1
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Sakharkar AJ, Ganesh CB. Leucine-enkephalin-immunoreactive neurons in the brain of the cichlid fish Oreochromis mossambicus. Neuropeptides 2020; 81:101999. [PMID: 31843219 DOI: 10.1016/j.npep.2019.101999] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 11/26/2019] [Accepted: 12/09/2019] [Indexed: 12/29/2022]
Abstract
Enkephalins are the pentapeptides involved in pain relief and neuroendocrine responses with high affinity for delta opioid receptors in vertebrates. In the present investigation, we studied the distribution of leucine-enkephalin-immunoreactive (L-ENK-ir) neurons in the brain of the cichlid fish Oreochromis mossambicus. Application of the antisera against L-ENK revealed the presence of numerous L-ENK-ir perikarya and fibres in subdivisions of the dorsal and the ventral telencephalon, the medial olfactory tract and the nucleus entopeduncularis, whereas intensely labelled L-ENK-ir fibres were noticed in the olfactory bulb. Furthermore, the presence of L-ENK-ir cells and dense accumulations of fibres in the preoptic area and its subdivisions, the nucleus preopticus pars magnocellularis and the nucleus preopticus pars parvocellularis suggested a role for this peptide in regulation of reproduction. While intensely labelled cells and fibres were found in the nucleus lateralis tuberis pars lateralis as well as the nucleus lateralis tuberis pars medialis, some L-ENK-ir fibres were seen at the hypothalamo-hypophyseal tract indicating the possible hypophysiotrophic role for this peptide. Numerous L-ENK-ir cells and dense network of fibres were observed in the subdivisions of the nucleus recess lateralis and the pretectal area, whereas intensely labelled thick network of L-ENK- fibres were found in the ventromedial thalamic nucleus, the sub-layers of the optic tectum and the rostral spinal cord. The widespread distribution of L-ENK-immunoreactivity in the olfactory bulb, the telencephalon, the diencephalon and the mesencephalon regions of the brain as well as the spinal cord suggests the possible involvement of this peptide in the regulation of diverse functions such as neuroendocrine, antinociceptive, visual and olfactory responses in O. mossambicus.
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Affiliation(s)
- Amul J Sakharkar
- Department of Biotechnology, Savitribai Phule Pune University, Pune 411007, India
| | - C B Ganesh
- Neuroendocrinology Research Laboratory, Department of Studies in Zoology, Karnatak University, Dharwad 580 003, India.
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2
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Vardy E, Sassano MF, Rennekamp AJ, Kroeze WK, Mosier PD, Westkaemper RB, Stevens CW, Katritch V, Stevens RC, Peterson RT, Roth BL. Single Amino Acid Variation Underlies Species-Specific Sensitivity to Amphibian Skin-Derived Opioid-like Peptides. ACTA ACUST UNITED AC 2016; 22:764-75. [PMID: 26091169 DOI: 10.1016/j.chembiol.2015.05.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 04/14/2015] [Accepted: 05/01/2015] [Indexed: 01/08/2023]
Abstract
It has been suggested that the evolution of vertebrate opioid receptors (ORs) follow a vector of increased functionality. Here, we test this idea by comparing human and frog ORs. Interestingly, some of the most potent opioid peptides known have been isolated from amphibian skin secretions. Here we show that such peptides (dermorphin and deltorphin) are highly potent in the human receptors and inactive in frog ORs. The molecular basis for the insensitivity of the frog ORs to these peptides was studied using chimeras and molecular modeling. The insensitivity of the delta OR (DOR) to deltorphin was due to variation of a single amino acid, Trp7.35, which is a leucine in mammalian DORs. Notably, Trp7.35 is completely conserved in all known DOR sequences from lamprey, fish, and amphibians. The deltorphin-insensitive phenotype was verified in fish. Our results provide a molecular explanation for the species selectivity of skin-derived opioid peptides.
