Central administration of an antisense oligodeoxynucleotide against type I pituitary adenylate cyclase-activating polypeptide receptor suppresses synthetic activities of LHRH-LH axis during the pubertal process

Female reproductive functions of the neuropeptide PACAP

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide originally isolated as a hypothalamic peptide. It has a widespread distribution in the body and has a diverse spectrum of actions. Among other processes, PACAP has been shown to be involved in reproduction. In this review we summarize findings related to the entire spectrum of female reproduction. PACAP is a regulatory factor in gonadal hormone production, influences follicular development and plays a role in fertilization and embryonic/placental development. Furthermore, PACAP is involved in hormonal changes during and after birth and affects maternal behavior. Although most data come from cell cultures and animal experiments, increasing number of evidence suggests that similar effects of PACAP can be found in humans. Among other instances, PACAP levels show changes in the serum during pregnancy and birth. PACAP is also present in the human follicular and amniotic fluids and in the milk. Levels of PACAP in follicular fluid correlate with the number of retrieved oocytes in hyperstimulated women. Human milk contains very high levels of PACAP compared to plasma levels, with colostrum showing the highest concentration, remaining steady thereafter for the first 7 months of lactation. All these data imply that PACAP has important functions in reproduction both under physiological and pathological conditions.

PACAP: A regulator of mammalian reproductive function

Pituitary adenylate cyclase-activating polypeptide (PACAP) is an ancestral molecule that was isolated from sheep hypothalamic extracts based on its action to stimulate cAMP production by pituitary cell cultures. PACAP is one of a number of ligands that coordinate with GnRH to control reproduction. While initially viewed as a hypothalamic releasing factor, PACAP and its receptors are widely distributed, and there is growing evidence that PACAP functions as a paracrine/autocrine regulator in the CNS, pituitary, gonads and placenta, among other tissues. This review will summarize current knowledge concerning the expression and function of PACAP in the hypothalamic-pituitary-gonadal axis with special emphasis on its role in pituitary function in the fetus and newborn.

Current State of Understanding of the Role of PACAP in the Hypothalamo-Hypophyseal Gonadotropin Functions of Mammals

PACAP was discovered 30 years ago in Dr. Akira Arimura's laboratory. In the past three decades since then, it has become evident that this peptide plays numerous crucial roles in mammalian organisms. The most important functions of PACAP are the following: 1. neurotransmitter, 2. neuromodulator, 3. hypophysiotropic hormone, 4. neuroprotector. This paper reviews the accumulated data regarding the distribution of PACAP and its receptors in the mammalian hypothalamus and pituitary gland, the role of PACAP in the gonadotropin hormone secretion of females and males. The review also summarizes the interaction between PACAP, GnRH, and sex steroids as well as hypothalamic peptides including kisspeptin. The possible role of PACAP in reproductive functions through the biological clock is also discussed. Finally, the significance of PACAP in the hypothalamo-hypophysial system is considered and the facts missing, that would help better understand the function of PACAP in this system, are also highlighted.

Effect of pituitary adenylate cyclase-activating polypeptide (PACAP) in the regulation of hypothalamic kisspeptin expression

Pituitary adenylate cyclase-activating polypeptide (PACAP) and its receptor are broadly distributed in the brain, and PACAP is known to work as a multifunctional peptide. However, it is still largely unknown how PACAP affects the hypothalamic-pituitary-gonadal (HPG) axis. In this study, we examined the effect of PACAP on hypothalamic kisspeptin expression, a known regulator of gonadotropin-releasing hormone. We used two hypothalamic cell models, mHypoA-50 and mHypoA-55, which were originated from kisspeptin-expressing neuron in anterioventral periventricular nucleus and arcuate nucleus regions in the hypothalamus, respectively. Expression of Kiss-1 gene, which encodes kisspeptin, was significantly increased by PACAP stimulation in both mHypoA-50 and mHypoA-55 cells, by up to 2.69 ± 0.93-fold and 4.89 ± 1.13-fold, respectively. PACAP6-38, a PACAP receptor antagonist did not antagonize the action of PACAP on Kiss-1 gene expression but increased Kiss-1 gene by itself in these cells. PACAP-induced Kiss-1 gene expression in both mHypoA-50 and mHypoA-55 cells was almost completely prevented in the presence of H89, a protein kinase A inhibitor. PACAP was expressed in both these hypothalamic cell models and its expression was up-regulated by estradiol in mHypoA-50 cells but not in mHypoA-55 cells. Stimulation of mHypoA-50 and mHypoA-55 cells with PACAP increased the expression levels of corticotropin-releasing hormone and neurotensin, both of which could modulate HPG axis. Our present observations suggest that hypothalamic PACAP might modulate the HPG axis by directly or indirectly modulating Kiss-1 gene expression.

