Effects of naftidrofuryl oxalate, a 5HT2 antagonist, on neurotransmission and transduction systems in the gerbil hippocampus

We investigated the effects of age and naftidrofuryl oxalate (Naftidrofuryl), a 5-HT₂ antagonist, on neurotransmission and transduction systems in the gerbil hippocampus using quantitative autoradiography. [³H]Quinuclidinyl benzilate (QNB), [³H]cyclohexyl-adenosine (CHA), [³H]MK-801, and [³H]muscimol were used to label muscarinic acetylcholine, adenosine A1, N-methyl-d-aspartate (NMDA), and γ-aminobutyric acid-A (GABA_A) receptors, respectively. [³H]PN200-110 labeled L-type Ca²⁺ channels. [³H]Forskolin, [³H]cyclic adenosine monophosphate (cAMP), [³H]phorbol 12,13-dibutyrate (PDBu), and [³H]inositol 1,4,5-triphosphate (IP₃) were used to label adenylate cyclase, cAMP-dependent protein kinase, protein kinase C (PKC), and IP₃ receptors, respectively. Approximately 20% reductions in [³H]QNB, [³H]forskolin, and [³H]PDBu binding were observed in the hippocampus of 9-month-old gerbils in comparison with 5-week-old gerbils. Treatment with Naftidrofuryl (10 mg/kg, i.p., once a day for 7 days) ameliorated these reductions. No changes were found in [³H]CHA, [³H]MK-801, [³H]muscimol, [³H]PN200-110, [³H]cAMP, and [³H]IP₃ binding. The results suggest that Naftidrofuryl may have beneficial effects on the age-related alterations in signal transmission and transduction systems in the brain. Because the acetylcholine system, adenylate cyclase, and PKC are considered to be involved in learning and memory processes, the result may have clinical implications.     

Immunohistochemical mapping of nitric oxide synthase in the rat hypothalamus and colocalization with neuropeptides

The localization and distribution of nitric oxide synthase in the hypothalamus have been studied with an immunohistochemical technique using antibodies to neuronal rat nitric oxide synthase. Subsequent double-labeling experiments examined the colocalization patterns of nitric oxide synthase and several peptides. Our results demonstrate a widespread occurrence of nitric oxide synthase-immunoreactive nerve cell bodies and processes throughout the hypothalamus, especially in various parts of the preoptic region, in the supraoptic and paraventricular nuclei, the lateral hypothalamic area, the ventromedial and dorsomedial nuclei, the arcuate nucleus and various parts of the mammillary region. Double labeling experiments showed that nitric oxide synthase-like immunoreactivity coexists with substance P-like immunoreactivity in the medial preoptic area, with oxytocin-, cholecystokinin- and galanin message-associated peptide-like immunoreactivity in the supraoptic nucleus, with enkephalin-, oxytocin- and corticotropin releasing factor-like immunoreactivity in the paraventricular nucleus and with enkephalin-like immunoreactivity in the arcuate nucleus. Furthermore, in the ventromedial nucleus, nitric oxide synthase-like immunoreactivity coexisted with enkephalin-, substance P-, and somatostatin-like immunoreactivity, and in the dorsomedial nucleus with enkephalin-, galanin message-associated peptide- and substance P-like immunoreactivity. In the mammillary region nitric oxide synthase-like immunoreactivity coexisted with enkephalin-, cholecystokinin-, and substance P-like immunoreactivity. Among these neuropeptides, enkephalin and substance P were most frequently found in nitric oxide synthase-immunoreactive neurons. We conclude that nitric oxide synthase-immunoreactive neurons contain neuropeptides in various parts of the hypothalamus, and that nitric oxide in the hypothalamus may be involved in a variety of neuroendocrine and autonomic functions.     

Interleukin-6 production by astrocytes: Induction by the neurotransmitter norepinephrine

Astrocytes contribute to the immunocompetence of the central nervous system (CNS) via their expression of class II major histocompatibility complex (MHC) antigens and the production of inflammatory cytokines such as interleukin-1 beta (IL-1β), tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6). Of these cytokines, IL-6 is of particular interest because one of its many immune and inflammatory actions is the promotion of immunoglobulin synthesis, and it is thought that IL-6 expression within the brain exacerbates autoimmune diseases of the CNS, which are marked by local immunoglobulin production. Several stimuli induce astrocyte IL-6 expression, including such inducible endogenous factors as IL-1β and TNF-α. We have investigated the possibility that a constitutively present endogenous factor, the neurotransmitter norepinephrine (NE), can induce astrocyte IL-6 production. We report that NE induces both IL-6 mRNA and protein in primary neonatal rat astrocytes, with optimal induction at 10 μM. IL-6 protein induction by NE is comparable to that seen with IL-1β or TNF-α, and NE synergizes with these cytokines for a ten-fold enhanced effect. In contrast to astrocytes, microglia are relatively unresponsive to NE, IL-1β and TNF-α for IL-6 production. Experiments with the β-adrenergic receptor agonist isoproterenol, and α and β-adrenergic receptor antagonists (propranolol, phentolamine, atenolol, and yohimbine) indicate that β₂ and α₁-adrenergic receptors are involved in NE induction of astrocyte IL-6 expression. These results help to further the understanding of neuron-glial interactions, and the role of astrocytes and adrenergic activity in immune responses within the CNS.     