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Affiliation(s)
- Eyal Vardy
- Department of Pharmacology, UNC Chapel Hill Medical School, 4072 Genetic Medicine Building, 120 Mason Farm Road, Chapel Hill, NC 27514, USA
| | - Maria F Sassano
- Department of Pharmacology, UNC Chapel Hill Medical School, 4072 Genetic Medicine Building, 120 Mason Farm Road, Chapel Hill, NC 27514, USA
| | - Andrew J Rennekamp
- Cardiovascular Research Center and Division of Cardiology, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, 149 13(th) Street, Charlestown, MA 02129, USA; Broad Institute, 7 Cambridge Center, Cambridge, MA 02142, USA
| | - Wesley K Kroeze
- Department of Pharmacology, UNC Chapel Hill Medical School, 4072 Genetic Medicine Building, 120 Mason Farm Road, Chapel Hill, NC 27514, USA
| | - Philip D Mosier
- Department of Medicinal Chemistry, Virginia Commonwealth University School of Pharmacy, Richmond, VA 23298, USA
| | - Richard B Westkaemper
- Department of Medicinal Chemistry, Virginia Commonwealth University School of Pharmacy, Richmond, VA 23298, USA
| | - Craig W Stevens
- Department of Pharmacology & Physiology, Oklahoma State University Center for Health Sciences, 1111 West 17(th) Street, Tulsa, OK 74107, USA
| | - Vsevolod Katritch
- Department of Biological Sciences and Chemistry, Bridge Institute, University of Southern California, Los Angeles, CA 90089, USA
| | - Raymond C Stevens
- Department of Biological Sciences and Chemistry, Bridge Institute, University of Southern California, Los Angeles, CA 90089, USA
| | - Randall T Peterson
- Cardiovascular Research Center and Division of Cardiology, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, 149 13(th) Street, Charlestown, MA 02129, USA; Broad Institute, 7 Cambridge Center, Cambridge, MA 02142, USA
| | - Bryan L Roth
- Department of Pharmacology, UNC Chapel Hill Medical School, 4072 Genetic Medicine Building, 120 Mason Farm Road, Chapel Hill, NC 27514, USA.
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3
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Stevens CW. Bioinformatics and evolution of vertebrate nociceptin and opioid receptors. VITAMINS AND HORMONES 2015; 97:57-94. [PMID: 25677768 DOI: 10.1016/bs.vh.2014.10.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
G protein-coupled receptors (GPCRs) are ancestrally related membrane proteins on cells that mediate the pharmacological effect of most drugs and neurotransmitters. GPCRs are the largest group of membrane receptor proteins encoded in the human genome. One of the most famous types of GPCRs is the opioid receptors. Opioid family receptors consist of four closely related proteins expressed in all vertebrate brains and spinal cords examined to date. The three classical types of opioid receptors shown unequivocally to mediate analgesia in animal models and in humans are the mu- (MOR), delta- (DOR), and kappa-(KOR) opioid receptor proteins. The fourth and most recent member of the opioid receptor family discovered is the nociceptin or orphanin FQ receptor (ORL). The role of ORL and its ligands in producing analgesia is not as clear, with both analgesic and hyperalgesic effects reported. All four opioid family receptor genes were cloned from expressed mRNA in a number of vertebrate species, and there are enough sequences presently available to carry out bioinformatic analysis. This chapter presents the results of a comparative analysis of vertebrate opioid receptors using pharmacological studies, bioinformatics, and the latest data from human whole-genome studies. Results confirm our initial hypotheses that the four opioid receptor genes most likely arose by whole-genome duplication, that there is an evolutionary vector of opioid receptor type divergence in sequence and function, and that the hMOR gene shows evidence of positive selection or adaptive evolution in Homo sapiens.
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Affiliation(s)
- Craig W Stevens
- Department of Pharmacology and Physiology, Oklahoma State University Center for Health Sciences, Tulsa, Oklahoma, USA.