Role of pituitary adenylate cyclase-activating polypeptide in modulating hypothalamus-pituitary neuroendocrine functions in mouse cell models

Pituitary adenylate cyclase-activating polypeptide (PACAP) was originally identified as a hypothalamic activator of cyclic adenosine monophosphate production in pituitary cells. PACAP and its receptor are expressed not only in the central nervous system, but also in peripheral organs, and function to stimulate pituitary hormone synthesis and secretion as both a hypothalamic-pituitary-releasing factor and an autocrine-paracrine factor within the pituitary. PACAP stimulates the expression of the gonadotrophin α, luteinising hormone (LH) β and follicle-stimulating hormone (FSH) β subunits, as well as the gonadotrophin-releasing hormone (GnRH) receptor and its own PACAP type I receptor (PAC1R) in gonadotrophin-secreting pituitary cells. In turn, GnRH, which is known to be a crucial component of gonadotrophin secretion, stimulates the expression of PACAP and PAC1R in gonadotrophs. In addition, PAC1R and PACAP modulate the functions of GnRH-producing neurones in the hypothalamus. This review summarises the current understanding of the possible roles of PACAP and PAC1R in modulating hypothalamus and pituitary neuroendocrine cells in the mouse models.

Advent and recent advances in research on the role of pituitary adenylate cyclase-activating polypeptide (PACAP) in the regulation of gonadotropic hormone secretion of female rats

PACAP (ADCYAP1) was isolated from ovine hypothalami. PACAP activates three distinct receptor types: G-protein coupled PAC1, VPAC1, and VPAC2 with seven transmembrane domains. Eight splice variants of PAC1 receptor are described. A part of the hypothalamic PACAP is released into the hypophyseal portal circulation. Both hypothalamic and pituitary PACAP are involved in the dynamic control of gonadotropic hormone secretion. In female rats, PACAP in the paraventricular nucleus is upregulated in the morning and pituitary PACAP is upregulated in the late evening of the proestrus stage of the reproductive cycle. PACAP mRNA peak in the hypothalamic PVN precedes the LHRH release into the portal circulation. It is supposed that PACAP peak is evoked by the elevated estrogen on proestrous morning. At the beginning of the so-called critical period of the same day, PACAP level starts to decline allowing LHRH release into the portal circulation, resulting in the LH surge that evokes ovulation. Just before the critical period, icv-administered exogenous PACAP blocks the LH surge and ovulation. The blocking effect of PACAP is mediated through CRF and endogenous opioids. The effect of the pituitary-born PACAP depends on the intracellular cross-talk between PACAP and LHRH.

PACAP modulates GnRH signaling in gonadotropes

Hypothalamic gonadotropin-releasing hormone is known to be critical for normal gonadotropin biosynthesis and secretion by the gonadotrope cells of the anterior pituitary gland. Additional regulation is provided by gonadal steroid feedback as well as by intrapituitary factors, such as activin and follistatin. Less well-appreciated is the role of pituitary adenylate-cyclase activating polypeptide (PACAP) as both a hypothalamic-pituitary releasing factor as well as an autocrine-paracrine factor within the pituitary. PACAP regulates gonadotropin expression alone and through modulation of GnRH responsiveness achieved by increases in GnRH receptor expression and interactions at the level of intracellular signaling pathways. In addition to direct effects on the gonadotrope, PACAP stimulates follistatin secretion by the folliculostellate cells and thereby contributes to differential expression of the gonadotropin subunits. Conversely, GnRH augments the ability of PACAP to regulate gonadotrope function by increasing pituitary PACAP and PACAP receptor expression. This review will summarize the current understanding of the mechanisms by which PACAP modulates gonadotrope function, with a focus on interactions with GnRH.

