M Mackie

Publications of M Mackie

• P boutons in lamina IX of the rodent spinal cord express high levels of glutamic acid decarboxylase-65 and originate from cells in deep medial dorsal horn.

  Authors: D I Hughes, M Mackie, G G Nagy, J S Riddell, D J Maxwell, G Szabó, F Erdélyi, G Veress, P Szucs, M Antal, A J Todd

  Proceedings of the National Academy of Sciences of the United States of America. 07/2005; 102(25):9038-43.

  Presynaptic inhibition of primary muscle spindle (group Ia) afferent terminals in motor nuclei of the spinal cord plays an important role in regulating motor output and is produced by a population ofPresynaptic inhibition of primary muscle spindle (group Ia) afferent terminals in motor nuclei of the spinal cord plays an important role in regulating motor output and is produced by a population of GABAergic axon terminals known as P boutons. Despite extensive investigation, the cells that mediate this control have not yet been identified. In this work, we use immunocytochemistry with confocal microscopy and EM to demonstrate that P boutons can be distinguished from other GABAergic terminals in the ventral horn of rat and mouse spinal cord by their high level of the glutamic acid decarboxylase (GAD) 65 isoform of GAD. By carrying out retrograde labeling from lamina IX in mice that express green fluorescent protein under the control of the GAD65 promoter, we provide evidence that the cells of origin of the P boutons are located in the medial part of laminae V and VI. Our results suggest that P boutons represent the major output of these cells within the ventral horn and are consistent with the view that presynaptic inhibition of proprioceptive afferents is mediated by specific populations of interneurons. They also provide a means of identifying P boutons that will be important in studies of the organization of presynaptic control of Ia afferents.

• Distribution and colocalisation of glutamate decarboxylase isoforms in the rat spinal cord.

  Authors: M Mackie, D I Hughes, D J Maxwell, N J K Tillakaratne, A J Todd

  Neuroscience. 02/2003; 119(2):461-72.

  The inhibitory neurotransmitter GABA is synthesized by glutamic acid decarboxylase (GAD), and two isoforms of this enzyme exist: GAD65 and GAD67. Immunocytochemical studies of the spinal cord haveThe inhibitory neurotransmitter GABA is synthesized by glutamic acid decarboxylase (GAD), and two isoforms of this enzyme exist: GAD65 and GAD67. Immunocytochemical studies of the spinal cord have shown that whilst both are present in the dorsal horn, GAD67 is the predominant form in the ventral horn. The present study was carried out to determine the pattern of coexistence of the two GAD isoforms in axonal boutons in different laminae of the cord, and also to examine the relation of the GADs to the glycine transporter GLYT2 (a marker for glycinergic axons), since many spinal neurons are thought to use GABA and glycine as co-transmitters.Virtually all GAD-immunoreactive boutons throughout the spinal grey matter were labelled by both GAD65 and GAD67 antibodies; however, the relative intensity of staining with the two antibodies varied considerably. In the ventral horn, most immunoreactive boutons showed much stronger labelling with the GAD67 antibody, and many of these were also GLYT2 immunoreactive. However, clusters of boutons with high levels of GAD65 immunoreactivity were observed in the motor nuclei, and these were not labelled with the GLYT2 antibody. In the dorsal horn, some GAD-immunoreactive boutons had relatively high levels of labelling with either GAD65 or GAD67 antibody, whilst others showed a similar degree of labelling with both antibodies. GLYT2 immunoreactivity was associated with many GAD-immunoreactive boutons; however, this did not appear to be related to the pattern of GAD expression.It has recently been reported that there is selective depletion of GAD65, accompanied by a loss of GABAergic inhibition, in the ipsilateral dorsal horn in rats that have undergone peripheral nerve injuries [J Neurosci 22 (2002) 6724]. Our finding that some boutons in the superficial laminae showed relatively high levels of GAD65 and low levels of GAD67 immunoreactivity is therefore significant, since a reduction in GABA synthesis in these axons may contribute to neuropathic pain.

• The expression of vesicular glutamate transporters VGLUT1 and VGLUT2 in neurochemically defined axonal populations in the rat spinal cord with emphasis on the dorsal horn.

  Authors: A J Todd, D I Hughes, E Polgár, G G Nagy, M Mackie, O P Ottersen, D J Maxwell

  The European journal of neuroscience. 02/2003; 17(1):13-27.

