive NTS neurones were not Fos-positive. In contrast, PE infusion produced a more restricted distribution of Fos-positive neurones in the NTS, with most neurones confined to a dorsolateral strip containing few TH-positive neurones. The medial NTS at the level of the AP and the AP itself were largely unresponsive, but rostral to the AP the medial NTS was labelled, including some TH-positive neurones. Both treatments produced labelling in the caudal and mid-VLM, but PE infusion had a stronger effect in the rostral VLM. In the PBN, CCK elevated Fos expression in several subregions, whereas PE infusion failed to specifically alter any subdivision. The results suggest that stimulation of baroreceptor and gastric afferents evoke both overlapping and cytoarchitectonically distinct pathways in the brainstem.     

Excitability of pontine startle processing neurones is regulated by the two-pore-domain K+ channel TASK-3 coupled to 5-HT2C receptors

The mammalian startle reflex is a fast response to sudden intense sensory stimuli that can be increased by anxiety or decreased by reward. The cellular integration of sensory and modulatory information takes place in giant neurones of the caudal pontine reticular formation (PnC). The startle reflex is known to be enhanced by 5-hydroxytryptamine (5-HT); however, signalling mechanisms that change the excitability of the PnC giant neurones are poorly understood. Possible molecular candidates are two-pore-domain K⁺ (K₂P) channels that generate a variable K⁺ background conductance and control neuronal excitability upon activation of G-protein-coupled receptors. We demonstrate by in situ hybridization that the K₂P channel TASK-3 is substantially expressed in PnC giant neurones. Brain slice recordings revealed a corresponding background K⁺ current in these cells that forms about 30% of the outward current at −30 mV. Inactivation of TASK-3 at pH 6.4 and by ruthenium red depolarized the cells by about 7 mV and increased the action potential frequency as well as duration. Specific activation of Gα_q-coupled 5-HT₂ receptors with α-methyl 5-HT evoked a similar increase of neuronal excitability. Consistently, we measured afferent synaptic inputs from serotonergic raphe neurones and detected 5-HT_2C receptors in PnC giant neurones by immunohistochemistry. Thus, neuronal excitability of PnC giant neurones in vivo is most likely increased by serotonergic projections via the K₂P channel TASK-3.     

The inhibitory effect of somatic inputs on the excitatory responses of vagal cardiomotor neurones to stimulation of the nucleus tractus solitarius in rabbits

Experiments were done in 41 rabbits anaesthetized with urethane and chloralose, paralyzed with Flaxedil and ventilated artificially. Extracellular recordings of 142 units were made in the dorsal vagal nucleus (DVN) and the nucleus ambiguus (NA), identified by antidromic response to stimulation of the cervical vagus nerve. In total 63.5% of them exhibited spontaneous activity and 22 units (17 in DVN and 5 in NA) showed a cardiac rhythm; their antidromic conduction velocity was 3.7-12.5 m/s, which suggests their having axons in the range of B fibres. These neurones were classified as vagal cardiomotor neurones. A total of 16 DVN and 4 NA vagal cardiomotor neurones were excited orthodromically by electrical stimulation of the contralateral nucleus tractus solitarius (NTS). Electrical stimulation of the superficial peroneal nerve (SP) with low intensity or the deep peroneal nerve (DP) with high intensity which activated C fibres inhibited excitatory responses of 16 neurones (14 in DVN and 2 in NA). The other 4 neurones were unaffected by SP inputs. These results provide electrophysiological evidence for the inhibitory effect of somatic inputs on the evoked discharges of vagal cardiomotor neurones in the DVN and the NA.     

Regional differences in the expression of Fos-like immunoreactivity after central salt loading in conscious rats: modulation by endogenous vasopressin and role of the area postrema

In this study, we examined the quantitative relationship between centrally administered hypertonic saline (HS) concentrations and the expression of Fos-like immunoreactivity (FLI) in brain regions involved in the homeostasis of body fluids. The regions examined were the organum vasculosum laminae terminalis (OVLT), the median preoptic nucleus (MnPO), the subfornical organ (SFO), the paraventricular nucleus (PVN), the supraoptic nucleus of the hypothalamus, the nucleus of the solitary tract (NTS), and the area postrema (AP). The experiments were performed in conscious rats with attention to the actual changes in central [Na(+)]. Hypertonic saline (0.3, 0.67, or 1.0 M) was delivered at 1 microl/min for 20 min. The changes in cerebrospinal fluid [Na(+)] during i.c.v. administration of 0.3 M hypertonic saline were compatible with those expected for thermal dehydration. FLI increased in a dose-dependent manner in the dorsomedial cap of the PVN and NTS. Although the pressor responses during central salt loading were not significantly affected by pretreatment with the peripheral vasopressin V(1) receptor antagonist OPC-21268, FLI expression in the PVN was significantly augmented. In addition, in AP-lesioned rats, FLI expression in the lateral magnocellular part of the PVN and NTS was significantly enhanced after central salt loading. These results suggest that the peripheral vasopressin system participates in negative feedback to modulate neuronal activities in the PVN, probably through the AP or direct action at the PVN in response to central osmotic and/or Na(+) stimulation.     