PACAP is transiently expressed in anterior pituitary gland of rats: in situ hybridization and cell immunoblot assay studies

In this work the expression of PACAP (pituitary adenylate cyclase activating polypeptide) in rat anterior pituitary was demonstrated for the first time using in situ hybridization. The number of cells showing PACAP signal in intact male rats was negligible similarly to that of diestrous rats. In proestrous rats sacrificed at 10h there was a moderate increase in the expression and after a decrease at 16 h and 18 h, there was a transient peak at 20 h and then the number of labeled cells was declined again (22 h). In the cell immunoblot assay study it was observed that the number of PACAP blot forming (PACAP releasing) cells in an anterior pituitary cell culture changed according to a similar pattern as the number of PACAP expressing cells. The number of blots was also the highest when the animals were sacrificed in the evening of proestrus at 20h. The results obtained by in situ hybridization and cell immunoblot assay well correlate with each other. The above-mentioned results support our hypothesis that the enhanced expression and secretion of PACAP in the pituitary gland may be involved in ceasing the LH surge.

Pituitary Adenylate Cyclase Activating Polypeptide Messenger RNA in the Paraventricular Nucleus and Anterior Pituitary During the Rat Estrous Cycle1

The neuropeptide pituitary adenylate cyclase activating polypeptide (ADCYAP 1, or PACAP) has been demonstrated to enhance gonadotropin-releasing hormone (GnRH)-induced gonadotropin secretion and regulate gonadotropin subunit gene expression in cultures of anterior pituitary cells. In the present study, we used in situ hybridization and real-time polymerase chain reaction to examine the expression of Pacap mRNA within the paraventricular nucleus (PVN) and anterior pituitary throughout the estrous cycle of the rat. Levels of luteinizing hormone in serum and pituitary gonadotropin subunit mRNAs were evaluated and displayed cyclic fluctuations similar to those reported previously. Pacap mRNA expression in the PVN and pituitary varied significantly during the estrous cycle, with the greatest changes occurring on the day of proestrus. Pacap mRNA levels in the PVN declined significantly on the morning of diestrus. During proestrus, PVN Pacap mRNA levels significantly increased 3 h before the gonadotropin surge and then declined. Pituitary expression of Pacap mRNA also varied on the afternoon of proestrus with a moderate decline at the time of the gonadotropin surge and a significant increase later in the evening. Expression of the mRNA species encoding the 288 amino acid form of follistatin increased significantly following the rise in pituitary Pacap mRNA, at the termination of the secondary surge in follicle-stimulating hormone beta (Fshb) gene expression. These results suggest that PACAP is involved in events before and following the gonadotropin surge, perhaps through increased gonadotroph sensitivity to GnRH and suppression of Fshb subunit expression through increased follistatin, as previously observed in vitro.

PAC1 receptors mediate pituitary adenylate cyclase-activating polypeptide- and progesterone-facilitated receptivity in female rats

Pituitary adenylate cyclase-activating polypeptide (PACAP) acts as a feed-forward, paracrine/autocrine factor in the hypothalamic ventromedial nucleus (VMN) for receptivity and sensitizes pituitary hormone release for ovulation. The present study examined receptor(s) and signaling pathway by which PACAP enhances rodent lordosis. PACAP binds to PACAP (PAC1)- and vasoactive intestinal peptide-preferring receptors (VPAC1, VPAC2). Ovariectomized rodents primed with estradiol (EB) were given PACAP or vasoactive intestinal peptide directly onto VMN cells. Only PACAP facilitated receptivity. Pretreatment with VPAC1 and VPAC2 inhibitors blocked both PACAP- and progesterone (P)-induced receptivity. Antisense (AS) oligonucleotides to PAC1 (not VPAC1 or VPAC2) inhibited the behavioral effect of PACAP and P. By real-time RT-PCR, EB, P and EB+P enhanced VMN mRNA expression of PAC1. Within the total PAC1 population, EB and EB+P induced expression of short form PAC1 and PAC1hop2 splice variants. Finally, blocking cAMP/protein kinase A signaling cascade by antagonists to cAMP activity and protein kinase A or by antisense to dopamine- and cAMP-regulated phosphoprotein of 32 kDa blocked the PACAP effect on behavior. Collectively, these findings provide evidence that progesterone receptor-dependent receptivity is, in part, dependent on PAC1 receptors for intracellular VMN signaling and delineate a novel, steroid-dependent mechanism for a feed-forward reinforcement of steroid receptor-dependent reproductive receptivity.

