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The formation of trigeminal motor nucleus (TMN) was studied in the early postnatal period in 21 female Wistar rats which received the serotonin biosynthesis inhibitor para-chloro-phenylalanine at prenatal Day 16 (the period of serotoninergic system formation). It was shown that the serotonin deficit during the prenatal period in rats resulted in the changes of TMN structural organization. In the early postnatal period, the delay of neuropil development, the reduction of cell body size with the partial loss of Nissl substance in some of the neurons, the presence of degenerating neurons with the signs of hyperchromatosis in all the parts of the nucleus, especially in TMN ventromedial part, were detected. At later stages, the destruction of motoneurons became slower, though some of them had morphological abnormalities. With the increase of the postnatal age (by Day 20) the number of motor neurons decreased, apparently, as a result of the gradual intensification of cell death. Simultaneously with the motor neuron degeneration in TMN parts studied, the astrocytic gliosis was observed.

Motor responses of low jaw to the microstimulation of the motor nucleus of the trigeminal nerve (MNTN) of albino mice have been recorded. They had the latency ranged of 2.5 to 13.5 ms. After microinjections of horseradish peroxidase into the MNTN, retrogradely labeled neurons were revealed ipsilaterally in both sensory and mesencephalic trigeminal nuclei, in the medullary reticular formation, etc.

Membrane resting and action potentials evoked by antidromic and direct stimulation were studied in neurons of the rat trigeminal motor nuclei. It is shown that in the given motor nuclei there are cell populations both with low and high membrane potentials. Motoneurons with high resting potentials were characterized by shorter latent period of antidromic activation, longer duration of spike and after depolarization and lower input resistance. Bimodal character of electrophysiological parameters distribution in the trigeminal motor nuclei show that "slow" and "fast" fibres of m. masseter may be innervated by different types of motoneurons.

Five types of neurons were studied in the sensory nuclei of the trigeminal nerve stained by the Golgi method in kittens aged 30 days with bilateral transection of the lingual branches of trigeminal nerve made on the fifth postnatal day. Partial deafferentation resulted in changes of dendrite apparatus of reticular, arborescent and bushy neurons (68.61 and 48% of neurons changed). Short-dendritic cells changed slightly. The multipolar giant neurons underwent practically no changes. All the changes could be divided into two groups: destructive changes and constructive changes. The destructive changes consisted in the decrease of cell body sizes, number, length and ramification of dendrites and constructive changes--in the increase of these parameters. Various types of trigeminal neurons responded to deafferentiation in different ways. Bushy neurons displayed mainly destructive changes and reticular and arborescent neurons--both destructive and constructive ones.

The paper presents a quantitative Golgi study of the kitten sensory trigeminal complex. Kittens of 1-5 and 30 days were used. Trigeminal neurons were divided into five groups. Neurons of two groups ramified sparsely and were defined as "reticular" and "short dendritic" neurons. Neurons of three other groups ramified densely and were defined as "bushy" neurons, "arbory dendritic" and "multipolar giant" neurons. The quantitative morphological data were obtained by measuring cell sizes, number, length, relative length, degree of branching of dendrites and total cell branching. The neurons of different groups had different parameters and a special mode of their maturation. "Bushy" neurons showed regressive changes during ontogenesis. All their parameters were reduced during the first month. Foci of maximal dendritic branching were displaced towards the distal portions of dendrites during the processes of cell maturation. All trigeminal neurons reached the high degree of maturity at birth.