Distribution of two distinct messenger ribonucleic acids encoding gastrin-releasing peptide in rat brain

Novel insight on GRP/GRPR axis in diseases

The gastrin-releasing peptide receptor (GRPR), a member of the G protein-coupled receptors (GPCRs), binds to ligands such as gastrin-releasing peptide (GRP) and plays a variety of biological roles. GRP/GRPR signalling is involved in the pathophysiological processes of many diseases, including inflammatory diseases, cardiovascular diseases, neurological diseases, and various cancers. In the immune system, the unique function of GRP/GRPR in neutrophil chemotaxis suggests that GRPR can be directly stimulated through GRP-mediated neutrophils to activate selective signalling pathways, such as PI3K, PKC, and MAPK, and participate in the occurrence and development of inflammation-related diseases. In the cardiovascular system, GRP increases intercellular adhesion molecule 1 (ICAM-1) and induces vascular cell adhesion molecule-1 (VCAM-1). GRP activates ERK1/2, MAPK, and AKT, leading to cardiovascular diseases, including myocardial infarction. Central nervous system signal transduction mediated by the GRP/GRPR axis plays a vital role in emotional responses, social interaction, and memory. The GRP/GRPR axis is elevated in various cancers, including lung, cervical, colorectal, renal cell, and head and neck squamous cell carcinomas. GRP is a mitogen in a variety of tumour cell lines. Its precursor, pro-gastrin-releasing peptide (ProGRP), may play an important role as an emerging tumour marker in early tumour diagnosis. GPCRs serve as therapeutic targets for drug development, but their function in each disease remains unclear, and their involvement in disease progression has not been well explored or summarised. This review lays out the above mentioned pathophysiological processes based on previous research conclusions. The GRP/GRPR axis may be a potential target for treating multiple diseases, and the study of this signalling axis is particularly important.

Gastrin-releasing peptide acts via postsynaptic BB2 receptors to modulate inward rectifier K+ and TRPV1-like conductances in rat paraventricular thalamic neurons

Gastrin-releasing peptide (GRP) is a bombesin-like peptide with a widespread distribution in mammalian CNS, where it has a role in food intake, circadian rhythm generation, fear memory, itch sensation and sexual behaviour. While it has been established that GRP predominantly excites neurons, details of the membrane mechanism involved in this action remain largely undefined. We used perforated patch clamp recording in acute brain slice preparations to investigate GRP-affected receptors and ionic conductances in neurons of the rat paraventricular thalamic nucleus (PVT). PVT is a component of the midline and intralaminar thalamus that participates in arousal, motivational drives and stress responses, and exhibits a prominence of GRP-like immunoreactive fibres. Exposure of PVT neurons to low nanomolar concentrations of GRP induced sustained TTX-resistant membrane depolarizations that could trigger rhythmic burst discharges or tonic firing. Membrane current analyses in voltage clamp revealed an underlying postsynaptic bombesin type 2 receptor-mediated inward current that resulted from the simultaneous suppression of a Ba(2+)-sensitive inward rectifier K(+) conductance and activation of a non-selective cation conductance with biophysical and pharmacological properties reminiscent of transient receptor potential vanilloid (TRPV) 1. A role for a TRPV1-like conductance was further implied by a significant suppressant influence of a TRPV1 antagonist on GRP-induced membrane depolarization and rhythmic burst or tonic firing. The results provide a detailed picture of the receptor and ionic conductances that are involved in GRP's excitatory action in midline thalamus.

Gastrin-releasing peptide messenger ribonucleic acid expression in the hypothalamic paraventricular nucleus is altered by melanocortin receptor stimulation and food deprivation

Gastrin-releasing peptide (GRP) is a bombesin-like peptide widely distributed in the gastrointestinal tract and central nervous system. In the brain, GRP mRNA is located in the hypothalamic paraventricular nucleus (PVN), a region that receives neural input from the arcuate nucleus and plays a critical role in food intake and energy balance. Because GRP neurons are localized in the vicinity of projection sites in the PVN for peptides that participate in energy homeostasis, we investigated whether GRP mRNA expression in the PVN may be sensitive to challenges imposed by either 38 h food deprivation or stimulation of the melanocortin system by the melanocortin 3/4 receptor agonist, melanotan II (MTII). We found that food deprivation significantly decreased GRP mRNA expression, whereas lateral ventricular MTII administration increased GRP mRNA expression in ad libitum-fed rats 4 h after administration. Furthermore, administration of MTII at a dose that reduces 24 h food intake and body weight prevented the decrease in GRP mRNA expression observed in animals that were pair fed to the amount of food consumed by those injected with MTII. These results demonstrate that food deprivation and stimulation of the melanocortin system produce opposing changes in GRP gene expression in the PVN, suggesting that GRP-containing neurons in the PVN may be part of the hypothalamic signaling pathway controlling food intake and energy balance.