Clocks and the black box: circadian influences on gonadotropin-releasing hormone secretion

Although the mechanisms underlying hypothalamic surge secretion of gonadotropin-releasing hormone (GnRH) in rodent models have remained enduring mysteries in the field of neuroendocrinology, the identities of two fundamental constituents are clear. Elevated ovarian oestrogen, in conjunction with circadian signals, combine to elicit GnRH surges that are confined to the afternoon of the proestrus phase. The phenomenon of oestrogen positive feedback, although extensively investigated, is not completely understood, and may involve the actions of this steroid directly on GnRH perikarya, as well as on the activity of neuronal afferents. Additionally, whereas many studies have focused upon regulation of GnRH surge secretion by the neuroanatomical biological clock, the suprachiasmatic nucleus, it remains unclear why this daily signal is capable of stimulating surges only in the presence of oestrogen. This review re-examines multiple models of circadian control of reproductive neurosecretion, armed with the recent characterisation of the intracellular transcriptional feedback loops that comprise the circadian clock, and attempts to evaluate previous studies on this topic within the context of these new discoveries. Recent advances reveal the presence of oscillating circadian clocks throughout the central nervous system and periphery, including the anterior pituitary and hypothalamus, raising the possibility that synchrony between multiple cellular clocks may be involved in GnRH surge generation. Current studies are reviewed that demonstrate the necessity of functional clock oscillations in generating GnRH pulsatile secretion in vitro, suggesting that a GnRH-specific intracellular circadian clock may underlie GnRH surges as well. Multiple possible steroidal and neuronal contributions to GnRH surge generation are discussed, in addition to how these signals of disparate origin may be integrated at the cellular level to initiate this crucial reproductive event.

Altered social behavior in pituitary adenylate cyclase-activating polypeptide type I receptor-deficient mice

The olfactory bulb plays a critical role in odor discrimination and in processing olfactory cues controlling social behavior in mammals. Given that the pituitary adenylate cyclase-activating polypeptide (PACAP) type 1 receptor (PAC1) is highly expressed in the olfactory bulb, we examined its role in regulating olfaction and social investigation. We found that olfactory detection of nonsocial stimuli was similar in PAC1-deficient mice and wild-type (WT) littermates. In contrast, PAC1-deficient mice displayed markedly abnormal social behaviors. PAC1-deficient mice exhibited a faster decrease in social investigation after repeated exposure to social cues or ovariectomized female urine compared with WT mice. Moreover, PAC1-deficient females exhibited delayed affiliative behavior when housed with novel males, and PAC1-deficient males displayed excessive sexual mounting toward both females and males as well as reduced aggression and increased licking and grooming toward intruder males. In aggregate, these results uncover PAC1 signaling as an important factor in the development and/or functioning of neural pathways associated with pheromone processing and the regulation of social interactions in mice. In turn, these studies raise the potential clinical relevance of PACAP signaling dysfunctions in neuropsychiatric disorders characterized by social reciprocity impairments such as autism spectrum disorders.

TTF-1, a homeodomain-containing transcription factor, participates in the control of body fluid homeostasis by regulating angiotensinogen gene transcription in the rat subfornical organ

In recent years, it has become increasingly evident that angiotensins synthesized in the brain contribute to regulating body fluid homeostasis. Although angiotensinogen, the unique angiotensin precursor, is produced in the brain, the factors that regulate its gene expression remain unknown. We recently found that TTF-1, a homeodomain-containing transcription factor essential for the development of the fetal diencephalon, is postnatally expressed in discrete areas of the hypothalamus. We now report that the subfornical organ, an important site of angiotensinogen synthesis, is an extra-hypothalamic site of TTF-1 expression. Double in situ hybridization histochemistry demonstrated the presence of TTF-1 mRNA in angiotensinogen-producing cells of the rat subfornical organ. RNase protection assays showed that TTF-1 and angiotensinogen mRNA levels are simultaneously increased in the subfornical organ by water deprivation. The angiotensinogen promoter contains seven presumptive TTF-1 binding motifs, four of which are recognized by the TTF-1 homeodomain. In the C6 glioma cell line, TTF-1 transactivates the angiotensinogen promoter in a dose-dependent manner. This transactivation is abolished by deletion of the TTF-1 binding motif at -125. Intracranial administration of an antisense TTF-1 oligodeoxynucleotide decreased angiotensinogen mRNA in the subfornical organ and dramatically reduced the animal's water intake while increasing urine excretion. Moreover, plasma arginine vasopressin content was decreased by the same treatment. These results demonstrate a novel role for TTF-1 in the regulation of body fluid homeostasis, exerted via the transactivational control of angiotensinogen synthesis in the subfornical organ.

