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At least 595 records · Page 33Linked to original sources
PubMed1993

Epidermal growth factor and transforming growth factor-alpha directly inhibit parietal cell function through a similar mechanism.

Epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) are naturally occurring peptides which are present throughout the gastrointestinal tract and are capable of inhibiting gastric acid secretion. Although previous studies have suggested that TGF-alpha may serve as an autocrine factor regulating parietal cell function, the cellular mechanisms by which it exerts its inhibitory action have not been fully elucidated. In addition, no systematic comparison has been undertaken of the effects of EGF and TGF-alpha on parietal cell function. The aims of the present studies were to compare the actions of EGF and TGF-alpha on basal and stimulated acid secretion by isolated rabbit parietal cells and to elucidate the intracellular mechanisms by which these growth factors inhibit acid secretion stimulated by agents that activate the adenylate cyclase and cyclic AMP second messenger system. Although EGF and TGF-alpha did not alter basal parietal cell function, they both inhibited histamine-stimulated [14C]aminopyrine accumulation in a identical time- and dose-dependent fashion. The maximal effect of approximately 40% inhibition for histamine-stimulated action was achieved with concentrations of 10(-6) M for both EGF and TGF-alpha. The inhibitory effect of EGF and TGF-alpha appeared to be at the postreceptor level as neither growth factor significantly altered binding of histamine to its receptor (H2) on parietal cells. Consistent with this postulated mechanism of action, both EGF and TGF-alpha dose-dependently inhibited forskolin-stimulated aminopyrine uptake with IC50 similar to those required for inhibiting the stimulatory effect of histamine. Of note, neither growth factor inhibited parietal cell activity stimulated by dibutyryl cyclic AMP.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylate Cyclase Toxin↗
PubMed1994

The responsiveness of cerebral cortical adrenergic receptors after chronic administration of atypical antidepressant mianserin.

The aim of this study was to evaluate the effect of mianserin, a second generation tetracyclic antidepressant agent, on the receptors' and second messenger systems related to noradrenergic transmission in the cerebral cortex of the rat. In in vitro experiments we confirmed that mianserin binds with equal potency to alpha 1- and alpha 2-adrenoceptors and does not affect beta 1-adrenoceptors. It inhibited the noradrenaline-stimulated inositol phosphate accumulation and did not change the cyclic AMP responses to noradrenaline and isoproterenol. The drug attenuated the inhibitory action of PKC activator, TPA, on the noradrenergic response from alpha 1-adrenoceptor and the potentiating action of TPA on the cyclic AMP stimulated with noradrenaline and isoproterenol. In chronic experiments we have found that, in contrast to most antidepressants, chronic treatment with mianserin does not produce strong beta-downregulation, but increases the maximal inositol phosphate response from alpha 1-adrenoceptor. The results indicate that alpha 1-upregulation might be a characteristic of those efficient antidepressant drugs which do not produce a strong beta-downregulatory effect.

Animals↗
PubMed1993

Effect of repeated organophosphate administration on carbachol-stimulated phosphoinositide hydrolysis in the rat brain.

The effects of repeated exposure to two organophosphates on the turnover of phosphoinositides, the second messenger system coupled to the M1 and M3 subtypes of muscarinic receptors, were examined in the rat hippocampus. Repeated diisopropylfluorophosphate (DFP) exposure (0.2-0.8 mg/kg, SC) decreased brain acetylcholinesterase activity and muscarinic receptor density. The incorporation of [3H]myoinositol into brain slices was also decreased. Phosphoinositide turnover was measured as the accumulation of [3H]inositol phosphates (IP) in the presence of lithium. DFP did not affect basal IP accumulation, but decreased carbachol-stimulated IP accumulation in the hippocampus after 0.4 and 0.8 mg/kg. The effects of repeated disulfoton administration (2.0 mg/kg, IP) were also examined in the hippocampus. Similar to DFP, repeated disulfoton exposure decreased acetylcholinesterase activity, receptor density, and carbachol-stimulated IP accumulation. The incorporation of myoinositol, however, was increased in disulfoton-treated rats. These data indicate that repeated organophosphate exposure results in a functional decrease in muscarinic receptor activity, as well as changes in myoinositol incorporation into phospholipids.

Animals↗
PubMed1993

Light evoked inositol trisphosphate release in the rat retina in vitro.