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4
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Effects of intramuscular meloxicam administration on prostaglandin E2 synthesis in the North American bullfrog (Rana catesbeiana). J Zoo Wildl Med 2012; 42:680-5. [PMID: 22204063 DOI: 10.1638/2011-0126.1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Meloxicam is a commonly used nonsteroidal anti-inflammatory drug (NSAID) in veterinary medicine, but its use in amphibians has not been reported in the literature. NSAIDs are known to act by providing anti-inflammatory and analgesic actions by inhibiting the synthesis of prostaglandin E2 (PGE2). The objective of this study was to evaluate whether the intramuscular administration of meloxicam would decrease the circulating serum PGE2 levels in the North American bullfrog (Rana catesbeiana) following tissue trauma induced by a punch biopsy. Eighteen adult North American bullfrogs were randomly assigned to two treatment groups: meloxicam (0.1 mg/kg i.m.) and control (0.9% saline i.m.). Blood was obtained via cardiocentesis immediately prior to administration of the two treatment regimes and serum was frozen. A 4-mm punch biopsy was taken from the right triceps femoris muscle to induce an inflammatory response. Twenty-four hours later, a second blood sample was collected and serum was harvested and frozen. Serum PGE2 concentrations were measured using a commercial PGE2 enzyme assay (EIA) kit. Twenty-four hours following the biopsy, the mean circulating PGE2 levels of animals treated with meloxicam was 57.79 +/- 12.35 pg/ml, which did not differ significantly from animals that were treated with saline (85.63 +/- 17.55 pg/ml, P > or = 0.05). The calculated means of the absolute change between the circulating baseline PGE2 levels and the postinjury circulating PGE2 levels were significantly lower in animals treated with meloxicam (13.11 +/- 17.31 pg/ml) than in control animals treated with saline (46.14 +/- 38.02 pg/ml) (P < or = 0.05). These results suggest that the systemic administration of meloxicam at a dosage of 0.1 mg/kg once daily suppresses circulating serum PGE2 levels postinjury in the North American bullfrog.
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Abstract
Preclinical studies of analgesia in amphibians or recommendations for clinical use of analgesics in amphibian species are extremely limited. This article briefly reviews the issues surrounding the use of analgesics in amphibians, starting with common definitions of pain and analgesia when applied to nonhuman animals. Nociceptive and endogenous opioid systems in amphibians are reviewed, and results of preclinical research on opioid and nonopioid analgesics summarized. Recommended opioid and nonopioid analgesics are summarized, and practical recommendations made for their clinical use.
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Affiliation(s)
- Craig W Stevens
- Department of Pharmacology & Physiology, Oklahoma State University-Center for Health Sciences, 1111 West 17th Street, Tulsa, OK 74107, USA.
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6
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Koeller CA. Comparison of buprenorphine and butorphanol analgesia in the eastern red-spotted newt (Notophthalmus viridescens). JOURNAL OF THE AMERICAN ASSOCIATION FOR LABORATORY ANIMAL SCIENCE : JAALAS 2009; 48:171-175. [PMID: 19383214 PMCID: PMC2679657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 08/11/2008] [Revised: 09/09/2008] [Accepted: 10/20/2008] [Indexed: 05/27/2023]
Abstract
The experimental use of amphibian models in biomedical research increases yearly, but there is a paucity of reports concerning analgesic use in many of these species. In this study, buprenorphine given by intracoelomic injection and butorphanol added to the tank water were compared for analgesic effect in the eastern red-spotted newt after bilateral forelimb amputations. Newts undergoing anesthesia but not surgery and newts having surgery but not given analgesia postoperatively were used as control groups. Animals were tested for food consumption, spontaneous movement, response to tapping on the tank, response to being touched, and body posture. Both buprenorphine by intracoelomic injection and butorphanol in tank water significantly promoted resumption of normal behavior after bilateral surgical amputation of the forelimbs. The difference between analgesic treatment and no analgesic treatment was maintained until 72 h after surgery.
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Affiliation(s)
- Craig A Koeller
- Department of Clinical Investigation, Madigan Army Medical Center, Tacoma, Washington, USA.
