CGRP-like Immunoreactivity Research Articles

Erratum: Involvement of capsaicin-sensitive sensory nerves in early and delayed cardioprotection induced by a brief ischaemia of the small intestine

Early cardioprotection can be achieved by a brief ischaemia of noncardiac tissues. Our study examined whether a brief ischaemia of the small intestine induces both early and delayed cardioprotection in the rabbit and assessed the possible mechanism involved in the activation of capsaicin-sensitive sensory nerves. The plasma concentration of creatine kinase (CK) and infarct size (necrotic zone/left ventricular zone) after 30 min coronary artery occlusion and 180 min reperfusion were determined in rabbits. Infarct size was 35.5+/-6.8% in the control non-preconditioned group. Preconditioning induced by a brief period of 10-min small intestine ischaemia significantly reduced infarct size (6.5+/-1.9%, P<0.01 vs. the control non-preconditioned group) and decreased CK release (3092+/-236 and 1094+/-117 U/l for myocardial ischaemia-reperfusion and preconditioning plus myocardial ischemia-reperfusion, respectively, P<0.01), and the protection was partly abolished by pretreatment with capsaicin (50 mg/kg, s.c.) 4 days before the experiments. A brief period of anterior mesenteric artery occlusion caused an increase in the plasma level of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI), an effect which was abolished by pretreatment with capsaicin. Similar protection was shown in the animals subjected to a brief period of anterior mesenteric artery occlusion 24 h before coronary artery occlusion, and this delayed protection was also abolished partly by pretreatment with capsaicin. Capsaicin treatment (50 mg/kg, s.c.) alone also protected the ischaemic myocardium. The results suggest that brief ischaemia of the small intestine induces both early and delayed protection against reperfusion-induced myocardial injury, and the effects are, at least partly, related to the activation of capsaicin-sensitive sensory nerves.

Exercise and variations in neuropeptide concentrations in rheumatoid arthritis

The aim of the present study was to investigate the influence of an exercise program on neuropeptide concentrations, disease activity, impairments and disabilities in rheumatoid arthritis (RA). Eleven females (median age 60 years, median disease duration 6.5 years, ARA functional classes I or II) exercised 30 min daily for 4 weeks. The urine concentrations of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) and neuropeptide Y-like immunoreactivity (NPY-LI) were analyzed 1 week prior to exercise start, at exercise start, after 2 and 4 weeks of exercise, and after a 4-week follow-up period. Measurements of disease activity, aerobic capacity, grip force, limb muscle function, and activities of daily living (ADL) were also undertaken. The results indicate a decrease (md 5.64 pM to md 3.48 pM, P≤0.05) of CGRP-LI concentrations after 4 weeks’ exercise. NPY-LI concentrations remained unchanged, as did disease activity and aerobic capacity. Muscle function and ADL capacity improved significantly ( P≤0.05) after the exercise period. Only the improved grip force remained after the follow-up period. In conclusion the results indicate that decreased CGRP-LI concentration, probably reflecting a decreased sympathetic tone, follows physical exercise and suggest that regular physical activity might be important among individuals with RA to maintain a decreased sympathetic tone and less symptoms from their disease.

Substance P and calcitonin gene-related peptide expression at the extensor carpi radialis brevis muscle origin: implications for the etiology of tennis elbow.

With use of immunohistochemistry and antibodies to substance P and calcitonin gene-related peptide, nerve fibers showing substance P-like and calcitonin gene-related peptide-like immunoreactivity were demonstrated at the origin of the extensor carpi radialis brevis muscle in patients with tennis elbow (n = 6) and in healthy controls (n = 6). The nerve fibers were distributed in association with a subpopulation of small blood vessels and in nerve bundles but were not distributed in the tunica media-adventitia junction of the arterioles. There were no inflammatory-cell infiltrates and few solitary mast cells. The present study gives further evidence to previous suggestions that tennis elbow is not an inflammatory process in the sense of involving inflammatory cells. Frequent mechanical involvement affects sensory innervation, and substance P and calcitonin gene-related peptide may have various important efferent effects, including microvascular leakage and local edema formation; therefore, the observations from this study constitute a morphological substrate for possible effects of substance P and calcitonin gene-related peptide at the origin of the extensor carpi radialis brevis muscle.

