Faculty of Medicine Cellullar and Mollecular Medicine

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Kenneth C. Marshall, Ph.D.

Emeritus Professor Faculty of Medicine 451 Smyth Road, Ottawa, ON K1H 8M5 Tel.: (613) 562-5800 ext. 8583 FAX: (613) 562-5434 Email: kmarshal@uottawa.ca

Mechanisms of Neurotransmission

Our laboratory uses brain slices or other in vitro preparations for electrophysiological studies of neurotransmitter mechanisms in the central nervous system. In recent years, we have studied cells of the Locus Coeruleus (LC), the largest nucleus of noradrenaline-releasing neurons in the brain. Since this nucleus is exclusively responsible for release of noradrenaline in the neocortex and hippocampus, we have studied factors responsible for governing electrical activity of this nucleus. In addition to its inherent interest, we have studied LC neurons as a model system for investigation of various aspects of neurotransmission - e.g. developmental changes in neurotransmitter responsiveness, and pre- and postsynaptic modulation of neurotransmitter responses (Dubé and Marshall, 1997).

We have also recently undertaken studies of the intriguing Mesencephalic Trigeminal nucleus (Me5). This nucleus is composed of primary sensory neurons for jaw-closing muscle spindles, and dentate ligaments and is uniquely located within the CNS (brain stem). Like dorsal root or trigeminal ganglion neurons, they are largely pseudo-unipolar in morphology, but unlike them, have a relatively high incidence of nerve terminals contacting the soma. Until recently, Me5 neurons were thought to be unresponsive to neurotransmitters, but we have now demonstrated clear responsiveness to GABA, to different excitatory amino acid agonists - AMPA, kainate, and NMDA (Hayar et al., 1997; Pelkey and Marshall, 1998), and to serotonin (Pelkey et al., 2003).

Selected Publications

1. Hayar A, Poulter MO, Pelkey K, Feltz P, and Marshall KC (1997). Mesencephalic trigeminal neuron responses to gamma-aminobutyric acid. Brain Res.753:120 - 127.  (See abstract.)
   
   
2. Dubé G and Marshall KC (1997). Modulation of excitatory synaptic transmission in locus coeruleus by multiple presynaptic metabotropic glutamate receptors. Neuroscience 80, 511-521.  (See abstract.)
   
   
3. Pelkey, KA and Marshall, KC (1998). Actions of excitatory amino acids on mesencephalic trigeminal neurons. Can. J. Physiol. Pharmacol. 76: 900-908.  (See abstract.)
   
   
4. Dubé GR and Marshall, KC (1999).  Testing of metabotropic glutamate inhibition of EPSPs in mGluR4 knockout mice.  Can. J. Physiol. Pharmacol. 77: Aiv.  (See abstract.)
   
   
5. Dubé GR and Marshall, KC Activity-dependent activation of presynaptic metabotropic glutamate receptors in locus coeruleus. J. Neurophysiol. (in press).  (See abstract.)

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