Identification of authentic substance P in striatonigral and amygdaloid nuclei using combined high performance liquid chromatography and radioimmunoassay

Sample preparation, high-performance liquid chromatographic separation and determination of substance P-related peptides

This review deals with the determination of low levels of substance P and peptide fragments derived from the undecapeptide, i.e. covers the whole amount of so-called substance P-like immunoreactivity (SPLI) in biological samples. First an overview of the most currently used sample pretreatment procedures is given, followed by a description of the most effective high-performance liquid chromatographic (HPLC) separation methods. Special attention is paid to the choice of the appropriate column and the possible pitfalls encountered in separation of fmol amounts of peptide material. Subsequently the most important techniques of detection are discussed. This section primarily focuses on the coupling of HPLC with radioimmunoassay (RIA), which is indispensable for detection of components in the fmol range at present. Finally, some aspects of preparation and chromatographic separation of radiolabelled antigens for use in RIA are discussed.

Recovery of substance P and related C-terminal fragments on solid-phase extraction cartridges for subsequent high-performance liquid chromatographic separation and radioimmunoassay

The recoveries of substance P (SP) and five related peptides were evaluated on different types of solid-phase extraction sorbent. Best results were obtained by use of a C18 silica gel cartridge. Marked differences of extraction yields occurred for the different peptide fragments and, in general, recovery increased with increasing hydrophobicity of the peptide when reversed-phase materials like C18 and C8 cartridges were used. This observation is indicative of a sorption-desorption mechanism by prevailing solvophobic interactions. A similar trend was found when phenylpropyl silica gel (CPhenyl), generally known as a reversed-phase adsorbent of lower hydrophobicity, was used. It was concluded that a substantial participation of analyte-matrix pi-pi interactions has to be taken into account when extraction yields are compared with corresponding values obtained by use of a C8 cartridge. With CN silica gel cartridges, marked differences in extraction yields were obtained by use of acetonitrile or methanol as the organic modifier. As an attempt to explain this observation, conformational effects were assumed for the sorption-desorption behaviour of the peptides on the polar matrix.

Enzymatic and radioimmunoassay procedures combined with electrophoresis and HPLC for the recovery and characterization of substance P in human brain

Immunoreactive substance P was recovered from human brain (hypothalamus and substantia nigra) by acetic acid extraction, ion exchange chromatography (SP-Sephadex), molecular sieving (Sephadex G-50) and column electrophoresis in agarose suspension. The chemical nature of the active material was further studied with various biochemical techniques including agarose suspension electrophoresis, HPLC and different kinds of enzyme radioimmunoassays. By combining these techniques it was possible to confirm structure identity between the recovered active component and substance P previously isolated from bovine brain. Thus, the major activity reacting with the substance P antibodies was indistinguishable from the synthetic bovine analogue in all chromatographic systems including analytical electrophoresis at different pH:s and HPLC. Furthermore, digestion of the active material with post-proline cleaving enzyme and trypsin yielded fragments identical with those expected from the bovine peptide as confirmed by specific radioimmunoassays in conjunction with electrophoresis or HPLC. The result also indicates the usefulness of the present procedures for identifying peptides structures available only in minute amounts.

Distribution of DARPP-32 in the basal ganglia: an electron microscopic study

DARPP-32, a dopamine and cyclic AMP-regulated phosphoprotein, has been studied by light and electron microscopical immunocytochemistry in the rat caudatoputamen, globus pallidus and substantia nigra. In the caudatoputamen, DARPP-32 was present in neurons of the medium-sized spiny type. Immunoreactivity for DARPP-32 was present in dendritic spines, dendrites, perikaryal cytoplasm, most but not all nuclei, axons and a small number of axon terminals. Immunoreactive axon terminals in the caudatoputamen formed symmetrical synapses with immunolabeled dendritic shafts or somata. Neurons having indented nuclei were never immunoreactive. In the globus pallidus and substantia nigra pars reticulata, DARPP-32 was present in myelinated and unmyelinated axons and in axon terminals. The labelled axon terminals in these regions formed symmetrical synaptic contacts on unlabelled dendritic shafts or on unlabelled somata. These data suggest that DARPP-32 is present in striatal neurons of the medium-sized spiny type and that these DARPP-32-immunoreactive neurons form symmetrical synapses on target neurons in the globus pallidus and substantia nigra. The presence of DARPP-32 in these striatal neurons and in their axon terminals suggests that DARPP-32 mediates part of the response of medium-size spiny neurons in the striatum to dopamine D-1 receptor activation.