Light exposure not only elicits a photic response but may also alter the metabolism and functional properties of the retina. This may be evoked by the stimulation of phospholipid derived second messenger systems. In this study, we investigated the light-evoked release of inositol 1,4,5-triphosphate in the isolated rat retina in vitro by means of high performance liquid chromatography (HPLC) detection. After prelabelling of isolated retinae with tritiated myo-inositol in darkness, they were exposed to no light or to white fluorescent light of 10,000 lux illuminance for 3,5 and 10 sec, respectively. We observed a 200% increase in the release of inositol 1,4,5-trisphosphate compared to basal values in darkness after 3 sec of light exposure with a decline after 5 sec and a return to basal values after 10 sec indicating a rapid breakdown of inositol 1,4,5-trisphosphate. Our data confirm previous studies in the amphibian retina and photoreceptors and demonstrate for the first time a light evoked inositol 1,4,5-trisphosphate release in the mammalian retina.

Animals↗
PubMed1994

Receptor binding profiles of KB-5492, a novel anti-ulcer agent, at sigma receptors in guinea-pig brain.

We studied the receptor binding profile of 4-methoxyphenyl 4-(3,4,5-trimethoxybenzyl)-1-piperazine acetate monofumarate monohydrate (KB-5492), a novel anti-ulcer agent, for the sigma receptor in guinea-pig brain membranes. KB-5492 selectively inhibited specific [3H]1,3-di(2-tolyl)guanidine (DTG) binding to the sigma receptor (IC50 = 3.15 microM) with a pseudo-Hill coefficient of 0.33. Computer-assisted analysis revealed that KB-5492 bound to high- and low-affinity sites. Although KB-5492 had weak affinity for alpha 2-adrenoceptors at 10 microM, it was almost inactive at a concentration of 10 microM in 33 other binding assays for receptors, second messenger systems and ion channels. sigma Receptor ligands such as haloperidol, DTG, (+)-3-(3-hydroxyphenol)-N-(1-propyl)piperidine (3-PPP), rimcazole and (-)-3-PPP inhibited specific [3H]DTG binding and their IC50 values were 0.003, 0.044, 0.33, 0.67 and 1.03 microM, respectively. On the other hand, various anti-ulcer agents such as cetraxate, cimetidine, omeprazole, sofalcone, sucralfate, teprenone and troxipide could hardly displace specific [3H]DTG binding at 100 microM. Scatchard-Rosenthal analysis indicated that [3H]DTG bound to a single site, and KD and Bmax values for [3H]DTG were 87.3 nM and 679.3 fmol/mg protein, respectively. KB-5492 significantly decreased the Bmax value, but did not affect the KD value. In contrast, haloperidol and DTG significantly increased the KD values, but did not affect the Kmax values. These findings indicate that KB-5492 selectively bound to the [3H]DTG-labeled sigma receptor and that other anti-ulcer agents had little affinity for the sigma receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Lysophosphatidates bound to serum albumin activate membrane currents in Xenopus oocytes and neurite retraction in PC12 pheochromocytoma cells.

Serum contains a factor that co-purifies with albumin and causes neurite retraction in PC12 cells, inhibits the proliferation of tumor cells in vitro, and activates the phosphatidylinositol/Ca2+ second messenger system in Xenopus oocytes and other cells. The activity of serum albumin depends on several lysophospholipids bound to albumin. Thin layer chromatographic analysis of the lipids extracted by methanol from serum albumin revealed over a dozen components, several of which evoked oscillatory currents in oocytes. In contrast to serum albumin, most of these lipids were absent in plasma, which lacks the biological activity. The most abundant naturally occurring active component was identified as stearoyl-lysophosphatidic acid. Synthetically prepared lysophosphatidates reproduced the biological activities of the natural serum factor. Adding synthetic lysophosphatidates to inactive fatty acid-free albumin restored activity to the albumin, making the active factor nondialyzable against aqueous solvents and protecting against digestion by various lipases. Since the biologically active lysophosphatidates were produced during blood clotting, in the presence of platelets, and lysophosphatidates have been shown previously to activate platelets, we propose that lysophosphatidates may play an important role in linking platelet activation to receptor-mediated tissue regeneration.

Animals↗
PubMed2001

Protein kinase C regulation of dopamine transporter initiated by nicotinic receptor activation in slices of rat prefrontal cortex.

