Expression of pituitary adenylate cyclase-activating polypeptide (PACAP) in the mesencephalic trigeminal nucleus of the rat after transsection of the masseteric nerve

Intrabladder PAC1 Receptor Antagonist, PACAP(6-38), Reduces Urinary Bladder Frequency and Pelvic Sensitivity in Mice Exposed to Repeated Variate Stress (RVS)

Stress causes symptom exacerbation in functional disorders of the urinary bladder. However, the potential mediators and underlying mechanisms of stress effects on micturition reflex function are unknown. We have characterized PACAP (Adcyap1) and PAC1 receptor (Adcyap1r1) signaling in stress-induced urinary bladder dysfunction in mice. We determined PACAP and PAC1 transcripts and protein expressions in the urinary bladder and lumbosacral dorsal root ganglia (DRG) and spinal cord in repeated variate stress (RVS) or control mouse (handling only) groups. RVS in mice significantly (p ≤ 0.01) increased serum corticosterone and urinary bladder NGF content and decreased weight gain. PACAP and PAC1 mRNA and protein were differentially regulated in lower urinary tract tissues with changes observed in lumbosacral DRG and spinal cord but not in urinary bladder. RVS exposure in mice significantly (p ≤ 0.01) increased (2.5-fold) voiding frequency as determined using conscious cystometry. Intrabladder administration of the PAC1 receptor antagonist, PACAP(6-38) (300 nM), significantly (p ≤ 0.01) increased infused volume (1.5-2.7-fold) to elicit a micturition event and increased the intercontraction interval (i.e., decreased voiding frequency) in mice exposed to RVS and in control mice, but changes were smaller in magnitude in control mice. We also evaluated the effect of PAC1 blockade at the level of the urinary bladder on pelvic sensitivity in RVS or control mouse groups using von Frey filament testing. Intrabladder administration of PACAP(6-38) (300 nM) significantly (p ≤ 0.01) reduced pelvic sensitivity following RVS. PACAP/receptor signaling in the CNS and PNS contributes to increased voiding frequency and pelvic sensitivity following RVS and may represent a potential target for therapeutic intervention.

PACAP/PAC1 Expression and Function in Micturition Pathways

Neural injury, inflammation, or diseases commonly and adversely affect micturition reflex function that is organized by neural circuits in the CNS and PNS. One neuropeptide receptor system, pituitary adenylate cyclase-activating polypeptide (PACAP; Adcyap1), and its cognate receptor, PAC1 (Adcyap1r1), have tissue-specific distributions in the lower urinary tract. PACAP and associated receptors are expressed in the LUT and exhibit changes in expression, distribution, and function in preclinical animal models of bladder pain syndrome (BPS)/interstitial cystitis (IC), a chronic, visceral pain syndrome characterized by pain, and LUT dysfunction. Blockade of the PACAP/PAC1 receptor system reduces voiding frequency and somatic (e.g., hindpaw, pelvic) sensitivity in preclinical animal models and a transgenic mouse model that mirrors some clinical symptoms of BPS/IC. The PACAP/receptor system in micturition pathways may represent a potential target for therapeutic intervention to reduce LUT dysfunction following urinary bladder inflammation.

PACAP38-Mediated Bladder Afferent Nerve Activity Hyperexcitability and Ca2+ Activity in Urothelial Cells from Mice

Pituitary adenylate cyclase-activating polypeptide (PACAP; Adcyap1) and its cognate PAC1 receptor (Adcyap1r1) have tissue-specific distributions in the lower urinary tract (LUT). The afferent limb of the micturition reflex is often compromised following bladder injury, disease, and inflammatory conditions. We have previously demonstrated that PACAP signaling contributes to increased voiding frequency and decreased bladder capacity with cystitis. Thus, the present studies investigated the sensory components (e.g., urothelial cells, bladder afferent nerves) of the urinary bladder that may underlie the pathophysiology of aberrant PACAP activation. We utilized bladder-pelvic nerve preparations and urothelial sheet preparations to characterize PACAP-induced bladder afferent nerve discharge with distention and PACAP-induced Ca²⁺ activity, respectively. We determined that PACAP38 (100 nM) significantly (p ≤ 0.01) increased bladder afferent nerve activity with distention that was blocked with a PAC1/VPAC2 receptor antagonist PACAP6-38 (300 nM). PACAP38 (100 nM) also increased Ca²⁺ activity in urothelial cells over that observed in control preparations. Taken together, these results establish a role for PACAP signaling in bladder sensory components (e.g., urothelial cells, bladder afferent nerves) that may ultimately facilitate increased voiding frequency.

PACAP/Receptor System in Urinary Bladder Dysfunction and Pelvic Pain Following Urinary Bladder Inflammation or Stress

Complex organization of CNS and PNS pathways is necessary for the coordinated and reciprocal functions of the urinary bladder, urethra and urethral sphincters. Injury, inflammation, psychogenic stress or diseases that affect these nerve pathways and target organs can produce lower urinary tract (LUT) dysfunction. Numerous neuropeptide/receptor systems are expressed in the neural pathways of the LUT and non-neural components of the LUT (e.g., urothelium) also express peptides. One such neuropeptide receptor system, pituitary adenylate cyclase-activating polypeptide (PACAP; Adcyap1) and its cognate receptor, PAC1 (Adcyap1r1), have tissue-specific distributions in the LUT. Mice with a genetic deletion of PACAP exhibit bladder dysfunction and altered somatic sensation. PACAP and associated receptors are expressed in the LUT and exhibit neuroplastic changes with neural injury, inflammation, and diseases of the LUT as well as psychogenic stress. Blockade of the PACAP/PAC1 receptor system reduces voiding frequency in preclinical animal models and transgenic mouse models that mirror some clinical symptoms of bladder dysfunction. A change in the balance of the expression and resulting function of the PACAP/receptor system in CNS and PNS bladder reflex pathways may underlie LUT dysfunction including symptoms of urinary urgency, increased voiding frequency, and visceral pain. The PACAP/receptor system in micturition pathways may represent a potential target for therapeutic intervention to reduce LUT dysfunction.

Pituitary adenylate cyclase-activating polypeptide receptors in the trigeminovascular system: implications for migraine

The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) has been implicated in a wide range of functions including vasodilatation, neuroprotection, nociception and neurogenic inflammation. PACAP activates three distinct receptors, the PAC₁ receptor, which responds to PACAP, and the VPAC₁ and VPAC₂ receptors, which respond to both PACAP and vasoactive intestinal polypeptide. The trigeminovascular system plays a key role in migraine and contains the trigeminal nerve, which is the major conduit of craniofacial pain. PACAP is expressed throughout the trigeminovascular system and in higher brain regions involved in processing pain. Evidence from human clinical studies suggests that PACAP may act outside the blood-brain barrier in the pathogenesis of migraine. However, the precise mechanisms involved remain unclear. PACAP potentially induces migraine attacks by activating different receptors in different cell types and tissues. This complexity prompted this review of PACAP receptor pharmacology, expression and function in the trigeminovascular system. Current evidence suggests that the PAC₁ receptor is the likely pathophysiological target of PACAP in migraine. However, multiple PACAP receptors are expressed in key parts of the trigeminovascular system and further work is required to determine their contribution to PACAP physiology and the pathology of migraine.

