In the present study, the responses of inhibitory gustatory neurons in the parabrachial nucleus (PBN) to four basic taste stimuli NaCl, HCl, quinine HCl (QHCl) and sucrose were examined using single-unit recording technique in anesthetized rats. A total of 18 inhibitory taste neurons in the PBN were obtained. Spontaneous firing rates of these inhibitory neurons were 0.2-5.5 Hz with mean firing rate of (2.15+/-0.31) Hz. Most of the neurons responded to more than one of the basic taste qualities. The inhibitory responses to taste occurred quickly and lasted 5-80 s in different PBN neurons. According to the responsive characteristics to the four basic taste stimuli, the neurons could be classified as NaCl-best (n=8), HCl-best (n=3), QHCl-best (n=3), and sucrose-best (n=4). The breadth of tuning of NaCl-best neurons was the highest (0.945). Inhibitory responsive neurons had feeble discrimination among sapid stimuli or aversive stimuli. These results suggest that there exist inhibitory taste neurons in the PBN. These neurons may play some useful roles in precise transmission of taste information and the taste coding for hedonic and aversive tastes.
Animals ; Male ; Neural Inhibition ; physiology ; Neurons ; physiology ; Pons ; physiology ; Rats ; Rats, Sprague-Dawley ; Taste ; physiology

OBJECTIVETo establishing the cochlea slice technique and infrared visual slice patch clamp method in order to observe the electrophysiological characteristics of rat spiral ganglion neurons (SGN) METHODS: SD rats were divided into three groups according to postnatal days old (0-2 d, 3-6 d and 7-14 d). Making slice of SD rat cochlear quickly, using infrared differential interference contrast (IR-DIC) technique, together with slice patch clamp, the electrophysiological characteristics of rat spiral ganglion neurons were observed, and factors which affected the quality of cochlear slice and recording of patch clamp were analyzed.

RESULTSThe success rate of 3-6 days SD was the highest, and 2-4 pieces of slice could be made from each cochlea. Cochlea connecting with partial skull and integrity of cochlear hull were the key for making slice, and the angle of modiolus axis should be adjusted to be parallel to the knife and the preparing time should be shorter. The SGN cell of good condition could be easily found and the seal test became easier with the help of infrared visual slice patch clamp method. The rest membrane potential was (-45.6 +/- 5.3) mV (x +/- s, n=52) and the current of Na+ and K+ could be activated.

CONCLUSIONSCochlear slice technique can retain structural integrity, cell viability and their association in cochlea, which suggest that this technique provides carrier for electrophysiological study of rat spiral ganglion neurons, and patch clamp with infrared videomicroscopy method can be used to make direct real-time observation in electrophysiological experiments of SGN, which can provide important technique support and reference for deep study of electrophysiological characteristics of SGN and auditory neurotransmission in cochlea.

Animals ; Cochlea ; physiology ; Microtomy ; Neurons ; physiology ; Patch-Clamp Techniques ; Rats ; Rats, Sprague-Dawley ; Spiral Ganglion ; physiology

Animals ; Calcitonin Gene-Related Peptide ; physiology ; Heart ; physiology ; Male ; Physical Exertion ; physiology ; Rats ; Rats, Sprague-Dawley

Animals ; Electric Stimulation ; Hippocampus ; physiology ; Male ; Nerve Endings ; physiology ; Rats ; Rats, Sprague-Dawley ; Vagus Nerve ; physiology

Intracortical microstimulation (ICMS) is a technique that was developed to derive movement representation of the motor cortex. Although rats are now commonly used in motor mapping studies, the precise characteristics of rat motor map, including symmetry and consistency across animals, and the possibility of repeated stimulation have not yet been established. We performed bilateral hindlimb mapping of motor cortex in six Sprague-Dawley rats using ICMS. ICMS was applied to the left and the right cerebral hemisphere at 0.3 mm intervals vertically and horizontally from the bregma, and any movement of the hindlimbs was noted. The majority (80%+/-11%) of responses were not restricted to a single joint, which occurred simultaneously at two or three hindlimb joints. The size and shape of hindlimb motor cortex was variable among rats, but existed on the convex side of the cerebral hemisphere in all rats. The results did not show symmetry according to specific joints in each rats. Conclusively, the hindlimb representation in the rat motor cortex was conveniently mapped using ICMS, but the characteristics and inter-individual variability suggest that precise individual mapping is needed to clarify motor distribution in rats.
Animals ; *Brain Mapping ; Electric Stimulation ; Electrodes ; Hindlimb/*physiology ; Male ; Motor Cortex/*physiology ; Rats ; Rats, Sprague-Dawley

AIMTo investigate the neural network and cellular mechanisms of hippocampal epileptogenesis contralateral or ipsilateral to the side of acute tetanization (60 Hz, 2 s, 0.4 - 0.6 mA) of the posterior dorsal hippocampus (ATPDH).

METHODS10 trains of the ATPDH were administered into the CA1 basal dendritic region of the right hemisphere at an interval of 10 minutes.

RESULTS(1) The firing rate of CA1 single neuron in the right or the left hippocampus was inhibited respectively after the ATPDH, and the effects weakened gradually while the trains of the ATPDH increased. The inhibited firing rate and the transformed firing pattern from tonic one to clonic one were more obvious at the side contralateral to the stimulation (62.94% +/- 3.68%, 36.61% +/- 3.14%, P < 0.01). (2) Synchronous primary afterdischarges of depth EEG and single unit discharges were more commonly observed at the side ipsilateral to the ATPDH (P < 0.01). (3) Primary or secondary hippocampal network afterdischarges at high frequency were only found in CA1 region ipsilateral to the ATPDH. (4) Secondary afterdischarges of CA3 basal dendritic neural network were completely synchronized with those of subicular single neuron, which reoccurred and persisted several hours.

