Both genetic and environmental factors are involved in establishing a behavior. An animal study was done to determine the characteristics of interaction between genetic (nature) and environmental (nurture) factors. Delivery of footshocks (0.8 mA x 60 times, at random) early in life was used as the environmental stimulus. As the footshock was delivered repeatedly, a rat showed helplessness behavior and the number of shocks necessary to elicit helplessness was measured to quantify the trait of an animal in coping with the aversive environmental stimulus. The nocturnal ambulatory activity at adulthood was measured as a behavioral expression of the nature-nurture interaction. Although the experience of footshocks early in life did not significantly alter average activity levels at adulthood, the activity was positively correlated with the number of shocks necessary to elicit helplessness (nature) while receiving footshocks (nurture) on postnatal day 14. Additionally, a second exposure to identical shock parameters on postnatal day 21 reversed the relationship. These results clearly showed that an interaction between nature and nurture during infancy leads to substantial behavioral alterations later in life, and suggest that the nature-dependent determination of an adult behavior can be modified in different directions by the conditions of an environmental experience early in life.
Aging/physiology* ; Animal ; Animals, Newborn/physiology* ; Animals, Newborn/growth & development ; Electroshock* ; Foot* ; Motor Activity/physiology* ; Rats ; Rats, Sprague-Dawley

Acclimatization ; physiology ; Animals ; Animals, Newborn ; Chickens ; Cold Temperature ; Endocrine Glands ; physiology ; Female ; Male ; Rats ; Rats, Wistar

The glutamatergic innervations and the GABAergic innervations are respectively the major excitatory and inhibitory inputs of preganglionic cardiac vagal neurons (CVNs). Whether and how these two kinds of innervations interact in the regulation of CVNs is unknown. Using retrograde fluorescent labeling of CVNs and voltage patch-clamp technique, we demonstrated that mixed global application of glutamatergic NMDA and non-NMDA antagonists AP(5) and CNQX, while had no effect on the GABAergic synaptic events of the CVNs in the nucleus ambiguus (NA), significantly decreased the GABAergic synaptic events of the CVNs in the dorsal motor nucleus of the vagus (DMNX). These results suggest that the GABAergic neurons preceding the CVNs in the DMNX receive tonic glutamatergic control, whereas the GABAergic neurons preceding the CVNs in the NA receive little, if any, glutamatergic innervations. This differential central regulation of the CVNs in the DMNX from those in the NA might be a possible mechanism that enables the CVNs in the DMNX play different roles from those in the NA in the parasympathetic control of heart rate and cardiac functions.
Animals ; Animals, Newborn ; Brain Stem ; physiology ; GABAergic Neurons ; physiology ; Glutamates ; physiology ; Heart ; physiology ; Heart Rate ; physiology ; Motor Neurons ; drug effects ; Rats ; Rats, Sprague-Dawley ; Vagus Nerve ; physiology

OBJECTIVETo explore the role of group II metabotropic glutamate receptors in the modulation of basic respiratory rhythm.

METHODSNeonatal (0-3 days) SD rats of either sex were used. The medulla oblongata brain slice containing the medial region of the nucleus retrofacialis (mNRF) and the hypoglossal nerve rootlets was prepared, and the surgical procedure was performed in the modified Kreb's solution (MKS) with continuous carbogen (95% O2 and 5% CO2) within 3 min. The brain slices were quickly transferred to a recording chamber and continuously perfused with oxygen-saturated MKS at a rate of 4-6 ml/min at 27-29 degrees celsius. Eighteen medulla oblongata slices were divided into 3 groups and treated for 10 min with group II metabotropic glutamate receptor-specific agonist 2R,4R-4-aminopyrrolidine-2,4-dicarboxylate (APDC) (at concentrations of 10, 20, 50 micromol/L), group II metabotropic glutamate receptor antagonist (2S)-alpha-ethylglutamic acid (EGLU) (300 micromol/L), or APDC (50 micromol/L)+EGLU (300 micromol/L) after a 10 min APDC (50 micromol/L) application. Respiratory rhythmical discharge activity (RRDA) of the rootlets of the hypoglossal nerve was recorded by suction electrodes.

RESULTSAPDC produced a dose-dependent inhibitory effect on the RRDA, prolonging the respiratory cycle and expiratory time and decreasing the integral amplitude and inspiratory time. EGLU induced a significant decrease in the respiratory cycle and expiratory time. The effect of APDC on the respiratory rhythm was partially reversed by the application of APDC+EGLU.