Neuromedin C microinjected into the amygdala inhibits feeding

Bombesin-like peptides including gastrin releasing peptide and neuromedin C are known to inhibit feeding. Bombesin receptors have been found in moderate to high densities in the amygdaloid body, which is essentially involved in the regulation of feeding and body weight. In the present experiments neuromedin C (15, 30, and 60 ng), a carboxyterminal decapeptid fragment of gastrin releasing peptide, was bilaterally microinjected into the central part of the amygdala in ad libitum fed male CFY rats. Food intake was measured every 5 min for 30 min and also 6 min following neuromedin C or vehicle microinjections. Fifteen nanograms neuromedin C significantly suppressed liquid food consumption for 5 min and 30 ng for 25 min. However, 60 ng was not effective. Neuromedin C effects were blocked by prior application of the bombesin receptor antagonist [Leu(13)-psi(CH(2)NH)-Leu(14)]-bombesin. Neuromedin C treatment increased latency to feeding, decreased food intake, decreased the time spent feeding and their ratio, the number and the duration of feeding episodes during the first 5 min, without modifying body temperature or stereotype activity. Results indicate that neuromedin C may decrease the efficiency of feeding and that activation of bombesin receptors in the central amygdala may reduce appetite.

Bombesin-like peptides and associated receptors within the brain: distribution and behavioral implications

As we commemorate the 25th anniversary of the journal Peptides, it is timely to review the functional significance of the bombesin (BB)-like peptides and receptors in the CNS. Over two decades ago we published an article in the journal Peptides demonstrating that BB-like peptides are present in high densities in certain rat brain regions (such as the paraventricular nucleus of the hypothalamus). Subsequently, one of the mammalian forms of BB, gastrin-releasing peptide (GRP) containing cell bodies were found in the suprachiasmatic nucleus of the hypothalamus and nucleus of the solitary tract of the hindbrain. Another related peptide, namely neuromedin (NM)B, was detected in the olfactory bulb and dentate gyrus. BB and GRP bind with high affinity to BB(2) receptors, whereas NMB binds with high affinity to BB(1) receptors. The actions of BB or GRP are blocked by BB(2) receptor antagonists such as (Psi(13,14)-Leu(14))BB whereas PD168368 is a BB(1) receptor antagonist. Exogenous administration of BB into the rat brain causes hypothermia, hyperglycemia, grooming and satiety. BB-like peptides activate the sympathetic nervous system and appear to modulate stress, fear and anxiety responses. GRP and NMB modulate distinct biological processes through discrete brain regions or circuits, and globally these peptidergic systems may serve in an integrative or homeostatic function.

Bombesin microinjection into the basolateral amygdala influences feeding behavior in the rat

It has been demonstrated that the basolateral amygdala (ABL) represents a satiety mechanism. Experimental data indicate that peripheral or central applications of neuropeptide bombesin (BN) and BN-like peptides inhibit feeding. Since the amygdala (AMY) is rich in BN-like immunoreactive elements, the present study was performed to determine whether 10 or 40 ng doses of BN microinjected bilaterally into the ABL could modify solid food intake. Twenty nanograms of BN (10 ng per injection site) in 24-h deprived rats caused transient inhibition of food intake and 80 ng resulted in a significant reduction of food consumption for 1 h. This inhibitory effect of BN on feeding was eliminated by prior BN antagonist treatment. Results of behavioral tests showed that BN microinjections into the ABL specifically reduced food intake without altering behavioral patterns or influencing the body temperature. Present results suggest that BN-like peptides may act as a complex satiety signal in the ABL.