Growth hormone-releasing hormone and pituitary adenylate cyclase-activating polypeptide in the reproductive system

Growth hormone-releasing hormone (GHRH) and pituitary adenylate cyclase-activating polypeptide (PACAP) are both members of the glucagon superfamily that, with gonadotropins, act at central and peripheral levels as paracrine and autocrine coregulators of reproductive function. GHRH and PACAP are ancient peptides. Their original forms (both 27 amino acids long) were encoded by a single ancestral gene, several duplications of which led to the genes that encode the neuropeptides of the glucagon superfamily. In the male and female reproductive tracts, GHRH and PACAP interact with a subset of G protein-coupled receptors that are structurally similar to the PACAP receptor and variants of the vasoactive intestinal peptide receptor, and share several biological actions. These are related mainly to the modulation of cAMP-dependent and other signal transduction pathways in several cells of the pituitary-gonadal axis. The recent discovery that antagonists of GHRH and PACAP suppress the growth of human cancer cell lines that are derived from reproductive tissues indicates the potential importance of these peptides as local regulators of cell division, cell cycle arrest, differentiation and cell death.

Ontogeny and the possible function of a novel epidermal growth factor-like repeat domain-containing protein, NELL2, in the rat brain

In this study we investigated the mRNA expression of NELL2, a neural tissue-specific epidermal growth factor (EGF)-like repeat domain-containing protein, in the developing and adult rat CNS using in situ hybridization histochemistry and northern blot analysis. The possible candidates that interact with or be regulated by NELL2 were screened with a cDNA expression array in antisense (AS) NELL2 oligodeoxynucleotide (ODN)-injected rat hypothalami. NELL2 mRNA was detected as early as embryonic day 10, and was predominant in the CNS throughout the pre-natal stages. Its expression gradually increased during embryonic development and its strong expression was observed throughout the CNS until embryonic day 20. It was detected in the ventricular zone of the spinal cord, medulla and pons in 12-day-old-embryos, suggesting that NELL2 plays a role in the neurogenesis of these areas. After birth its expression gradually decreased, but high levels of expression could be observed in the tenia tecta, piriform cortex, hippocampus, dentate gyrus, cerebellar cortex, ambiguus nucleus, and inferior olivary nucleus of adult rat brains. The analysis of cDNA expression arrays revealed that the administration of AS NELL2 ODN markedly decreased the expression of several Ca2+-binding proteins and those involved in the transport and release of vesicles such as EF-hand Ca2+-binding protein p22 and rab7. This finding was confirmed by relative reverse transcription-polymerase chain reaction. The effect of NELL2 on synaptic vesicle content in median eminence (ME) nerve terminals was determined with synaptophysin levels as a marker protein in the AS NELL2 ODN-injected rat. It was significantly decreased by the AS ODN. These data suggest that NELL2 may play an important role in the development of the CNS as well as maintenance of neural functions, by regulating the intracellular machinery involving Ca2+ signaling, synaptic transport and/or release of vesicles.

Sex steroid metabolism in the tibial growth plate of the rat

To assess whether growth plate-specific production of sex steroids is possible, we have surveyed the presence of several key-enzymes involved in androgen and estrogen metabolism in the tibial growth plate of female and male rats during development. Using in situ hybridization, mRNAs of aromatase p450, type I and II 17beta-hydroxysteroid dehydrogenase (HSD), steroid sulfatase (STS), and 5alpha-reductase were detected in proliferating and hypertrophic chondrocytes of the growth plate. The former three were strongly up-regulated around sexual maturation (7 wk), whereas the latter two were expressed at a relatively constant level during development. These data were supported by measuring aromatase, type I 17beta-HSD, and STS enzyme activities in chondrocytes collected from tibial growth plates at 1 and 7 wk of age. Of the enzymes studied, there were minor differences between the sexes in aromatase and 5alpha-reductase expression only. In conclusion, our findings clearly indicate the presence of various enzymes involved in sex steroid metabolism in the tibial growth plate, especially in sexually maturing rats, a timepoint at which sex steroids have major effects on longitudinal growth. Our data suggest that intracrinology in the rat growth plate can occur and may be a major source of local sex steroid delivery.

