Substance P: does it produce analgesia or hyperalgesia?

In the hot plate test, substance P given intravenously at doses of 5 x 10-5 and 5 x 10-4 gram per kilogram caused analgesia, while lower doses caused hyperalgesia. The influence of substance P on nociception depended on the individual mouse's sensitivity to pain (control response latency). Analgesia was produced by substance P administered to mice with high sensitivity to thermic stimulation, whereas hyperalgesia occurred in mice whose control latencies were longer than normal. This result is interpreted as an indication that substance P is capable of normalizing responsiveness to pain and could be classified as a regulatory peptide.

Effect of desamino-cholecystokinin-octapeptide (CCK-7) on the intraluminal pressure and myoelectrical activity of the gall-bladder, stomach, and small intestine in conscious dogs.

Desamino-cholecystokinin-octapeptide (CCK-7) increased the gall-bladder pressure and decreased the gastric pressure following i.v. infusion in conscious dogs. In small intestine and Heidenhain pouch CCK-7 exerted an initial excitatory effect followed by an inhibitory effect on intraluminal pressure and peristalsis. In all organs the effect of CCK-7 on pressure was correlated with a change of spike discharge. CCK-7 is more potent on gastrointestinal motor activity than a Boots preparation of pancreozymin. The results suggest that CCK-7 at doses within the physiological range could be involved in the regulation of gastrointestinal motility.

Modulation of locomotor activity by substance P in rats.

The effects of intraperitoneally or intracerebrally (DA A-10 area) administered substance P (SP) on locomotor activity of rats were studied in an exact 12-h light/12-h dark cycle changing from dark to light at 6 a.m. SP was administered either at 11 a.m. (light phase, minimal locomotor activity) or at 7 p.m. (dark phase, maximal locomotor activity). The effects of 12.5 micrograms/kg SP intracerebral and 125 micrograms/kg SP intraperitoneal were very similar. In the light phase SP produces excitation but inhibition of locomotion in darkness. Hence, the effect of SP depends on the internal mechanisms controlling motor activity and tends to level off the spontaneous circadian oscillation. We found a long lasting SP effect during both the light and dark period. The present experiments led us to the conclusion that SP has a levelling effect on locomotor activity. Probably this effect might be explained as SP's action on the dopaminergic pathway or dopamine metabolism, because the dopamine content in neurons also has a circadian rhythm.

Catecholamine release from fractionated chromaffin cells.

Bovine chromaffin cells were separated by density gradient centrifugation into subfractions. After centrifugation on a self-generating Percoll gradient (42.75% isotonic Percoll, 30,000 x g for 22 min at 20 degrees C), the chromaffin cells were found in two clearly distinguishable peaks. The peak with the lower density contained most of the noradrenaline-producing cells (approximately 80%), whereas the adrenaline-producing cells were equally distributed between the two peaks. After collection of suitable fractions from the gradient, cell cultures were obtained, which were enriched with either > 90% adrenaline- or approximately 65% noradrenaline-producing cells. When stimulated by nicotine or carbachol, the dose-response curves of both cell fractions yielded similar EC50s for the release of adrenaline and noradrenaline. On the other hand, the cells of the less dense fraction released 30% more catecholamines (adrenaline as well as noradrenaline) than the cells of the more dense fraction. It is suggested that there are subpopulations among the adrenaline- and noradrenaline-producing cells with differences in receptor-effector coupling.

Substance P and epibatidine-evoked catecholamine release from fractionated chromaffin cells.