Bombesin-like peptides depolarize rat hippocampal interneurones through interaction with subtype 2 bombesin receptors

1. Whole-cell patch-clamp recordings were made from visually identified hippocampal interneurones in slices of rat brain tissue in vitro. Bath application of the bombesin-like neuropeptides gastrin-releasing peptide (GRP) or neuromedin B (NMB) produced a large membrane depolarization that was blocked by pre-incubation with the subtype 2 bombesin (BB2) receptor antagonist [D-Phe6, Des-Met14]bombesin-(6-14)ethyl amide. 2. The inward current elicited by NMB or GRP was unaffected by K+ channel blockade with external Ba2+ or by replacement of potassium gluconate in the electrode solution with caesium acetate. 3. Replacement of external NaCl with Tris-HCl significantly reduced the magnitude of the GRP-induced current at -60 mV. In contrast, replacement of external NaCl with LiCl had no effect on the magnitude of this current. 4. Photorelease of caged GTPgammaS inside neurones irreversibly potentiated the GRP-induced current at -60 mV. Similarly, bath application of the phospholipase C (PLC) inhibitor U-73122 significantly reduced the size of the inward current induced by GRP. 5. Reverse transcription followed by the polymerase chain reaction using cytoplasm from single hippocampal interneurones demonstrated the expression of BB2 receptor mRNA together with glutamate decarboxylase (GAD67). 6. Although bath application of GRP or NMB had little or no effect on the resting membrane properties of CA1 pyramidal cells per se, these neuropeptides produced a dramatic increase in the number and amplitude of miniature inhibitory postsynaptic currents in these cells in a TTX-sensitive manner.

Breast cancer cell-associated endopeptidase EC 24.11 modulates proliferative response to bombesin

We have investigated the production, growth and inactivation of gastrin-releasing peptide (GRP)-like peptides in human breast cancer cell lines. Radioimmunoassay detected GRP-like immunoreactivity (GRP-LI) in T47D breast cancer cells but not in the conditioned medium, indicating rapid clearance. No GRP-LI was found in the ZR-75-1 or MDA-MB-436 cells or their conditioned medium. High-performance liquid chromatography (HPLC) analysis of the GRP-LI in the T47D cells revealed a major peak, which co-eluted with GRP(18-27), and a minor more hydrophilic peak. In vitro stimulation of T47D cell growth by bombesin (BN) was enhanced to 138% of control levels (bombesin alone) by the addition of the selective endopeptidase EC 3.4.24.11 inhibitor phosphoramidon (0.1 ng ml(-1)). Fluorogenic analysis using whole cells confirmed low levels of this phosphoramidon-sensitive enzyme on the T47D cells. This enzyme, previously unreported in human breast cancer cells, significantly modulates both T47D growth and its response to BN-induced growth.

Bombesin receptors in the brain

We have shown that in the central nervous system BN receptors are closely associated with 5-HT systems. On a subpopulation of dorsal raphe neurons, NMB receptors are able to depolarize cells by reducing gK+. In one of the target regions of the dorsal raphe 5-HT neurons, the SCN, we have also shown that neurons are excited by BN-related peptides. In the SCN, the GRP receptors excite neurons by two different mechanisms: closure of gK+ and opening of an unidentified cation conductance. Expression of human BN receptors from the brain in CHO cells or Xenopus oocytes shows a very similar pharmacological profile to that seen in the rat brain slice preparations. In the CHO cell line, following BN receptor activation, a major second-messenger path involves hydrolysis of PIP2 by phospholipases to yield IP3, which releases Ca2+ from intracellular stores. In the oocyte expression system, a similar second messenger pathway is clearly apparent, and Ca2+-sensitive gCl- represents the last phase in a cascade of events. The final phase of the mechanism of action in the artificial systems does not involve gK+, suggesting a different second messenger cascade to that in neurons. However, the involvement of phospholipases and their phospholipid products have not been excluded in neurons.

Distribution of gastrin-releasing peptide/bombesin-like immunoreactive cell bodies and fibres in the brainstem of the cat

Using an indirect immunoperoxidase technique, the location of gastrin-releasing/bombesin-like immunoreactive fibres and cell bodies in the cat brainstem was studied. A moderate or low density of immunoreactive cell bodies was observed in the nucleus of the brachium of the inferior colliculus, pericentral nucleus of the inferior colliculus, ventral nucleus of the lateral lemniscus and in the external division of the lateral reticular nucleus. The densest network of immunoreactive fibres was visualized in the interpeduncular nucleus, marginal nucleus of the brachium conjunctivum, alaminar and laminar spinal trigeminal nuclei and in the substantia nigra. The periaqueductal gray, brachium of the inferior colliculus, nucleus of the brachium of the inferior colliculus, locus coeruleus, nucleus incertus, Kölliker-Fuse nucleus, facial nucleus, medial nucleus of the solitary tract and the area postrema contained a moderate density of immunoreactive fibres, whereas the pericentral nucleus of the inferior colliculus, nucleus sagulum, cuneiform nucleus, dorsal nucleus of the raphe, superior central nucleus, central, lateral and paralemniscal tegmental fields, ventral nucleus of the lateral lemniscus, dorsal tegmental nucleus, postpyramidal nucleus of the raphe, nucleus ambiguus, accessory dorsal tegmental nucleus, dorsal motor nucleus of the vagus and the inferior olive had the lowest density of immunoreactive fibres.

