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Title: The origins of electrical discharge patterns in the main olfactory bulb of the rat
Author: Bramley, Jayne R.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2001
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In the studies described in this thesis, the electrical activity of single neurones was recorded extracellularly from the olfactory bulb of anaesthetised rats. Mitral cells were identified electrophysiologically by antidromic activation following stimulation of the lateral olfactory tract. Early in these studies, it became apparent that the mitral cells consistently showed a patterned discharge behaviour that has not been previously reported. Mitral cells displayed a characteristic slow, cyclic spontaneous firing pattern, with peaks of activity occurring with a constant periodicity. During the peaks of activity the mitral cell fired at two distinct frequencies, with a short delay in the onset of the higher frequency mode, at the start of each peak of activity. Analysis of these cyclic patterns show that they are not due to a respiratory influence, which is seen as a separate waveform within the phasic firing pattern. Granule cells are the most numerous, of various types of interneurone in the bulb, and are involved in reciprocal synapses with mitral cells. The granule cells fired in a very different manner to that described for the mitral cell, their spontaneous activity was characteristically non-phasic and at only one frequency mode. Dual recordings of two individual mitral cells indicate that the phasic pattern ins not uniform throughout the bulb, mitral cells drift in and out of phase with each other. This would suggest that the generation of the phasic firing pattern is intrabulbar and not entirely controlled by an extrabulbar influence. In addition to recording the spontaneous activity of mitral and granule cells, I looked at their activity during stimulation of the lateral olfactory tract. During stimulation at a threshold intensity, the mitral cells exhibited a period of inhibition following the stimulus pulse. This is consistent with the general consensus that upon activation, mitral cells activate granule cells, which in turn feedback to inhibit the mitral cells in a process known as reciprocal inhibition. Granule cells did not display an inhibition to the stimulus.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available