Expression of GAD65/67 and VGLUT2 in Mediobasal Nuclei of Rat Hypothalamus during Aging.

The expression of glutamate decarboxylase GAD65/67, an enzyme of GABA synthesis, and vesicular glutamate transporter 2 (VGLUT2) in the arcuate, dorsomedial, and ventromedial nuclei of the hypothalamus of young (3 months), adult (12 months), and old male rats (24 months) was studied by Western blotting. In old rats, an increase in the expression of GAD65/67 in the arcuate and dorsomedial, VGLUT2 in the arcuate, dorsomedial, and ventromedial nuclei was observed. Thus, an increase in opposite processes of inhibition and excitation is observed in the hypothalamic nuclei during aging.

Spike Activity in the Ventromedial Nucleus of Rat Hypothalamus during Aging.

Spike activity of neurons in the ventromedial nucleus (VMN) of the hypothalamus in adult (6-8 months) and aged (2 years) male rats was studied by the in vivo extracellular method using stereotaxic insertion of microelectrodes. In all animals, firing frequency of most VMN neurons increased in response to glucose administration. However, in aged rats, the mean baseline and glucose-induced spike frequencies of VMN neurons were lower than in adult animals. These results support the hypothesis that aging is associated with a decrease in the functional activity of hypothalamic neurons.

Age-Dependent Effects of NO on Rhythmic Activity of Postganglionic Sympathetic Fibers.

We studied the effects of exogenous NO donor (sodium nitroprusside) and NO synthesis blocker (100 µM L-NAME) on baseline electrical activity of postganglionic fibers in the sympathetic superior cervical in rats during postnatal ontogeny. Starting the age of 20 days, sodium nitroprusside increased the mean discharge amplitude and the spectrum power in the respiratory (0.7-1.5 Hz) and cardiac (4-7 Hz) frequency bands. In contrast, application of L-NAME for 1 h decreased the spectrum power in these bands. Both agents produced no significant effect on the rhythmic sympathetic discharges at frequencies >8 Hz.

Role of neuropeptide Y in myocardial contractility of rats during early postnatal ontogeny.

We studied the effect of neuropeptide Y in concentrations of 10(-10)-10(-6) M on myocardial contractility of rats at the age of 7, 21, and 100 days. Studying the isometric contraction of myocardial strips showed that neuropeptide Y decreases the force of myocardial contraction in 7-day-old rat pups. Exogenous neuropeptide Y produced a biphasic effect in 21-day-old rats, which was manifested in the increase and subsequent decrease in myocardial contractility. Neuropeptide Y had little effect on myocardial contractility of 100-day-old animals.

Age-related changes in rhythmic electrical activity in the cervical sympathetic trunk in rats and cats.

Baseline electrical activity in the cervical sympathetic trunk was studied in neonatal rats and cats and at ages 10, 20, and 30 days and two and six months, using spectral analysis. Rats from the neonatal period to the end of the first month of life and cats to 20 days of life showed increases at the amplitudes of electrical oscillations. From birth, all animals showed oscillations in the respiratory and cardiac rhythms. From day 20, frequencies with a cardiac component in rats dominated the power spectrum. The proportion of other frequencies, not associated with the cardiac or respiratory rhythms, was smaller. In cats, unlike the situation in rats, there were no age-related changes in the spectral composition of baseline electrical activity. High-frequency oscillations were recorded in cats from birth.

Neurotransmitter composition of neurons in the cranial cervical and celiac sympathetic ganglia in postnatal ontogenesis.

The neurotransmitter composition of neurons in the cranial cervical ganglion (CCG) and celiac ganglia (CG) in rats of different ages (neonatal, 10, 12, 30, and 60 days) was studied by immunohistochemical methods. The results showed that most neurons in these sympathetic ganglia contain tyrosine hydroxylase (TH). Most TH-positive neurons were also neuropeptide Y (NPY)-positive. In all ganglia, the proportions of neurons containing NPY increased from the moment of birth to the end of the first month of life. In the CG, NPY was present in a significantly greater proportion of neurons than in the CCG. Substance P, vasoactive intestinal peptide, and choline acetyltransferase were present in occasional neurons in the CCG and CG from birth. There was no change in the proportion of this type of neuron with age. Definitive establishment of the neurotransmitter composition in the sympathetic ganglia studied here occurred by the end of the first month of life.

Development of rat stellate ganglion neurons containing membrane-bound muscarinic receptors and purinoreceptors.

The aim of the study reported here was to investigate the locations and morphometric characteristics of neurons in the stellate ganglion (SG) containing muscarinic cholinoreceptors and purinoreceptors in rat pups of different ages (neonatal, 10, 20, 30, 60, and 180 days) using immunohistochemical methods. The results showed that in all animals, most neurons were immunoreactive to M1 cholinoreceptors and P2X2 and P2X6 purinoreceptors from birth. Sections showed isolated neurons containing P2X3 purinoreceptors, the numbers of which increased from day 10 of life to day 20 and then decreased again. During ontogenesis, the proportions of neurons expressing M1 cholinoreceptors and P2X2 and P2X6 purinoreceptors did not change significantly. Thus, by the moment of birth, muscarinic synaptic transmission already occurred in the SG in rats, while the final set of purinoreceptors in the neurons of this sympathetic ganglion formed by age 30 days.