LINKED ARTICLES

This article is part of a themed section on Molecular Pharmacology of GPCRs. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.21/issuetoc.

Accelerated retinal aging in PACAP knock-out mice

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neurotrophic and neuroprotective peptide. PACAP and its receptors are widely distributed in the retina. A number of reports provided evidence that PACAP is neuroprotective in retinal degenerations. The current study compared retina cell type-specific differences in young (3-4months) and aged adults (14-16months), of wild-type (WT) mice and knock-out (KO) mice lacking endogenous PACAP production during the course of aging. Histological, immunocytochemical and Western blot examinations were performed. The staining for standard neurochemical markers (tyrosine hydroxylase for dopaminergic cells, calbindin 28 kDa for horizontal cells, protein kinase Cα for rod bipolar cells) of young adult PACAP KO retinas showed no substantial alterations compared to young adult WT retinas, except for the specific PACAP receptor (PAC1-R) staining. We could not detect PAC1-R immunoreactivity in bipolar and horizontal cells in young adult PACAP KO animals. Some other age-related changes were observed only in the PACAP KO mice only. These alterations included horizontal and rod bipolar cell dendritic sprouting into the photoreceptor layer and decreased ganglion cell number. Also, Müller glial cells showed elevated GFAP expression compared to the aging WT retinas. Furthermore, Western blot analyses revealed significant differences between the phosphorylation state of ERK1/2 and JNK in KO mice, indicating alterations in the MAPK signaling pathway. These results support the conclusion that endogenous PACAP contributes to protection against aging of the nervous system.

PACAP-38 but not VIP induces release of CGRP from trigeminal nucleus caudalis via a receptor distinct from the PAC1 receptor

OBJECTIVE

To investigate if PACAP and VIP have an effect on CGRP release or NOS activity in the trigeminal ganglion and trigeminal nucleus caudalis and if there can be a difference in effect between PACAP and VIP on these two systems. Furthermore, we investigate if PACAP co-localize with CGRP and/or nNOS in the two tissues.

BACKGROUND

The structurally related neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating peptide-38 (PACAP-38) partially share receptors and are both potent vasodilators. However, PACAP-38 but not VIP is an efficient inducer of migraine attacks in migraineurs. Calcitonin gene-related peptide (CGRP) and nitric oxide (NO) are two signaling molecules known to be involved in migraine.

METHODS

Rat tissue was used for all experiments. Release of CGRP induced by VIP and PACAP in dura mater, trigeminal ganglion (TG) and trigeminal nucleus caudalis (TNC) was quantified by EIA. Regulation of NOS-enzymes caused by VIP and PACAP was investigated in dura mater, TG and TNC by measuring the conversion of L-[3H]arginine to L-[3H]citrulline. Co-expression of PACAP, neuronal nitric oxide synthase (nNOS) and CGRP was explored by immunohistochemistry in TG and TNC. mRNA expression studies of VPAC1, VPAC2 and PAC1-receptors were performed by qRT-PCR.

RESULTS

PACAP-38 administered in increasing concentrations caused a concentration-dependent CGRP-release in the TNC, but not in TG. VIP was without effect in both tissues examined. The PAC1 receptor agonist maxadilan had no effect on CGRP release and the PAC1 antagonist M65 did not inhibit PACAP-38 induced CGRP release. PACAP-38 or VIP did not affect NOS activity in homogenates of TG and TNC. Quantitative PCR demonstrated the presence of VPAC1, VPAC2 and PAC1 receptors in TG and TNC. Immunohistochemistry of PACAP and CGRP showed co-expression in TG and TNC. PACAP and nNOS were co-localized in TG, but not in TNC. PACAP was found to co-localize with glutamine synthetase in TG satellite glial cells.

CONCLUSION

PACAP-38 cause release of CGRP from TNC but not from TG. We suggest that the release is not caused via activation of PAC1, VPAC1 or VPAC2 receptors. PACAP has no effect on NOS activity in TG or TNC. In TG PACAP was found in neuronal cells and in satellite glial cells. It co-localized with CGRP and nNOS in the neuronal cells. In TNC PACAP was co-localized with CGRP but not with nNOS.

Effect of PACAP in central and peripheral nerve injuries

Pituitary adenylate cyclase activating polypeptide (PACAP) is a bioactive peptide with diverse effects in the nervous system. In addition to its more classic role as a neuromodulator, PACAP functions as a neurotrophic factor. Several neurotrophic factors have been shown to play an important role in the endogenous response following both cerebral ischemia and traumatic brain injury and to be effective when given exogenously. A number of studies have shown the neuroprotective effect of PACAP in different models of ischemia, neurodegenerative diseases and retinal degeneration. The aim of this review is to summarize the findings on the neuroprotective potential of PACAP in models of different traumatic nerve injuries. Expression of endogenous PACAP and its specific PAC1 receptor is elevated in different parts of the central and peripheral nervous system after traumatic injuries. Some experiments demonstrate the protective effect of exogenous PACAP treatment in different traumatic brain injury models, in facial nerve and optic nerve trauma. The upregulation of endogenous PACAP and its receptors and the protective effect of exogenous PACAP after different central and peripheral nerve injuries show the important function of PACAP in neuronal regeneration indicating that PACAP may also be a promising therapeutic agent in injuries of the nervous system.

Changes in pituitary adenylate cyclase-activating Peptide 27-like immunoreactive nervous structures in the porcine descending colon during selected pathological processes

This study reports on changes in the pituitary adenylate cyclase-activating peptide 27-like immunoreactive (PACAP-27-LI) nerve structures of the enteric nervous system (ENS) in the porcine descending colon, caused by chemically induced inflammation, nerve injury, and proliferative enteropathy (PE), which is a "natural" inflammation of the porcine digestive tract. The distribution pattern of PACAP-27-LI structures was studied using the immunofluorescence technique in the circular muscle layer, enteric plexuses (i.e., myenteric plexus (MP), outer submucous plexus (OSP), and inner submucous plexus (ISP)), and in the mucosal layer. Under physiological conditions, PACAP-27-LI perikarya have been shown to constitute 4.04 ± 0.66, 6.66 ± 0.77, and 11.19 ± 0.74 % in the MP, OSP, and ISP, respectively. Changes in PACAP-27 immunoreactivity depended on the pathological factor studied. The numbers of the PACAP-27-LI perikarya amounted to 12.26 ± 1.43, 12.28 ± 0.79, and 21.13 ± 1.19 % in chemically induced colitis, 17.83 ± 0.88, 9.03 ± 1.05, and 20.72 ± 1.35 % during PE and 10.65 ± 0.82, 6.88 ± 1.04, and 14.04 ± 1.09 % after axotomy in MP, OSP, and ISP, respectively. All of the studied processes generally resulted in an increase in the number of PACAP-27-LI nerve fibers in the circular muscle and mucosal layers. The obtained results suggest that PACAP-27-LI nerve structures of ENS may participate in various pathological states within the porcine descending colon, and their functions probably depend on the type of pathological factor.