Bovine chromaffin cells were separated by density gradient centrifugation into subfractions enriched with either > 90% adrenaline- or 70-80% noradrenaline-producing cells. Concentrations of epibatidine (an alkaloid with nicotinic receptor activity) as low as 10 nM released adrenaline and noradrenaline from both fractions of cells maintained as monolayer cultures. The maximal effect was evoked by 30 nM epibatidine and was comparable to that evoked by 10 microM nicotine. The catecholamine release from the noradrenaline fraction was 30-40% higher than from the adrenaline fraction. Initial exposure to 50 nM epibatidine reduced release induced by a second exposure to the drug. There was cross-desensitization between epibatidine and nicotine. Substance P inhibited the epibatidine-evoked catecholamine release from both fractions by up to 85% (IC50 = 3-5 microM). The release of noradrenaline was inhibited more than that of adrenaline. In addition, substance P protected the chromaffin cells against desensitization of the nicotinic receptor by epibatidine. The C-terminal heptapeptide sequence of substance P was 10 x less active, two N-terminal sequences did not modulate the catecholamine release.

Does a relationship exist between the quality of stress and the motivation to ingest alcohol?

Previous experimental findings on the relationship between emotional stress and motivation to ingest alcohol are contradictory. To obtain information about this relationship we tested the effects on alcohol consumption in rats subjected to two types of chronic unavoidable stressors, intermittent immobilization and social isolation, which differ in their influence on the functional state of the endogenous opioid system. To characterize the nature and magnitude of the stress induced by these stressors, we measured their effects on functional parameters which have a close relationship to the regulatory influence of endogenous opioid peptides (endogenous opioid dependence, pain sensitivity, blood pressure). Our investigations have shown that chronic intermittent immobilization, which induced development of endogenous opioid dependence, presumably due to activation of endogenous opioid systems, did not produce increased alcohol consumption. On the contrary, chronic social isolation, which did not induce development of endogenous opioid dependence, was followed by a significant increase in alcohol consumption. It is concluded that not all types of stress produce increased alcohol consumption, but that the effect on the endogenous opioid system may be a decisive factor in determining whether a stressor produces increased alcohol consumption.

Suc-Tyr(SE)-Met-Gly-Trp-Met-Asp-beta-phenethylamide(410): a competitive antagonist of cholecystokinin-induced contractions in smooth muscles in vitro.

Suc-Tyr(SE)-Met-Gly-Trp-Met-Asp-beta-phenethylamide(410) has been studied for its ability to antagonize contractile responses of guinea pig gall bladder, ileum and stomach muscle strips to desamino-cholecystokinin-octapeptide (CCK-7) and cholecystokinin octapeptide (CCK-8). Both CCK-7 and CCK-8 at concentrations of 10(-11)M to 10(-7)M produced dose-dependent tonic contractions in all muscle strips. Suc-Tyr(SE)-Met-Gly-Trp-Met-Asp-beta-phenethylamide (10(-8)M-10(-5)M) inhibited reversibly in a dose-dependent manner the contractile responses to CCK-7 and CCK-8. At the same concentrations the antagonist shifted to the right in parallel to the dose-response curves for CCK-7 and CCK-8 without decreasing their maximum response. Analysis of the data after Schild gave pA2 values (410 potency as antagonist) of CCK-7 in gall bladder, ileum and stomach of 8.36; 8.0 and 7.56, respectively, and pA2 values of CCK-8 of 7.64; 8.94 and 8.52, respectively. The slope of the Schild plots for both CCKs did not differ significantly from the unity, which suggests that 410 is a competitive antagonist. The antagonistic action of 410 is reversible and appeared to be specific since at concentrations of 5 X 10(-6), it had no effect on contractile responses of the gall bladder, ileum and gastric muscle strips to acetylcholine or histamine.

Responses of guinea-pig gastric, ileal and gall bladder smooth muscle to desamino-cholecystokinin-octapeptide (CCK 7).

