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Insect J3-K1 assemblage from Tasgorosay in Kazakhstan was dominated by cockroaches. Biologia (Bratisl) 2023. [DOI: 10.1007/s11756-022-01307-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Cressman A, Amsalem E. Impacts and mechanisms of CO2 narcosis in bumble bees: narcosis depends on dose, caste and mating status and is not induced by anoxia. J Exp Biol 2023; 226:286149. [PMID: 36541091 DOI: 10.1242/jeb.244746] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 12/05/2022] [Indexed: 12/24/2022]
Abstract
Carbon dioxide (CO2) is commonly used to immobilize insects and to induce reproduction in bees. However, despite its wide use and potential off-target impacts, its underlying mechanisms are not fully understood. Here, we used Bombus impatiens to examine whether CO2 impacts are mediated by anoxia and whether these mechanisms differ between female castes or following mating in queens. We examined the behavior, physiology and gene expression of workers, mated queens and virgin queens following exposure to anoxia, hypoxia, full and partial hypercapnia, and controls. Hypercapnia and anoxia caused immobilization, but only hypercapnia resulted in behavioral, physiological and molecular impacts in bees. Recovery from hypercapnia resulted in increased abdominal contractions and took longer in queens. Additionally, hypercapnia activated the ovaries of queens, but inhibited those of workers in a dose-dependent manner and caused a depletion of fat-body lipids in both castes. All responses to hypercapnia were weaker following mating in queens. Analysis of gene expression related to hypoxia and hypercapnia supported the physiological findings in queens, demonstrating that the overall impacts of CO2, excluding virgin queen ovaries, were unique and were not induced by anoxia. This study contributes to our understanding of the impacts and the mechanistic basis of CO2 narcosis in insects and its impacts on bee physiology. This article has an associated ECR Spotlight interview with Anna Cressman.
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Affiliation(s)
- Anna Cressman
- Department of Entomology, Center for Chemical Ecology, Center for Pollination Research, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
| | - Etya Amsalem
- Department of Entomology, Center for Chemical Ecology, Center for Pollination Research, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
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Singh Y, Cullere M, Kovitvadhi A, Chundang P, Dalle Zotte A. Effect of different killing methods on physicochemical traits, nutritional characteristics, in vitro human digestibility and oxidative stability during storage of the house cricket (Acheta domesticus L.). INNOV FOOD SCI EMERG 2020. [DOI: 10.1016/j.ifset.2020.102444] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Impacts of Killing Process on the Nutrient Content, Product Stability and In Vitro Digestibility of Black Soldier Fly (Hermetia illucens) Larvae Meals. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10176099] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The black soldier fly (BSF, Hermetia illucens) is considered a potential sustainable insect alternative source of protein for animal feed. The quality of a BSF meal is greatly influenced by the killing method and the purpose of this article is to compare the influences of different killing methods. BSFs at the 18-day-old prepupae stage were separated into six different killing methods with three replicates: 1. blending, 2. freezing, 3. CO2 treatment, 4. vacuum, 5. blanching and 6. CO2 plus blanching. After killing, BSF larvae meals were obtained by hot air oven drying and grinding. The chemical composition and in vitro digestibility calculated from sediments were not affected by the killing method, except that blending provided the worst BSF quality for all measured parameters (p < 0.05). The highest quality of BSF was obtained from the heat treatment procedures (blanching and the CO2 plus blanching methods), as they produced lower acidity after killing, total viable counts, browning reaction (enzymatic and non-enzymatic), darkness, moisture, fat acidity, protein and lipid oxidation during storage compared with other killing procedures (p < 0.05). Interestingly, the highest free amino acids in the supernatant after in vitro digestibility of BSF samples was observed with the CO2 plus blanching killing method (p < 0.05), whereas other parameters were similar to those obtained with blanching. The CO2 plus blanching method did not produce clearly different outcomes to blanching; therefore, the selection of one of these techniques over the other should depend on the regulations in each country.