Early and delayed cardioprotection by heat stress is mediated by calcitonin gene-related peptide.

Brief ischaemia or heat stress protects the myocardium against ischaemia-reperfusion injury. Heat stimulus evokes release of sensory nerve transmitters, including calcitonin gene-related peptide (CGRP). Since CGRP has been shown to play an important role in the mediation of ischaemic preconditioning, the present study examined whether early or delayed preconditioning induced by retrograde hyperthermic perfusion in vitro or by whole-body hyperthemia in vivo also involves endogenous CGRP. Isolated rat hearts were perfused in the Langendorff mode and subjected to 30 min global ischaemia and 30 min reperfusion. Heart rate, coronary flow, left ventricular pressure and its first derivatives (+/-dp/dt) were recorded and the CGRP-like immunoreactivity (CGRP-LI) content and the release of creatine kinase (CK) during reperfusion were measured. Retrograde hyperthermic perfusion (42 degrees C) for 5 min improved the recovery of cardiac function, decreased the release of CK and elevated the content of CGRP-LI in the coronary effluent. CGRP(8-37) (10(-7 mol/l), a selective CGRP receptor antagonist, abolished the cardioprotection by heat stress. Pretreatment with capsaicin (50 mg/kg s.c.), which specifically depletes sensory nerve transmitter content, abolished both the cardioprotection and the increased release of CGRP-LI. Whole-body hyperthermia (42 degrees C for 15 min) caused an increase in the plasma concentration of CGRP-LI. Early or delayed protection was shown in the hearts obtained from the animals subjected to whole-body hyperthermia 10 min or 48 h before the experiments. The early or delayed protection by heat stress was also abolished by pretreatment with capsaicin. The present study suggests that, in the rat, the early and delayed cardioprotection induced by heat stress involves endogenous CGRP.

Sensory stimulation (acupuncture) increases the release of calcitonin gene-related peptide in the saliva of xerostomia sufferers

Over the last decade, several patients afflicted with xerostomia have been treated with acupuncture. Their salivary flow rates increased significantly and the improvement lasted during a long observation period. We also found that the release of several neuropeptides in the saliva of healthy subjects can be increased by acupuncture stimulation. The concentration of vasoactive intestinal polypeptide increased significantly in the saliva of xerostomic patients after acupuncture treatment. The release of the neuropeptide calcitonin gene-related peptide (CGRP) was investigated in the saliva of xerostomic patients in order to elucidate further the mechanisms of the effect of sensory stimulation (acupuncture) on the salivary secretion. CGRP-like immunoreactivity was measured with radioimmunoassay (RIA) before and after a double series of acupuncture treatment, in stimulated saliva of 14 patients who suffered from xerostomia. The results showed that the concentration of CGRP increased significantly (P<0.001) in the saliva of these patients after the end of acupuncture treatment as compared to base-line levels. Taking into consideration the influence of CGRP on the salivary flow, as well as its trophic effect, we concluded that the increased release of CGRP could be one of the factors that affect positively the salivary flow rates of xerostomic patients who were treated with acupuncture.

Different ion channel control pH6-induced bronchoconstriction and calcitonin gene-related peptide release in the guinea-pig lung.

We have studied the bronchoconstriction and the release of calcitonin gene-related peptide-like immunoreactivity induced by perfusion of pH6 buffer in the isolated guinea-pig perfused lung. Both bronchoconstriction and peptide release were completely abolished after systemic capsaicin pretreatment. Ca(2+)-free pH6 buffer infusion also completely inhibited the bronchial response, whereas the calcitonin gene-related peptide-like immunoreactivity overflow was significantly reduced. omega-Conotoxine and omega-agatoxin IVA known as N-, L- and P-type Ca2+ channel blocker, respectively, and the Na+ channel blocker tetrodotoxin decreased significantly the pH6-induced bronchial response and calcitonin gene-related peptide like immunoreactivity overflow. Nifedipine was without influence suggesting the involvement of both P- and N-type Ca2+ channel as well as the activation of an axon reflex. Ruthenium red had a more pronounced reduction effect on the functional response than on the peptide release. Ryanodine and caffeine are both agents known to influence Ca2+ release from sarcoplasmic reticulum. Ryanodine significantly reduced both bronchoconstriction and calcitonin gene-related peptide-like immunoreactivity overflow. Caffeine as well as theophylline and the Na(+)-H+ blocker, dimethylamiloride, largely depressed the functional response while producing a significant increase of calcitonin gene-related peptide-like immuno-reactivity basal value. The pH6-induced peptide overflow was slightly inhibited after caffeine and dimethylamiloride pre-treatment whereas no significant change was observed after theophylline. It is concluded that multiple ion channels including different type of Ca2+ channels appear to participate in pH6-induced bronchoconstriction and calcitonin gene-related peptide-like immunoreactivity release in the guinea-pig lung.

