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3 Acta Neurobiologiae Experimentalis

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Lamina IV-VI neurones of the second sacral segment projecting to the sixth cervical segment of the cat's spinal cord

100%

Mrowczynski W.

tom 57

nr 3

189-195

Cervical projections of neurones located in the second sacral segment of the spinal cord were electrophysiologically investigated in 12 adult cats under alpha-chloralose anaesthesia. Extracellular or intracellular antidromic potentials from 41 neurones following stimulation of their axons in the spinal grey matter in the C6 segment brought evidence of sacro - cervical connections. Cell bodies of the investigated neurones were found mainly in the medial part of laminae IV, V and VI. Axons of these neurones ran in lateral funiculi, mostly in their dorsal parts (dlf). Most of the axons (26) ascended bilaterally. Fibres of 15 cells ran unilaterally - on the ipsilateral (13) or the contralateral side (2). Conduction velocites of axons measured between S2 and C6 segments were in the range from 38.4 to 69.1 m/s. It is suggested that these neurones may play an important role in movement coordination between hindlimbs and forelimbs.

Afferent input from distal forelimb nerves to branching spinoreticular-spinocerebellar neurones in the cat

63%

Krutki P. , Mrowczynski W.

tom 62

nr 4

271-276

Patterns of afferent connections from receptors of the distal forelimb were investigated in neurones located in C6-C7 segments of the spinal cord with branching axons projecting to the lateral reticular nucleus and the cerebellum. Experiments were made on five adult cats under alpha-chloralose anaesthesia. After antidromic identification, EPSPs and IPSPs were recorded from 22 neurones following stimulation of deep radial, superficial radial, median and ulnar nerves. Both excitatory and inhibitory effects were found in the majority of the cells, however, in 2 cases no synaptic actions were recorded. EPSPs were evoked from group I or II muscle, or cutaneous afferents ? mostly monosynaptically. IPSPs from muscle, cutaneous or flexor reflex afferents were mostly polysynaptic. Seven various types of convergence were established in the cells investigated. Significance of parallel transmission of integrated information from various receptors of the distal forelimb to the reticular formation and cerebellum is discussed.

Double stimulation modulates afterhyperpolarization phase following action potentials evoked in rat motoneurones

51%

Mrowczynski W. , Krutki P. , Celichowski J.

2007

tom 67

nr 4

439-446

The influence of a pair of stimuli running in time sequence between 5-10 ms (a doublet) on the basic parameters of antidromic action potentials was studied in rat motoneurones. Electrophysiological experiments were based on stimulation of axons in the sciatic nerve and intracellular recording of antidromic action potentials from individual motoneurones located in L4-L5 segments of the spinal cord. The following parameters were analyzed after application of a single stimulus and a doublet: amplitude and duration of the antidromic spike, amplitude, total duration, time to minimum, half-decay time of the afterhyperpolarization (AHP). It was demonstrated that application of a pair of stimuli resulted in: (1) a prolongation of action potentials, (2) a prolongation of the total duration and half-decay time of the AHP, (3) a decline of the time to minimum of the AHP, (4) an increase of the AHP amplitude of the spike evoked by the second stimulus. Significant differences in AHP parameters were found either in fast or slow motoneurones. We suppose that doublet-evoked changes in the AHP amplitude and duration are linked to intrinsic properties of individual motoneurones and may lead to the prolongation of the time interval to subsequent motoneuronal discharges during voluntary activity.