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Larouche J, Deschamps MH, Saucier L, Lebeuf Y, Doyen A, Vandenberg GW. Effects of Killing Methods on Lipid Oxidation, Colour and Microbial Load of Black Soldier Fly ( Hermetia illucens) Larvae. Animals (Basel) 2019; 9:E182. [PMID: 31010069 PMCID: PMC6523926 DOI: 10.3390/ani9040182] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 04/13/2019] [Accepted: 04/15/2019] [Indexed: 11/30/2022] Open
Abstract
Black soldier fly (BSF) larvae represent a promising alternative ingredient for animal feed. Post-production processing can, however, affect their quality. This project aimed to optimize larval killing by comparing the effects on the nutritional and microbiological quality of 10 methods, i.e., blanching (B = 40 s), desiccation (D = 60 °C, 30 min), freezing (F20 = -20 °C, 1 h; F40 = -40 °C, 1 h; N = liquid nitrogen, 40 s), high hydrostatic pressure (HHP = 3 min, 600 MPa), grinding (G = 2 min) and asphyxiation (CO2 = 120 h; N2 = 144 h; vacuum conditioning, V = 120 h). Some methods affected the pH (B, asphyxiation), total moisture (B, asphyxiation and D) and ash contents (B, p < 0.001). The lipid content (asphyxiation) and their oxidation levels (B, asphyxiation and D) were also affected (p < 0.001). Killing methods altered the larvae colour during freeze-drying and in the final product. Blanching appears to be the most appropriate strategy since it minimizes lipid oxidation (primary = 4.6 ± 0.7 mg cumen hydroperoxide (CHP) equivalents/kg; secondary = 1.0 ± 0.1 mg malondialdehyde/kg), reduces microbial contamination and initiates dehydration (water content = 78.1 ± 1.0%). We propose herein, an optimized protocol to kill BSF that meet the Canadian regulatory requirements of the insect production and processing industry.
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Affiliation(s)
- Jennifer Larouche
- Département des Sciences Animales, Pavillon Paul-Comtois Université Laval, Quebec, QC G1V 0A6, Canada.
| | - Marie-Hélène Deschamps
- Département des Sciences Animales, Pavillon Paul-Comtois Université Laval, Quebec, QC G1V 0A6, Canada.
| | - Linda Saucier
- Département des Sciences Animales, Pavillon Paul-Comtois Université Laval, Quebec, QC G1V 0A6, Canada.
| | - Yolaine Lebeuf
- Département des Sciences Animales, Pavillon Paul-Comtois Université Laval, Quebec, QC G1V 0A6, Canada.
| | - Alain Doyen
- Département des Sciences des Aliments, Pavillon Paul-Comtois Université Laval, Quebec, QC G1V 0A6, Canada.
| | - Grant W Vandenberg
- Département des Sciences Animales, Pavillon Paul-Comtois Université Laval, Quebec, QC G1V 0A6, Canada.
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Amsalem E, Grozinger CM. Evaluating the molecular, physiological and behavioral impacts of CO 2 narcosis in bumble bees (Bombus impatiens). JOURNAL OF INSECT PHYSIOLOGY 2017; 101:57-65. [PMID: 28666863 DOI: 10.1016/j.jinsphys.2017.06.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 06/25/2017] [Accepted: 06/26/2017] [Indexed: 06/07/2023]
Abstract
Exposure to carbon dioxide (CO2) has pleiotropic effects in many insect species, ranging from eliciting rapid behavioral responses such as attraction, to dramatic physiological changes, including ovary activation. In bumble bees, CO2 narcosis causes queens to bypass diapause and initiate egg laying, but its mode of action is not well-understood. Here, we evaluated the effects of CO2 narcosis on the behavior, physiology and immune function of virgin bumble bee queens (Bombus impatiens). We tested the hypothesis that CO2 induces these changes by stimulating oxidative stress response pathways. We found that CO2 stimulates ovarian activation and egg production and suppresses lipid (but not glycogen) accumulation in virgin queens. Additionally, CO2 treated queens were more active (particularly in terms of flight) and performed, but did not receive, more aggressive behaviors compared to controls. Moreover, CO2 positively affected immune function in queens, reduced transcript levels of 5/6 antioxidant enzyme genes and had no effect on longevity. Thus, although CO2 treatment stimulated reproduction, we did not observe any evidence of a trade-off in queen health parameters, aside from a reduction in lipids. Overall CO2 narcosis does not appear to stimulate a typical stress response in virgin bumble bee queens. On the contrary, CO2 narcosis appears to stimulate changes that prepare queens to cope with the nutritional, metabolic and behavioral challenges associated with reproduction and colony-founding.