Involvement of capsaicin-sensitive sensory nerves in early and delayed cardioprotection induced by a brief ischaemia of the small intestine.

Early cardioprotection can be achieved by a brief ischaemia of noncardiac tissues. Our study examined whether a brief ischaemia of the small intestine induces both early and delayed cardioprotection in the rabbit and assessed the possible mechanism involved in the activation of capsaicin-sensitive sensory nerves. The plasma concentration of creatine kinase (CK) and infarct size (necrotic zone/left ventricular zone) after 30 min coronary artery occlusion and 180 min reperfusion were determined in rabbits. Infarct size was 35.5+/-6.8% in the control non-preconditioned group. Preconditioning induced by a brief period of 10-min small intestine ischaemia significantly reduced infarct size (6.5+/-1.9%, P<0.01 vs. the control non-preconditioned group) and decreased CK release (3092+/-236 and 1094+/-117 U/l for myocardial ischaemia-reperfusion and preconditioning plus myocardial ischemia-reperfusion, respectively, P<0.01), and the protection was partly abolished by pretreatment with capsaicin (50 mg/kg, s.c.) 4 days before the experiments. A brief period of anterior mesenteric artery occlusion caused an increase in the plasma level of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI), an effect which was abolished by pretreatment with capsaicin. Similar protection was shown in the animals subjected to a brief period of anterior mesenteric artery occlusion 24 h before coronary artery occlusion, and this delayed protection was also abolished partly by pretreatment with capsaicin. Capsaicin treatment (50 mg/kg, s.c.) alone also protected the ischaemic myocardium. The results suggest that brief ischaemia of the small intestine induces both early and delayed protection against reperfusion-induced myocardial injury, and the effects are, at least partly, related to the activation of capsaicin-sensitive sensory nerves.

The cardioprotective effects of nitroglycerin-induced preconditioning are mediated by calcitonin gene-related peptide

Previous investigations have shown that endogenous calcitonin gene-related peptide (CGRP) may play an important role in the mediation of ischemic preconditioning and that nitroglycerin evokes the release of CGRP. In the present study, we examined whether nitroglycerin provides a preconditioning stimulus, and whether the cardioprotective effects of nitroglycerin-induced preconditioning involve endogenous CGRP. Thirty minutes of global ischemia and 30 min of reperfusion caused a significant impairment of cardiac contractile function and an increased release of creatine kinase. Pretreatment with nitroglycerin at the concentration of 3×10 −7 or 10 −6 M for 5 min produced a significant improvement of cardiac function and a decrease in the release of creatine kinase. The content of CGRP-like immunoreactivity in coronary effluent was increased during nitroglycerin perfusion. However, the cardioprotection afforded by nitroglycerin was abolished by CGRP-(8-37) (10 −7 M), a selective CGRP receptor antagonist. Pretreatment with capsaicin (50 mg/kg, s.c.), which specifically depletes the transmitter content of sensory nerves, also abolished the protective effects of nitroglycerin and markedly reduced the release of CGRP from the heart during nitroglycerin perfusion. These findings suggest that nitroglycerin-induced preconditioning is related to stimulation of CGRP release in rat hearts.