An atlas of glycine- and GABA-like immunoreactivity and colocalization in the cochlear nuclear complex of the guinea pig

Summary The distribution and colocalization of -aminobutyric acid (GABA)- and glycine-like immunoreactivity in the cochlear nuclear complex of the guinea pig have been studied to produce a light microscopic atlas. The method used was based on post-embedding immunocytochemistry in pairs of 0.5-m-thick plastic sections treated with polyclonal antibodies against conjugated GABA and glycine respectively. Immunoreactive cells, presumably short axon neurones, predominated in the dorsal cochlear nucleus, with mostly single-GABA-labelled cells in the superficial layer, double-labelled in the middle, and single-glycine-labelled in the deep layers. A few large single-glycine-labelled cells, interpreted as commissural neurons, occurred in the ventral nucleus. Scattered double-labelled cells, probably Golgi cells, were seen in the granule cell domain. Immunolabelled puncta of all three staining categories occurred in large numbers throughout the complex, apposed to somata and in the neuropil, showing a differential distribution onto different types of neuron. Three immunolabelled tracts were noted: the tuberculoventral tract, the commissural acoustic stria, and the trapezoidal descending fibres. Most of the fibres in these tracts were single-labelled for glycine, although in the last mentioned tract single-GABA- and double-labelled fibres were also found. Some of the immunolabelled cell types described here are proposed as the origins of the similarly labelled puncta and fibres on the basis of known intrinsic connections.Abbreviations 1-4 DCN layers 1 to 4 - as acoustic stria - AVCN anteroventral cochlear nucleus - C caudal - cap cap area - cas commissural acoustic stria - cnr cochlear nerve root - co commissural cell - CRVCN central region of the VCN - cw cartwheel cell - CZ confluence zone - d dendrite - D dorsal - das dorsal acoustic stria - DCN dorsal cochlear nucleus - df descending fibres - ep ependyma - flocc flocculus - g glial cell - GABA -aminobutyric acid - GLY glycine - gi giant cell - gl/gla globular cell/area - Go Golgi cell - gr granule cell - ias intermediate acoustic stria - icp inferior cerebellar peduncle - lam granule cell lamina - mp/mpa multipolar cell/area - oc/oca octopus cell/area - PVCN posteroventral cochlear nucleus - py pyramidal cell - R rostral - sgl superficial granule cell layer - spcg subpeduncular corner of granule cells - sph/spha spherical cell/area - st stellate cell - tb trapezoid body - tv tuberculoventral cell - TVT tuberculoventral tract - V ventral - VCN ventral cochlear nucleus - vn vestibular nerve     

Neurotransmitters regulate the migration and cytotoxicity in natural killer cells

Natural killer (NK) cells and cytotoxic T lymphocytes (CTL), the functional coordination of which are governed by various signal substances, are crucial in the body’s defense of tumor and virus-infected cells. We investigated the role of various neurotransmitters and hormones on the regulation of functional parameters, including NK cell cytotoxicity, and the migration of NK cells and CTL within a three-dimensional collagen lattice. Using peripheral blood CTL and NK cells, we show that the neurotransmitters endorphin, histamine and substance P increase NK cell cytotoxicity, while norepinephrine inhibits cytotoxicity. Moreover, substance P reduces migratory activity, while norepinephrine increases NK cell and CTL migration. Furthermore, all three steroid hormones which were investigated, namely cortisone, testosterone, and estradiol, had regulatory influence on both cytotoxicity and migration of NK cells. These results further specify the functional basis of the complex interconnection between the immune and neuro-endocrine systems.     

In vivo release of neurotransmitters in the medial basal hypothalamus of the monkey

Summary In vivo release rates of norepinephrine (NE), epinephrine (E), dopamine (DA), gammaaminobutyric acid (GABA), glutamate (GLU) and beta-endorphin (E) in the medial basal hypothalamus (MBH) of unanaesthetized female macaca fascicularis monkey, and the effects thereon of estrogen (E2) treatment, have been estimated using pushpull perfusion methodology. DA, NE, E, GABA, GLU and E were all detectable in 30 min perfusate fractions. No direct correlation between their release rates and those of LH and PRL could be observed. E2 induced an initial decrease, then an increase, in LH and PRL secretion, and concomitant changes in the release patterns of DA, NE, E. GABA and GLU were apparent. This study demonstrates that in vivo push-pull perfusion methodology may be applied to the unanaesthetized monkey, and when combined with venous catheterization for serial blood sampling may prove to be a powerful tool in the investigation of the central molecular events governing neuroendocrine functions.     