CONCLUSIONGroup II metabotropic glutamate receptors are probably involved in the modulation of the RRDA in isolated neonatal rat brainstem slice.

Animals ; Animals, Newborn ; In Vitro Techniques ; Medulla Oblongata ; physiology ; Rats ; Rats, Sprague-Dawley ; Receptors, Metabotropic Glutamate ; physiology ; Respiratory Center ; physiology

To investigate the intracellular mechanism of activity-dependent synapses formation and redistribution, we studied the electrophysiological and morphological characteristics of neurons of the developing visual cortex, and observed the level of synchronism of age and changes in the properties. Whole cell patch-clamp recordings and intracellular biocytin staining were used to record postsynaptic currents (PSCs) from neurons in the visual cortex of Sprague-Dawley rats (postnatal d 4-28). The histological processing was made. There were three types of PSCs in 156 cells: silent response, monosynaptic response and polysynaptic response, during the first developmental month. Before eyes opened the number of the neurons with the silent response (57.3%) was significantly higher than that after the eyes opened (11.9%) (P<0.001). However, the incidence of polysynaptic PSCs increased from 12.4% before eyes opened to 28.9% after eyes opened (P<0.01). During postnatal week 1, all cells were classified as immature. The immature cells had very high input resistances (R(N)>1.0 G Omega), low amplitude (-0.87 mA) and short decay time (-0.98 ms). During postnatal week 4, all cells were mature with lower input resistance (R(N)<310 M Omega), larger amplitude (-66 mA), and longer decay time (-225 ms). From postnatal weeks 1 to 3, the cells had electrophysiological properties that were intermediate between the immature and mature types of cells. With biocytin intracellular staining, five types of neurons were obtained: pyramidal cells, satellite cells, basket cells, neuroglial cells and immature cells. On the basis of their electrophysiological and morphological characteristics, pyramidal cells were classified into three categories: immature, intermediate, and mature cell types. During postnatal week 1, cells were immature with very high input resistance. Morphologically immature cells had short simple dendritic arborizations which incompletely penetrated the layer where the cell body lies. From postnatal weeks 2 to 4, the cells were mature with low input resistance. They were morphologically more complex with dendritic arborizations which completely penetrated the whole layers of the visual cortex. From postnatal weeks 1 to 2, a third, intermediate cell type had electrophysiological properties that were intermediate between the immature and mature cell types. Three distinctive types of pyramidal cells in visual cortex only co-exist during postnatal weeks 1 to 2. Data show that activity-dependent synapes are formed and integrated into local neuronal networks with visual stimulation. In the critical period of visual development, the level of synchronism of age and changes in electrophysiological and morphological properties in the visual cortex is higher than that in the subcortex.
Animals ; Animals, Newborn ; Excitatory Postsynaptic Potentials ; physiology ; Neurons ; cytology ; physiology ; Pyramidal Cells ; cytology ; physiology ; Rats ; Rats, Sprague-Dawley ; Synapses ; metabolism ; physiology ; Visual Cortex ; cytology ; growth & development ; physiology

AIMTo investigate the intrinsic mechanisms underlying spike programming at pyramidal neurons and interneurons in layer II/III of sensorimotor cortex.

METHODSElectrical signals at the cortical neurons were recorded in current clamp model with multi-clamp700B Amplifiers. Signals were inputted into pClamp and Origin for data acquisition and analyses.

RESULTSCompared to pyramidal neurons, interneurons express the higher capacity of spikes and the more stability of spike programming, which are mechanistically caused by lower threshold potentials and shorter refractory periods.

CONCLUSIONThe refractory periods and threshold potentials directly influence the programming of sequential spikes.

Action Potentials ; physiology ; Animals ; Animals, Newborn ; Cerebral Cortex ; cytology ; physiology ; Differential Threshold ; physiology ; Interneurons ; physiology ; Neurons ; physiology ; Patch-Clamp Techniques ; Pyramidal Cells ; physiology ; Rats ; Rats, Sprague-Dawley ; Refractory Period, Electrophysiological ; physiology ; Synaptic Transmission ; physiology

OBJECTIVETo investigate the role of histamine H1 receptors in modulating the discharge activities of the inspiratory neurons in the nucleus retrofacialis of neonatal rats.

METHODSBrainstem slices were obtained from neonatal rats containing the medial region of the nucleus retrofacialis (mNRF) with the hypoglossal nerve (XII nerve) rootlets retained. The rhythmic discharges of the inspiratory neurons (I neurons) and activities of the XII nerve rootlets were simultaneously recorded using microelectrodes and suction electrodes, respectively. The role of H1 receptors in modulation of the discharge activities of the inspiratory neurons was investigated using the H1 receptor agonist histamine and its specific antagonist pyrilamine dissolved in modified Kreb's solution for slice perfusion.