Identification and characterization of immunoreactive calcitonin gene-related peptide from lymphocytes of the rat

There is accumulating evidence that the immune system can produce neuropeptides. In the light of these facts, we obtained direct evidences to prove that T lymphocytes also synthesize and secrete calcitonin gene-related peptide (CGRP), a neuropeptide localized within primary sensory nerves. By using CGRP specific RIA, CGRP-like immunoreactivity (LI) was found in the extracts of rat lymphocytes from thymus and mesenteric lymph node. The intracellular concentration of lymphocyte-derived CGRP-LI of rat thymus and mesenteric lymph node was 745±39 and 447±33 fg/10 6 cells, respectively. CGRP-LI in lymphocytes was shown to co-elute with synthetic rat CGRP and sensory neuron-derived CGRP by reverse-phase HPLC. In addition, the CGRP-LI located in the T lymphocytes was also shown by immunocytochemical method examined by electron microscopy. The CGRP mRNA detected by RT-PCR was also present in these lymphocytes and was also identified to be the same one in sensory neurons. These data suggest that CGRP is synthesized and secreted in T lymphocytes of both thymus and lymph node in the rat, and this is identified to be the same one in neuronal tissue. Lymphocyte-derived CGRP may act in an autocrine/paracrine mode and play an important role in certain physiological and pathophysiological conditions.

Effect of omega-conotoxin GVIA and omega-agatoxin IVA on the capsaicin-sensitive calcitonin gene-related peptide release and autoregulatory vasodilation in rat pial arteries.

This study assesses the effect of neuronal voltage-sensitive Ca2+ channel blockers, omega-conotoxin GVIA (CTX), and omega-agatoxin IVA (AgTX) on the vasodilation and release of calcitonin gene-related peptide (CGRP), both of which were induced by either application of capsaicin or acute stepwise hypotension. Changes in pial arterial diameter were determined directly through a closed cranial window. The vasodilation of pial artery induced by either CGRP (0.1 micromol/L) or capsaicin (0.3 micromol/L) was significantly inhibited by CGRP(8-37) (0.1 micromol/L) (P < 0.05 and P < 0.05, respectively). The autoregulatory vasodilation to acute stepwise hypotension was severely attenuated by pretreatment with either CTX or AgTX. When the hypotension was kept for 2, 4, and 10 minutes, the releasable CGRP-like immunoreactivity (CGRP-LI) level (vehicle, 13.4+/-1.5 fmol/mm2/30 min) by 10 micromol/L capsaicin from the isolated pial arteries was significantly reduced in the 4- and 10-minute hypotension groups (11.3+/-1.2 fmol/mm2/30 min, P < 0.05, and 11.1+/-1.5 fmol/mm2/30 min, P < 0.05, respectively), but not in 2-min group. Moreover, the CGRP-LI level released by 10 micromol/L capsaicin (13.7+/-0.9 fmol/mm2/30 min) also was significantly depressed by pretreatment with 1 micromol/L CTX to 10.4+/-1.0 fmol/mm2/30 min (P < 0.01) and with 0.1 micromol/L AgTX to 8.7(1.7 fmol/mm2/30 min (P < 0.001), as well as by pretreatment with 10 micro-mol/L capsaicin (6.0+/-1.6 fmol/ mm2/30 min, P < 0.001). These results suggest that the neuronal N- and P-type voltage-sensitive Ca2+ channels are implicated in the release of CGRP from capsaicin-sensitive perivascular sensory nerves in response to acute hypotension, and that the released CGRP may contribute to the autoregulatory vasodilation in the cerebral microcirculation.

Unilateral injection of calcitonin gene-related peptide (CGRP) induces bilateral oedema formation and release of CGRP-like immunoreactivity in the rat hindpaw.