Cholecystokinin 7 (CCK 7), a synthetic analogue of cholecystokinin/pancreozymin (CCK 33), increased in a dose-dependent manner the tone of the guinea-pig ileal, gastric and gall bladder smooth muscle preparations. In all these preparations CCK 7 was more potent than CCK 8 and CCK 33 and all three cholecystokinins were more potent than acetylcholine (ACH). Atropine and tetrodotoxin (TTX) did not influence the CCK 7 action in fundus and gall bladder muscle strips but reduced non-competitively its effect in ileal muscle strips. Neither GE 410 nor dbcGMP affected the ACH and histamine (His) response of the muscle strips but both antagonists shifted the dose-response curve of CCK 7 to the right, GE 410 (cholecystokinin antagonist) being a much more potent antagonist of CCK 7 as compared to dbcGMP. In all muscle strips a competitive action on the CCK 7 responses was found for GE 410. In gastric muscle strips a competitive influence on the CCK 7 responses was found for dbcGMP at low concentration (1 x 10(-5)M) and a non-competitive influence at high concentration (5 x 10(-4)M). The results suggest that the contractile effects of CCK 7 in the isolated ileal smooth muscle are realized by cholinergic and direct myogenic mechanisms, whereas in the isolated gall bladder and gastric smooth muscles, by a direct myogenic mechanism only.

[Differences in activity between substance P and substance P-heptapeptide as studied on the phenomenon of "gut dependence" in rats (author's transl)]. / Wirkungsunterschiede zwischen Substanz P und Substanz P-Heptapeptid, untersucht am Phänomen der "gut dependence" bei Ratten.

Naloxone causes a tonic contraction (= "gut dependence") of the ileum in morphine-dependent rats. This "gut dependence" can be antagonized by morphine (2.5 X 10(-7) g/ml). Substance P-undecapeptide (SP1-11) produces a tonic contraction of the ileum in morphine-independent rats and also in morphine-dependent rats. In the latter, this tonic contraction is comparable with the naloxone-induced contraction. When morphine-dependent rats with naloxone-induced "gut dependence" are given SP1-11, they show an additional increase in tonus followed by a rapid tonus inhibition. Substance P-heptapeptide (SP5-11) also causes a naloxone-like contraction in both the morphine-dependent and the morphine-independent rats. In contrast to SP1-11, SP5-11 produces neither a tonus superposition nor a tonus inhibition in morphine-dependent rats with naloxone-induced "gut dependence". The fact that SP5-11 does not, in contrast to SP1-11, exert these two effects (tonus superposition and subsequent tonus inhibition) is indicative of differences between the mechanisms of the two Substance P sequences.

Stress-induced dependence on endogenous opioid peptides--a fundamental process in the pathophysiology of a disturbed adaptation--its influence by substance P.

Using previous findings of stress-induced disturbances in regulation of peripheral and central function within the general adaptation process and hints from the literature to a multiple participation of opioid peptides in adaptive processes, this paper represents experimental data which gives hints to a functional relation in the etiopathophysiology between the development of stress-induced dependence on endogenous opioid peptides and stress-induced disturbances in blood pressure regulation and to the adaptive effect of substance P within the peptidergic interaction with endogenous opioid peptides and its importance for the physiology or pathophysiology of adaptive processes.

Action of substance P on neurotico-hypertensive rats.

The action of an eledoisin-hexapeptide analogue (EH) upon learning and memorising processes of 48 male Wistar laboratory rats aged between 5 and 6 months was studied and is reported in this paper. The animals suffered from neurogenic hypertension which had been experimentally induced by applying emotional stress. A comparison between the action of EH (Lys-Phe-Ile-Gly-Leu-MetNH2) and that of Substance P (Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-MetNH2) on conditioned-reflex learning in the intact rat had been reported by the authors in one of their previous papers [7]. The following results were obtained with regard to EH and its action upon rats with neurogenic hypertension. The learning process was favoured, as it had been by 2 or 3 weeks of exercise. Defective learning and memorizing process as well as impaired behavioural patterns, interpreted as neurotic phenomena, were normalized by doses of 250 microgram/kg and 500 microgram/kg. Blood pressures were reduced, depending on dosage. The action of the EH analogue used on the central nervous system was stronger than that on blood pressure. Discontinuance of peptide application was followed by the phenomenon of "state-dependent learning". The results are likely to suggest possible involvement of such peptide sequences in the regulation of processes which are relevant to the whole. That effect is of particular interest, as Substance P is under discussion as a transmitter or modulator in mammals.