Striatal substance P cell clusters coincide with the high density terminal zones of the discontinuous nigrostriatal dopaminergic projection system in the cat: a study by combined immunohistochemistry and autoradiographic axon-tracing

A portion of the nigrostriatal projection that originates from presumably dopaminergic neurons in the caudal pars compacta of the substantia nigra and the suprajacent pars dorsalis (retrorubral area), was shown by [3H]amino acid autoradiographic tracing to distribute nonhomogeneously in the head of the caudate nucleus, such that zones of high density termination are in register with the archipelago of substance P cell clusters revealed immunohistochemically in the same and adjacent tissue sections of the cat's brain. Axons from this same portion of the substantia nigra distribute densely at caudal levels of the putamen where again substance P-immunoreactive striatal cells are numerous. In nearby tissue sections from the same cases, tyrosine hydroxylase-like immunoreactivity suggested only subtle variations in the density of the catecholamine axon network within the striatum. Thus, whereas dopamine axons are distributed densely throughout the striatum, those originating from cells in the caudal pars compacta et dorsalis of the substantia nigra and ending in the head of the caudate nucleus appear to terminate preferentially within the substance P cell clusters. These data suggest that the striatal substance P cells, which send their axons selectively to the entopeduncular nucleus and substantia nigra, but much less so the globus pallidus, are a major target of nigrostriatal dopamine transmission. This result is discussed with respect to the anatomical, neurochemical and functional organization of the striatifugal projection system.

A substance P-like peptide in bullfrog autonomic nerve terminals: anatomy biochemistry and physiology

Substance P immunoreactivity was localized to dense-cored vesicles in parasympathetic preganglionic nerve terminals in the bullfrog cardiac ganglion. Analysis with radioimmunoassay and high pressure liquid chromatography indicated that the immunoreactive substance was more similar to substance P than to substance K but was not identical to either. The bullfrog substance P was also shown to be different than kassinin, eledoisin, ranatensin, bombesin, neuromedin K and physalaemin. Although the peptide was present in most of the terminals in the ganglion and appeared to be releasable in a calcium-dependent manner, intracellular recordings from ganglion neurons during stimulation revealed no electrophysiological events that might be mediated by an endogenous peptide. In addition, the direct application of substance P to ganglion neurons generally produced no changes in membrane potential, membrane conductance, somal calcium spikes or nerve-evoked release of acetylcholine. High concentrations of substance P did cause an apparent increase in the rate of desensitization of the nicotinic receptors but there was little indication that this phenomenon would occur under physiological conditions. It is suggested that bullfrog substance P is released as a neurotransmitter but is involved in electrically silent events in the postsynaptic neurons or is acting on non-neuronal cells near the terminals. The possible implications of these results for peptidergic systems in general are discussed.

Immunohistochemical demonstration of differential substance P-, met-enkephalin-, and glutamic-acid-decarboxylase-containing cell body and axon distributions in the corpus striatum of the cat

The immunohistochemical localization of neuronal cell bodies and axons reactive for substance P (SP) and methionine-enkephalin (ME) was investigated in the corpus striatum of the adult cat brain and compared with that of glutamate decarboxylase (GAD), synthetic enzyme for gamma-aminobutyric acid. Striatal cell bodies reactive for ME could be identified only in colchicine treated cats, are medium size, ovoid striatal cells, and are found in large numbers in a more or less even distribution throughout the caudate nucleus, putamen, and nucleus accumbens. The striatal region most densely occupied by ME-immunoreactive cells is the ventral and central part of the caudate head. Modest numbers of larger ME-reactive neurons are dispersed throughout the entopeduncular nucleus and the pars reticulata of the substantia nigra. Striatal cells of medium size reactive for SP could be identified, with or without colchicine, in largest numbers in the medial half of the caudal three-fourths of the putamen and in clusters of irregular size and shape in the head of the caudate nucleus. Cells reactive for SP are also common in layer II and the islands of Calleja of the olfactory tubercle. We could not reliably visualize GAD-positive cell bodies in the striatum, even with colchicine treatment; however, they could be seen readily in all pallidal structures such as the globus pallidus, ventral pallidum, entopeduncular nucleus, and substantia nigra. Axons reactive for ME are found mainly in the globus pallidus where they form a dense and even network throughout the nucleus. The globus pallidus is almost devoid of SP reactivity except near its extreme caudal pole. Conversely, SP-immunoreactive axons form dense meshworks in the entopeduncular nucleus and substantia nigra where ME immunoreactivity is minimal. Fewer, but still ample numbers, of SP-reactive axons are present also in the ventral tegmental and retrorubral areas of the midbrain tegmentum and in the ventral pallidum of the basal forebrain, but only sparse ME-reactive axons are present in these areas. This differential distribution of SP- and ME-containing axons in the pallidal and nigral structures stands in contrast to the relatively homogeneous and dense distribution of GAD-containing axons throughout the dorsal and ventral pallidum, entopeduncular nucleus, and substantia nigra.(ABSTRACT TRUNCATED AT 400 WORDS)