Apamin distinguishes two types of relaxation mediated by enteric nerves in the guinea-pig gastrointestinal tract

Summary Eight smooth muscle preparations from the stomach, small intestine and large intestine of the guinea-pig were used to compare apamin's actions in reducing the effectiveness of transmission from enteric inhibitory nerves and in reducing responses to inhibitory agonists ,-methylene ATP, VIP and isoprenaline. The effects of apamin on inhibitory reflexes in the ileum and colon were also evaluated. Apamin had little or no effect on responses to VIP and isoprenaline in any region, but consistently and substantially reduced responses to ,-methylene ATP. Responses to stimulation of enteric inhibitory neurons were substantially reduced by apamin in the antrum circular muscle, ileum longitudinal and circular muscle, taenia coli and distal colon longitudinal muscle, but it was ineffective in the fundus circular muscle, proximal colon longitudinal muscle and distal colon circular muscle. It caused a small reduction of the relaxation of the ileal circular muscle caused reflexly by distension, but did not modify the similar descending inhibitory reflex in the circular muscle of the colon. It is concluded that apamin can be used to distinguish two types of non-noradrenergic transmission from enteric inhibitory nerves to gastrointestinal muscle. Furthermore, neither VIP nor ATP can be the sole transmitter chemical released from enteric inhibitory neurons throughout the gastrointestinal tract.     

Functional transmitters at retinal ganglion cells in the cat

The effects of iontophoretically applied putative neurotransmitters and their antagonists on the responses of retinal ganglion cells were studied in the optically intact eye of anaesthetized cats. L-aspartate enhanced and a N-methyl-D-aspartate receptor blocker, 2-amino-5-phosphonovalerate, blocked visual excitations of "sustained" cells, whereas acetylcholine enhanced, and the nicotinic receptor blocker, dihydro-beta-erythroidine, blocked those of "transient" cells. GABA enhanced and bicuculline blocked inhibitions of on-centre cells, but glycine enhanced and strychnine blocked those of off-centre cells, whether the cells were "sustained" or "transient". The possibility that: (A) aspartate may be an excitatory transmitter at both "on-" and "off-sustained" cells and acetylcholine, at both "on-" and "off-transient" cells; (B) GABA may be an inhibitory transmitter for on-centre, and glycine, for off-centre cells, is discussed.     

Pharmacological interactions with circling behaviour induced by the piperidinyl indole derivative RU 23686

When administered i.p. from doses of 10 mg/kg, RU 23686 [5-methoxy 3-(4-piperidinyl) 1H-indole hydrochloride], a drug with relatively weak stimulant properties, induces contralateral (C) circling behaviour in rats with a unilateral electrolytic lesion in the striatum and a more complex effect with ipsilateral (1) and/or C circling in rats with a 6-hydroxydopamine (6-OHDA) lesion in the dopamine (DA) nigro-striatal tract. Interactions of RU 23686 with pharmacological agents have been studied in order to investigate the extent to which different neurotransmitters may be implicated in the circling behaviour induced by this compound.In striatal of 6-OHDA lesioned rats, methyl p-tyrosine (MT) did not modify C turns, while in the latter case only I turns were decreased. FLA 63, propranolol, and desipramine were also inactive in rats with a unilateral striatal lesion. Haloperidol reduced the effects of a 10 mg/kg dose of RU 23686 in striatal lesioned rats but was without effect against a dose of 20 mg/kg; in 6-OHDA lesioned rats, haloperidol blocked induced I turns but either did not affect or increased C turns. Phenoxybenzamine and p-chlorophenylalanine (PCPA), but not methysergide, p-chloroamphetamine (PCA), or fluoxetine, reduced the effect of RU 23686 in rats with a striatal lesion. In nigro-striatal lesioned rats, PCPA exhibited a differing effect according to the predominance of I or C turns: in rats with a mainly C response, C turns were decreased and I turns preserved, whereas in rats with a majority of I responses, these were depressed. In both types of lesions, animals reserpinized 48 h before RU 23686 exhibited an increase in their C circling, even in 6-OHDA lesioned animals where I turns predominated. In both rotational models, apomorphine-induced circling was potentiated by RU 23686.It is concluded that I circling, which is blocked by haloperidol and MT, could be related to a presynaptic action causing DA release. On the other hand, C turns do not depend on apomorphine-sensitive DA receptors in the striatum. A minor or indirect role of 5-hydroxytryptamine (5-HT) containing areas is suggested from the response to PCPA and the lack of effect of other drugs interfering with 5-HT. Results obtained from interactions with phenoxybenzamine, caffeine, and reserpine and the bimodal response to RU 23686 observed in 6-OHDA lesioned rats could indicate an interference with adrenergic processes.