| 1. |
- Deliagina, TG, et al.
(författare)
-
Asymmetrical effect of GABA on the postural orientation in Clione
- 2000
-
Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 84:3, s. 1673-1676
-
Tidskriftsartikel (refereegranskat)abstract
- The marine mollusk Clione limacina, when swimming, normally stabilizes the vertical body orientation by means of the gravitational tail reflexes. Horizontal swimming or swimming along inclined ascending trajectories is observed rarely. Here we report that GABA injection into intact Clione resulted in a change of the stabilized orientation and swimming with a tilt of ∼45° to the left. The analysis of modifications in the postural network underlying this effect was done with in vitro experiments. The CNS was isolated together with the statocysts. Spike discharges in the axons of two groups of motoneurons responsible for the left and right tail flexion, as well as in the axons of CPB3 interneurons mediating signals from the statocyst receptors to the motoneurons, were recorded extracellularly when the preparation was rotated in space. Normally the tail motoneurons of the left and right groups were activated with the contralateral tilt of the preparation. Under the effect of GABA, the gravitational responses in the right group of motoneurons and in the corresponding interneurons were dramatically reduced while the responses in the left group remained unchanged. The most likely site of the inhibitory GABA action is the interneurons mediating signals from the statocysts to the right group of tail motoneurons. The GABA-induced asymmetry of the left and right gravitational tail reflexes, observed in the in vitro experiments, is consistent with a change of the stabilized orientation caused by GABA in the intact Clione.
|
|
| 2. |
- Deliagina, TG, et al.
(författare)
-
Neuronal mechanisms for the control of body orientation in Clione I. Spatial zones of activity of different neuron groups
- 1999
-
Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 82:2, s. 687-699
-
Tidskriftsartikel (refereegranskat)abstract
- The marine mollusk Clione limacina,when swimming, can stabilize different body orientations in the gravitational field. Here we describe one of the modes of operation of the postural network in Clione—maintenance of the vertical, head-up orientation. Experiments were performed on the CNS-statocyst preparation. Spike discharges in the axons of different types of neurons were recorded extracellularly when the preparation was rotated in space through 360° in different planes. We characterized the spatial zones of activity of the tail and wing motor neurons as well as of the CPB3 interneurons mediating the effects of statocyst receptor cells on the tail motor neurons. It was found that the activity of the tail motor neurons increased with deviation of the preparation from the normal, rostral-side-up orientation. Their zones of activity were very wide (∼180°). According to the zone position, three distinct groups of tail motor neuron (T1–T3) could be distinguished. The T1 group had a center of the zone near the ventral-side-up orientation, whereas the zones of T2 and T3 had their centers near the left-side-up and the right-side-up positions, respectively. By comparing the zone of activity with the direction of tail bending elicited by each of the groups, one can conclude that gravitational reflexes mediated by the T1, T2, and T3 groups will evoke turning of the animal toward the head-up orientation. Two identified wing motor neurons, 1A and 2A, causing the wing beating, were involved in gravitational reactions. They were activated with the downward inclination of the ipsilateral side. Opposite reactions were observed in the motor neurons responsible for the wing retraction. A presumed motor effect of these reactions is an increase of oscillations in the wing that is directed downward and turning of Clionetoward the head-up orientation. Among the CPB3 interneurons, at least four groups could be distinguished. In three of them (IN1, IN2, and IN3), the zones of activity were similar to those of the three groups (T1, T2, and T3) of the tail motor neurons. The group IN4 had the center of its zone in the dorsal-side-up position; a corresponding group was not found among the tail motor neurons. In lesion experiments, it was found that gravitational input mediated by a single CPB3 interneuron produced activation of its target tail motor neurons in their normal zones, but the strength of response was reduced considerably. This finding suggests that several interneurons with similar spatial zones converge on individual tail motor neurons. In conclusion, because of a novel method, activity of the neuronal network responsible for the postural control in Clione was characterized in the terms of gravitational responses in different neuron groups comprising the network.
|
|
| 3. |
- Deliagina, TG, et al.
(författare)
-
Neuronal mechanisms for the control of body orientation in clione II. Modifications in the activity of postural control system
- 2000
-
Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 83:1, s. 367-373
-
Tidskriftsartikel (refereegranskat)abstract
- The marine mollusk Clione limacina, when swimming, can stabilize different body orientations in the gravitational field. The stabilization is based on the reflexes initiated by activation of the statocyst receptor cells and mediated by the cerebro-pedal interneurons that produce excitation of the motoneurons of the effector organs; tail and wings. Here we describe changes in the reflex pathways underlying different modes of postural activity; the maintenance of the head-up orientation at low temperature, the maintenance of the head-down orientation at higher temperature, and a complete inactivation of the postural mechanisms during defense reaction. Experiments were performed on the CNS-statocyst preparation. Spike discharges in the axons of different types of neurons were recorded extracellularly while the preparation was rotated in space through 360° in different planes. We characterized the spatial zones of activity of the tail and wing motoneurons and the CPB3 interneurons mediating the effects of statocyst receptor cells on the tail motoneurons. This was done at different temperatures (10 and 20°C). The “fictive” defense reaction was evoked by electrical stimulation of the head nerve. At 10°C, a tilt of the preparation evoked activation in the tail motoneurons and wing retractor motoneurons contralateral to the tilt and in the wing locomotor motoneurons ipsilateral to the tilt. At 20°C, the responses in the tail motoneurons and in the wing retractor motoneurons occurred reversed; these neurons were now activated with the ipsilateral tilt. In the wing locomotor motoneurons the responses at 20°C were suppressed. During the defense reaction, gravitational responses in all neuron types were suppressed. Changes in the chains of tail reflexes most likely occurred at the level of connections from the statocyst receptor cells to the CPB3 interneurons. The changes in gravitational reflexes revealed in the present study are sufficient to explain the corresponding modifications of the postural behavior in Clione.
|
|
| 4. |
|
|