Localization of substance P-like immunoreactivity in neurons and nerve terminals in the neostriatum of the rat: a correlated light and electron microscopic study

An antiserum, to substance P has been used to study the neostriatum of rats which has received intracerebral injections of colchicine. Both cell bodies and nerve fibres were found to display immunoreactivity. Some of the fibres were swollen and could be traced back to their parent cell body. Examination in the electron microscope of structures that had first been identified in the light microscope showed that there are two different types of substance P-immunoreactive cell body. The first kind (type I) of immunoreactive cell body was of medium size and had a smooth surfaced nucleus. It displayed the ultrastructural features typical of medium-size spiny neurons. Identified axons of type I neurons gave rise to immunoreactive axon collaterals within the neostriatum: boutons along these collaterals were found to form symmetrical synaptic contacts. The second kind (type II) of immunoreactive cell body was also of medium-size and had a round or oval shape, but the nucleus was deeply indented and was surrounded by a thin rim of cytoplasm. Synaptic input to this neuron was sparse and consisted of small boutons that made symmetrical contacts with the perikaryon and proximal dendrites. Many immunoreactive dot-like structures could be seen in the light microscope: upon examination in the electron microscope these were found to be boutons. All fifty-six synaptic boutons that were studied made symmetrical synaptic contacts. These boutons were indistinguishable from the boutons of axon collaterals of identified type I immunoreactive neurons. The most common postsynaptic structures were dendrites, including some dendritic spines, although synapses between immunoreactive boutons and several perikarya, and an axon initial segment were observed. The morphological features of the immunoreactive boutons in the neostriatum were very similar to one type of substance P-immunoreactive bouton in the substantia nigra and to a bouton type in the substantia nigra which is labelled following the anterograde transport of horseradish peroxidase from the striatum. It is suggested that there are two kinds of substance P-containing neurons in the striatum and that one of these is likely to belong to the medium-spiny class. The latter type of neuron is probably the source of the striatonigral substance P-containing projection and of the immunoreactive boutons within the striatum. The finding of substance P-immunoreactive synaptic boutons within the neostriatum provides a morphological basis for the view that substance P might serve as a neurotransmitter in the neostriatum.

Characterization of substance P-like immunoreactivity in peripheral sensory nerves and enteric nerves by high pressure liquid chromatography and radioimmunoassay

Material exhibiting immunoreactivity for substance P in enteric nerves, obtained from the myenteric plexus of the guinea pig small intestine, and in the peripheral ends of sensory nerves of the ureter, atrium and superior mesenteric artery, was characterized by separation by high pressure liquid chromatography, and quantified by radioimmunoassay of fractions collected from the chromatograph. Capsaicin, which depletes substance P-like immunoreactivity from sensory, but not from other substance P-containing nerves, reduced the content of substance P-like immunoreactivity in ureter, atrium and superior mesenteric artery by more than 99.5%, whereas the reduction in immunoreactive material in the myenteric plexus was less than 10%. Separation of extracts of myenteric plexus, ureter and atrium on a reversed-phase column gave major peaks corresponding to authentic substance P and minor peaks that coeluted with oxidized substance P. If the extracts were oxidized with hydrogen peroxide before chromatography, all the immunoreactivity was found in the peak corresponding to oxidized substance P. In the superior mesenteric artery extracts, in addition to the components corresponding to substance P and its oxidized derivative, there was a small intermediate peak that has yet to be identified. Physalaemin, which has been suggested to be present in mammalian nerves, was not detectable in any of the extracts. It is concluded that both enteric nerves and the peripheral processes of sensory nerves which show immunoreactivity for substance P in this species contain the authentic peptide.

Light and electron microscopic localization of substance P-like immunoreactivity in the cerebral ganglion of locust with a monoclonal antibody

The occurrence of substance P-like immunoreactivity was studied in the locust brain at light and electron microscopic level using monoclonal IgG fraction to substance P. Small immunoreactive perikarya have been found beside the medial neurosecretory cells in horizontal brain sections. Widespread immunoreactivity was also observed in the protocerebral neuropil notably in the central body and bordering on the corpora pedunculata. The reaction endproduct appeared as fine, more or less round particles in the central body, and as coarse varicosities and wavy fibres bordering the peduncles. The roundish particles probably represent nerve terminals, while the wavy fibers correspond to neural processes. In the vicinity of the beta lobe immunoreactivity was not observed. Electron microscopically, a number of immunoreactive terminals were found in the protocerebral neuropil. The reaction endproduct was accumulated mostly in large dense core granules/average diameter 80 nm/however reaction endproduct was also observed on the external surface membranes of clear vesicles and mitochondria. Our results suggest the widespread occurrence of a substance-P immunoreactive neuropeptide in the cerebral ganglia of the migratory locust.