Mice deficient in pituitary adenylate cyclase activating polypeptide (PACAP) are more susceptible to retinal ischemic injury in vivo

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuroprotective peptide exerting protective effects in neuronal injuries. We have provided evidence that PACAP is neuroprotective in several models of retinal degeneration in vivo. Our previous studies showed that PACAP treatment ameliorated the damaging effects of chronic hypoperfusion modeled by permanent bilateral carotid artery occlusion. We have also demonstrated in earlier studies that treatment with PACAP antagonists further aggravates retinal lesions. It has been shown that PACAP deficient mice have larger infarct size in cerebral ischemia. The aim of this study was to compare the degree of retinal damage in wild type and PACAP deficient mice in ischemic retinal insult. Mice underwent 10 min of bilateral carotid artery occlusion followed by 2-week reperfusion period. Retinas were then processed for histological analysis. It was found that PACAP deficient mice had significantly greater retinal damage, as shown by the thickness of the whole retina, the morphometric analysis of the individual retinal layers, and the cell numbers in the inner nuclear and ganglion cell layers. Exogenous PACAP administration could partially protect against retinal degeneration in PACAP deficient mice. These results clearly show that endogenous PACAP reacts as a stress-response peptide that is necessary for endogenous protection against different retinal insults.

Expression of PACAP-like compounds during the caudal regeneration of the earthworm Eisenia fetida

The regeneration of the ventral nerve cord ganglion and peripheral tissues was investigated by radioimmunoassay and immunohistochemistry in the model animal, Eisenia fetida (Annelida, Oligochaeta). It is now well-established that pituitary adenylate cyclase-activating polypeptide (PACAP) is a neurotrophic factor, playing important roles in the development of the nervous system in vertebrate animals. Based on the apparent evolutionary conservation of PACAP and on the several common mechanisms of vertebrate and invertebrate nervous regeneration, the question was raised whether PACAP has any role in the regeneration of the earthworm nervous system. As a first step, we studied the distribution, concentration, and time-course of PACAP-like immunoreactivity during caudal regeneration of both lost segments and the ventral nerve cord ganglia in E. fetida. A strong upregulation of PACAP-like immunoreactivity was observed in most tissues following injury as determined by radioimmunoassay and immunohistochemistry. Significant increases in the concentration of PACAP-like compounds were found in the body wall, alimentary canal, and in coelomocytes. The most characteristic morphological feature was the accumulation of immunolabeled neoblasts in the injured tissues, especially in the ventral nerve cord ganglion that initiates and mediates regeneration processes. Our present results show that PACAP/PACAP-like peptides accumulate in the regenerating tissues of the earthworm, suggesting trophic functions of these compounds in earthworm tissues similarly to vertebrate species.

Neurobiology of orofacial proprioception

Primary sensory fibers innervating the head region derive from neurons of both the trigeminal ganglion (TG) and mesencephalic trigeminal nucleus (MTN). The trigeminal primary proprioceptors have their cell bodies in the MTN. Unlike the TG cells, MTN neuronal somata are centrally located within the brainstem and receive synaptic inputs that potentially modify their output. They are a crucial component of the neural circuitry responsible for the generation and control of oromotor activities. Gaining an insight into the chemical neuroanatomy of the MTN is, therefore, of fundamental importance for the understanding of neurobiology of the head proprioceptive system. This paper summarizes the recent advances in our knowledge of pre- and postsynaptic mechanisms related to orofacial proprioceptive signaling in mammals. It first briefly describes the neuroanatomy of the MTN, which is involved in the processing of proprioceptive information from the face and oral cavity, and then focuses on its neurochemistry. In order to solve the puzzle of the chemical coding of the mammalian MTN, we review the expression of classical neurotransmitters and their receptors in mesencephalic trigeminal neurons. Furthermore, we discuss the relationship of neuropeptides and their corresponding receptors in relaying of masticatory proprioception and also refer to the interactions with other atypical neuromessengers and neurotrophic factors. In extension of previous inferences, we provide conclusive evidence that the levels of transmitters vary according to the environmental conditions thus implying the neuroplasticity of mesencephalic trigeminal neurons. Finally, we have also tried to give an integrated functional account of the MTN neurochemical profiles.

Changes of PACAP levels in the brain show gender differences following short-term water and food deprivation

Pituitary adenylate cyclase activating polypeptide (PACAP) is a pleiotropic neuropeptide exerting diverse actions in the central and peripheral nervous systems. A few studies indicate that PACAP is involved in the regulation of feeding and water homeostasis. The aim of the present study was to investigate changes in PACAP38 concentrations in different brain areas following food or water deprivation in male and female rats. Rats were sacrificed 12, 36 and 84h after water or food removal. PACAP levels were determined by radioimmunoassay. Our results show that levels of PACAP decreased in the hypothalamus in both sexes after water deprivation, with a more marked, significant decrease in females at 12h. A decrease was observed also in the telencephalon, with a similar pattern in both genders: levels were lowest after 12h, and showed a gradual increase at the other two time-points. PACAP levels increased in the brainstem of male rats, while females had a decrease 12h after water deprivation. The pattern of changes in PACAP levels was very different after food deprivation. In male rats, PACAP levels showed a significant increase in the hypothalamus, telencephalon and brainstem 12h after the beginning of starvation. In females, a less marked increase was observed only in the hypothalamus while no changes were found in the other brain areas. Our results show a sensitive reaction in changes of endogenous PACAP levels to water and food deprivation in most brain areas, but they are differentially regulated in male and female rats.