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8
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Abstract
The proteins that mediate the analgesic and other effects of opioid drugs and endogenous opioid peptides are known as opioid receptors. Opioid receptors consist of a family of four closely-related proteins belonging to the large superfamily of G-protein coupled receptors. The three types of opioid receptors shown unequivocally to mediate analgesia in animal models are the mu (MOR), delta (DOR), and kappa (KOR) opioid receptor proteins. The role of the fourth member of the opioid receptor family, the nociceptin or orphanin FQ receptor (ORL), is not as clear as hyperalgesia, analgesia, and no effect was reported after administration of ORL agonists. There are now cDNA sequences for all four types of opioid receptors that are expressed in the brain of six species from three different classes of vertebrates. This review presents a comparative analysis of vertebrate opioid receptors using bioinformatics and data from recent human genome studies. Results indicate that opioid receptors arose by gene duplication, that there is a vector of opioid receptor divergence, and that MOR shows evidence of rapid evolution.
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Affiliation(s)
- Craig W Stevens
- Department of Pharmacology and Physiology, Oklahoma State University-Center for Health Sciences, Tulsa, OK, USA.
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9
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Stevens CW, Tóth G, Borsodi A, Benyhe S. Xendorphin B1, a novel opioid-like peptide determined from a Xenopus laevis brain cDNA library, produces opioid antinociception after spinal administration in amphibians. Brain Res Bull 2007; 71:628-32. [PMID: 17292806 PMCID: PMC1945180 DOI: 10.1016/j.brainresbull.2006.12.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2006] [Revised: 11/29/2006] [Accepted: 12/05/2006] [Indexed: 11/25/2022]
Abstract
Prodynorphins (PDYNs) from the African clawed frog (Xenopus laevis), originally described as 'proxendorphins', are novel members of the family of opioid-like precursor polypeptides and were recently discovered based on polymerase chain reaction (PCR) isolates from a Xenopus brain cDNA library. This amphibian prodynorphin was found in two isoforms, (Xen)PDYN-A and (Xen)PDYN-B, consisting of 247 and 279 amino acids, respectively. Each prepropeptide contains five potential opioid-like peptides, collectively named xendorphins. One of these, xendorphin B1 ((Xen)PDYN-B sequence 96-111: YGGFIRKPDKYKFLNA), is a hexadecapeptide that displaced [3H]naloxone and the radiolabelled kappa opioid, [3H]dynorphin A (1-17), with nanomolar affinity from rat brain membranes. Using the acetic acid pain test, the present study examined the antinociceptive effects of spinally administered xendorphin B1 in amphibians. Xendorphin B1 produced a long-lasting and dose-dependent antinociceptive effect in the Northern grass frog (Rana pipiens) with an ED50 value of 44.5 nmol/frog. The antinociceptive effects of xendorphin B1 were significantly blocked by pretreatment with the non-selective opioid antagonist, naltrexone. This is the first report of the in vivo characterization of a non-mammalian prodynorphin-derived peptide and suggests that xendorphin peptides may play a role in the modulation of noxious information in vertebrates.