We previously reported that activation of nicotinic receptors causes an enhancement in amphetamine-stimulated release of dopamine via its transporter from slices of prefrontal cortex, but no such enhancement of release from slices of nucleus accumbens or striatum. The nicotinic receptors mediating the enhancement most likely contain alpha4 and beta2 subunits based upon pharmacological characterization. In this study, we sought to characterize the second messenger systems associated with the nicotine-mediated response. Sodium channel involvement was confirmed by the observation that tetrodotoxin blocked nicotine-mediated enhancement, whereas veratridine or elevated K(+) mimicked the enhancement seen with nicotine. Inclusion of EGTA blocked nicotine-mediated enhancement, suggesting that, even though no exogenous Ca(2+) was added, endogenous stores were required for the enhancement. The enhancement by nicotine was also abolished by the L-type voltage-dependent calcium channel (VDCC) antagonist nitrendipine, but not by the N-type VDCC antagonist omega-conotoxin GVIA. Finally, inhibition of protein kinase C also abolished the nicotine-mediated enhancement of amphetamine-stimulated dopamine release, whereas inhibitors of Ca(2+)/calmodulin kinase II did not. These findings establish that nicotine can exert selective effects on dopamine transporter activity in prefrontal cortex, an area involved in cognition and learning.

Alkaloids↗
PubMed1991

Effects of peptides of the secretin-glucagon family and cyclic nucleotides on tyrosine hydroxylase activity in sympathetic nerve endings.

Previous studies have shown that certain peptides of the secretin-glucagon family stimulate tyrosine hydroxylase activity in sympathetic neurons of the superior cervical ganglion and three of its end organs, i.e., the iris, pineal gland, and submaxillary gland. To determine whether a similar regulation occurs in other sympathetic neurons, the effects of two of these peptides, secretin and vasoactive intestinal peptide, were examined in the right cardiac ventricle of the rat, a tissue innervated primarily by the middle and inferior cervical ganglia. Both peptides stimulated tyrosine hydroxylase activity, measured in situ, in this tissue. In addition, several second messenger systems were investigated as possible mediators of this peptidergic stimulation of tyrosine hydroxylase activity in autonomic end organs. 8-Bromoadenosine 3',5'-cyclic monophosphate and forskolin elevated tyrosine hydroxylase activity in slices of both the right ventricle and the submaxillary gland. 8-Bromoguanosine 3',5'-cyclic monophosphate also stimulated tyrosine hydroxylase activity in both tissues, whereas nitroprusside stimulated activity only in the submaxillary slices. Furthermore, the phosphodiesterase inhibitors 3-isobutyl-1-methylxanthine and/or Ro 20-1724 potentiated the stimulation by secretin, as well as the stimulations by forskolin and nitroprusside. Phorbol 12,13-dibutyrate also stimulated tyrosine hydroxylase activity in cardiac and submaxillary slices; however, no potentiation of these effects was seen following addition of either phosphodiesterase inhibitor. These data, taken together with those of previous studies, suggest a role for a cyclic nucleotide, probably adenosine 3',5'-cyclic monophosphate, in the peptidergic stimulation of tyrosine hydroxylase activity in sympathetic nerve terminals.

1-Methyl-3-isobutylxanthine↗
PubMed1991

Neuronal localization of cannabinoid receptors and second messengers in mutant mouse cerebellum.

Four lines of mutant mice were used to investigate (1) the neuronal localization of cannabinoid receptors in the cerebellar molecular layer and (2) the anatomical association of these receptors with elements of the two second messenger systems in the brain. Two of the mutant lines--Purkinje cell degeneration and nervous--are selectively deficient in Purkinje cells; the other two--weaver and reeler--are deficient in granule cells. In the heterozygous mice, [3H]CP 55,940 binding to cannabinoid receptors was discretely and densely localized to the molecular layer, as was [3H]forskolin binding to adenylate cyclase and [3H]phorbol 12,13-dibutyrate binding to protein kinase C, a component of the phosphoinositide cycle. [3H]CP 55,940 and [3H]forskolin binding was selectively reduced in weaver and reeler homozygous mice but unchanged in Purkinje cell deficient and nervous homozygotes. No decreases in [3H]phorbol 12,13-dibutyrate binding were found in any of the homozygous mutants relative to the heterozygous littermates. The results suggest that cannabinoid receptors and adenylate cyclase are localized to granule cell axons in the molecular layer, whereas protein kinase C is equally distributed in parallel fibers and Purkinje cell dendrites.