Cellular localization of pituitary adenylate cyclase-activating peptide (PACAP) following traumatic brain injury in humans

The pituitary adenylate cyclase-activating peptide (PACAP) is involved in many processes of the developing and mature central nervous system, such as proliferation, differentiation, apoptosis, neurotransmission, inflammation and neuroprotection. Alternative posttranslational processing of PACAP results in two biologically active, amidated 27- and 38-amino acid peptides termed PACAP27 and PACAP38. In the present study, we examined whether traumatic brain injury (TBI) affects cellular immunopositivity for PACAP27 and PACAP38. Patients (n = 55) were classified into three groups dependent on their survival time (under 24 h, between 24 h and 7 days and between 7 days and 99 days postinjury). PACAP27 and PACAP38 were expressed by neurons and glial cells in normal human neocortex (n = 10). Following TBI, the total number of PACAP27- and PACAP38-positive cells was significantly decreased for a prolonged survival period within the traumatized neocortex. In the pericontusional cortex, the number of cells expressing PACAP27 and PACAP38 was significantly increased at all survival times examined. Triple immunofluorescence examinations revealed a significant increase in the absolute numbers of GFAP-positive reactive astrocytes as well as a decrease in the CNP-positive oligodendrocytes, each coexpressing PACAP27 or PACAP38 in the contusional and pericontusional cortex. We hypothesize that the increase of glial PACAP immunoreactivity may be interpreted as part of a complex endogenous neuroprotective response in the pericontusional regions, but the precise role of PACAP following TBI is yet to be determined.

Bone morphogenetic protein down-regulation of neuronal pituitary adenylate cyclase-activating polypeptide and reciprocal effects on vasoactive intestinal peptide expression

Among bone morphogenetic proteins (BMPs), the decapentaplegic (Dpp; BMP2, BMP4) and glass bottom boat (Gbb/60A; BMP5, BMP6, BMP7) subgroups have well-described functions guiding autonomic and sensory neuronal development, fiber formation and neurophenotypic identities. Evaluation of rat superior cervical ganglia (SCG) post-ganglionic sympathetic neuron developmental regulators identified that selected BMPs of the transforming growth factor beta superfamily have reciprocal effects on neuronal pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) expression. Dpp and Gbb/60A BMPs rapidly down-regulated PACAP expression, while up-regulating other sympathetic neuropeptides, including PACAP-related VIP. The suppressive effects of BMP on PACAP mRNA and peptide expression were potent, efficacious and phosphorylated mothers against decapentaplegic homolog (Smad) signaling-dependent. Axotomy of SCG dramatically increases PACAP expression, and the possibility that abrogation of inhibitory retrograde target tissue BMP signaling may contribute to this up-regulation of sympathetic neuron PACAP was investigated. Replacement of BMP6 to SCG explant preparations significantly blunted the injury-induced elevated PACAP expression, with a concomitant decrease in sympathetic PACAP-immunoreactive neuron numbers. These studies suggested that BMPs modulate neuropeptide identity and diversity by stimulating or restricting the expression of specific peptidergic systems. Furthermore, the liberation of SCG neurons from target-derived BMP inhibition following axotomy may be one participating mechanism associated with injury-induced neuropeptidergic plasticity.

Descriptive and functional neuroanatomy of locus coeruleus-noradrenaline-containing neurons involvement in bradykinin-induced antinociception on principal sensory trigeminal nucleus

The present study was carried out in Wistar rats, using the jaw-opening reflex and dental pulp stimulation, to investigate noradrenaline- and serotonin-mediated antinociceptive circuits. The effects of microinjections of bradykinin into the principal sensory trigeminal nucleus (PSTN) before and after neurochemical lesions of the locus coeruleus noradrenergic neurons were studied. Neuroanatomical experiments showed evidence for reciprocal neuronal pathways connecting the locus coeruleus (LC) to trigeminal sensory nuclei and linking monoaminergic nuclei of the pain inhibitory system to spinal trigeminal nucleus (STN). Fast blue (FB) injections in the locus coeruleus/subcoeruleus region retrogradely labeled neurons in the contralateral PSTN and LC. Microinjections of FB into the STN showed neurons labeled in both ipsilateral and contralateral LC, as well as in the ipsilateral Barrington's nucleus and subcoeruleus area. Retrograde tract-tracing with FB also showed that the mesencephalic trigeminal nucleus sends neural pathways towards the ipsilateral PSTN, with outputs from cranial and caudal aspects of the brainstem. In addition, neurons from the lateral and dorsolateral columns of periaqueductal gray matter also send outputs to the ipsilateral PSTN. Microinjections of FB in the interpolar and caudal divisions of the STN labeled neurons in the caudal subdivision of STN. Microinjections in the STN interpolar and caudal divisions also retrogradely labeled serotonin- and noradrenaline-containing nucleus of the brainstem pain inhibitory system. Finally, the gigantocellularis complex (nucleus reticularis gigantocellularis/paragigantocellularis), nucleus raphe magnus and nucleus raphe pallidus also projected to the caudal divisions of the STN. Microinjections of bradykinin in the PSTN caused a statistically significant long-lasting antinociception, antagonized by the damage of locus coeruleus-noradrenergic neuronal fibres with (N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine) (DSP4), a neurotoxin that specifically depleted noradrenaline from locus coeruleus terminal fields. These data suggest that serotonin- and noradrenaline-containing nuclei of the endogenous pain inhibitory system exert a key-role in the antinociceptive mechanisms of bradykinin and the locus coeruleus is crucially involved in this effect.

Role for pituitary adenylate cyclase activating polypeptide in cystitis-induced plasticity of micturition reflexes

Pituitary adenylate cyclase activating polypeptide (PACAP) peptides are expressed and regulated in sensory afferents of the micturition pathway. Although these studies have implicated PACAP in bladder control, the physiological significance of these observations has not been firmly established. To clarify these issues, the roles of PACAP and PACAP signaling in micturition and cystitis were examined in receptor characterization and physiological assays. PACAP receptors were identified in various tissues of the micturition pathway, including bladder detrusor smooth muscle and urothelium. Bladder smooth muscle expressed heterogeneously PAC(1)null, PAC(1)HOP1, and VPAC(2) receptors; the urothelium was more restricted in expressing preferentially the PAC(1) receptor subtype only. Immunocytochemical studies for PAC(1) receptors were consistent with these tissue distributions. Furthermore, the addition of 50-100 nM PACAP27 or PACAP38 to isolated bladder strips elicited transient contractions and sustained increases in the amplitude of spontaneous phasic contractions. Treatment of the bladder strips with tetrodotoxin (1 muM) did not alter the spontaneous phasic contractions suggesting direct PACAP effects on bladder smooth muscle. PACAP also increased the amplitude of nerve-evoked contractions. By contrast, vasoactive intestinal polypeptide had no direct effects on bladder smooth muscle. In a rat cyclophosphamide (CYP)-induced cystitis paradigm, intrathecal or intravesical administration of PAC(1) receptor antagonist, PACAP6-38, reduced cystitis-induced bladder overactivity. In summary, these studies support roles for PACAP in micturition and suggest that inflammation-induced plasticity in PACAP expression in peripheral and central micturition pathways contribute to bladder dysfunction with cystitis.