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Affiliation(s)
- Craig W Stevens
- Oklahoma State University-Center for Health Sciences, College of Osteopathic Medicine, Tulsa, OK, USA
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10
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Bradford CS, Walthers EA, Stanley DJ, Baugh MM, Moore FL. Delta and mu opioid receptors from the brain of a urodele amphibian, the rough-skinned newt Taricha granulosa: cloning, heterologous expression, and pharmacological characterization. Gen Comp Endocrinol 2006; 146:275-90. [PMID: 16375901 DOI: 10.1016/j.ygcen.2005.11.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2005] [Revised: 10/31/2005] [Accepted: 11/03/2005] [Indexed: 11/20/2022]
Abstract
Two full-length cDNAs, encoding delta (delta) and mu (mu) opioid receptors, were cloned from the brain of the rough-skinned newt Taricha granulosa, complementing previous work from our laboratory describing the cloning of newt brain kappa (kappa) and ORL1 opioid receptors. The newt delta receptor shares 82% amino acid sequence identity with a frog delta receptor and lower (68-70%) identity with orthologous receptors cloned from mammals and zebrafish. The newt mu receptor shares 79% sequence identity with a frog mu receptor, 72% identity with mammalian mu receptors, and 66-69% identity with mu receptors cloned from teleost fishes. Membranes isolated from COS-7 cells transiently expressing the newt delta receptor possessed a single, high-affinity (Kd = 2.4 nM) binding site for the nonselective opioid antagonist [3H]naloxone. In competition binding assays, the newt delta receptor displayed highest affinity for Met-enkephalin, relatively low affinity for Leu-enkephalin, beta-endorphin, and [D-penicillamine, D-penicillamine] enkephalin (DPDPE) (a delta-selective agonist in mammals), and very low affinity for mu-, kappa-, or ORL1-selective agonists. COS-7 cells expressing the newt mu receptor also possessed a high-affinity (Kd = 0.44 nM) naloxone-binding site that showed highest affinity for beta-endorphin, moderate-to-low affinity for Met-enkephalin and Leu-enkephalin and DAMGO (a mu-selective agonist in mammals), and very low affinity for DPDPE and kappa- or ORL1-selective agonists. COS-7 cells expressing either receptor type (delta or mu) showed very high affinity (Kd = 0.1-0.3 nM) for the nonselective opioid antagonist diprenorphine. Taricha granulosa expresses the same four subtypes (delta, mu, kappa, and ORL1) of opioid receptors found in other vertebrate classes, but ligand selectivity appears less stringent in the newt than has been documented in mammals.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Brain Chemistry
- COS Cells
- Chlorocebus aethiops
- Cloning, Molecular
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/metabolism
- Enkephalin, D-Penicillamine (2,5)-/metabolism
- Enkephalin, Leucine/metabolism
- Enkephalin, Methionine/metabolism
- Humans
- Molecular Sequence Data
- Naloxone/metabolism
- Phylogeny
- Receptors, Opioid, delta/genetics
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, mu/genetics
- Receptors, Opioid, mu/metabolism
- Salamandridae/physiology
- Sequence Alignment
- beta-Endorphin/metabolism
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Affiliation(s)
- C Samuel Bradford
- Department of Zoology, Oregon State University, Corvallis, OR 97331, USA.
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Mohan S, Stevens CW. Systemic and spinal administration of the mu opioid, remifentanil, produces antinociception in amphibians. Eur J Pharmacol 2006; 534:89-94. [PMID: 16487509 PMCID: PMC3070367 DOI: 10.1016/j.ejphar.2006.01.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2005] [Revised: 12/16/2005] [Accepted: 01/10/2006] [Indexed: 11/27/2022]
Abstract
Remifentanil is a relatively new opioid analgesic related to the fentanyl family of mu opioid receptor agonists and is used clinically for its unique property of having an ultra-short duration of action. However, there is little preclinical data on the analgesic (antinociceptive) effects of remifentanil and none obtained in non-mammalian animal models. The antinociceptive effects of remifentanil were assessed by using the acetic acid test in amphibians. Systemic and spinal administration of remifentanil was made by subcutaneous and intraspinal injections in the Northern grass frog, Rana pipiens. After administration, remifentanil produced dose-dependent and long-lasting antinociceptive effects which persisted for five hours after systemic administration but gave a shorter duration of action after spinal delivery. The antinociceptive effects of remifentanil were significantly blocked by pretreatment with systemic naltrexone. Systemic and spinal administration of remifentanil produced log dose-response curves which yielded ED50 values of 7.1 nmol/g and 3.2 nmol/animal respectively. The relative antinociceptive potency of remifentanil compared to other opioids administered to amphibians is similar to that found in mammalian models.