The Carboxy-Terminal Glycopeptide of the Vasopressin Precursor in the Guinea-Pig: Release Studies Using a Specific and Sensitive Homologous Radioimmunoassay

The glycopeptide corresponding to the C-terminal portion of the vasopressin precursor (CPP)has been isolated from guinea-pig posterior pituitary glands and used to generate a specific and sensitive radioimmunoassay. The antiserum is directed to the peptide rather than sugar moieties, and detects two components in pituitary extracts: CPP itself, and a biosynthetic intermediate (NP-CPP) containing both neurophysin and CPP sequences. Release of CPP from neurointermediate lobes incubated in vitro was stimulated five-fold by high K⁺ in a Ca²⁺ dependent manner: in vivo studies suggest that CPP is released under conditions stimulating vasopressin release. Chronic dehydration depleted neural lobe stores of CPP in parallel with other vasopressin-related components, and plasma levels of CPP were raised from 68±18 to 320 + 89 fmol/ml (SEM, n = 6). In anaesthetized guinea-pigs, intraperitoneal injections of increasingamounts of hypertonic saline increased plasma levels of CPP in a graded manner compared with isotonic saline injections. Acute haemorrhage also stimulated CPP release into plasma, and the half-time of clearance of CPP after infusion to steady state levels in guinea-pig plasma was 24 min. Cerebrospinal fluid withdrawn from the cisterna magna also contained detectable amounts of CPP (390 + 25 fmol/ml) suggesting that CPP is released from both hypophysical and extra-hypophysical projections. This assay may now be used to study the biosynthesis, processing and release of endogenous CPP under different physiological conditions.     

Rapid Action of Oestrogen in Luteinising Hormone-Releasing Hormone Neurones: The Role of GPR30

Previously, we have shown that 17β-oestradiol (E₂) induces an increase in firing activity and modifies the pattern of intracellular calcium ([Ca²⁺]_i) oscillations with a latency < 1 min in primate luteinising hormone-releasing hormone (LHRH) neurones. A recent study also indicates that E₂, the nuclear membrane impermeable oestrogen, oestrogen-dendrimer conjugate, and the plasma membrane impermeable oestrogen, E₂-BSA conjugate, all similarly stimulated LHRH release within 10 min of exposure in primate LHRH neurones, indicating that the rapid action of E₂ is caused by membrane signalling. The results from a series of studies further suggest that the rapid action of E₂ in primate LHRH neurones appears to be mediated by GPR30. Although the oestrogen receptor antagonist, ICI 182, 780, neither blocked the E₂-induced LHRH release nor the E₂-induced changes in [Ca²⁺]_i oscillations, E₂ application to cells treated with pertussis toxin failed to result in these changes in primate LHRH neurones. Moreover, knockdown of GPR30 in primate LHRH neurones by transfection with human small interference RNA for GPR30 completely abrogated the E₂-induced changes in [Ca²⁺]_i oscillations, whereas transfection with control siRNA did not. Finally, the GPR30 agonist, G1, resulted in changes in [Ca²⁺]_i oscillations similar to those observed with E₂. In this review, we discuss the possible role of G-protein coupled receptors in the rapid action of oestrogen in neuronal cells.     

Ca2+ Channels and Ca2+-Activated K+ Channels in Adult Rat Gonadotrophin-Releasing Hormone Neurones

Gonadotrophin-releasing hormone (GnRH) neurones represent the final output neurones in the neuroendocrine system for the control of reproduction. To understand the reproductive neuroendocrine system, an investigation of the intrinsic and extrinsic properties of GnRH neurones is essential. In this review, we focus on the intrinsic properties and summarise our recent findings of ion channels expressed in rat GnRH neurones. Rat GnRH neurones express all four types of high voltage-activated Ca²⁺channel (L, N, P/Q, R) and the low voltage-activated Ca²⁺ channel (T). GnRH neurones also express two types of Ca²⁺-activated K⁺ [K(Ca)] channel: the small conductance Ca²⁺-activated K⁺ (SK) channel and the large conductance Ca²⁺- and voltage-activated K⁺ (BK) channel. The activities of these Ca²⁺ and K(Ca) channels regulate cell excitability and cellular calcium homeostasis.     

Central administration of neuropeptide FF causes activation of oxytocin paraventricular hypothalamic neurones that project to the brainstem

Neuropeptide FF (NPFF), a morphine modulatory peptide, is emerging as an important neuromodulator in the context of central autonomic and neuroendocrine regulation. NPFF immunoreactivity and receptors have been identified in discrete autonomic regions within the brain and spinal cord, including the hypothalamic paraventricular nucleus (PVN). In this study, we examined the effects of intracerebroventricular (i.c.v.) administration of NPFF on activation of chemically identified PVN neurones that project to the brainstem nucleus of the solitary tract (NTS). In conscious rats, i.c.v. NPFF at a dose of 10 micro g, but not 8 micro g, caused an increase in arterial blood pressure. Immunohistochemical analysis revealed a dose-dependent increase in activated (Fos positive) PVN neurones following i.c.v. NPFF administration compared to controls receiving i.c.v. saline. Activated PVN neurones were located predominantly in the parvocellular compartment of the nucleus with relatively few Fos positive cells in the magnocellular subdivision. Chemical identification of activated neurones revealed significant number of activated cells to be oxytocin positive, whereas only few vasopressin, tyrosine hydroxylase (TH) or corticotrophin-releasing factor (CRF) neurones were double-labelled. Injection of the retrograde tracer fluorogold into the NTS resulted in labelling of significant numbers of parvocellular oxytocin, but not vasopressin, TH or CRF, PVN neurones. We conclude that centrally administered NPFF stimulates brainstem-projecting oxytocin PVN neurones. Oxytocin released from terminals within the NTS oxytocin thus modulate the activity of ascending visceral autonomic pathways that synapse initially within the NTS.     