Endogenous opioid dependence--a basic pathophysiological phenomenon of stress-induced and genetically fixed disturbances in adaptation--influence of substance P.

Disturbances in adaptive processes can be induced by chronic exposition to stress or can result from a genetical predisposition. Experimental data of chronically stressed Wistar rats and of spontaneously hypertensive rats (SHR) demonstrate a relation between a decreased level of substance P (SP) in adrenals, the existence of a dependence on endogenous opioid peptides and an increased regulatory level of blood pressure. The endogenous level of SP was determined by using a RIA. The dependence (physical) on endogenous opioid peptides was detected by using the method of "gut dependence". SP injection i.p. once a day for 4 d antagonized the dependence on endogenous opioid peptides and normalized the increased level of blood pressure in both animal models. Investigations on SHR had shown that the adaptive effect of SP on blood pressure and endogenous opioid dependence is bound to the premise of an acute stimulated endogenous opioid system at the moment of SP-application. Experimental findings suggest that different systems of opioid peptides take part in the etiopathogenesis of genetically predisposed hypertension of SHR and in stress-induced increase of blood pressure level of Wistar rats. The effect of SP on blood pressure and endogenous opioid dependence will be discussed as a result of the modulatory influence on the cholinergic-opioid-peptidergic interaction.

Different action of substance P on gastric and ileal smooth muscle.

On the smooth muscle of the gastrointestinal system, substance P (SP) has both a stimulatory and an inhibitory effect. The effect depends on dose and route of application (in vivo or in vitro). In vivo (stomach and ileum of dog) at low dose, SP inhibits the amplitude and frequency of peristaltic contractions without influencing tone. In higher dose, SP stimulates the tone and inhibits peristaltic contractions. In vitro (circular preparations of fundus and corpus of guinea pig stomach and longitudinal preparations of guinea pig ileum), only the stimulatory effect of SP is found. At high SP concentrations, stimulation of tone is accompanied by a postexcitatory inhibition of peristaltic contractions. The results demonstrate that there are two types of inhibitory activity of SP on contractions of smooth muscles. One of these can be seen only during in vivo experiments at low concentrations. This primary inhibitory effect could be the result of the action of SP on the neuronal elements. The other kind of inhibitory effect on contraction is a secondary effect, and is only induced at high concentrations of SP and only in connection with a stimulatory effect on tone. The secondary inhibitory effect of SP may be connected with the direct effect of SP on smooth muscle cells.

Action of substance P and an SP-hexapeptide analogue on avoidance learning in rats.

The effects of Substance P (SP) (Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-MetNH2) and of a SP hexapeptide analogue (SP-A) (Lys-Phe-Ile-Gly-Leu-MetNH2) on active avoidance learning were investigated in spontaneously hypertensive rats (SHR) and Wistar rats. Active avoidance learning was slower in SHR than in Wistar rats. SP-A "normalized" the slower active avoidance learning in SHR, whereas SP did not. Some possible causes of this difference as well as the mechanism of the normalizing effect of SP-A are discussed.

[Stress-induced changes in blood glucose level in normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) aged 13-14 and 26 weeks]. / Stressbedingte Veränderungen im Blutglucosegehalt bei normotensiven Wistar-Kyoto-Ratten (WKY) und spontanhypertensiven Ratten (SHR) im Alter von 13-14 und 26 Wochen.

In normotensive WKY-rats and spontaneously hypertensive rats relations were investigated between the general stress related behaviour of adaptation and the blood glucose level under fasting condition. In respect to the level of blood glucose differences were existent specifically depending on age and strain. Compared with WKY-rats, spontaneously hypertensive rats on the same age had shown a higher stress related increase of blood glucose level. Furthermore an age depending increase of blood glucose level was found in both SHR and WKY-rats. These differences depending on strain and age are discussed including the further results about the influence of peptides on catecholamins and blood pressure regulation.