Expression of the genes encoding bombesin-related peptides and their receptors in anterior pituitary tissue

The bombesin-related peptides gastrin-releasing peptide (GRP) and neuromedin B (NMB) have been demonstrated in the anterior pituitary (AP) on an immunological basis. We studied the presence of mRNAs for these peptides and for their receptors by RNAse protection assay using fresh adult male rat AP, AP cell reaggregates cultured in the presence of estradiol and the rat AP derived GH3 cell line. In total RNA from fresh AP we detected high amounts of NMB mRNA and much smaller amounts of GRP mRNA, while finding a weak signal for GRP-receptor (GRP-R) and NMB-receptor (NMB-R) mRNAs. In total RNA from the reaggregate cell cultures we detected high levels of NMB mRNA as well as a strong signal for GRP-R mRNA. Finally, in GH3 cells, high levels of NMB mRNA and GRP-R mRNA were found, while GRP mRNA and NMB-R mRNA remained undetectable even in high amounts (200 micrograms) of total RNA. We conclude that mRNAs encoding both bombesin-related peptides and each of the mRNAs encoding their receptors are expressed in rat AP tissue. NMB mRNA is more prominent than GRP mRNA in all AP-like tissues examined (fresh AP, estradiol-treated reaggregate AP cell cultures and GH3 cells). NMB-R mRNA and GRP-R mRNA are both present in low levels in fresh AP whereas the GRP-R mRNA is predominant in GH3 cells and estradiol treated AP reaggregate cell cultures. Compared to fresh AP tissue, NMB mRNA and GRP-R mRNA expression is enhanced in estradiol-treated reaggregate cell cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrophysiological effects of pressure-ejected bombesin-like peptides on hamster suprachiasmatic nucleus neurons in vitro

The suprachiasmatic nuclei (SCN) of the rodent hypothalamus function as a light entrainable circadian pacemaker. The SCN contain moderate to high concentrations of a number of neuropeptides including peptides showing structural homology with the amphibian derived tetradecapeptide, bombesin (BN), called bombesin-like peptides (BNLPs). BNLPs include the 27 amino acid peptide, gastrin releasing peptide (GRP1-27), a smaller decapeptide (GRP18-27) and another decapeptide with less structural homology, neuromedin B (NmB). Immunoreactivity for BN and receptors for BNLPs have been demonstrated in the region of the rat SCN receiving photic input. We studied the effects of local pressure ejections of BNLPs dissolved in saline/1% bovine serum albumin (BSA) vehicle on the extracellularly recorded firing rates of Syrian hamster SCM neurons in a hypothalamic slice preparation. In one study, an ejecting electrode containing BN (10(-8) to 10(-4) M) was positioned 20 to 60 microm from a recording electrode. Of 74 cells tested with BN, 50 (67.6%) showed significant increases in firing rate, while 3 of 29 cells (15.8%) tested with vehicle ejections were activated. In a second study, a single electrode was used for both recordings and pressure ejections. Of 48 cells tested, BN (10(-6) to 10(-4) M) activated 30 (62.5%) and suppressed firing in 4 (8.3%). Of 208 cells tested with GRP1-27 (10(-9) to 10(-4) M), 105 (50.5%) were activated and 2 (1.0%) were suppressed. The percentage of cells responding increased with the concentration of GRP1027 used in the electrode. No circadian variation in responsiveness to GRP1-27 was detected. GRP18-27 (5 x 10(-5) to 10(-4) M) activated 10 out of 18 cells tested (55.6%), while NmB (10(-4) M) activated 2 out of 30 cells tested (6.7%) and vehicle ejections activated 1 out of 36 cells tested (2.8%). GRP1-27, GRP18-27 and BN, the BNLPs showing the greatest degree of structural homology, activate approximately 50% of SCN cells, apparently via the BN/GRP-preferring receptor subtype, and may play a role in photic entrainment.