Neurochemical plasticity and the role of neurotrophic factors in bladder reflex pathways after spinal cord injury

Transection of the spinal cord that interrupts the spinobulbospinal micturition reflex pathway, abolishes voluntary voiding and initially produces an areflexic bladder with complete urinary retention. However, depending upon the species, reflex bladder activity slowly recovers over the course of weeks or months. In chronic spinal animals, reflex mechanisms in the lumbosacral spinal cord are capable of duplicating many of the functions performed by reflex pathways in animals with an intact spinal cord and can induce bladder hyperreflexia. However, the bladder does not empty efficiently due to a loss of bladder-sphincter coordination (bladder-sphincter dyssynergia). In contrast to normal animals in which the sphincter relaxes during voiding, animals with a spinal cord injury exhibit sphincter contractions during voiding, an increase in urethral outlet resistance, urinary retention, bladder hyperreflexia, bladder overdistension, and an increase in bladder afferent cell size. Changes in electrophysiological or neurochemical properties of bladder afferent cells in the dorsal root ganglia and of spinal pathways could contribute to the emergence of the spinal micturition reflex, bladder hyperreflexia and changes in the pharmacologic responses of reflex pathways in the lumbosacral spinal cord after spinal cord injury. Urinary bladder hyperreflexia after spinal cord injury may reflect a change in the balance of neuroactive compounds in bladder reflex pathways. This review will detail: (1) changes in the neurochemical phenotype of bladder afferent neurons and of spinal neurons mediating micturition reflexes after spinal cord injury, with an emphasis on three neuroactive compounds, neuronal nitric oxide synthase (nNOS), galanin, and pituitary adenylate cyclase activating polypeptide (PACAP); (2) possible functional consequences on bladder reflexes of changes in spinal cord neurochemistry after spinal cord injury, and (3) the potential role of neurotrophic factors expressed in the urinary bladder or spinal cord after spinal cord injury in mediating these neurochemical changes.

Endothelial and lipoprotein lipases in human and mouse placenta

Placenta expresses various lipase activities. However, a detailed characterization of the involved genes and proteins is lacking. In this study, we compared the expression of endothelial lipase (EL) and LPL in human term placenta. When placental protein extracts were separated by heparin-Sepharose affinity chromatography, the EL protein eluted as a single peak without detectable phospholipid or triglyceride (TG) lipase activity. The major portion of LPL protein eluted slightly after EL. This peak also had no lipase activity and most likely contained monomeric LPL. Fractions eluting at a higher NaCl concentration contained small amounts of LPL protein (most likely dimeric LPL) and had substantial TG lipase activity. In situ hybridization studies showed EL mRNA expression in syncytiotrophoblasts and endothelial cells and LPL mRNA in syncytiotrophoblasts. In contrast, immunohistochemistry showed EL and LPL protein associated with both cell types. In mouse placentas, lack of LPL expression resulted in increased EL mRNA expression. These results suggest that the cellular expression of EL and LPL in human placenta is different. Nevertheless, the two lipases might have overlapping functions in the mouse placenta. Our data also suggest that the major portions of both proteins are stored in an inactive form in human term placenta.

Changes in pituitary adenylate cyclase activating polypeptide expression in urinary bladder pathways after spinal cord injury

These studies examined changes in the pituitary adenylate cyclase activating polypeptide (PACAP) expression in micturition reflex pathways after spinal cord injury (SCI) of various durations. In spinal-intact animals, PACAP immunoreactivity (IR) was expressed in fibers in the superficial dorsal horn in all segmental levels examined (L1, L2, L4-S1). Bladder-afferent cells (35-45%) in the dorsal root ganglia (DRG; L1, L2, L6, S1) from spinal-intact animals also exhibited PACAP-IR. After SCI (6 weeks), PACAP-IR was dramatically increased in spinal segments and DRG (L1, L2, L6, S1) involved in micturition reflexes. The density of PACAP-IR was increased in the superficial laminae (I-II) of the L1, L2, L6, and S1 spinal segments. No changes in PACAP-IR were observed in the L4-L5 segments. Staining was also dramatically increased in a fiber bundle extending ventrally from Lissauer's tract (LT) in lamina I along the lateral edge of the dorsal horn to the sacral parasympathetic nucleus (SPN) in the L6-S1 spinal segments (lateral collateral pathway of Lissauer, LCP). After SCI (range 48 h to 6 weeks), PACAP-IR in cells in the L1, L2, L6, and S1 DRG significantly (P < or = 0.001) increased and the percentage of bladder-afferent cells expressing PACAP-IR also significantly (P < or = 0.001) increased (70-92%). No changes were observed in the L4-L5 DRG. PACAP-IR was reduced throughout the urothelium and detrusor smooth muscle whole mounts after SCI. These studies demonstrate changes in PACAP expression in micturition reflex pathways after SCI that may contribute to urinary bladder dysfunction or reemergence of primitive voiding reflexes after SCI.

Expression of the endothelial lipase gene in murine embryos and reproductive organs

Endothelial lipase (EL) is a recently discovered member of the triglyceride-lipase family that is involved in plasma HDL metabolism. In this study, we investigated the putative role of EL in mouse reproduction by studying EL gene expression in mouse embryos and adult reproductive organs. PCR analysis revealed that EL mRNA is expressed in mouse embryos on embryonic day 8.5 (E8.5) to E11.5, but not later in development. In situ hybridization studies on E10.5 whole embryos and embryonic sections showed expression of EL mRNA in multiple tissues, although of varying intensity. High expression was found in the neuroepithelium of the brain and the neural tube, the mesenchymal cells between organs, the optic lens and cup, and the otocyst. In adult mice, EL mRNA expression was high in ovaries from pregnant mice but low in ovaries from nonpregnant mice. EL mRNA was also highly expressed in placenta and testes. In situ hybridization studies demonstrated intense EL mRNA staining of lutein cells in corpora lutei in ovaries, of spermatocytes in the late pachytene and diplotene stages in testes, and of principal cells in epididymis. These results suggest that EL, in addition to its effects on plasma lipoprotein metabolism, plays a role in murine reproduction.

Developmental changes in the expression of growth hormone-releasing hormone and pituitary adenylate cyclase-activating polypeptide in zebrafish

Growth hormone-releasing hormone (GHRH) and pituitary adenylate cyclase-activating polypeptide (PACAP) are structurally and functionally related members of the glucagon superfamily, a group of hormones important in development, growth, and metabolism. Our objectives were to determine the developmental expression pattern of the ghrh-pacap1 gene using the zebrafish model. The temporal and spatial expression pattern of the ghrh-pacap1 gene was examined by RT-PCR and in situ hybridization. In zebrafish, the ghrh-pacap1 mRNA transcript was expressed throughout development beginning at the transition between the blastula and gastrula periods. During midgastrulation, alternative splicing resulted in the generation of a novel transcript lacking the cryptic peptide. During the segmentation period, expression was localized to the neural tube, developing eye, and neural crest; strong expression was found in the developing cerebellum. Later in development, expression was localized in the hatching gland and developing pharyngeal arches. The temporal and spatial expression pattern of the ghrh-pacap1 transcript suggests that these hormones may modulate patterning during development.