Adenylyl Cyclases↗
PubMed1993

Characterization of neurotensin-stimulated phosphoinositide hydrolysis in brain regions of long sleep and short sleep mice.

Previous studies have shown that long sleep (LS) and short sleep (SS) mice, which were selectively bred for differences in brain sensitivity to ethanol, differ in neurotensin (NT) receptor densities in specific brain regions. The present study was designed to determine whether these receptor differences mediate differences in the effects of NT on the phosphoinositide (PI) second messenger system in four brain regions from LS and SS mice. Baseline and NT- or carbachol-stimulated PI hydrolysis were Ca(2+)-dependent. Stimulation of PI hydrolysis by NT or carbachol was region specific; NT effect was approximately equal in ventral midbrain (VMB) and entorhinal cortex (EC) with slightly less stimulation in nucleus accumbens (NA) and no effect in the cerebellum (CE). Carbachol-enhanced PI hydrolysis was greatest in the VMB followed by EC and NA with no stimulation in the CE. There were no between line (LS vs. SS) differences in carbachol effects, but stimulation by NT was greater in EC and NA from LS than from SS mice. Ethanol enhanced NT-stimulated, but not carbachol-stimulated, PI metabolism in SS and LS NA brain slices. Results with levocabastine, an inhibitor of low-affinity NT receptor (NTL) binding, suggest that NT may stimulate PI hydrolysis via NTL, as well as high-affinity receptors.

Animals↗
PubMed1993

Effects of tacrine on brain muscarinic-receptor-mediated second-messenger signals.

The purpose of this study was to investigate the effects of 9-amino-1,2,3,4-tetrahydroacridine (THA; Tacrine) on muscarinic-receptor-linked second-messenger systems in rat brain and to determine the selectivity and mechanisms of these effects. Both competitive and noncompetitive antagonism was revealed in saturation radioligand binding studies performed in cortical and striatal tissue, depending on THA concentration. Micromolar THA concentrations blocked muscarinic-receptor-mediated inhibition of cAMP formation and stimulation of phosphoinositide (PI) hydrolysis with poor selectivity between the two responses. While both responses were blocked in the same concentration range (4-60 mumol/l), non-competitive antagonism of PI hydrolysis occurred at THA concentrations greater than 10 mumol/l while competitive antagonism was displayed for the cAMP response at concentrations of THA up to 40 mumol/l. THA was equally effective at inhibiting PI hydrolysis stimulated by histamine, phenylephrine or oxotremorine-M, when these agonists were employed in concentrations equal to their EC50s for the response. THA did not antagonize PI hydrolysis mediated by the quisqualate receptor at any agonist concentration used. Furthermore, THA blocked carbachol- but not morphine-induced inhibition of forskolin-stimulated cAMP formation in the striatum.

Animals↗
PubMed1990

Bradykinin induces inositol 1,4,5-trisphosphate-dependent hyperpolarization in K+ M-current-deficient hybrid NL308 cells: comparison with NG108-15 neuroblastoma x glioma hybrid cells.

External application of bradykinin (BK) to mouse neuroblastoma X mouse fibroblast hybrid NL308 cells and mouse neuroblastoma X rat glioma hybrid NG108-15 cells produced a transient outward (hyperpolarizing) current. In NG108-15 cells, BK also induced an inward (depolarizing) current associated with a decrease in input membrane conductance, which results from the inhibition of a voltage-sensitive potassium current, the M-current. However, in NL308 cells, either no depolarization was elicited by BK or, even if the BK-induced depolarization was evoked, it was associated with an increased conductance. To explain the above difference, the intracellular second messenger system of NL308 cells was examined in detail. BK induced the rapid accumulation (three- to fivefold higher than the control level) of inositol 1,4,5-trisphosphate (InsP3) in NL308 cells. The cytosolic Ca2+ concentration was also elevated to 540 nM from 180 nM at a basal level. This seems to be enough to activate a voltage-independent and Ca2(+)-sensitive K+ current, resulting in the hyperpolarization. Intracellular injection of InsP3 replicated the hyperpolarization. NL308 cells possess protein kinase C (C-kinase), with specific activities of C-kinase in cytosolic and membrane fractions being 233 and 24 pmol/min/mg protein, respectively. The activity associated with particulates became higher after phorbol dibutyrate (PDBu) treatment. But NL308 cells did not show the characteristic inward relaxation by step hyperpolarizations and the outward rectification in the current-voltage relationship, indicating that the M current is deficient in NL308 cells. Therefore, application of PDBu failed to mimic the inward current. The results suggest the role of InsP3 and C-kinase in controlling two K+ currents.

