Rat Brain Atlas Research Articles

BOLD fMRI mapping of brain responses to nociceptive stimuli in rats under ketamine anesthesia

Ketamine is one of the most commonly used anesthetics, but its effects on nociceptive responses are not clearly defined. This study used blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to hemodynamically map responses to formalin stimuli under ketamine anesthesia. All imaging was performed on a 4.7-T fMRI system. During dynamic image acquisition, formalin was injected into the rat hindpaw as a painful stimulant. Correlation coefficients were calculated, and each image was registered and fused with the corresponding rat brain atlas so as to avoid inaccuracies arising from manual definition of the brain area and to achieve atlas-based normalization among subjects. Formalin injections were found to increase BOLD signals in the cingulate cortex, sensory-motor cortices, insular cortex, striatum, nucleus accumbens, medial thalamus, ventrolateral thalamic group, and hippocampus. Moreover, in contrast to previous pain investigations, the frontal subcortical regions were strongly activated in ketamine-anesthetized rats.

Modulation of hypothalamic arcuate nucleus on gastric motility in rats.

AIM:To investigate whether the arcuate nucleus (ARC) could modulate gastric motility, and if so, what are the mechanisms or pathways.METHODS:Wistar rats, anaesthetized with urethan, parameters of stimulation and electrolytic lesion sites were determined according to the Paxinos and Watson ATLAS of rat brain in steriotaxic coordinate. Intragastric pressure (IGP) and gastric motility were measured by Reybould's method.RESULTS:Electrical stimulation of ARC could obviously decrease the IGP by 42.2% plus minus 5.4%, n =15,P < 0.01, and the phasic gastric contractions disappeared.The analysis showed that the locus coeruleus (LC) and dorsal raphe (DR) nuclei may be involved in central,but without the invovement of alpha-endorphinergic neurons rich in the ARC, while in periphery, the peripheral neural pathways are both vagus and sympathetic nerves.The fibers in vagus may be non-cholinergic. Humoral factors may also be involved.At the receptor level, Tonic action of adrenergic nerve in the stomach is mainly inhibitory;alpha-receptors, which may be present on the stomach wall and mediate inhibition; and -alpha-receptors, which come into play through vagus, mediate inhibition, but those present on the smooth muscle mediate sympathetic excitation.Microinjection of TRH into ARC could significantly increase the IGP by 183.02% (0.53kPa plus minus 0.08kPa vs 1.5k Pa plus minus 0.6kPa, n =10,P < 0.001), the rate and amplitude of phasic gastric contraction were also increased (3cpm vs 6cpm-8cpm). The peripheral pathway of such excitatory effects were transmitted with cholinergic vagus nerve mediated by M-receptor.CONCLUSION:ARC could modulate gastric motility biphasically, inhibitory and excitatory, depending on the nature of stimuli.

Horizontal stereotaxic atlas of the albino rat brain

An atlas of the albino rat brain was prepared in the horizontal plane, extending from the olfactory bulbs through the hind brain. It was drawn to the scale of König and Klippel's rat brain atlas so as to be used in conjunction with their atlas. Corresponding histological sections were also prepared.