Chemical characterization of substance P-like immunoreactivity in primary afferent neurones

Substance P-like immunoreactivity (SPLI) in rat dorsal root ganglia and dorsal spinal cord was characterized by high-performance liquid chromatography followed by radioimmunoassay. In spinal cord and ganglia, respectively, 87% and 64% of SPLI eluted with authentic SP. The remainder of the SPLI in ganglia eluted as a single peak which did not represent the sulphoxide of SP or any of its C-terminal fragments.

Reduction in basal ganglia and substantia nigra substance P levels in Huntington's disease

Substance P (SP) levels were determined by radioimmunoassay (RIA) in several regions of post-mortem brain of controls and Huntington's disease (HD) patients. In controls, highest SP levels were found in basal ganglia, substantia nigra and hypothalamus. Nigral pars reticulata contained 3--4-fold higher levels than pars compacta. In HD, SP levels were reduced in all basal ganglia and substantia nigra. The reductions ranged from 48% in caudate nucleus to over 90% in nigral pars reticulata. There were no changes in SP levels in HD frontal cortex, thalamus or hypothalamus.

Characterization and determination of neuropeptides by high-performance liquid chromatography and radioimmunoassay

A method is described for the separation and analysis of a variety of neuropeptides using reversed-phase high-performance liquid chromatography coupled with radioimmunoassay. The solvent system (an acetonitrile gradient containing 0.08% trifluoroacetic acid) allows UV detection at 206 nm, gives good resolution and, by being volatile, is readily compatible with radioimmunoassay. Three applications of the method are described: (a) thyrotropin releasing hormone immunoreactivity in the rat brain has been characterized; (b) ACTH immunoreactivity in the rat pituitary pars intermedia has been resolved into its component peptides; (c) degradation of luteinizing hormone releasing hormone in vitro has been followed.

Characterization of neuropeptides by reversed-phase, ion-pair liquid chromatography with post-column detection by radioimmunoassay. Application to thyrotropin-releasing hormone, substance P, and vasopressin

Neuropeptide contents of rat brain samples were determined by radioimmunoassay (RIA) after fractionation of tissue extracts by high-performance liquid chromatography (HPLC). Solvent systems were composed of acetic acid, acetonitrile and short-chain (5--8 carbons) alkylsulfonic acids. Separate solvent systems were developed for thyrotropin-releasing hormone, substance P. arginine vasopressin and biologic analogs, and the enkephalins. All separation systems tested gave 80--90% recovery of picogram quantities of peptides. When lyophilized, the HPLC solvents did not interfere significantly with the RIAs, allowing quantitation of tissue concentrations of isolated neuropeptides using the lyophilized eluent from the HPLC. The combination of liquid chromatography with RIA should allow for very accurate identification and quantification of peptides in biologic samples containing large numbers of potentially cross-reacting species of molecules.

Identification by high-performance liquid chromatography of immunoreactive substance P released from isolated rat spinal cord

An attempt was made to identify the immunoreactive substance P (SP) released from isolated rat spinal cords using reversed-phase high-performance liquid chromatography (HPLC) combined with radioimmunoassay (RIA) for SP. Soaking the spinal cords of newborn rats in Krebs solution containing 90 mM K+ evoked a release of immunoreactive SP as well as of GABA and glycine in a calcium-dependent manner. Capsaicin also evoked a release of immunoreactive SP but not of GABA and glycine. The immunoreactive SP released from rat spinal cords by high K+ or capsaicin was analyzed by HPLC. A single peak was detected by RIA whose elution position coincided with that of synthetic SP.

Elevation of substance P-like immunoreactivity in rat central nervous system by protease inhibitors

Several substance P-rich areas in rat CNS had increased levels of substance P-like immunoreactivity following the intraventricular injection of the protease inhibitors SQ 20881, SQ 14225, and leupeptin. There were significant differences in response patterns from region to region, possibly on account of an interaction of anatomical, biochemical, or physiological variables. Although the compound SQ 14225 appeared to be the most potent of the inhibitors examined, it had no apparent effect on CNS substance P-like immunoreactivity when administered peripherally.