The contribution of calcitonin gene-related peptide (CGRP) to bilateral oedema formation in the rat hindpaw following an unilateral challenge with CGRP was investigated. Rats were injected into the left hindpaw with either saline, CGRP or a CGRP antagonist (CGRP8-37). All injections were given in a double blind fashion and in a volume of 100 microl. CGRP and CGRP8-37 were administered in concentrations of 75, 150 or 300 pmol. Volumes of the right and left hindpaw were measured every hour for 5 h by plethysmometry. Injection of CGRP 300 pmol into the left hindpaw resulted in a bilaterally increased hindpaw volume after 5 h as compared with the groups given saline. No changes were found in hindpaw volumes following the injection of either 75 or 150 pmol of CGRP or 75, 150 or 300 pmol of CGRP8-37 as compared with saline injection. To elucidate whether or not the bilateral oedema formation was related to a release of endogenous CGRP, microdialysis of the contralateral hindpaw was carried out, and concentrations of CGRP-like immunoreactivity (-LI) were determined by radioimmunoassay and high performance liquid chromatography. Injection of CGRP 300 pmol into the left hindpaw increased the release of CGRP-LI into the right hindpaw perfusate after 4 and 5 h. No changes in CGRP-LI were detected in the right hindpaw perfusate following challenge with saline or CGRP8-37. To study the contribution of the nervous system to the contralateral release of CGRP-LI, sciatic nerve ligated and intact sham-operated rats were used. Sciatic nerve ligation but not sham-operation on the non-injected side abolished the increased release of CGRP-LI following contralateral administration of CGRP 300 pmol. To study the spinal cord mechanisms resulting in the bilateral oedema formation following unilateral challenge with 300 pmol of CGRP, intrathecal pretreatment with either 10 nmol bicuculline (GABA(A) receptor antagonist) or 10 nmol CGRP8-37 was carried out. Bicuculline but not CGRP8-37 abolished the bilateral oedema formation induced by CGRP 300 pmol. In order to study the mechanisms by which administration of CGRP 300 pmol induces oedema, CGRP 300 pmol was administered concomitantly with either 300 pmol of CGRP8-37 (CGRP receptor antagonist), or 3 nmol of promethazine (H1 receptor antagonist), or 3 nmol of s(-)-propranolol (5-HT1 receptor antagonist), or 3 nmol of cyproheptadine (5-HT2 receptor antagonist) or 3 nmol of ICS 205-930 (5-HT3 receptor antagonist). Oedema formation was measured at 1, 5, 7 and 24 h. Injection of CGRP 300 pmol into the left hindpaw induced a bilateral oedema formation which was still significant at 24 h. Concomitant administration of either CGRP8-37, ICS 205-920 or cyproheptadine blocked the oedema formation at 24 h. No effect on oedema formation was found when CGRP 300 pmol was co-administered with either promethazine or s(-)-propranolol (H1 and 5-HT1 receptor antagonists, respectively). The results of the present study show that both the nervous system and local inflammatory processes contribute to bilateral hindpaw oedema formation following unilateral challenge with CGRP 300 pmol. Our results indicate that endogenous release of CGRP following inflammatory response may play an important role in inducing oedema formation.

Effects of diabetes on tissue content and evoked release of calcitonin gene-related peptide-like immunoreactivity from rat sensory nerves

We measured the evoked release of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) from sensory nerve terminals in tracheas from control and diabetic rats using an in vitro perfusion system and also the CGRP-LI content of the vagus nerve and trachea. Diabetes caused a 29% ( P<0.05) reduction in CGRP-LI content of the vagus nerve and a decrease in CGRP-LI release from nerve endings in the trachea evoked by either capsaicin (30% decrease, P<0.05) or electrical field stimulation (50% decrease: P<0.05). In contrast, there was a 50% increase in the CGRP-LI content of the unstimulated trachea. Thus, diabetes induces an impairment in neuropeptide release from peripheral terminals of sensory nerves that corresponds to decreased levels in the supplying nerve but is not reflected in tissue measurements that incorporate nerve terminals. Impaired neuropeptide release may contribute to peripheral and central sensory dysfunction in diabetic rats.

Action of substance P and interaction of calcitonin gene-related peptide and substance P on the cat antral circular muscle

The actions of substance P (SP) and calcitonin gene-related peptide (CGRP) and their interaction were examined in vitro in the feline antrum and colon. Circular muscle contraction was seen in the antrum to both peptides, but only to SP in the proximal colon. Antral contraction was enhanced when both peptides were given together. This interaction was inhibited by tetrodotoxin or atropine. SP acted at the antrum via a smooth muscle neurokinin receptor which is not a (NK)-1 receptor. SP binding was displaced by neurokinin A but not by the NK-1 receptor antagonist, CP-96345. The colonic response was inhibited by CP-96345. Immunohistochemistry revealed SP-like immunoreactivity (SP-LI) in fibers in the antral myenteric plexus and circular muscle, while CGRP-like immunoreactivity (CGRP-LI) was seen in the myenteric plexus only, without co-localization. These studies supported the hypothesis that SP acted via the NK-2 receptor at the feline circular muscle in the antrum to induce contraction and at the NK-1 receptor in the proximal colon. CGRP enhanced the effect of SP via a cholinergic pathway.