Animals↗
PubMed2002

Learning-induced reduction in post-burst after-hyperpolarization (AHP) is mediated by activation of PKC.

We studied the role of protein kinase C (PKC) and protein kinase A (PKA) in mediating learning-related long lasting reduction of the post-burst after-hyperpolarization (AHP) in cortical pyramidal neurons. We have shown previously that pyramidal neurons in the rat piriform (olfactory) cortex from trained (TR) rats have reduced post-burst AHP for 3 days after odour-discrimination learning, and that this reduction is due to decreased conductance of calcium-dependent potassium current. In the present study, we examined whether this long-lasting reduction in AHP is mediated by second messenger systems. The broad-spectrum kinase inhibitor, H7, increased the AHP in neurons from TR rats, but not in neurons from pseudo-trained (pseudo-TR) and naive rats. Consequently, the difference in AHP amplitude between neurons from TR and control animals was diminished. This effect was also obtained by application of the specific PKC inhibitor, GF-109203x. The PKC activator, 1-Oleoyl-2-acetyl-sn-glycerol (OAG), significantly reduced the AHP in neurons from naive and pseudo-TR rats, but not in neurons from TR rats, so that the difference between the groups was abolished. The PKA-specific inhibitor, H-89, increased the AHP in neurons from all groups to a similar extent, and the difference in AHP amplitude between neurons from TR rats and neurons from controls was maintained. We suggest that while the post-burst AHP in piriform cortex pyramidal neurons is modulated by both PKC and PKA, a PKC-dependent process maintains the learning-related reduction of the AHP in these cells.

Action Potentials↗
PubMed1991

Phospholipid metabolism in the cochlea: differences between base and apex.

Phospholipid-derived second messenger systems are one of the primary means for the transduction of extracellular signals to intracellular effector sites. We have investigated the longitudinal distribution of phospholipid metabolism in the guinea pig cochlea because of increasing evidence that the apex and base process auditory signals differently. Phospholipid metabolism was assayed by measuring the incorporation of radioactive phosphate (32Pi) into lipids of the organ of Corti and the lateral wall tissues (stria vascularis and spiral ligament). 32P-labeling of total phospholipids was higher in the apex than the base, and individual phospholipids exhibited a tissue-specific base/apex distribution. Phosphatidylinositol was the most abundant of the labeled lipids in all tissues except the basal lateral wall, where phosphatidylinositol and phosphatidylcholine were labeled to a similar extent. Experiments on the availability of [32P]-ATP and other non-lipid substrates (inositol, choline, and cytidine) suggested that the base/apex distribution of phospholipid metabolism is based on differences in enzymatic activities. Additional evidence for this is an increased hydrolysis of phosphoinositides in the apex. The base/apex distribution of lipid metabolism suggests that physiological and pathological mechanisms involving phospholipids differ between the turns of the cochlea.

Animals↗
PubMed1991

Effects of various secretagogues on [Ca2+]i in cultured human nasal epithelial cells.

Recent studies conducted on cultured canine tracheal cells have suggested that a complex relationship exists between cAMP and Ca2+ in the control of electrolyte secretion. The goal of this study was to determine if the Ca2+ second messenger system functions in a similar fashion in cultured human nasal epithelial cells, a tissue in which control of electrolyte secretion is known to be disrupted in the genetic disease, cystic fibrosis. Human nasal epithelial tissue was obtained as a by-product of surgery and put into monolayer cell culture. After 4-5 days in culture, cells were loaded with fura-2 and intracellular free Ca2+ measured as previously reported. We found that bradykinin increased intracellular free Ca2+ in all cells tested, whereas isoproterenol increased intracellular free Ca2+ in only half the cells tested, suggesting that more than one transporting cell type may be present in this tissue. Epinephrine and prostaglandin E2 had no effect on intracellular free Ca2+. We found that the voltage-sensitive Ca2+ channel blocker verapamil had no effect on the bradykinin-induced change in intracellular free Ca2+. Removal of Ca2+ from the bathing saline only slightly attenuated the increase in intracellular free Ca2+ that resulted from stimulation with bradykinin. We conclude that the source of the increased intracellular free Ca2+, observed during stimulation with secretagogues, was primarily intracellular stores.

