Release Of Substance P-like Immunoreactivity Research Articles

Hypertonic KCI, NaCl and capsaicin intracamerally causes release of substance P-like immunoreactive material into the aqueous humor in rabbits.

We have investigated release of substance P-like immunoreactivity (SPLI) into the anterior chamber of the rabbit eye evoked by stimuli which cause non-cholinergic miosis. In a recent study such miosis was reported to be blocked by the substance P analogue (D-Arg1, D-Pro2, D-Trp7,9, Leu11)-SP. Mechanical intracranial antidromic trigeminal nerve stimulation caused marked SPLI release presumably from primary sensory nerve endings in the anterior part of the eye. Intermittent stimulation for 20 min was not more effective than stimulation for 10 min. Intracameral injection of either 20 microliters 4.65 M KCI, 20 microliters 4.65 M NaCl or 100 micrograms capsaicin also caused SPLI release. Intracameral injection of 70 microliters 150 mM KCI, 28 micrograms prostaglandin E1 or 200 micrograms of compound 48/80 did not cause detectable SPLI release.

In vitro release of immunoreactive substance P from putative afferent nerve endings in bovine pia arachnoid

The release of substance P-like immunoreactivity was examined using bovine pia arachnoid and its attendant blood vessels in vitro. At concentrations of 20,51 and 100 mM, potassium ions evoked the release of substance P-like immunoreactivity in a dose-dependent manner. The drug capsaicin released substance P at concentrations greater than 10 −8 M. Both potassium- and capsaicin-induced release were abolished by omitting calcium ions from the superfusion buffer. When subjected to separation by reverse phase high performance liquid chromatography, the superfusate from capsaicin perfused tissues contained a peak of immunoreactivity which migrated at the retention time corresponding to substance P. During basal and stimulated states, the percent endogenous substance P released ranged between 0.4–6.5 × 10 −2 and 1.3–11.6 × 10 −2 per minute, rates comparable to those previously reported by others using slices of dorsal horn or spinal cord segments. The immunoreactivity measurable in the conditioned buffer probably reflected release from afferent nerve endings in as much as most of the substance P immunoreactivity in pia arachnoid arises from trigeminal ganglia. Release of substance P, a cerebrovasodilating peptide from perivascular nerve endings in pia arachnoid suggests a possible role for substance P in the pathophysiology of disorders associated with pain of cerebrovascular origin.

Evidence that substance P is a mediator of antidromic vasodilatation using somatostatin as a release inhibitor

The effect of somatostatin on nerve-induced vasodilatation and the release of substance P (SP) was studied in the dental pulp of anesthetized cats. Changes in pulpal blood flow were determined by measuring the rate of disappearance of a local depot of radioactive tracer. The release of SP was studied indirectly by determining the residual amounts of substance P-like immunoreactivity (SPLI) in the pulps by radioimmunoassay. Electrical stimulation (3 min at 10 V, 15 Hz and 5 ms) of the distal end of the cut inferior alveolar nerve (IAN) increased pulpal blood flow. After pretreatment (10 min) with somatostatin (30 pmol/min) similar nerve stimulation was without effect on pulpal blood flow. Intra-arterial infusion of somatostatin (30 pmol/min) had no effect on pulpal blood flow and did not influence the vasodilator response to SP. Following IAN stimulation (3--45 min) and subsequent incubation (30 min, 37 degrees C) of the lower canine teeth, the SPLI levels in ipsilateral pulps were significantly lower (47.5% reduction) than those in contralateral, unstimulated controls. In cats pretreated with somatostatin (30 pmol/min for 10 min, i.a.) similar nerve stimulation (3 min) did not reduce the pulpal SPLI levels as compared to controls. The results show that nerve-induced vasodilatation and release of SPLI are inhibited by somatostatin. They are consistent with the hypothesis that vasodilatation in the cat dental pulp produced by stimulation of the IAN is mediated by substance P.

Tissue concentration and release of substance P-like immunoreactivity in the dental pulp.

The concentration of substance P-like immunoreactivity (SPLI) was determined in dental pulps from cat, dog and man by radioimmunoassay. Pulps from mature cats showed the highest SPLI-levels (mean 32 pmol/g); these are comparable to or higher than those found in any other organ outside the central nervous system. The SPLI concentrations were lower in pulp from immature teeth. The immunological and chromatographic behaviour of the pulpal SPLI from cat and man resembled that of synthetic substance P (SP), indicating that the assayed substance is closely related to or identical with SP. Release of pulpal SPLI in canine teeth was evoked by stimulation of the inferior alveolar nerve in anaesthetized cats. In 9 of 16 experiments the amounts of SPLI found in pulp suprafusates following stimulation (4-31 fmol) were larger than those in unstimulated controls (0-7 fmol). Stimulation also reduced the pulpal tissue concentration of SPLI to 60% of that in homologous control pulps. The high concentration of SPLI found in the dental pulp and the demonstration of nerve-induced release strengthen the hypothesis that SP serves some function in the dental pulp.

Striatal substance P-like immunoreactivity: Characterization by high-performance liquid chromatography and aspects of subcellular distribution and in vitro release by potassium

Substance P-like immunoreactivity (SPLI) in acetic acid extracts of striatum elutes in a single peak that corresponds to that for synthetic substance P, using reverse-phase high-performance liquid chromatography. This finding suggests that striatal SPLI, as detected with the radioimmunoassay used here, largely represents a single molecular species. Striatal SPLI is highly concentrated in the crude mitochondrial fraction (P2); over 70% of this P2-SPLI is recovered in the synaptosomal subfraction. The potassium-induced release of SPLI from striatal tissue in vitro occurs only when enough extracellular calcium is available. These data suggest that substance P in striatal neurons may participate in neural transmission locally, exclusive of its probable role in maintaining the substance P supply to nerve terminals in the substantia nigra.

Release of substance P-like immunoreactivity by a meal and bombesin

Release of substance P-like immunoreactivity by a meal and bombesin

Release of substance P-like immunoreactivity into the antral lumen of cats.

SPLI can be detected in antral perfusates of cats. Experiments were performed in anesthetized cats provided with antral pouches. The pouches were perfused with 0.1 M HCl and 0.15 M NaCl. The concentration of SPLI in the perfusates was determined by radioimmunoassay. Basal output varied between 0--60 pg/min. Electrical vagal stimulation (2--10 Hz) caused release responses varying between 100--800 pg. Ach given i.v. or intraantrally also released SPLI into the antral lumen as well as adrenaline given i.v.

Release of substance P-like immunoreactivity from isolated spinal cord of newborn rat.

EVIDENCE is accumulating that substance P (H–Arg–Pro–Lys–Pro–Gln–Gln–Phe–Phe–Gly–Leu–Met–NH2)1 is an excitatory transmitter released from primary afferent nerve terminals in mammalian spinal cord (for reviews see refs 2 and 3). An important criterion for identification of a transmitter is the demonstration of release of the candidate substance from the nerve terminals in response to presynaptic stimulation. We report here the release of substance P-like immunoreactivity from isolated rat spinal cord into the bathing fluid during stimulation of dorsal roots.