Examination of colocalization of calcitonin gene-related peptide- and substance P-like immunoreactivity in the knee joint of the dog

It is generally assumed that the majority of substance P (SP)-containing afferents are also immunoreactive for calcitonin gene-related peptide (CGRP). In order to determine whether this is also the case in articular afferents where the contents of these peptides are low, we carried out a double labeling study using Fast Blue (FB) as a retrograde tracer injected into the center of the knee joint cavity of the dog together with immunohistochemistry for SP and CGRP. After 7–36 days of survival, dorsal root ganglia (DRGs, L4–S1) were removed. Labeled cells were found mainly (94%) in L5 - 6 DRGs, and SP- and CGRP-like immunoreactivity was found in about 17 and 29% of FB-labeled cells, respectively. The coexistence of SP and CGRP was observed in 10.4% of articular afferents and only 62.7% of SP-positive articular neurons contained CGRP, a much lower ratio than in other afferents of the dog such as testicular afferents. Our data suggest that these peptides are not always released together and that they do not always work together in the joint under normal conditions.

Alteration of capsaicin and endotoxin-induced calcitonin gene-related peptide release from mesenteric arterial bed and spinal cord slice in 18-month-old rats.

In the present study, we investigated the changes in capsaicin- and endotoxin-induced calcitonin gene-related peptide (CGRP) release from mesenteric arterial bed (MAB) and spinal cord slices (SCS) in 2-month-old and 18-month-old Wistar rats. The isolated MAB or SCS was perfused or incubated in vitro. The CGRP-like immunoreactivity in perfusate or supernatant was measured by radioimmunoassay. The results showed that endotoxin triggered CGRP release from isolated rat MAB and SCS, which represent the peripheral and central terminals of CGRP-containing sensory nerves, respectively. Either basal or stimulated CGRP release induced by capsaicin and endotoxin was significantly decreased as the rats aged from 2 to 18 months. The basal CGRP release was 14.9 +/- 1.8 and 5.8 +/- 1.0 pg/ml from MAB and 3.50 +/- 0.54 and 1.78 +/- 0.16 pg/ml/mg from SCS in 2-month-old and 18-month-old rats, respectively. The release of CGRP evoked by capsaicin (10(-7) mol/L) and endotoxin (1 to approximately 5 microg/ml) from MAB and SCS was significantly decreased by more than 50% in 18-month-old rats. These data suggest that both the basal and capsaicin- or endotoxin-stimulated CGRP release from MAB and SCS display a significant decrement in aged rats that may have some physiological, pathological, and behavioural relevance in age-related diseases.

Sequential changes in CGRP-like immunoreactivity in NIDDM model Otsuka Long-Evans Tokushima Fatty (OLETF) rat pancreatic islets.

We describe the changes in B cells and calcitonin gene-related peptide (CGRP)-like immunoreactivity in the pancreatic islets of Otsuka Long-Evans Tokushima Fatty (OLETF) rats, an animal model of human non-insulin-dependent diabetes mellitus (NIDDM). In the OLETF rat pancreatic islets, CGRP immunoreactivity was seen in the nerve fibers with multiple varicosities and in endocrine cells that were identical to somatostatin-containing cells, but some somatostatin-immunoreactive cells lacked CGRP immunoreactivity. In the OLETF rats, plasma insulin levels were significantly higher than in the control rats (Long-Evans Tokushima Otsuka; LETO) only at 7 weeks of age. From 7 through 32 weeks of age, OLETF rats had a greater B-cell area than LETO rats. The length of CGRP-immunoreactive nerve fibers per area and the numbers of CGRP-immunoreactive cells per area did not differ between the groups at 7 weeks of age. After 16 weeks of age, both of these CGRP parameters in the OLETF rats became increasingly higher than in the LETO rats. These results suggest that CGRP is a B-cell growth factor and probably an inhibitory factor for insulin secretion.