  Two vesicular glutamate transporters, VGLUT1 and VGLUT2, have recently been identified, and it has been reported that they are expressed by largely nonoverlapping populations of glutamatergic neuronsTwo vesicular glutamate transporters, VGLUT1 and VGLUT2, have recently been identified, and it has been reported that they are expressed by largely nonoverlapping populations of glutamatergic neurons in the brain. We have used immunocytochemistry with antibodies against both transporters, together with markers for various populations of spinal neurons, in an attempt to identify glutamatergic interneurons in the dorsal horn of the mid-lumbar spinal cord of the rat. The great majority (94-100%) of nonprimary axonal boutons that contained somatostatin, substance P or neurotensin, as well as 85% of those that contained enkephalin, were VGLUT2-immunoreactive, which suggests that most dorsal horn neurons that synthesize these peptides are glutamatergic. In support of this, we found that most somatostatin- and enkephalin-containing boutons (including somatostatin-immunoreactive boutons that lacked calcitonin gene-related peptide and were therefore probably derived from local interneurons) formed synapses at which AMPA receptors were present. We also investigated VGLUT expression in central terminals of primary afferents. Myelinated afferents were identified with cholera toxin B subunit; most of those in lamina I were VGLUT2-immunoreactive, whereas all those in deeper laminae were VGLUT1-immunoreactive, and some (in laminae III-VI) appeared to contain both transporters. However, peptidergic primary afferents that contained substance P or somatostatin (most of which are unmyelinated), as well as nonpeptidergic C fibres (identified with Bandeiraea simplicifolia isolectin B4) showed low levels of VGLUT2-immunoreactivity, or were not immunoreactive with either VGLUT antibody. As all primary afferents are thought to be glutamatergic, this raises the possibility that unmyelinated afferents, most of which are nociceptors, express a different vesicular glutamate transporter.

• Distribution and colocalisation of glutamate decarboxylase isoforms in the rat spinal cord

  Authors: M Mackie, D.I Hughes, D.J Maxwell, N.J.K Tillakaratne, A.J Todd

  Neuroscience.

  The inhibitory neurotransmitter GABA is synthesised by glutamic acid decarboxylase (GAD), and two isoforms of this enzyme exist: GAD65 and GAD67. Immunocytochemical studies of the spinal cord haveThe inhibitory neurotransmitter GABA is synthesised by glutamic acid decarboxylase (GAD), and two isoforms of this enzyme exist: GAD65 and GAD67. Immunocytochemical studies of the spinal cord have shown that whilst both are present in the dorsal horn, GAD67 is the predominant form in the ventral horn. The present study was carried out to determine the pattern of coexistence of the two GAD isoforms in axonal boutons in different laminae of the cord, and also to examine the relation of the GADs to the glycine transporter GLYT2 (a marker for glycinergic axons), since many spinal neurons are thought to use GABA and glycine as co-transmitters.Virtually all GAD-immunoreactive boutons throughout the spinal grey matter were labelled by both GAD65 and GAD67 antibodies; however, the relative intensity of staining with the two antibodies varied considerably. In the ventral horn, most immunoreactive boutons showed much stronger labelling with the GAD67 antibody, and many of these were also GLYT2 immunoreactive. However, clusters of boutons with high levels of GAD65 immunoreactivity were observed in the motor nuclei, and these were not labelled with the GLYT2 antibody. In the dorsal horn, some GAD-immunoreactive boutons had relatively high levels of labelling with either GAD65 or GAD67 antibody, whilst others showed a similar degree of labelling with both antibodies. GLYT2 immunoreactivity was associated with many GAD-immunoreactive boutons; however, this did not appear to be related to the pattern of GAD expression.It has recently been reported that there is selective depletion of GAD65, accompanied by a loss of GABAergic inhibition, in the ipsilateral dorsal horn in rats that have undergone peripheral nerve injuries [J Neurosci 22 (2002) 6724]. Our finding that some boutons in the superficial laminae showed relatively high levels of GAD65 and low levels of GAD67 immunoreactivity is therefore significant, since a reduction in GABA synthesis in these axons may contribute to neuropathic pain.

• The expression of vesicular glutamate transporters VGLUT1 and VGLUT2 in neurochemically defined axonal populations in the rat spinal cord with emphasis on the dorsal horn

  Authors: AJ Todd, DI Hughes, E Polgar, GG Nagy, M Mackie, OP Ottersen, DJ Maxwell

• P boutons in lamina IX of the rodent spinal cord express high levels of glutamic acid decarboxylase-65 and originate from cells in deep medial dorsal horn

  Authors: DI Hughes, M Mackie, GG Nagy, JS Riddell, DJ Maxwell, G Szabo, F Erdelyi, G Veress, P Szucs, M Antal, AJ Todd

• Distribution and colocalisation of glutamate decarboxylase isoforms in the rat spinal cord

  Authors: M Mackie, DI Hughes, DJ Maxwell, NJK Tillakaratne, AJ Todd