The mouse Dlx-2 (Tes-1) gene is expressed in spatially restricted domains of the forebrain, face and limbs in midgestation mouse embryos

The pattern of RNA expression of the murine Dlx-2 (Tes-1) homeobox gene is described in embryos ranging in age from E8.5 through E11.5. Dlx-2 is a vertebrate homologue of the Drosophila Distal-less (Dll) gene. Dll expression in the Drosophila embryo is principally limited to the primordia of the brain, head and limbs. Dlx-2 is also expressed principally in the primordia of the forebrain, head and limbs. Within these regions it is expressed in spatially restricted domains. These include two discontinuous regions of the forebrain (basal telencephalon and ventral diencephalon), the branchial arches, facial ectoderm, cranial ganglia and limb ectoderm. Several mouse and human disorders have phenotypes which potentially are the result of mutations in the Dlx genes.

Distribution of preproatrial natriuretic peptide mRNA in rat brain detected by in situ hybridization of DNA oligonucleotides: enrichment in hypothalamic and limbic regions

The expression and distribution of mRNA encoding preproatrial natriuretic peptide (ppANP) in rat brain has been investigated by in situ hybridization of two 35S-labeled synthetic DNA oligonucleotides, based on a cDNA clone sequence that encodes rat ppANP. The highest relative concentrations of ppANP mRNA were detected in the medial preoptic hypothalamic nucleus ("anteroventral/third ventricle region") and the medial habenula. Moderate concentrations of ppANP mRNA were observed in the CA1 pyramidal cells of the hippocampus, the endopiriform nucleus, the arcuate nucleus, the zona incerta, and cells of the pontine tegmental and peduculopontine nuclei. Several of these regions, including the habenula and the hypothalamic areas, have previously been reported to contain atrial natriuretic peptide (ANP)-like immunoreactivity, but the expression of ppANP mRNA in CA1 pyramidal cells suggests the occurrence of differential translation of ppANP mRNA into protein product in different brain regions, or the existence of different immunological forms of the peptide. The abundance of ppANP mRNA in brain was relatively low in comparison with that previously reported for many other mRNA species encoding other brain neuropeptides. These results demonstrate that ANP gene expression occurs in discrete neuronal populations of the CNS and that studies of the regulation of this expression should now be possible using quantitative in situ hybridization.

Preprogastrin-releasing peptide messenger ribonucleic acid: neuroanatomical localization in rat brain by in situ hybridization with synthetic oligodeoxynucleotide probes

Gastrin-releasing peptide (GRP) is a 27 amino acid peptide that is present in both the central and peripheral nervous systems and that shares immunological and functional properties with the amphibian peptide, bombesin. GRP has multiple putative biological functions including effects on feeding behaviour and carbohydrate metabolism, body temperature, and effects on hormone release, but little is known about the regulation of GRP gene expression in the brain. This study examined the distribution of neurones expressing preproGRP mRNA in rat brain by in situ hybridization of [35S]-labelled DNA oligonucleotides. PreproGRP mRNA was detected in several regions of brain, with highest concentrations in the parvocellular paraventricular and suprachiasmatic nuclei of the hypothalamus, the lateral and basolateral nuclei of the amygdala, the amygdaloid-hippocampal area and the ventral part of the granule cell layer of the dentate gyrus. Moderate levels were seen in layers II and III of the cingulate and retrosplenial cortex, the medial and mediobasal nuclei of the amygdala, the anteroventral thalamic nucleus; medial geniculate nucleus and the parabrachial nucleus. These findings are largely consistent with the cellular localization of GRP-like immunoreactivity in rat brain and recent studies of preproGRP mRNA localization using cRNA probes. The distribution of preproGRP mRNA observed further suggests the involvement of GRP in the central regulation of several functions including regulation of hypothalamic/pituitary hormone release.

Cellular levels of messenger ribonucleic acids encoding vasoactive intestinal Peptide and gastrin-releasing Peptide in neurons of the suprachiasmatic nucleus exhibit distinct 24-hour rhythms

