Lateral Geniculate Nucleus Of Rat Research Articles

Optic nerve components may not be equally susceptible to damage by acrylamide

Cells in the lateral geniculate nucleus of rats treated with the neurotoxin acrylamide were classified as X or Y according to the criterion of linear summation. Compared with control animals, they had a lower ratio of X to Y cells. It is argued that this effect may be related to differences in axon diameter, the thinner fibres in the optic nerve being more susceptible to damage.

Persistence of visual responsiveness in the lateral geniculate nucleus of rats treated with monosodium- l-glutamate

Normal treatment of rats with monosodium- l-glutamate (MSG) resulted in extensive degeneration of the inner nuclear layer of the retina. The retino-hypothalamic projection was still functional as these rats entrained their circadian food intake rhythm to the light-dark cycle. A normal proportion of dorsal lateral geniculate nucleus (LGNd) cells in MSG rats responded to visual stimulation. The response pattern, latency and variability of LGNd cells at different times (3–18 months) after treatment were comparable to those of normal rats. These results demonstrate the MSG-induced retinal damage does not lead to blindness in the rat. The similarity in pathophysiology between MSG lesioned rats and animals exposed to constant illumination is discussed.

The presence and nature of inhibition in small slices of the dorsal lateral geniculate nucleus of rat and cat incubated in vitro

The presence and nature of inhibition in small slices of the dorsal lateral geniculate nucleus of rat and cat incubated in vitro

Receptive-field properties of cells in the dorsal part of the albino rat's lateral geniculate nucleus.

Receptive-field properties of 273 relay (principal, P-) cells of the dorsal lateral geniculate nucleus (LGd) were studied in urethane-anesthetized albino rats, in an attempt to see if there is some relation between the visual property and the conduction velocity of afferent optic nerve fibers. According to properties of the receptive-field center, P-cells were classified into two types, common (89%) and uncommon (11%). The common type consists of OFF-phasic, ON-phasic, ON-tonic and ON-OFF-phasic cells, while the uncommon type includes ON-inhibited, moving-sensitive, ON-OFF-inhibited, simple-cell-like and complex-cell-like cells. The mean response latency to single optic chiasm shocks increases in the order of OFF-phasic (1.94 msec), ON-phasic (2.35 msec), ON-tonic (2.87 msec), ON-OFF-phasic cells (3.04 msec) and uncommon type (3.18 msec). The mean size of the receptive-field center in each of the four common types was smaller than that in the uncommon type; 6 degrees--7 degrees vs. 11 degrees. From responsiveness to moving light spots with speeds faster than 25 degrees--30 degrees/sec, P-cells of the common type were divided into the fast- and slow-movement-sensitive cells. The ratio of occurrences of fast- to slow-movement-sensitive cells decreases in the order of the OFF-phasic (2.7), ON-phasic (2.4), ON-tonic (1.1) and ON-OFF-phasic types (0.06). The optic chiasm latencies were shorter than 2.5 msec in most of the fast-movement-sensitive cells while the reverse was true for most of the slow-movement-sensitive cells. From these findings discussions were made to point out that the rat LGd mainly consists of Y- and W-like P-cells and that the Y/W dichotomy of P-cells approximately corresponds to the previously established fast/slow classification.

Control of thalamic transmission by corticofugal and ascending reticular pathways in the visual system.

Control of thalamic transmission by corticofugal and ascending reticular pathways in the visual system.

The postnatal development of neurons in the dorsal lateral geniculate nucleus of the rat: A Golgi study

The postnatal differentiation of neurons in the dorsal lateral geniculate nucleus of the albino rat was studied using the Golgi-Cox technique. At least four animals were used at postnatal ages 12 hours, 2, 4, 6, 8, 10, 11, 12, 13, 14, 15, 16, 18, 20, 24, 28, 35 days and adult. Presumptive thalamo-cortical projection cells (Class A cells of Grossman et al., '73) and non-projection, intrinsic neurons (Class B cells) are distinguishable at 12 hours after birth. At this stage both types of neuron are immature, with prominent growth cones at their dendritic extremities. Dendritic growth and differentiation appear to be complete by 18 days. Relay cells display two apparent "growth spurts" characterized by noticeable enlargement of the perikaryon and a marked increase in dendritic length and complexity. One occurs between days 4 and 6 and coincides with a period of enhanced synaptogenesis and gliogenesis: the second occurs between days 14 and 15, around the time of eye opening (day 14) and may be related to a further phase of increased synaptogenesis and gliogenesis (Karlsson, '67; Biesold et al., '76). Class B cells appear to "lag" behind class A cells in their initial postnatal differentiation, but also reach their mature condition by day 18.

The neurons and their postnatal development in the ventral lateral geniculate nucleus of the rat.