Regulation of pituitary adenylate cyclase-activating polypeptide gene transcription by TTF-1, a homeodomain-containing transcription factor

Pituitary adenylate cyclase-activating polypeptide (PACAP) is an important hypophysiotrophic factor as well as a regulator for immune, reproductive, and neural tissues. We recently found that TTF-1, a homeodomain-containing transcription factor essential for the development of the fetal diencephalon, is postnatally expressed in the hypothalamic area and plays a transcription regulatory role for certain neurohormones. Based on the similarity of synthesis sites between PACAP and TTF-1 and, moreover, on the presence of conserved core TTF-1 binding motifs in the 5'-flanking region of the PACAP gene, we sought to uncover a regulatory role of TTF-1 in PACAP gene transcription. The TTF-1 homeodomain binds to six of the seven putative binding domains observed in the 5'-flanking region of the PACAP gene. In the C6 glioma cell-line, TTF-1 activates the PACAP promoter in a dose-dependent manner. This transactivation of PACAP by TTF-1 was totally removed when the core TTF-1 binding motif at -369 was deleted. RNase protection assays showed that TTF-1 and PACAP mRNAs have daily fluctuations in the rat hypothalamus. They both were at low levels during the day and high levels during the night. Intracerebroventricular administration of an antisense TTF-1 oligodeoxynucleotide significantly decreased the PACAP mRNA level as well as TTF-1 protein content in the rat hypothalamus, suggesting that TTF-1 also regulates PACAP transcription in vivo. Moreover, the TTF-1 promoter was inhibited by molecular oscillators of CLOCK and BMAL-1. Taken together, these data suggest that TTF-1 plays an important regulatory role in the gene transcription for PACAP, which may be important for the generation of a daily rhythm of hypothalamic PACAP gene expression.

Pituitary adenylate cyclase-activating polypeptide stimulates nitric-oxide synthase type I expression and potentiates the cGMP response to gonadotropin-releasing hormone of rat pituitary gonadotrophs

Nitric-oxide synthase type I (NOS I) is expressed primarily in gonadotrophs and in folliculo-stellate cells of the anterior pituitary. In gonadotrophs, the expression and the activity of NOS I are stimulated by gonadotropin-releasing hormone (GnRH) under both experimental and physiological conditions. In the present study, we show that pituitary adenylate cyclase-activating polypeptide (PACAP) is twice as potent as GnRH at increasing NOS I levels in cultured rat anterior pituitary cells. The action of PACAP is detectable after 4-6 h and maximal at 24 h, this effect is mimicked by 8-bromo-cAMP and cholera toxin and suppressed by H89 suggesting a mediation through the cAMP pathway. Surprisingly, NADPH diaphorase staining revealed that these changes occurred in gonadotrophs exclusively although PACAP and cAMP, in contrast to GnRH, have the potential to target several types of pituitary cells including folliculo-stellate cells. There was no measurable alteration in NOS I mRNA levels after cAMP or PACAP induction. PACAP also stimulated cGMP synthesis, which was maximal within 15 min and independent of cAMP, however, only part resulted from NOS I/soluble guanylate cyclase activation implying that in contrast to GnRH, PACAP has a dual mechanism in cGMP production. Interestingly, induction of NOS I by PACAP markedly enhanced the capacity of gonadotrophs to produce cGMP in response to GnRH. The fact that PACAP may act on gonadotrophs to alter NOS I levels, generate cGMP, and potentiate the cGMP response to GnRH, suggests that cGMP could play important cellular functions.

Simultaneous determination of multiple transcripts and splice variants of a primary transcript using ribonuclease protection assays

The ribonuclease (RNase) protection assay (RPA) is an extremely sensitive technique used to determine specific mRNAs from cell and tissue extracts. The present protocol presents detailed procedures for a conventional RPA using antisense RNA probes purified with a Fullengther apparatus. The Fullengther has the advantage of being a relatively quick and safe procedure compared to more conventional methods for purification of full-length RNA probes. Using this protocol, we sought to simultaneously determine multiple mRNA species, including splice variants of the type I receptor (PAC(1)) of pituitary adenylate cyclase-activating polypeptide (PACAP), an important mediator in the regulation of luteinizing hormone-releasing hormone (LHRH) synthesis by ovarian steroids such as progesterone [7]. PAC(1) has more than eight splice variants. We have been able to discriminate the hop1 variant from other splice variants. To improve our understanding of the regulation mechanism of genes that are related to each other, such as LHRH and PACAP, it is most important to simultaneously determine genes that are involved in the same physiological areas of regulation. Using only 5 microg of total RNA sample from a single rat preoptic area, we simultaneously determined five different transcripts, including four rare mRNA species such as LHRH, PACAP, and hop1 variant and other splice variants of PAC(1), as well as the internal control of cyclophilin mRNA. This protocol provides a method for the simultaneous determination of multiple transcripts using the RPA.