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Affiliation(s)
| | - Craig W. Stevens
- Corresponding author. Tel.: +1 918 561 8234; fax: +1 918 561 8276. (C.W. Stevens)
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12
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Nociception. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/s1546-5098(06)25004-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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13
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Stevens CW. Opioid research in amphibians: an alternative pain model yielding insights on the evolution of opioid receptors. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 2004; 46:204-15. [PMID: 15464208 PMCID: PMC3069712 DOI: 10.1016/j.brainresrev.2004.07.003] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 07/07/2004] [Indexed: 11/20/2022]
Abstract
This review summarizes the work from our laboratory investigating mechanisms of opioid analgesia using the Northern grass frog, Rana pipiens. Over the last dozen years, we have accumulated data on the characterization of behavioral effects after opioid administration on radioligand binding by using opioid agonist and antagonist ligands in amphibian brain and spinal cord homogenates, and by cloning and sequencing opioid-like receptor cDNA from amphibian central nervous system (CNS) tissues. The relative analgesic potency of mu, delta, and kappa opioids is highly correlated between frogs and other mammals, including humans. Radioligand binding studies using selective opioid agonists show a similar selectivity profile in amphibians and mammals. In contrast, opioid antagonists that are highly selective for mammalian mu, delta, and kappa opioid receptors were not selective in behavioral and binding studies in amphibians. Three opioid-like receptor cDNAs were cloned and sequenced from amphibian brain tissues and are orthologs to mammalian mu, delta, and kappa opioid receptors. Bioinformatics analysis of the three types of opioid receptor cDNAs from all vertebrate species with full datasets gave a pattern of the molecular evolution of opioid receptors marked by the divergence of mu, delta, and kappa opioid receptor sequences during vertebrate evolution. This divergence in receptor amino acid sequence in later-evolved vertebrates underlies the hypothesis that opioid receptors are more type-selective in mammals than in nonmammalian vertebrates. The apparent order of receptor type evolution is kappa, then delta, and, most recently, the mu opioid receptor. Finally, novel bioinformatics analyses suggest that conserved extracellular receptor domains determine the type selectivity of vertebrate opioid receptors.
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Affiliation(s)
- Craig W Stevens
- Department of Pharmacology and Physiology, College of Osteopathic Medicine, Center for Health Sciences, Oklahoma State University, 1111 West 17th Street, Tulsa, OK 74107-1898, USA.
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14
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Affiliation(s)
- Thelma Lee Gross
- California Dermatopathology Service, 2825 KOVR Dr, West Sacramento, CA 95605-1600, USA
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15
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Salio C, Cottone E, Conrath M, Franzoni MF. CB1 cannabinoid receptors in amphibian spinal cord: relationships with some nociception markers. J Chem Neuroanat 2002; 24:153-62. [PMID: 12297261 DOI: 10.1016/s0891-0618(02)00040-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The role of cannabinoids in spinal analgesia has so far been investigated in mammals and the interactions between cannabinoid receptors and markers involved in nociception have been described in the rat spinal cord. An endocannabinoid system is well developed also in the amphibian brain. However, the anatomical substrates of pain modulation have been scarcely investigated in anamniotes, neither is there reference to such a role for cannabinoids in lower vertebrates. In the present paper we employed multiple cytochemical approaches to study the distribution of CB1 cannabinoid receptors and their morphofunctional relationships with some nociception markers (i.e. Substance P, nitric oxide synthase, GABA and mu opioid receptors) in the spinal cord of the anuran amphibian Xenopus laevis. We found a co-distribution of CB1 receptors with the aforementioned signaling molecules, as well as a more limited cellular co-localization, in the dorsal and central fields of the spinal cord. These regions correspond to the mammalian laminae I-IV and X, respectively, areas strongly involved in spinal analgesia. Comparison of these results with those previously obtained in the mammalian spinal cord, reveals a number of similarities between the two systems and suggests that cannabinoids might participate in the control of pain sensitivity also in the amphibian spinal cord.