Galanin down-regulates microglial tumor necrosis factor-alpha production by a post-transcriptional mechanism

The neuropeptide galanin (GAL) is up-regulated following neuronal axotomy or inflammation. Since other neuropeptides act as immunomodulatory agents, we sought to determine whether GAL might affect the murine microglial cell line BV2, which expresses the GAL2 receptor. Even at very low concentrations, GAL inhibited tumor necrosis factor-alpha (TNF alpha) release but not TNF alpha mRNA levels in LPS-stimulated BV2 cells. Northern blot analysis showed that GAL inhibited the addition of a poly(A) tail, and stability assays showed that it also destabilized TNF alpha mRNA. Thus, GAL inhibits TNF alpha production by a post-transcriptional mechanism that both prevents the efficient addition of the poly(A) tail and accelerates TNF alpha mRNA degradation.

Pituitary adenylate cyclase-activating peptide in the rat central nervous system: an immunohistochemical and in situ hybridization study

In the present study the localization of pituitary adenylate cyclase-activating peptide (PACAP)-expressing cell bodies and PACAP projections were mapped in the adult rat brain and spinal cord by using immunohistochemistry and in situ hybridization histochemistry. A widespread occurrence of PACAP-containing cell bodies was found, with the greatest accumulation in several hypothalamic nuclei and in several brainstem nuclei, especially the habenular nuclei, the pontine nucleus, the lateral parabrachial nucleus (LPB), and the vagal complex. PACAP was also present in cell bodies in the olfactory areas, in neocortical areas, in the hippocampus, in the vestibulo- and cochlear nuclei, in cell bodies of the intermediolateral cell column of the spinal cord and in Purkinje cells of the cerebellum, in the subfornical organ, and in the organum vasculosum of the lamina terminalis. An intense accumulation of PACAP-immunoreactive (-IR) nerve fibers was observed throughout the hypothalamus, in the amydaloid and extended amygdaloid complex, in the anterior and paraventricular thalamic nuclei, in the intergeniculate leaflet, in the pretectum, and in several brainstem nuclei, such as the parabrachial nucleus, the sensory trigeminal nucleus, and the nucleus of the solitary tract. PACAP-IR nerve fibers were also found in the area postrema, the posterior pituitary and the choroid plexus, and the dorsal and ventral horn of the spinal cord. The widespread distribution of PACAP in the brain and spinal cord suggests that PACAP is involved in the control of many autonomic and sensory functions as well as higher cortical processes.

Comparative analysis of the chemical neuroanatomy of the mammalian trigeminal ganglion and mesencephalic trigeminal nucleus

A characteristic peculiarity of the trigeminal sensory system is the presence of two distinct populations of primary afferent neurons. Most of their cell bodies are located in the trigeminal ganglion (TG) but part of them lie in the mesencephalic trigeminal nucleus (MTN). This review compares the neurochemical content of central versus peripheral trigeminal primary afferent neurons. In the TG, two subpopulations of primary sensory neurons, containing immunoreactive (IR) material, are identified: a number of glutamate (Glu)-, substance P (SP)-, neurokinin A (NKA)-, calcitonin gene-related peptide (CGRP)-, cholecystokinin (CCK)-, somatostatin (SOM)-, vasoactive intestinal polypeptide (VIP)- and galanin (GAL)-IR ganglion cells with small and medium-sized somata, and relatively less numerous larger-sized neuropeptide Y (NPY)- and peptide 19 (PEP 19)-IR trigeminal neurons. In addition, many nitric oxide synthase (NOS)- and parvalbumin (PV)-IR cells of all sizes as well as fewer, mostly large, calbindin D-28k (CB)-containing neurons are seen. The majority of the large ganglion cells are surrounded by SP-, CGRP-, SOM-, CCK-, VIP-, NOS- and serotonin (SER)-IR perisomatic networks. In the MTN, the main subpopulation of large-sized neurons display Glu-immunoreactivity. Additionally, numerous large MTN neurons exhibit PV- and CB-immunostaining. On the other hand, certain small MTN neurons, most likely interneurons, are found to be GABAergic. Furthermore, NOS-containing neurons can be detected in the caudal and the mesencephalic-pontine junction portions of the nucleus. Conversely, no immunoreactivity to any of the examined neuropeptides is observed in the cell bodies of MTN neurons but these are encircled by peptidergic, catecholaminergic, serotonergic and nitrergic perineuronal arborizations in a basket-like manner. Such a discrepancy in the neurochemical features suggests that the differently fated embryonic migration, synaptogenesis, and peripheral and central target field innervation can possibly affect the individual neurochemical phenotypes of trigeminal primary afferent neurons.

Herpesvirus quiescence in neuronal cells IV: virus activation induced by pituitary adenylate cyclase-activating polypeptide (PACAP) involves the protein kinase A pathway

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a naturally occurring peptide found in the central nervous system that plays a role in somatosensory processing and activation of protein kinase A (PKA) and protein kinase C (PKC). Because activation of PKA or PKC results in reactivation of HSV-1 from latently infected embryonic neuronal cells, PACAP was used to evaluate HSV-1 activation from quiescently infected (QIF)-PC12 cells. Our studies demonstrate that physiologically relevant concentrations of PACAP38 and PACAP27 induce HSV-1 activation from QIF-PC12 cell cultures in a dose-dependent fashion. PACAP-induced activation of virus was significantly impaired by the PKA-inhibitor, H-89 (20 microM), whereas treatment with the PKC-inhibitor, GF109203X (1 microM), was without affect. Additionally, direct activation of PKA with cAMP analogs, 8-(4-chlorophenylthio)- and dibutyryl-cAMP, only partially mimicked the effect of PACAP on virus activation. Taken together, PACAP induced HSV-1 activation from QIF-PC12 cells involves the PKA and possibly cAMP-independent pathways. This report is the first to demonstrate that PACAP induces HSV-1 activation from a quiescent state and that this in vitro cell model is useful for studying early inductive events that lead to virus production from quiescence.