RESULTSHistamine shortened the respiratory cycle (RC) and expiratory time (TE) of the neurons in the brain slices, and pyrilamine produced the opposite effects. Neither histamine nor pyrilamine affected the inspiratory time (TI), integral amplitude (IA) or the peak discharge frequency (PF) of the I neurons.

CONCLUSIONH1 receptors play an excitatory role in the modulation of the discharge activities of the inspiratory neurons in neonatal rat brainstem slices.

Animals ; Animals, Newborn ; Electrophysiological Phenomena ; Female ; In Vitro Techniques ; Inhalation ; physiology ; Male ; Medulla Oblongata ; cytology ; physiology ; Neurons ; physiology ; Rats ; Rats, Sprague-Dawley ; Receptors, Histamine H1 ; physiology

Animals ; Animals, Newborn ; Carbon Monoxide ; metabolism ; Heme Oxygenase (Decyclizing) ; metabolism ; Lung ; metabolism ; Oxygen ; physiology ; Rats

AIMTo explore the influence of cold strss on DNA oxidative damage of lung in chicken.

METHODSTook 15-day-old healthy chicks as the experimental object, carried on the cold stress (12 +/- 1 degrees C) to process. Detected the change of the MDA content, SOD and GSH-Px activity of the lung, and performed KCl-SDS precipitation method and fluorescence detection method to identify the influence of cold strss on DNA-protein crosslinks (DPC) and DNA-DNA crosslinks (DDC) of lung cell in different time.

RESULTSThe results were as follow: with the time lapsing during acute cold stress, MDA content gradually increased, the SOD and GSH-Px activity of the lung increased compared with their control group at each stress time point, and the lung cell DPC and DDC coefficient were all gradually increased with the time lapsing.

CONCLUSIONCold stress could bring about destruction in the lung tissue oxidation-antioxidant balance, and causes the oxidation damage of DNA.

Animals ; Animals, Newborn ; Chickens ; Cold Temperature ; DNA Damage ; Lung ; pathology ; Male ; Oxidative Stress ; physiology ; Stress, Physiological ; physiology

OBJECTIVETo investigate the change of behavior, as well as the plasticity of somatosensory cortex after whisker trimming.

METHODSSD rats were divided into 4 groups. Group A is the normal control group; group B: bilateral vibrissotomy on the second postnatal day; group C: unilateral right vibrissotomy on the second postnatal day; group D: right unilateral whisker trimmed during 1-5 days after birth, and leave untreated after the 5th postnatal day. Their body weight, length of the left D2 whiskers was measured on the 30th postnatal day. At the same time, the changes of their behavior (including the slit-detection test, the home exploring behavior and thigmotaxis test) were also recorded on the 30th postnatal day. Cytochrome oxydase histochemistry (CO reaction)was applied to study the development and arrangement of barrel cortex.

RESULTSIn the slit-detection test, control rats could find and get into the right slit very quickly. The rats in group B could get into the slit only if their noses touched the slit. The rats in group C couldn't identify the slit by right face, but if they turned their body and touched the slit with the left whiskers, they could get into the slit very quickly. The behavior of rats in group D was similar to that in group C. The time spent for finding out the right slit of the rats in group A, B, C was obviously longer than that of group A (P < 0.01, P < 0.05, P < 0.01). In the exploring behavior and thigmotaxis test, the time for left thigmotaxis, right thigmotaxis and total thigmotaxis of rats in group B was longer than that of control animals. The time for right thigmotaxis of group C was significantly shorter than that of group A (P < 0.05). Both the weight of the rats and the length of left D2 whiskers of rats in all the four groups had no significant difference. CO reaction showed that the barrels became smaller, the septum was not clear, the arrangement of the barrels was not tidy in the mice whose right whiskers were trimmed from 2-30 days after birth.

CONCLUSIONDeafferentation doesn't change the body weight and length of the whiskers left. But the stimulation of whiskers is important for rodent especially in thigmotaxis and exploring behavior. Deafferentation can also induce the plastic change of barrel cortex.

Animals ; Animals, Newborn ; Cerebral Cortex ; physiology ; Male ; Neuronal Plasticity ; Physical Stimulation ; Rats ; Rats, Sprague-Dawley ; Somatosensory Cortex ; physiology ; Vibrissae