NADPH-diaphorase-positive neurons in sympathetic ganglia during postnatal ontogenesis.

The locations and morphometric characteristics of NADPH-diaphorase (NADPH-d)-positive neurons were identified in the cranial cervical (CCG), stellate (SG), and celiac (CG) ganglia in neonatal rats, mice, and cats and animals aged 10, 20, 30, 60, and 180 days. No NADPH-d-positive neurons were found in rats and mice in any of the age groups studied. In kittens, the majority of NADPH-d-positive neurons were located in the SG, with fewer in the CCG and only occasional neurons in the CG, regardless of age. The proportion of NADPH-d-positive neurons in the SG increased during the first 20 days of life and decreased after 30 days, to the end of the second month of life. The proportion of NADPH-d-reactive neurons in the CCG and CG did not change during ontogenesis. The mean sizes of NADPH-d-positive neurons in different ganglia in animals of the same age were not significantly different. These data lead to the conclusion that the development of NADPH-d-positive neurons with age occurs heterochronously and is complete by the end of the second month of life.

Efferent innervation of the cervical segment of the trachea in early postnatal ontogenesis.

A method based on retrograde axonal transport of horseradish peroxidase was used to study the efferent innervation of the cervical segment of the trachea in neonatal kittens and kittens aged 10, 20, and 30 days and two months. Labeled neurons in all animals were located in the cranial cervical, middle cervical, and cervicothoracic sympathetic ganglia on the right and left sides, at the level of the medulla oblongata, and in the dorsal and ambiguus nuclei of the vagus nerves. Up to age 30 days, neurons were also seen in the ventral horns of the spinal cord in segments C1 to C5. The number of sympathetic neurons innervating the trachea increased from the moment of birth, reaching a maximum by 10-20 days and then decreasing to age two months. The number of parasympathetic neurons gradually decreased during ontogenesis.

Rhythmic electrical activity in branches of the stellate ganglion in the cat during postnatal ontogenesis.

Electrical activity in branches of the stellate ganglion was studied in neonatal cats and cats aged 10, 20, and 30 days and two and six months, with subsequent spectral analysis. Maturation of the pattern of the baseline rhythmic activity in branches of the ganglion differed during ontogenesis in the kittens. The neonatal period until the end of the second month of life was accompanied by an increase in the amplitude of electrical oscillations. Synchronous discharges in postganglionic fibers consisted of slow, low-amplitude oscillations at the respiratory frequency and heart rate in neonatal and 10-day-old-kittens. Synchronous spike activity with a frequency of about 10 Hz appeared from day 20 of life. The formation of the pattern of sympathetic nerve fiber discharges was complete by the second month of life.

Age-related characteristics of the neurotransmitter composition of neurons in the stellate ganglion.

The neurotransmitter composition of neurons in the stellate ganglion of rats of different ages (neonatal, 10, 20, 30, and 60 days) was studied by an immunocytochemical method using double labeling. Most neurons in rat pups of all age groups contained tyrosine hydroxylase. Most choline acetyltransferase-positive neurocytes in neonatal and 10-day-old rat pups were also tyrosine hydroxylase-positive. Only occasional cells in 30-and 60-day rat pups contained both of these enzymes. There were increases in the proportions of cells containing tyrosine hydroxylase and neuropeptide Y from birth to all time points of the study. In addition, there was a decrease in the proportion of somatostatin-positive neurons. The proportions of VIP-positive cells and choline acetyltransferase-containing neurons increased to age 10 days and then decreased. Somatostatin-positive neurons in all rat pups were small cells, while those containing choline acetyltransferase were large. Maturation of the neurotransmitter set in the rat stellate ganglion was complete by the end of the second month of life.

Immunocytochemical characteristics of neurons in the stellate ganglion of the sympathetic trunk in mice during postnatal ontogenesis.

The neurotransmitter composition of neurons in the stellate ganglion of mice of different ages (neonatal and aged 10, 20, 30, and 60 days) was studied using an immunocytochemical method. Most of the neurons in the mice of these age groups contained tyrosine hydroxylase (TH). Most choline acetyltransferase (CAT)-positive neurons in neonatal and 10-day mice were also TH-positive. From birth and at all subsequent ages, there were increases in the proportion of cells contained TH and neuropeptide Y. The proportion of neurons containing vasoactive intestinal peptide and CAT increased to 10 days of life and then decreased. Somatostatin-and galanin-positive neurons were absent from all animals. Maturation of the set of neurotransmitters in stellate ganglia was complete by age two months.

Preganglionic inputs to the stellate ganglion of the cat during postnatal ontogenesis.

The localization of preganglionic neurons forming, connections with the stellate ganglion was studied using a method based on retrograde axonal transport of horseradish peroxidase in cats during postnatal ontogenesis from birth to six months of life. The number of preganglionic neurons and spinal cord segments connected to the ganglion increased from birth to 10 days of age, and then decreased. The proportion of preganglionic neurons in different spinal cord nuclei changed during life and became comparable with that in adults by age six months. This was accompanied by an increase in the proportion of cells in the nucleus intermediolateralis thoracolumbaris pars principalis, with a decrease in the number of neurons in the nucleus intermediolateralis thoracolumbaris parts funicularis and in the ventral horns of the spinal cord.