The origin and function of the pituitary adenylate cyclase-activating polypeptide (PACAP)/glucagon superfamily

The pituitary adenylate cyclase-activating polypeptide (PACAP)/ glucagon superfamily includes nine hormones in humans that are related by structure, distribution (especially the brain and gut), function (often by activation of cAMP), and receptors (a subset of seven-transmembrane receptors). The nine hormones include glucagon, glucagon-like peptide-1 (GLP-1), GLP-2, glucose-dependent insulinotropic polypeptide (GIP), GH-releasing hormone (GRF), peptide histidine-methionine (PHM), PACAP, secretin, and vasoactive intestinal polypeptide (VIP). The origin of the ancestral superfamily members is at least as old as the invertebrates; the most ancient and tightly conserved members are PACAP and glucagon. Evidence to date suggests the superfamily began with a gene or exon duplication and then continued to diverge with some gene duplications in vertebrates. The function of PACAP is considered in detail because it is newly (1989) discovered; it is tightly conserved (96% over 700 million years); and it is probably the ancestral molecule. The diverse functions of PACAP include regulation of proliferation, differentiation, and apoptosis in some cell populations. In addition, PACAP regulates metabolism and the cardiovascular, endocrine, and immune systems, although the physiological event(s) that coordinates PACAP responses remains to be identified.

Regulation of pituitary adenylate cyclase activating polypeptide and its receptor type 1 after traumatic brain injury: comparison with brain-derived neurotrophic factor and the induction of neuronal cell death

Neurotrophic factors are known to promote neuronal survival during development and after acute brain injury. Recent data suggest that some neuropeptides also exhibit neurotrophic activities, as shown for the pituitary adenylate cyclase activating polypeptide, which increases the survival of various neuronal populations in culture. Employing in situ hybridization techniques, we have studied the regulation of messenger RNA for pituitary adenylate cyclase activating polypeptide and its receptor type 1 after a moderate traumatic brain injury to rat brain cortex. We have further compared their messenger RNA expression to that of brain-derived neurotrophic factor and to the amount of cell death occurring in the brain at various times after the brain injury. Levels of brain-derived neurotrophic factor messenger RNA increased rapidly within 2 h after trauma in cortex and hippocampus, and returned to control levels thereafter. The levels of messenger RNA for pituitary adenylate cyclase activating polypeptide also increased with time in the injured brains and reached maximal expression at 72 h, i.e. the end of the observation period. The alterations in pituitary adenylate cyclase activating polypeptide messenger RNA levels were particularly pronounced in the perifocal region and in the ipsilateral dentate gyrus of the brain injury. In contrast, the messenger RNA levels encoding pituitary adenylate cyclase activating polypeptide receptor type 1 first decreased after trauma and were then normalized in the dentate gyrus. There was a large increase in the number of cells labelled for DNA breaks at 12 h post-trauma, indicative of enhanced cell death. The number of labelled cells, however, decreased at later stages concomitant with an increase in the expression of pituitary adenylate cyclase activating polypeptide messenger RNA. Pituitary adenylate cyclase activating polypeptide rescued cortical neurons in cultures against ionomycin-induced cell death, supporting the concept of a neuroprotective effect for the peptide. These results demonstrate a differential regulation of messenger RNA for brain-derived neurotrophic factor and the pituitary adenylate cyclase activating polypeptide and its receptor after brain trauma. The data also suggest that pituitary adenylate cyclase activating polypeptide might have a beneficial effect in brain injury by counteracting neuronal cell death.

Increased expression, axonal transport and release of pituitary adenylate cyclase-activating polypeptide in the cultured rat vagus nerve

The expression and axonal transport of pituitary adenylate cyclase-activating polypeptide (PACAP) was studied in the cultured vagus nerve of the rat by immunocytochemistry and in situ hybridization. The number of neurons immunoreactive for PACAP increased markedly within the nodose ganglion during a 24-48 h culture period, as did the number of cells containing messenger RNA for PACAP. PACAP was found to be axonally transported and accumulated at the site of a crush injury. The peptide was also released at this site. Addition of PACAP to regenerating nerves in culture did not affect axonal outgrowth, neither did antibodies against PACAP. Separate experiments showed that neither PACAP-27 nor PACAP-38 affected proliferation of non-neuronal cells measured as the incorporation of [3H]thymidine. In contrast, forskolin, another potent stimulator of adenylate cyclase besides PACAP, dramatically decreased [3H]thymidine incorporation. The results showed that, during regeneration of peripheral nerves, PACAP expression increases and the peptide is transported into the regenerating nerve, where it is released. The functional significance of this release is unknown, but it does not seem to be directly related to the initiation of proliferation of Schwann cells or initial axonal outgrowth.

Brainstem mechanisms underlying feeding behaviors

The essential elements controlling trigeminal motoneurons during feeding lie between the trigeminal and facial motor nuclei. These include populations of neurons in the medial reticular formation and pre-motoneurons in the lateral brainstem that reorganize to generate various patterns. Orofacial sensory feedback, antidromic firing in spindle afferents and intrinsic properties of motoneurons also contribute to the final masticatory motor output.

Embryonic expression of pituitary adenylate cyclase-activating polypeptide in sensory and autonomic ganglia and in spinal cord of the rat

Pituitary adenylate cyclase-activating polypeptide (PACAP), a neuropeptide that is related structurally to vasoactive intestinal polypeptide (VIP), has been shown to stimulate neuronal growth and differentiation, indicating a possible function in the development of the nervous system. Studies have indicated that the PACAP receptor is expressed during development, but data on PACAP expression are limited mainly to postnatal development. In the present study, we used immunohistochemistry and in situ hybridization histochemistry to examine the expression of PACAP in autonomic and sensory ganglia and spinal cord of rat fetuses at embryonic days 12-21 (E12-E21). PACAP immunoreactivity was visualized by using a specific monoclonal anti-PACAP antibody to detect both PACAP-38 and PACAP-27, and PACAP mRNA was visualized by using a [33P]-labeled cRNA-probe. PACAP- nerve fibers were observed in the spinal cord as early as E13. At E14, PACAP-immunoreactive nerve fibers projected to the sympathetic trunk, where few PACAP- nerve cell bodies were seen from E15. On the same embryonic day, PACAP-immunoreactive nerve cell bodies appeared in the intermediolateral column of the spinal cord. From E15 to E16, PACAP-immunoreactive nerve cell bodies were visible within sensory and autonomic ganglia, such as the dorsal root, the trigeminal, the sphenopalatine, the otic, the submandibular, and the nodose ganglia. At E16, PACAP+ nerve fibers were innervating the adrenal medulla, and immunoreactive fibers could also be observed in the superior cervical ganglion, in which PACAP-immunoreactive cell bodies were detected occasionally from E18. The synthesis of PACAP in neuronal cell bodies was confirmed by the demonstration of PACAP mRNA with in situ hybridization histochemistry. Thus, in all of the structures examined, PACAP appeared at roughly the same embryonic stage and, thereafter, increased to the adult level before birth. Because PACAP occurred with the same distribution pattern as that described in the adult rat, there is no evidence for transient expression. The early expression of PACAP suggests a possible role for the peptide in the developing nervous system.

