Morphology and membrane properties of neurones in the cat ventrobasal thalamus in Vitro

Abstract

1. The morphological (n = 66) and electrophysiological (n = 41) properties of eighty-six thalamocortical (TC) neurones and those of one interneurone in the cat ventrobasal (VB) thalamus were examined using an in vitro slice preparation. The resting membrane potential for thirty-seven TC neurones was −61·9 ± 0·7 mV, with thirteen neurones exhibiting delta oscillation with and without DC injection. 2. The voltage-current relationships of TC neurones were highly non-linear, with a mean peak input resistance of 254·4 MÙ and a mean steady-state input resistance of 80·6 MÙ between −60 and −75 mV. At potentials more positive than −60 mV, outward rectification led to a mean steady-state input resistance of 13·3 MÙ. At potentials more negative than −75 mV, there was inward rectification, consisting of a fast component leading to a mean peak input resistance of 14·5 MÙ, and a slow time-dependent component leading to a mean steadystate input resistance of 10·6 MÙ. 3. Above −60 mV, three types of firing were exhibited by TC neurones. The first was an accelerating pattern associated with little spike broadening and a late component in the spike after-hyperpolarization. The second was an accommodating or intermittent pattern associated with spike broadening, while the third was a burst-suppressed pattern of firing also associated with spike broadening, but with broader spikes of a smaller amplitude. All TC neurones evoked high frequency (310-520 Hz) burst firing mediated by a low threshold Ca¥ potential. 4. Morphologically TC neurones were divided into two groups: Type I (n = 31 neurones) which had larger soma, dendritic arbors that occupied more space, thicker primary dendrites and daughter dendrites that followed a more direct course than Type II (n = 35). The only electrophysiological differences were that Type I neurones (n = 16) had smaller peak input and outward rectification resistance and spike after-hyperpolarization, but greater peak inward rectification resistance, and exhibited delta oscillation less often than Type II (n = 13). 5. The morphologically identified interneurone exhibited no outward rectification, only moderate inward rectification, and no high frequency firing associated with the offset of negative current steps below −55 mV. This interneurone had a regular accommodating firing pattern, but the spike after-hyperpolarization had a late component, unlike the accommodating firing in TC neurones. 6. Therefore, the differentiation of TC neuronal types in the cat VB thalamus based on their morphology was reflected by differences in peak input resistance, outward rectification and spike after-hyperpolarization, which could be accounted for by their difference in soma size. More importantly, the firing pattern of the majority of TC neurones in the cat VB thalamus were different from those of TC neurones in other sensory thalamic nuclei. 7. Thalamocortical neurones in the cat VB thalamus were also clearly distinguishable from the interneurone based on the presence of their prominent outward rectification, pea...

Analysis of morphological features of thalamocortical neurons from the ventroposterolateral nucleus of the cat

“…observed in this and previous studies (Spreafico et al, 1983;Yen et al, 1985;Ohara and Havton, 1994;Ohara et al, 1995;Turner et al, 1997;Jones, 2007) were generally similar. However, we report some differences.…”

“…Previous studies proposed a correlation between the morphology of TC neurons and their electrophysiological features (Yen et al, 1985;Turner et al, 1997). Our GR value data suggest that in different dendrites attenuation of back-propagating potentials takes place and that attenuation has different strength and range depending on the dendritic diameters.…”

“…Recent studies have demonstrated, however, that the morphology of the neuron plays a critical role in cell responsiveness (Turner et al, 1997). It has been shown that with the same active and passive properties of the dendritic tree, the geometrical (e.g., area) and topological (e.g., partition symmetry) properties strongly influence the neuronal firing patterns and modify the efficacy of back-propagating action potentials or forward propagation of postsynaptic potentials (Duijnhouwer et al, 2001;Sterratt and van Ooyen, 2002;Chklovskii, 2004;van Pelt and Schierwagen, 2004;Gulledge et al, 2005;Timofeeva et al, 2008;Weaver and Wearne, 2008;Katz et al, 2009;Komendantov and Ascoli, 2009).…”

Rare and spatially segregated release sites mediate a synaptic interaction between two identified network neurons

“…Neuronal geometry, as well as the distribution and density of membrane channels and receptors, play a crucial role in information processing by a single neuron (Buhl et al, 1994;Zhang et al, 1995;Boyd et al, 1996;Mainen and Sejnowski, 1996;Renehan et al, 1996;Yang et al, 1996;Nambu and Llinas, 1997;Turner et al, 1997). Clearly, also the location and number of synaptic contacts have important physiological consequences both for a neuron's integrative capability and for the operation of the network to which it belongs.…”

Cell types and response properties of neurons in the ventral division of the medial geniculate body of the rabbit

“…Although they have been well-documented both in the LGN as well as the VP complex (Guillery, 1966;Friedlander et al, 1981;Landry and Descheñ es, 1981;Yen and Jones, 1983;Yen et al, 1985;Turner et al, 1997), this is the first description of two classes of presumptive relay neurons within the MGV based on dendritic morphology. Both single-and double-labeling retrograde studies have provided independent evidence for multiple classes of relay neurons in the MGV (Winer, 1984b;de Venecia et al, 1998).…”