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Affiliation(s)
- Etya Amsalem
- Department of Entomology, Center for Pollinator Research, Center for Chemical Ecology, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA.
| | - Christina M Grozinger
- Department of Entomology, Center for Pollinator Research, Center for Chemical Ecology, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
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Spears J, Kamunde C, Stevens ED. Effect of TRIS and bicarbonate as buffers on anesthetic efficacy of tricaine methane sulfonate in Zebrafish (Danio rerio). Zebrafish 2014; 11:590-6. [PMID: 25264822 DOI: 10.1089/zeb.2014.0975] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Tricaine methane sulfonate (TMS), often called MS-222, is the most common anesthetic used with fishes. Because it is very acidic (pKa about 3) it must be neutralized especially when used in soft fresh water. Much of the literature on fish anesthetics recommends neutralizing with bicarbonate. However, much of the zebrafish literature uses the protocol in "The Zebrafish Book" that recommends neutralizing with TRIS. Three considerations when comparing these buffers are: first, TRIS has the advantage that the pH tends to remain constant, whereas the pH of solutions containing bicarbonate tends to increase as CO2 diffuses from the water to air; second, the CO2 produced by bicarbonate may have some sedative effects in and of itself; and third, there is some evidence that the efficacy of TMS changes with pH. In the present study, we compared the efficacy of TMS using these two buffers and show that there is no substantial difference in anesthetic properties in zebrafish.
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Affiliation(s)
- Jonathan Spears
- Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island , Charlottetown, Prince Edward Island, Canada
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Hustert R, Frisch M, Böhm A, Pass G. A new kind of auxiliary heart in insects: functional morphology and neuronal control of the accessory pulsatile organs of the cricket ovipositor. Front Zool 2014; 11:43. [PMID: 25018774 PMCID: PMC4094452 DOI: 10.1186/1742-9994-11-43] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Accepted: 05/31/2014] [Indexed: 11/18/2022] Open
Abstract
Introduction In insects, the pumping of the dorsal heart causes circulation of hemolymph throughout the central body cavity, but not within the interior of long body appendages. Hemolymph exchange in these dead-end structures is accomplished by special flow-guiding structures and/or autonomous pulsatile organs (“auxiliary hearts”). In this paper accessory pulsatile organs for an insect ovipositor are described for the first time. We studied these organs in females of the cricket Acheta domesticus by analyzing their functional morphology, neuroanatomy and physiological control. Results The lumen of the four long ovipositor valves is subdivided by longitudinal septa of connective tissue into efferent and afferent hemolymph sinuses which are confluent distally. The countercurrent flow in these sinuses is effected by pulsatile organs which are located at the bases of the ovipositor valves. Each of the four organs consists of a pumping chamber which is compressed by rhythmically contracting muscles. The morphology of the paired organs is laterally mirrored, and there are differences in some details between the dorsal and ventral organs. The compression of the pumping chambers of each valve pair occurs with a left-right alternating rhythm with a frequency of 0.2 to 0.5 Hz and is synchronized between the dorsal and ventral organs. The more anteriorly located genital chamber shows rhythmical lateral movements simultaneous to those of the ovipositor pulsatile organs and probably supports the hemolymph exchange in the abdominal apex region. The left-right alternating rhythm is produced by a central pattern generator located in the terminal ganglion. It requires no sensory feedback for its output since it persists in the completely isolated ganglion. Rhythm-modulating and rhythm-resetting interneurons are identified in the terminal ganglion. Conclusion The circulatory organs of the cricket ovipositor have a unique functional morphology. The pumping apparatus at the base of each ovipositor valve operates like a bellow. It forces hemolymph via sinuses delimited by thin septa of connective tissue in a countercurrent flow through the valve lumen. The pumping activity is based on neurogenic control by a central pattern generator in the terminal ganglion.