Calcium-Dependent Regulation of Genetically Determined Spike and Waves by the Reticular Thalamic Nucleus of Rats

Summary: The pathophysiologic role of the reticular thalamic nucleus (RT) in rat generalized nonconvulsive epilepsy was investigated in the selected strain GAERS (genetic absence epilepsy rats from Strasbourg). After the RT was lesioned by the excitotoxic agent ibotenic acid stereotaxically injected in previously callosotomized rats, a disruption of ipsilateral spike and wave discharges (SWD) was observed in freely moving animals. In a second group of animals Cd²⁺ (0.5–1.5 μl, 1 m M ), which is known to block Ca²⁺ and Ca²⁺-dependent K⁺ conductances (gK⁺ (Ca²⁺), was injected into the thalamus. Cd²⁺reversibly suppressed ipsilateral SWD when injected in RT, whereas it slightly reduced SWD expression when injected in the ventrobasal (VB) complex. The difference was highly significant. We conclude that Ca²⁺-dependent oscillatory properties of the RT are critical for expression of genetically determined SWD in GAERS.     

CD4 and CD8 lymphocyte subsets in cerebrospinal fluid and peripheral blood from patients with multiple sclerosis, meningitis and normal controls

Objectives - To study the distribution of CD4⁺ and CD8⁺ T-cell subsets in cerebrospinal fluid (CSF) and peripheral blood from patients with multiple sclerosis (MS), meningitis, other neurological diseases and healthy controls.
Material and methods - The expression of markers for naive and memory cells (CD45RA⁺ and CD45RO⁺), and helper/inducer cells (CD29⁺) on CD4⁺ cells as well as CD45RO⁺ and killer/effector (S6F1⁺) on CD8⁺ cells was investigated in cerebrospinal fluid (CSF) and peripheral blood from patients with multiple sclerosis (n=28), meningitis (n = 13), other neurological diseases (n = 16), and healthy controls (n = 16) by 2-color flow cytometry.
Results - The majority of T cells in the CSF of the 4 groups exhibited the phenotype of memory cells (CD45RO⁺) on both CD4⁺ and CD8⁺ cells. The proportion of helper/inducer (CD29TD4⁺ in CD4⁺) cells was also larger in the CSF compared to peripheral blood in the 3 patient groups and controls investigated. In contrast, CD8⁺ cells with killer/effector (S6F1+) phenotype were fewer in CSF compared to peripheral blood in all 4 groups. There were no significant differences between patients and controls regarding the distribution of these activation markers in the CSF or peripheral blood.
Conclusion - Our observations support the notion that activated T cells of both CD4⁺ and CD8⁺ phenotype selectively pass the blood-brain barrier under both pathological and normal conditions.     

Dual modulation of synaptic transmission in the nucleus tractus solitarius by prostaglandin E2 synthesized downstream of IL-1beta

The activation of the innate immune system induces the production of blood-borne proinflammatory cytokines like interleukin-1β (IL-1β), which in turn triggers brain-mediated adaptative responses referred to as sickness behaviour. These responses involve the modulation of neural networks in key regions of the brain. The nucleus tractus solitarius (NTS) of the brainstem is a key nucleus for immune-to-brain signalling. It is the main site of termination of vagal afferents and is adjacent to the area postrema, a circumventricular organ allowing blood-borne action of circulating IL-1β. Although it is well described that IL-1β activates cerebral endothelial and glial cells, it is still unknown if and how IL-1β or downstream-synthesized molecules impact NTS synaptic function. In this study we report that IL-1β did not modulate NTS synaptic transmission per se , whereas prostaglandin E₂ (PGE₂), which is produced downstream of IL-1β, produced opposite effects on spontaneous and evoked release. On the one hand, PGE₂ facilitated glutamatergic transmission between local NTS neurons by enhancing the frequency of spontaneous excitatory postsynaptic currents through a presynaptic receptor different from the classical EP1–4 subtypes. On the other hand, PGE₂ also depressed evoked excitatory input from vagal afferent terminals through presynaptic EP3 receptors coupled to G-proteins linked to adenylyl cyclase and protein kinase A activity. Our data show that IL-1β-induced PGE₂ can modulate evoked and spontaneous release in the NTS differentially through different mechanisms. These data unravel some molecular mechanisms by which innate immune stimuli could signal to, and be integrated within, the brainstem to produce central adaptative responses.