Bradykinin↗
PubMedDate not supplied

Growth hormone releasing hexapeptide (GHRP-6) activates the inositol (1,4,5)-trisphosphate/diacylglycerol pathway in rat anterior pituitary cells.

Growth hormone-releasing hexapeptide (GHRP-6) is known to stimulate secretion of growth hormone (GH) in vivo and in vitro in a variety of species. However, the cellular effects of GHRP-6 remain largely unknown. We have tested the influence of GHRP-6 on the inositol phospholipid second messenger system in cultured anterior pituitary cells. Cultured pituitary cells responded upon challenge with GHRP-6 with a dose-dependent release of GH. Moreover, incubation of GHRP-6 with pituitary cell cultures labelled with myo-[3H]inositol resulted in a dose-dependent rise in [3H]inositol phosphates. Brief stimulation of pituitary cells with GHRP-6 increased phosphorylation of MBP4-14, a specific protein kinase C substrate, when incubated with the cytosol- or plasma membrane fraction from the stimulated cells. Furthermore, introduction of MBP4-14 into the cytosol in digitonin permeabilized pituitary cells caused increased phosphorylation of this substrate. GHRP-6 induced a rise in intracellular Ca2+ in individual somatotrophs loaded with the Ca2+ indicator, Fura-2. Preincubation (3 min) with somatostatin (SRIF) diminished the Ca2+ spike elicited by GHRP-6, while no effect of SRIF was observed when added simultaneously with GHRP-6. These results indicate that GHRP-6-stimulated GH-secretion involves the diacylglycerol/inositol(1,4,5)trisphosphate pathway with a resulting rise in cytosolic Ca2+.

Amino Acid Sequence↗
PubMed1993

Second messenger regulation of mRNA for corticotropin-releasing factor.

An understanding of how second messengers and their ligands are coupled to CRF gene activation is necessary if we are to understand the regulation of the CRF gene in physiological and pathological states. The protein kinase A, protein kinase C and glucocorticoid second messenger systems mediate most of the regulation of the CRF gene. In in vitro systems, CRF gene expression is stimulated 20-30-fold by activation of either the protein kinase A or the protein kinase C system. Glucocorticoid is able to inhibit stimulation via both pathways, but appears to be more effective in repressing activation mediated by protein kinase C. Glucocorticoid negative regulation requires the presence of glucocorticoid receptor possessing an intact DNA-binding domain, suggesting that this effect involves binding of the receptor to the CRF promoter. These in vitro studies should serve to guide investigators towards the possible mechanisms underlying CRF gene regulation in vivo.

Animals↗
PubMed1997

A novel neuropeptide-endocrine interaction controlling ecdysteroid production in ixodid ticks.

Ixodid (hard) ticks are blood-feeding arthropods that require a blood meal to complete each stage of development. However, the hormonal events coordinating aspects of feeding and development are only poorly understood. We have delineated a new neuropeptide-endocrine interaction in the adult tick, Amblyomma hebraeum, that stimulates the synthesis of the moulting hormones, the ecdysteroids. In adult female ticks, ecdysteroid synthesis could be demonstrated in integumental tissue incubated in vitro with a synganglial (central nervous system) extract, but not in its absence. Stimulation by the synganglial extract is both time- and dose-dependent, but is completely abolished by trypsin treatment, suggesting that the activity is due to a peptide/protein. Integumental tissue ecdysteroidogenesis is also stimulated by elevation of the cAMP concentration using forskolin and 3-isobutyl-l-methyl-xanthine, or by 8-bromo-cAMP. This suggests the involvement of at least a cAMP second messenger system in the neuropeptide-ecdysteroidogenesis axis, without precluding a role for other second messengers as well. Despite involving a quite different steroidogenic tissue, the foregoing system has some parallels with the known prothoracicotropic hormone (neuropeptide)-prothoracic gland endocrine axis of insects.

Animals↗