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Affiliation(s)
- Reinhold Hustert
- Department of Neurobiology, JFB-Institute for Zoology, University of Göttingen, Berliner Straße 28, 37073 Göttingen, Germany
| | - Matthias Frisch
- Department of Neurobiology, JFB-Institute for Zoology, University of Göttingen, Berliner Straße 28, 37073 Göttingen, Germany
| | - Alexander Böhm
- Department of Integrative Zoology, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Günther Pass
- Department of Integrative Zoology, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
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Kozak PR, Currie RW. Laboratory study on the effects of temperature and three ventilation rates on infestations of Varroa destructor in clusters of honey bees (Hymenoptera: Apidae). JOURNAL OF ECONOMIC ENTOMOLOGY 2011; 104:1774-1782. [PMID: 22299336 DOI: 10.1603/ec08278] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In this study, reduced levels of ventilation were applied to small clusters of bees under controlled conditions to determine whether lowered ventilation rates and the resulting increased levels of CO2 could increase the mortality rates of varroa. Two experiments were performed at two different temperatures (10 degrees C and 25 degrees C). Both experiments compared varroa mortality among high (360 liters/h), medium (42.5 liters/h), and low (14 liters/h) rates of ventilation. The clusters of bees (approximately 300 worker bees) in bioassay cages with 40 introduced varroa mites were placed into self-contained glass chambers and were randomly assigned to one of the three ventilation treatments within incubators set at either of the two temperatures. Bee and varroa mortality and the levels of CO2 concentration were measured in each of the experimental chambers. In both experiments, CO2 levels within the chamber increased, with a decrease in ventilation with CO2 reaching a maximum of 1.2 +/- 0.45% at 10 degrees C and 2.13 +/- 0.2% at 25 degrees C under low ventilation. At high ventilation rates, CO2 concentration in chamber air was similar at 10 degrees C (1.1 +/- 1.5%) and 25 degrees C (1.9 +/- 1.1%). Both humidity and CO2 concentration were higher at 25 degrees C than at 10 degrees C. Bee mortality was similar within all ventilation rate treatments at either 10 degrees C (11.5 +/- 2.7-19.3 +/- 3.8%) or 25 degrees C (15.2 +/- 1.9-20.7 +/- 3.5%). At 10 degrees C, varroa mortality (percentage dead) was greatest in the high ventilation treatment (12.2 +/- 2.1%), but only slightly higher than under low (3.7 +/- 1.7%) and medium ventilation (4.9 +/- 1.6%). At 25 degrees C, varroa mortality was greatest under low ventilation at 46.12 +/- 7.7% and significantly greater than at either medium (29.7 +/- 7.4%) or low ventilation (9.5 +/- 1.6.1%). This study demonstrates that at 25 degrees C, restricted ventilation, resulting in high levels of CO2 in the surrounding environment of small clusters of honey bees, has the potential to substantially increase varroa mortality.