The morphology and distribution of neurons in the ventral lateral geniculate nucleus (vLGN) of adult rats, and the postnatal growth and differentiation of these neurons were studied in Golgi-Cox preparations. In the adult, two main cell classes were recognized: class A cells and class B cells. The former are assumed to be projection neurons. The latter closely resemble the class B cells of the dorsal lateral geniculate nucleus and are interpreted as presynaptic dendrite-bearing interneurons. Class A cells predominated and three subtypes were tentatively identified: small--medium size multipolar neurons, with short, branched spiny dendrites (most numerous in dorsolateral vLGN); medium--large fusiform cells with one or two stem dendrites at each pole (most numerous in medial vLGN); large multipolar neurons with long, sparsely branched dendrites (most numerous in ventral vLGN). Class A and B cells were distinguishable at birth and showed parallel cell body size increases up to postnatal day 24. The dendrites of both classes of cell also reached the adult stage of differentiation at about day 24 but the differentiation of class B cell dendrites lags slightly behind that of class A cell dendrites.

Relation of the visual field to the lateral geniculate body of the albino rat.

Relation of the visual field to the lateral geniculate body of the albino rat.

Three-dimensional studies of neurons in the lateral geniculate nucleus of the rat: III. Specialized neuronal contacts in the neuropil

Interneuronal contact relationships were investigated by electron microscopy in the neuropil of the rat lateral geniculate nucleus, partly utilizing three-dimensional analysis technique. Specialized contacts composed of (a) V and no-V processes, (b) spines, V, no-V processes and glia and (c) spines, two V processes, one no-V process and glia were described and discussed in relation to morphological features. Morphological characteristics were found distinct for each of the two V process components participating in the most complex type of interneuronal contact. A symmetrical membrane specialization and intracellular content was found to differ for all three components. Contents of V and no-V processes were described and related to previously published data. Also, the ultrastructure of nodes of Ranvier was established using this technique of preparation. Extracellular space at the nodal region was consistently observed. Glia investment was found to be sparser on thinner no-V processes as compared with that on perikarya.

Recovery of responsiveness of cells of lateral geniculate nucleus of rat

1. Recovery of responsiveness of single cells in lateral geniculate nucleus of rat has been determined in both P and I cells. There are three types of recovery curve among P cells; (a) early recovery, (b) early partial recovery followed by depression and then complete recovery, (c) prolonged depression followed by cyclic recovery. Type (c) is by far the commonest recovery curve. In contrast to the spike in a P cell, the synaptic potential recovers to its full amplitude in about 20 msec. All I cells exhibit similar rapid recovery curves after a prolonged depression.2. Conditioning stimuli applied to visual cortex also produce a prolonged depression in most P cells but I cells can be re-excited at short intervals from cortex. Decortication does not prevent the prolonged depression of the multineuronal response produced by optic nerve stimulation.3. A neuronal model is proposed to explain these observations. It is supposed that I cells (interneurones) are innervated by axon collaterals of the P cells (principal cells, projecting to visual cortex) and that the I cells exert an inhibitory influence on the P cells.

Discharge patterns of principal cells and interneurones in lateral geniculate nucleus of rat.

1. The cells of the lateral geniculate nucleus of the rat are classified into one of two distinct groups on the basis of their responses to a single shock to optic nerve or visual cortex. The distinctive difference between these two groups is that the P cells (87% of all cells) responded with short bursts of 1-5 spikes, whereas the I cells (13%) responded with long bursts of about 10 spikes. Both groups give recurring bursts at intervals of 100 msec or more for a total duration of up to about 5 sec.2. The majority of P cells (75%) have a lower threshold for late firing than for early firing. The majority of I cells (62%) have about the same threshold and all I cells have very low thresholds.3. To stimulation of the optic nerve the mean latency of the first spikes of all P cells is 4.4 msec. The mean latency of the first spikes of all I cells is 5.8 msec. The latency of the earliest spike in an I cell is 0.9 msec longer than the earliest spike in a P cell.4. To stimulation of the visual cortex the latency of the earliest spike in an I cell is 1.0 msec longer than the earliest spike in a P cell. Most P cells (78%) respond with either very short latency (less than 1.7 msec) or with a wave form characteristic of antidromic invasion or both. No I cell has either of these characterstics.5. It is concluded that P cells are principal cells projecting to visual cortex and that I cells are interneurones.

Inhibitory mechanisms in lateral geniculate nucleus of rat

1. An examination was made of the mechanisms responsible for the inhibition of synaptic transmission through the lateral geniculate nucleus (LGN) of the rat following a single shock to the optic nerve.2. In the rat anaesthetized with paraldehyde we found no evidence that optic nerve stimulation produced any presynaptic inhibition in LGN. In agreement with other workers it was found that repetitive stimulation of visual cortex produced effects attributable to presynaptic inhibition. However, this was of small magnitude in the conditions of our experiments.3. Stimulation of the optic nerve elicited an action potential in a P cell (principal cell) which was followed by a wave of hyperpolarization lasting about 150 msec (inhibitory post-synaptic potential, IPSP, wave).4. The IPSP wave was chloride-dependent and was associated with inhibition of the P cell discharge. Occasional rippling on the IPSP wave suggests that it was produced by the repetitive discharge of I cells (interneurones).5. These observations support the model proposed previously wherein P cells are inhibited by I cells which in turn are excited by axon collaterals of P cells. There is evidence for diffuse interconnexions between P cells and I cells.6. The observation that the extracellularly recorded wave of hyperpolarization (P-wave) is usually negative suggests that most of the inhibitory synapses are not on the soma of the P cell.