[Effect of substance P on dopamine-beta-hydroxylase and phenethanolamine-N-methyltransferase in the adrenal glands of rats]. / Zur Wirkung von Substanz P auf Dopamin-beta-Hydroxylase und Phenylethanolamin-N-Methyltransferase in der Nebenniere der Ratte.

Resulting from literature data concerning interactions between catecholamines and Substance P (SP) the influence of SP on the activity of dopamine-beta-hydroxylase (DBH) and phenylethanolamine-N-methyltransferase (PNMT) was studied in rat adrenals. Intraperitoneal application of SP (500 micrograms/kg) to male Wistar rats 15 minutes before decapitation induced a decrease of PNMT activity in the adrenals, while DBH activity remained unchanged. After incubation of adrenals with SP (10(-6) mol/l) a decrease of activity of both PNMT and DBH was observed. The experimental results are discussed in connection with a normalizing function of SP during stress induced disorders.

[Effect of substance P on blood pressure in rats, with and without hypokinetic stress]. / Wirkung von Substanz P auf den Blutdruck von Ratten mit und ohne Hypokinesebelastung.

The effect of substance P (SP) on blood pressure was studied in normotensive rats and in rats with hypokinesia-induced hypertension. To characterize the SP effect, the influence on the blood pressure value, intra-individual variation and interindividual changes was investigated. Whereas SP corrected the hypokinesia-induced changes (increased blood pressure, increase in the intra-individual blood pressure variations) in the stressed animals, no SP effect was observed in the normotensive control rats. These findings are discussed with a view to the assumed ability of SP to act as a regulatory peptide (regulide).

Conditioned-reflex learning of normal juvenile and adult rats exposed to action of substance P and of an SP analogue.

The actions of both Substance P, a potential neurotransmitter or modulator and of a shortened analogue on learning and memorizing processes are reported in this paper. Sixty male rats, aged 22, 14, and 10 weeks, were exposed to Substance P (Arg-Pro-Gln-Gln-Phe-Gly-Leu-MetNH2) and to a shortened hexapeptide analogue (Lys-Phe-Ile-Gly-Leu-MetNH2), doses being 250 microgram/kg and 500 microgram/kg, to test their action upon learning and memorizing processes, such as acquisition, retention, and ecphoration, by means of a conditioned-reflex locomotor defense method. Response time of all three age groups as well their retention and ecphoration were normal under the impact of hexapeptide. The effects of Substance P were decline of retention in juvenile animals (10 weeks of age) and coupling between the processes of central-nervous afference synthesis, on the one hand, and the efference integral related to motoricity, on the other, in both juvenile and adult animals. A retention test was conducted and showed that discontinuation of application of either peptide over 4 d was followed by complete inhibition of ecphoration. Learning and memorising processes were restorable by reapplication of the peptides. These findings were defined as "state-dependent learning". Only slight variation under the impact of both Substance P and the analogue was recordable by non-invasive measurement of systolic blood pressure.

Nicotinic stimulation of polyphosphoinositide turnover in rat adrenal medulla slices.

When rat adrenal medulla slices, treated with atropine (1 X 10(-6) mol X l-1], were stimulated with acetylcholine (1 X 10(-5) mol X l-1), an enhanced 32P incorporation into phosphatidylinositol-bis-phosphate (PIP2) and phosphatidylphosphate (PIP) was observed. On the ather hand, stimulation of myo-[3H] inositol prelabelled slices led to a decline in radioactivity of PIP2, indicating an increased turnover of this phospholipid. A possible affection of monoesterphosphate groups of PIP2 or of both PIP2 and PIP during cholinergic nicotinic stimulation is assumed.