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Affiliation(s)
- Paul R Kozak
- Department of Entomology, University of Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2
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Abstract
SUMMARYThe sequential behaviours shown by insects at ecdysis are due to the sequential release of various hormones, but the transition from one phase to the next can be fine-tuned by inhibitory influences. The ecdysis sequence in the moth Manduca sexta was initiated by injecting sensitive animals with the neuropeptide ecdysis-triggering hormone (ETH). Exposure to ETH stimulates the release of eclosion hormone (EH) which, in turn, activates a set of neurons containing crustacean cardioactive peptide (CCAP) by elevating their levels of intracellular cyclic GMP. We characterized a set of non-CCAP containing neurons that also appear to be EH targets because of their response to cyclic GMP at ecdysis. The neurons did not display leucokinin-,diuretic-hormone- or FMRFamide-like immunoreactivity. They are probably the bursicon-containing cells described previously. After release of EH, there is a transient inhibition of the abdominal centers responsible for ecdysis. Transection experiments suggested that this suppression is viadescending inhibitory units from the suboesophageal and thoracic ganglia. The duration of this inhibition appears to depend on the levels of cyclic GMP and can be extended by pharmacologically suppressing cyclic GMP breakdown. We further found that brief exposure to CO2 caused premature ecdysis. Since the CO2 treatment was effective only after EH release, it probably acts by suppressing descending inhibition. Studies on adult eclosion suggest that CO2, given at the appropriate time, can uncouple the basic larval motor program from modulatory influences provided by the adult pterothoracic ganglion. CO2 therefore appears to be a novel and non-invasive tool for studies of ecdysis behavior in insects.
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Affiliation(s)
- Megumi Fuse
- Department of Zoology, University of Washington, Seattle, WA 98195-38100, USA
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Abstract
Hypoventilation produces hypercapnia which can elevate pain thresholds. Hypercapnia is a potent stressor which releases catecholamines and activates the sympathetic nervous system. Some stressors produce analgesia by releasing endogenous opioids. To determine the roles of endogenous opioids and catecholamines in hypercapnic analgesia, we administered CO2 in the inspired gas mixture to conscious rats. CO2 in the range 5-10% elevated tail flick and leg flexion latencies 2- to 3-fold in both intact and spinalised animals. The effects on reflex latencies but not on paCO2 or pHa were blocked by naloxone (2 mg/kg), and were not present in morphine-tolerant animals. The effects were reduced by dexamethasone but were not changed either by adrenalectomy or by systemic guanethidine, propanolol or phentolamine. Hypercapnia delayed the onset of the late phase of behavioural responses to formalin injected into the plantar surface of the hindpaw. We conclude that moderate hypercapnia powerfully depresses flexor withdrawal responses to noxious stimuli, by a mechanism involving release of endogenous opioids but not systemic catecholamines. This effect may account in part for the elevation in pain threshold during hypoventilation.
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Affiliation(s)
- G D Gamble
- Department of Physiology, University of Auckland, New Zealand
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Szabolcs MJ, Kopp M, Schaden GE. Carbonic anhydrase activity in the peripheral nervous system of rat: the enzyme as a marker for muscle afferents. Brain Res 1989; 492:129-38. [PMID: 2502300 DOI: 10.1016/0006-8993(89)90895-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The distribution of carbonic anhydrase (CA) activity was determined histochemically using Hansson's cobalt phosphate method in cross-sections of peripheral nerves from rats. As the studied nerves contain either efferent, proprioceptive or exteroceptive myelinated fibres, our survey particularly focused on the question whether CA-reactive nerve fibres are functionally related. Intense CA activity was detected in all large diameter (8-12 microns) muscle afferents. The amount of similarly reactive cutaneous afferents was negligibly low (3.6%). Efferent fibres displayed only weak CA activity, which was confined to the small myelinated fibres (3-6 microns). Moderate staining could be assessed in medium-sized (4-11 microns) proprioceptive fibres. The same reactivity occurred in a sizeable percentage (11.4%) of exteroceptive afferents. Their diameters ranged from 4 to 11 microns. These results indicated, that high enzyme activity is found predominantly in large-calibre proprioceptive afferents, which according to Hunt's classification were identified as group IA and IB fibres. Further confirmation for our observations was obtained by demonstrating high levels of enzyme activity in primary nerve endings of muscle spindles (IA fibres) and in axon terminals of Golgi tendon organs (IB fibres) constantly. Finally possible functions for neuronal CA are discussed with respect to its high activity in a functionally related subpopulation of nerve fibres.