Induction of Calcitonin Gene-Related Peptide-like Immunoreactivity in Hippocampal Neurons Following Ischemia: A Putative Regional Modulator of the CNS Injury/Immune Response

Calcitonin gene-related peptide (CGRP) is a potent vasodilator and immune cell modulator. In two studies within the hippocampal formation (HF), CGRP-like immunoreactivity (CGRP-LI) was increased in the inner molecular layer of the dentate gyrus after adrenalectomy and in mossy cells after colchicine-induced destruction of granule neurons. Given the increase in CGRP-LI following damage to the granule cell region of the HF, we investigated another trauma model, ischemia, that targeted different areas of the HF, CA1 region, and subiculum to ascertain the regional expression of this peptide after insult. Following ischemia, light microscopic evaluation showed CGRP-LI in basket cell-like neuronal perikarya within the dorsal subiculum and CA1 region of the hippocampus and in varicose fibers within the CA2 region of the hippocampus. Control rats rarely expressed CGRP-LI within neurons in these regions. In ischemic brains, double-labeled immunocytochemistry with antibodies to various neural markers demonstrated co-localization of CGRP-LI primarily within surviving subicular and CA1 cells resembling interneurons containing parvalbumin-LI or calbindin-LI. Electron microscopic analysis of the CA1 region from ischemic brains showed that CGRP-LI was contained in terminals with numerous small synaptic vesicles that formed symmetric synapses with perikarya and large dendrites of pyramidal cells, some of which were degenerating. Collectively, the data from this study and our previous study indicate that damage induces CGRP-LI expression in interneurons and nonprincipal cells in the area of damage, and we hypothesize that CGRP expression in surviving neurons within damage-related regions of the hippocampus is likely to be an important, and possibly a protective, component of the response of the nervous system to injury.

Labeling of calcitonin gene-related peptide and substance P increases in subnucleus caudalis of rabbit during maxillary sinusitis

Calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) and substance P-like immunoreactivity (SP-LI) were evaluated in subnucleus caudalis following induction of sinusitis. Three days after induction, intensity of labeling for CGRP-LI and SP-LI increased in ipsilateral subnucleus caudalis. Labeling for CGRP-LI and SP-LI appeared normal at later time points (20 and 28 days). Early changes in these neuropeptides may contribute to the inflammatory process and painful symptoms accompanying sinusitis.

Increased concentrations of calcitonin gene-related peptide-like immunoreactivity in rat brain and peripheral tissue after ischaemia: correlation to flap survival.

The effects of experimentally induced ischaemia after free-flap surgery on concentrations of neuropeptide Y (NPY), neurokinin A (NKA), substance P (SP) and calcitonin gene-related peptide (CGRP)-like immunoreactivity (-LI) were studied in flap tissue and in different regions of the rat brain (striatum, hippocampus, pituitary, hypothalamus, frontal and occipital cortex). Ten days after the operation, CGRP-LI and NKA-LI were decreased in the ischaemic tissue but increased in the surrounding tissue. In the brain, CGRP-LI was increased in five of six regions analysed, with the exception of the striatum. SP-LI and NKA-LI were increased in the pituitary and hippocampus, but decreased in other brain regions. Changes of CGRP-LI in the brain correlated positively with the CGRP-LI concentrations in the surrounding flap tissue and the CGRP-LI concentrations in the ischaemic flap tissue with the extent of flap survival. The results of the present study suggest that higher concentrations of CGRP-LI are related to tissue survival and that endogenous CGRP has a regulatory effect in ischaemia.

Calcitonin gene-related peptide: distribution and effects on spontaneous rhythmic activity in embryonic chick spinal cord

Immunohistochemical and in vitro electrophysiological techniques were utilized to examine the distribution and possible role of calcitonin gene-related peptide (CGRP) in the spinal cord of the developing chick. CGRP-like immunoreactivity first appeared in the lateral motor column of the lumbosacral spinal cord at embryonic day 6 followed by the emergence of fiber immunoreactivity in the dorsal horn at embryonic day 11. A rostrocaudal survey of the cervical to lumbosacral spinal cord in embryonic day 18 chick demonstrated robust CGRP-like immunoreactivity at all levels in both putative motor neurons and dorsal horn fibers. Additionally, small immunoreactive lamina VII neurons were observed in sections of lumbosacral cord. In the embryonic day 10 (E10) in vitro reduced spinal cord preparation, bath application of the calcitonin gene-related peptide antagonist human α-CGRP fragment 8-37 decreased the frequency and increased the duration of episodes of spontaneously occurring rhythmic activity. Conversely, application of α or β forms of calcitonin gene-related peptide increased the frequency of the rhythmic episodes. The electrophysiological results suggest there is a constitutive release of calcitonin gene-related peptide contributing to the spontaneous rhythmic activity. Immunohistochemical results from E10 animals suggest that CGRP-like immunoreactive putative motoneurons may be the source of the released CGRP.