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Affiliation(s)
- C Salio
- Dipartimento di Biologia Animale e dell'Uomo, Università degli Studi di Torino, Via Accademia Albertina 13, 10123, Torino, Italy
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16
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Newman LC, Sands SS, Wallace DR, Stevens CW. Characterization of mu, kappa, and delta opioid binding in amphibian whole brain tissue homogenates. J Pharmacol Exp Ther 2002; 301:364-70. [PMID: 11907194 DOI: 10.1124/jpet.301.1.364] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Opioid agonists produce analgesia in mammals through the activation of mu, kappa, or delta opioid receptors. Previous behavioral and binding studies from our laboratory using an amphibian model suggested that mu, kappa, or delta opioid agonists may activate a single type of opioid receptor in the grass frog, Rana pipiens. In the present study, kinetic, saturation, and competitive binding profiles for three opioid radioligands, [(3)H]DAMGO ([D-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin) (mu-selective), [(3)H]U65953 [(5 alpha, 7 alpha,8 beta)-(+)-N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro[4.5]dec-8-yl]-benzeneacetamide] (kappa-selective), and [(3)H]DPDPE ([D-Pen(2),D-Pen(5)]-enkephalin) (delta-selective) were determined using frog whole brain homogenates. Kinetic analyses and experimentally derived values from saturation experiments gave affinity constants (K(D)) in the low nanomolar range. The density of opioid binding sites (B(max)) was 224.4, 118.6, and 268.9 fmol/mg for mu, kappa, and delta opioid radioligands, respectively. The affinity values did not significantly differ among the three opioid radioligands, but the kappa radioligand bound to significantly fewer sites than did the mu or delta radioligands. K(i) values for unlabeled mu, kappa, and delta competitors, including highly selective opioid antagonists, were consistent with each radioligand selectivity profile. The present data suggest that mu, kappa, and delta opioid radioligands bind to distinct opioid receptors in amphibians that are surprisingly similar to those found in mammalian brain.
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MESH Headings
- Animals
- Benzeneacetamides
- Binding, Competitive/drug effects
- Brain Chemistry/drug effects
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/metabolism
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
- Enkephalin, D-Penicillamine (2,5)-/pharmacology
- In Vitro Techniques
- Kinetics
- Membranes/drug effects
- Membranes/metabolism
- Pyrrolidines/pharmacology
- Radioligand Assay
- Rana pipiens
- Receptors, Opioid, delta/agonists
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, kappa/agonists
- Receptors, Opioid, kappa/metabolism
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/metabolism
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Affiliation(s)
- Leslie C Newman
- Department of Pharmacology and Physiology, Oklahoma State University Center for Health Sciences, College of Osteopathic Medicine, Tulsa, Oklahoma 74107, USA
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17
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Stevens CW, MacIver DN, Newman LC. Testing and comparison of non-opioid analgesics in amphibians. CONTEMPORARY TOPICS IN LABORATORY ANIMAL SCIENCE 2001; 40:23-7. [PMID: 11451391 PMCID: PMC3075466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
Because of the lack of information about effective analgesics in non-mammalian vertebrates, the potency of various non-opioid agents were tested in a model of analgesia by using Northern grass frogs (Rana pipiens). This alternative model has been used widely for investigating opioid analgesic action. Potential non-opioid analgesics tested included antipsychotic, benzodiazepine, barbiturate, antihistamine, non-steroidal anti-inflammatory (NSAID), and partial opioid agents. Northern grass frogs were acclimated to lab conditions in individual cages. Drugs were administered systemically through the dorsal lymph sac, and analgesic effects were estimated by using the acetic acid test (AAT). The AAT is done by placing logarithmic dilutions of acid dropwise on the dorsum of the animal's thigh until a wiping response is obtained. At various doses, chlorpromazine and haloperidol (antipsychotics), chlordiazepoxide (a benzodiazepine), buprenorphine (a partial opioid agonist), and diphenhydramine (a histamine antagonist) produced moderate to strong analgesic effects. Indomethacin and ketorolac (NSAIDs), butorphanol (a partial opioid agonist), and pentobarbital (a barbiturate) produced weaker but noticeable analgesic effects. Our results are the first to document the effectiveness of a wide array of pharmacologically active agents in a novel amphibian model for analgesia. These findings provide needed data regarding the use of alternative, non-opioid agents for the treatment of pain in amphibians and other poikilothermic species.
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Affiliation(s)
- C W Stevens
- Department of Pharmacology and Physiology, Oklahoma State University-College of Osteopathic Medicine, Tulsa, Oklahoma 74107, USA
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