Pharmacokinetics of HI-6 and atropine in anaesthetized pigs after administration by a new autoinjector.

A newly developed autoinjector (Astra Tech, Sweden) containing 500 mg HI-6 and 2 mg atropine sulphate was tested in anaesthetized normal pigs. The pharmacokinetics and pharmacodynamics of the drugs after administration by the autoinjector were compared with those after conventional needle and syringe delivery intramuscularly and intravenously. Cardiopulmonary parameters were monitored and serum concentrations of oxime, atropine, and acetylcholinesterase were determined in blood samples taken at intervals over a 6 h period postinjection.

Treatment of organophosphate poisoning in pigs: antidote administration by a new binary autoinjector.

The therapeutic effectiveness of a new binary autoinjector containing 500 mg HI-6 and 2 mg atropine sulphate was tested in anesthetized pigs poisoned by a lethal dose of soman i.v. (9 micrograms/kg per 20 min).

Termination in posterior and anterior cerebellum of a climbing fibre pathway activated from the nucleus of Darkschewitsch in the cat.

Climbing fibre projections to the C2 zone of the cerebellar cortex activated from structures in the midbrain were studied by electrophysiological technique in chloralose-anaesthetized cats. The C2 zone was identified in the paramedian lobule and in the intermediate part of the anterior lobe by peripheral nerve stimulation. Foci in the medial midbrain, which upon low intensity stimulation selectively evoked climbing fibre responses in the C2 zone, were localized by careful mapping procedures.

An excitatory pathway through dorsal columns to rubrospinal cells in the cat.

A somaesthetic excitatory pathway to rubrospinal cells, via other than cortico- or cerebello-rubral relays, has been demonstrated in cats, using intracellular recording techniques. After lesions of the rostral part of the cerebral cortex and the cerebellum, electrical stimulation of the contralateral forepaw and low intensity stimulation of the dorsal columns produced excitatory post-synaptic potentials (e.p.

Cerebral cortical areas of origin of excitation and inhibition of rubrospinal cells in the cat.

The relations between the cerebral cortex and the red nucleus have been studied in acute, chloralose anaesthetized cats using intracellular recording techniques. Stimulation of the cerebral cortex induces in rubrospinal cells a short latency excitation followed by a long lasting silent period. The evidence is presented that at least a great part of the latter is due to genuine IPSP evoked in these cells.

Zonal termination of the tecto-olivocerebellar pathway in the cat.

The climbing fibre pathway from the tectum to posterior cerebellar cortex was investigated in chloralose anaesthetized cats. With low threshold electrical stimulation within the deeper layers of the superior colliculus, climbing fibre responses were recorded in a centrally located, longitudinal area of lobulus VII, oriented perpendicular to the long axis of the folia. This same area showed climbing fibre evoked activity regardless of the side of tectum stimulated.

On climbing fibre projections to cerebellar paramedian lobule activated from mesencephalon in the cat.

Climbing fibre projections to cerebellar paramedian lobule activated from structures in medial midbrain tegmentum were studied in chloralose anaesthetized cats. Three sagittal zones were identified, from medial to lateral c1, c2 and d1 zones. The c1 and d1 zones were activated, at the same short latency, from a dorsal tegmental region with a location similar to the composite bundle called the central tegmental tract.

Identification of a tecto-olivocerebellar path to posterior vermis in the cat.

Climbing fibre projections to posterior cerebellar vermis (lobule VII) activated from midbrain tegmentum and tectum were studied in chloralose anaesthetized cats. Only a medial, possibly bilateral, region of lobule VII was activated by fibres proceeding in a dorsal tegmental region, located within and dorsally to the red nucleus. The same area of lobule VII was also activated from tectum, in the deeper layers of superior colliculi at slightly longer latency.

Inhibition of rubro-spinal cells by somesthetic afferent activity.

A somesthetic inhibitory projection onto rubrospinal cells in the cat is described. It is suggested that the pathway, which is not dependent upon an intact cerebellum or motor cortex, travels through the dorsal columns of the spinal cord. The second order neurons seem to impinge upon inhibitory interneurons situated within the red nucleus itself.

Inhibitory actions from low and high threshold cutaneous afferents on groups II and III muscle afferent pathways in the spinal cat.

The inhibitory effects caused by volleys in cutaneous afferents on the transmission through some polysynaptic segmental pathways activated by high threshold muscle afferents were studied in chloralose anesthetized, spinal cats. Pathways studied were groups II and III to motoneurones as well as group II to primary afferents. The results suggested that two different mechanisms were involved.

The rubro-bulbospinal path. A descending system known to influence dynamic fusimotor neurones and its interaction with distal cutaneous afferents in the control of flexor reflex afferent pathways.

The inhibitory effect of electrical stimulation in the near-rubral region on polysynaptic segmental as well as ascending pathways activated by the flexor reflex afferents (FRA) in hind limb nerves was studied in chloralose anaesthetized cats. The effective stimulating region totally coincided with the one from which a D zone climbing fibre response may be elicited in the contralateral cerebellar cortex. The descending path was dependent upon an intact dorsolateral spinal funiculus, where also a characteristic volley could be recorded with a surface electrode on short train central stimulation.

Rubrospinal control of static and dynamic fusimotor neurones.

Rubrospinal effects on about 60 extracellularyl recorded gamma-motoneurones were studied in anesthetized cats. All cells were antidromically identified from various muscle nerves. 23 cells were regarded as dynamic as they were activated from a mesencephalic region previously known to influence selectively muscle spindle dynamic sensitivity.