CONCLUSIONIt is possible that post-inhibition bursting of single neuron and recurrent network seizures in the hippocampus contralateral to the artificial focus be the important manifestation of the formation of "epileptic networks" across from one hemisphere to another.

Animals ; Electric Stimulation ; Hippocampus ; physiology ; Male ; Neural Pathways ; physiology ; Rats ; Rats, Sprague-Dawley ; Seizures ; etiology

AIMTo observe the effects of different periods of exercise on the iron status.

METHODSFemale rats were randomly divided into 3-, 6-, 12-month swimming exercise groups and their corresponding sedentary groups. The hematological indices of iron status and the non-heme iron (NHI) and total NHI (TNHI) of the organs were determined at the end of the desired period.

RESULTSAs compared with the corresponding sedentary groups, plasma iron and transferrin-iron saturation of three exercise groups were decreased without significant changes of blood hemoglobin and hematocrit. The NHI contents and TNHI of the liver, spleen and kidney were decreased. Although the NHI contents of the heart decreased, TNHI was not significantly changed. TNHI of the organs in both the exercised and sedentary rats were found to increase with age.

CONCLUSIONThe exercise-induced low iron status with depleted iron storage is similar to the iron-deficiency status, but it could not be explained using the hypothesis of iron deficiency. Both the NHI redistribution and the maintained iron storage suggests the adaptation of low iron status to exercise. Therefore, the so-called exercise-induced iron deficiency could not exist.

Animals ; Female ; Hematocrit ; Iron ; deficiency ; metabolism ; Physical Conditioning, Animal ; physiology ; Rats ; Rats, Sprague-Dawley ; Swimming ; physiology

BACKGROUNDAs the widespread use of electric devices in modern life, human are exposed to extremely low frequency magnetic fields (ELF MF) much more frequently than ever. Over the past decades, a substantial number of epidemiological and experimental studies have demonstrated that ELF MF (50 Hz) exposure is associated with increased risk of various health effects. The present study examined the effects of chronic exposure to ELF MF on anxiety level and spatial memory of adult rats.

METHODSThe 50-Hz ELF MF was used during the whole experimental procedures and the value of magnetic field (MF) was set to 2 mT. Adult rats were divided randomly to control, MF 1 hour and MF 4 hours group. Anxiety-related behaviors were examined in the open field test and the elevated plus maze; changes in spatial learning and memory were determined in Morris water maze after 4 weeks of daily exposure.

RESULTSRats in MF 4 hours group had increased anxiety-like behaviors with unaltered locomotor activity. In the Morris water maze test, rats had reduced latency to find the hidden platform and improved long-term memory of former location of platform without changes in short-term memory and locomotor activity.

CONCLUSIONChronic ELF MF exposure has anxiogenic effect on rats, and the promoting effects on spatial learning and long-term retention of spatial memory.

Animals ; Anxiety ; physiopathology ; Electromagnetic Fields ; Male ; Maze Learning ; physiology ; Memory ; physiology ; Rats ; Rats, Sprague-Dawley

AIMTo investigate the regulatory network of hippocampal-systemic arterial blood pressure during epileptic network reestablishment.

METHODS7.2 microg picrotoxin (PTX) was microinjected into the right HPC (RHPC) to induce rat epilepsy. Contralateral hippocampal EEG, single unit discharges, femoral artery blood pressure and ECG were recorded simultaneously.

RESULTSPTX might induce: (1) A resemblance interspike intervals (ISI) spot distribution of long duration neuronal burst and unit after discharges in contralateral HPC. (2) Delayed the initiation time of hippocampal neuronal bursts coupled with arterial blood pressure depression. (3) Hippocampal neuronal burst or unit after discharges coupled complexly with arterial blood pressure depression. (4) Resemblance hippocampal EEG interpeak intervals (IPI) and neuronal firing ISI spot distribution coupled with arterial blood pressure depression.

CONCLUSIONDuring contralateral hippocampal epileptic network reestablishment after microinjection of PTX to the RHPC, the function of the hippocampal-arterial blood pressure regulatory network could be modulated by characteristic network and neuronal temporal code patterning.

Animals ; Blood Pressure ; physiology ; Electrocardiography ; Electroencephalography ; Epilepsy ; physiopathology ; Hippocampus ; physiology ; physiopathology ; Male ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo examine the effect of docosahexaenoic acid (DHA) deficiency in brain on spatial learning and memory in rats.

METHODSSprague Dawley rats were fed with an n-3 fatty acid deficient diet for two generations to induce DHA depletion in brain. DHA in seven brain regions was analyzed using the gas-liquid chromatography. Morris water maze (MWM) was employed as an assessing index of spatial learning and memory in the n-3 fatty acid deficient adult rats of second generation.

RESULTSFeeding an n-3 deficient diet for two generations depleted DHA differently by 39%-63% in the seven brain regions including cerebellum, medulla, hypothalamus, striatum, hippocampus, cortex and midbrain. The MWM test showed that the n-3 deficient rats took a longer time and swam a longer distance to find the escape platform than the n-3 Adq group.

CONCLUSIONThe spatial learning and memory in adult rats are partially impaired by brain DHA depletion.

Animals ; Brain ; metabolism ; Docosahexaenoic Acids ; metabolism ; Maze Learning ; physiology ; Memory ; physiology ; Rats ; Rats, Sprague-Dawley