Pituitary adenylate cyclase activating polypeptide immunoreactivity in capsaicin-sensitive nerve fibres supplying the rat urinary tract

Pituitary adenylate cyclase activating peptide is a new member of the vasoactive intestinal polypeptide family of peptides which is present in the brain as well as neuronal elements of a number of peripheral organs. Pituitary adenylate cyclase activating peptide occurs in two forms, pituitary adenylate cyclase activating peptide-38 and the C-terminally truncated 27 amino acid form, pituitary adenylate cyclase activating peptide-27, both derived from the same precursor which in addition gives rise to a structurally-related peptide, pituitary adenylate cyclase activating peptide-related peptide. Using specific radioimmunoassays for pituitary adenylate cyclase activating peptide-38, pituitary adenylate cyclase activating peptide-27 and pituitary adenylate cyclase activating peptide-related peptide we found that all three pituitary adenylate cyclase activating peptide-precursor-derived peptides were present in tissue extracts from the ureter, the urinary bladder and the urethra. Pituitary adenylate cyclase activating peptide-38 was the dominating peptide with the highest concentration in the ureter. When extracts from the urinary bladder were fractionated by reverse phase high pressure liquid chromatography immunoreactive components corresponding to synthetic pituitary adenylate cyclase activating peptide-38, pituitary adenylate cyclase activating peptide-27 and pituitary adenylate cyclase activating peptide-related peptide were identified with the respective antisera. By immunohistochemistry, using a specific monoclonal mouse anti-pituitary adenylate cyclase activating peptide antibody, pituitary adenylate cyclase activating peptide-immunoreactivity was shown to have a widespread distribution in the rat urinary tract, localized exclusively to nerve fibres. No immunoreactive neuronal cell bodies were observed in any of the tissues. Pituitary adenylate cyclase activating peptide was shown to be located in varicose nerve fibres associated with blood vessels and smooth muscle. The majority of pituitary adenylate cyclase activating peptide-positive nerve fibres and bundles were, however, present in subepithelial plexuses from which delicate varicose nerve fibres entered the urothelium. Double immunostaining for pituitary adenylate cyclase activating peptide and a marker for sensory neurons, calcitonin-gene related peptide, disclosed that the two peptides were almost completely co-localized while the co-existence between pituitary adenylate cyclase activating peptide and the structurally related peptide vasoactive intestinal polypeptide, was scarce. Neonatal capsaicin-treatment caused a marked reduction in the concentration of immunoreactive pituitary adenylate cyclase activating peptide in all regions of the rat urinary tract, being most prominent in the ureter. By immunohistochemistry it was shown that the sensory neurotoxin caused a reduction in the number and intensity of pituitary adenylate cyclase activating peptide-immunoreactive nerve fibres in all organs of the urinary tract which was most prominent in the epithelial and subepithelial layers. Identical changes were observed for the calcitonin-gene related peptide-containing nerve fibres, while vasoactive intestinal polypeptide-positive nerve fibres were unaffected by capsaicin-treatment. In conclusion pituitary adenylate cyclase activating peptide is present in the rat urinary tract mainly in the form of pituitary adenylate cyclase activating peptide-38. Immunoreactive nerve fibres were associated with the epithelium, blood vessels and smooth musculature. Pituitary adenylate cyclase activating peptide was almost completely co-localized with calcitonin-gene related peptide and by neonatal capsaicin treatment the two peptides were identically affected. The findings suggest that pituitary adenylate cyclase activating peptide is a sensory neurotransmitter in the rat urinary tract.

Pituitary adenylate cyclase-activating peptide (PACAP) and PACAP type 1 receptor expression in regenerating adult mouse and rat superior cervical ganglia in vitro

Pituitary adenylate cyclase-activating polypeptide (PACAP), a regulatory peptide belonging to the vasoactive intestinal peptide (VIP) family, is widely distributed in the central and peripheral nervous system. Recent studies have shown that PACAP expression is upregulated in sensory neurons in response to axonal injury. Here we report that PACAP and PACAP type 1 receptors are located in rat and mouse superior cervical ganglia (SCG). PACAP-immunoreactivity (-IR) was demonstrated in preganglionic fibers, whereas only occasional PACAP-IR cell bodies could be observed. In situ hybridization histochemistry using 35S-labeled deoxyribonucleotide probes confirmed that PACAP mRNA was present only in occasional cell bodies. In contrast, PACAP type 1 receptor mRNA was expressed in virtually all cell bodies within the ganglia. After removal and culturing of the SCG for 24 h, there was a marked increase in PACAP mRNA, whilst PACAP type 1 receptor mRNA expression appeared to be downregulated in most nerve cell bodies except for a few scattered neurons displaying a strong upregulation. The total specific binding of PACAP to isolated SCG membranes as assayed by [125I]PACAP-27 binding showed an increase in SCG cultured for 48 h. PACAP-27 neither affected axonal outgrowth from the cultured SCG nor the survival of cells within the SCG. We conclude that PACAP and PACAP receptors are rapidly upregulated in sympathetic ganglia in response to axonal injury and that PACAP may play a role during nerve regeneration.

The effects of axotomy and preganglionic denervation on the expression of pituitary adenylate cyclase activating peptide (PACAP), galanin and PACAP type 1 receptors in the rat superior cervical ganglion

The effects of axotomy, chemical sympathectomy and preganglionic denervation on the expression of the neuropeptides, pituitary adenylate cyclase-activating peptide (PACAP), galanin (GAL), and the PACAP type 1 receptor in the rat superior cervical ganglion (SCG) were investigated by immunocytochemistry, in situ hybridization and receptor autoradiography. An antibody recognizing the rat vesicular acetylcholine transporter (VAChT) was used for the detection of preganglionic cholinergic fibers. In the normal SCG, PACAP-immunoreactivity (-IR) was present in numerous, basket-forming, preganglionic nerve fibers, while very few SCG neurons expressed PACAP. GAL-IR was restricted to occasional neurons, and a few nerve fibers, most of which were, in addition, PACAP-IR. PACAP type 1 receptors were expressed in all nerve cell bodies. Axotomy resulted in a rapid and prominent upregulation of PACAP in a large number of nerve cell bodies. There was a large increase also in GAL expression in many nerve cell bodies. In contrast, there was a marked decline in PACAP type 1 receptor expression. Chemical sympathectomy by administration of the catcholaminergic neurotoxin, 6-hydroxydopamine (6-OHDA), gave rise to similar changes. Preganglionic denervation led to the disappearance of PACAP- and VAChT-IR baskets and to the upregulation of PACAP and GAL expression in neurons located close to the entrance of the sympathetic chain, whereas PACAP type 1 receptor expression was not affected. PACAP and GAL were coexpressed in most neurons after axotomy and chemical sympathectomy. Taken together, these results indicate that disruption of target contact and/or the infliction of an injury to the axons of the sympathetic neurons, rather than the preganglionic output, regulates the expression of PACAP, GAL and the PACAP type 1 receptor.