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Affiliation(s)
- M J Szabolcs
- Institute for Anatomy Div. III, University of Vienna, Austria
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Colwell CS, Page TL. The electroretinogram of the cockroach Leucophaea maderae. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. A, COMPARATIVE PHYSIOLOGY 1989; 92:117-23. [PMID: 2567651 DOI: 10.1016/0300-9629(89)90752-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
1. We have previously found that two components, the off-transient and the sustained component, of the electroretinogram (ERG) recorded from the eye of the cockroach Leucophaea maderae exhibit circadian rhythms in amplitude (Wills et al., 1985). 2. Analysis of the intensity-response functions of the two rhythmic components reveals that the circadian modulation of this visual system involves at least two independent regulatory processes. 3. Surgical and pharmacological manipulations suggest anatomically distinct sites of origin for the off-transient and the sustained component. 4. The results suggest that in this system the circadian pacemaker regulates visual processing both peripherally, at the level of the photoreceptors, and centrally, at the source of the off-transient.
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Affiliation(s)
- C S Colwell
- Department of General Biology, Vanderbilt University, Nashville, TN 37235
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Oswald T, Riley DA. Peripheral nerve carbonic anhydrase activity and chronic acetazolamide treatment of rats. Brain Res 1987; 406:379-84. [PMID: 3105815 DOI: 10.1016/0006-8993(87)90811-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Examination of cranial nerves shows that the sensory infraorbital branch of the trigeminal nerve contains many carbonic anhydrase-reactive axons whereas axons of the motor facial nerve are non-reactive. This motor/sensory axon staining difference holds for both cranial and spinal nerves. Chronic treatment with acetazolamide produced no apparent changes in carbonic anhydrase histochemical activity or the structure of peripheral nerve fibers.
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Jodkowski JS, Lipski J. Decreased excitability of respiratory motoneurons during hypercapnia in the acute spinal cat. Brain Res 1986; 386:296-304. [PMID: 3779412 DOI: 10.1016/0006-8993(86)90166-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
This study was undertaken to examine the effects of hypercapnia on the excitability of respiratory motoneurons. The action of CO2 on phrenic (inspiratory) and internal intercostal (expiratory) motoneurons was compared with that exerted on non-respiratory motoneurons of the musculocutaneous nerve. The experiments were performed on spinalized (C1 segment), partially deafferented cats that were exposed to different CO2/O2 mixtures (end-tidal CO2 3 +/- 0.3, 6 +/- 0.5 and 9 +/- 0.5%). Changes in neuronal excitability were assessed by: measuring the amplitudes of antidromic field potentials recorded from a population of motoneurons; analysis of the amplitude and latency of the orthodromic response recorded from a given nerve and evoked by microstimulation within the corresponding motor nucleus; monitoring the membrane potentials during intracellular recordings from phrenic motoneurons; and recording ongoing activity of the phrenic and internal intercostal nerves. Hypercapnia (end-tidal CO2 6 +/- 0.5 or 9 +/- 0.5%) decreased the excitability of phrenic and musculocutaneous motoneurons, the effect being larger at the higher CO2 level. Internal intercostal motoneurons were generally more resistant to the effects of CO2. A depression of their excitability was observed only at end-tidal CO2 9 +/- 0.5%. The decreased excitability of phrenic motoneurons was associated with membrane hyperpolarization. It is concluded that the depressant action of CO2 is present in both respiratory and non-respiratory spinal motoneurons. The action of hypercapnia on respiratory motoneurons may oppose the excitatory effects exerted through specific chemoreflexes.
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Abstract
The Drosophila melanogaster male produces a species-specific courtship song by wing vibration. The most conspicuous feature of the song is a series of pulses with a 30-40-ms interpulse interval (IPI) which oscillate in wild-type males with a period of 50-60 s. This short-term biological rhythm in IPI is influenced by several gene mutations at the period (per) locus, which alter the normal 24-h free-running period of the circadian clock and have corresponding effects on the song cycle. The present study reveals that, under restrictive conditions, temperature-sensitive mutations which affect neuronal membrane excitability seem to stop the biological clock underlying the fruitfly's song rhythm.
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