There is strong evidence supporting the view that the Suprachiasmatic nucleus (SCN) functions as a circadian clock; however, the neural and molecular events underlying SCN function remain unclear. A specific subpopulation of neurons within the ventrolateral aspect of the SCN that contains three peptides, vasoactive intestinal peptide (VIP), peptide histidine isoleucine (PHI) and gastrin-releasing peptide (GRP), play an important role in SCN function. VIP-containing neurons of the SCN receive synapses from photic projections, and co-injection of all three peptides mimics the phase-delaying effects of light on circadian activity rhythms. In principle, the signaling potential of a neuron containing several transmitters may be affected by the concentration ratio of co-released factors; hence, one mechanism by which VIP/PHI/GRP-containing neurons could influence SCN function is by changing the concentration ratio of these peptides throughout the light-dark cycle. The present study was performed to examine this possibility. Relative cellular levels of mRNA encoding both VIP/PHI and GRP were determined within the SCN every 4 h in rats housed in a 14 h light: 10 h dark cycle. Quantitative in situ hybridization revealed a statistically significant (P<0.005) 24-h profile of changes in VIP/PHI mRNA that peaked during the dark phase, and a significant (P<0.005) 24-h profile of changes in GRP mRNA that peaked during the light phase. These data support the interpretation that cellular levels of mRNAs encoding VIP/PHI and GRP within the SCN exhibit distinct profiles of changes throughout the light-dark cycle. Further, these findings are consistent with the hypothesis that the concentration ratio of VIP and PHI to GRP changes over the light-dark cycle, and that this may be an important mechanism by which circadian rhythms are generated or entrained.

Isolation and characterization of a novel cDNA clone encoding a homeodomain that is developmentally regulated in the ventral forebrain

A complementary DNA, Tes-1, of a novel homeodomain protein has been cloned, and its pattern of expression has been characterized. It is a structural homolog of Distal-less, a homeodomain-encoding gene in D. melanogaster. Its expression is developmentally regulated and is limited to structures in the head. Within the central nervous system of the midgestation mouse embryo, it is expressed exclusively in the ventral forebrain. It is likely that Tes-1 plays a regulatory role in the development of this complex neural structure.

Cloning of cDNAs encoding amphibian bombesin: evidence for the relationship between bombesin and gastrin-releasing peptide

Bombesin is a tetradecapeptide originally isolated from frog skin; its mammalian homologue is the 27-amino acid peptide gastrin-releasing peptide (GRP). cDNAs encoding GRP have been cloned from diverse species, but little is yet known about the amphibian bombesin precursor. Mass spectrometry of HPLC-separated skin exudate from Bombina orientalis was performed to demonstrate the existence of authentic bombesin in the skin of this frog. A cDNA library was prepared from the skin of B. orientalis and mixed oligonucleotide probes were used to isolate cDNAs encoding amphibian bombesin. Sequence analysis revealed that bombesin is encoded in a 119-amino acid prohormone. The carboxyl terminus of bombesin is flanked by two basic amino acids; the amino terminus is not flanked by basic amino acids but is flanked by a chymotryptic-like cleavage site. Northern blot analysis demonstrated similarly sized bombesin mRNAs in frog skin, brain, and stomach. Polymerase chain reaction was used to show that the skin and gut bombesin mRNAs encoded the identical prohormones. Prohormone processing, however, differed between skin and gut. Chromatography showed the presence of only authentic bombesin in skin whereas gut extracts contained two peaks of bombesin immunoreactivity, one consistent in size with bombesin and one closer in size to mammalian GRP. Thus the same bombesin prohormone is processed solely to bombesin in skin but is processed to a peptide similar in size to bombesin and to a peptide similar in size to mammalian GRP in stomach.

Structural characterization of a brain-specific promoter region directing transcription of the rat prepro-gastrin-releasing peptide gene

Expression of the mammalian prepro-gastrin-releasing peptide (preproGRP) gene has been shown to be restricted to neural and neuroendocrine cell types. In this paper, the structure and nucleotide sequence of the rat preproGRP gene coding regions and promoter is described and analyzed. The gene is divided into 3 exons, encoding a signal sequence, the 29 amino acid rat GRP, and a 92 amino acid extension peptide. While the overall prohormone structure is similar to that predicted from the sequence of the human gene, differences in transcription are apparent. Several forms of the rat preproGRP mRNA are found in brain: a 1.1 kb form which initiates in both brain and gut primarily from a TATAA-directed promoter, and less abundant forms of about 1.5 kb, whose initiation sites are heterogeneous, located 300-400 base pairs upstream of the 1.1 kb initiation site, and found only in spinal cord and a subset of brain nuclei expressing preproGRP mRNA. Comparison of the human and rat promoter region sequences identifies regions of high similarity upstream from both the 1.1 kb and 1.5 kb mRNA initiation sites, which may be important in the cell type-specific regulation of the preproGRP gene.