ABSTRACT
Background: Since the neural structures of the crayfish brain closely resemble their equivalent in the mammals. This can be suggested by observing the similarity that exists in the brain divided by the surgical transection of the crayfish brain in which the protocerebrum remains attached to the first two cranial nerves, findings also described by Frederic Bremer in 1935 in cats with cerebral transection.Methods: Total 11 Adult male crayfish were trained to respond with defense reflex, the animals were placed in water at 0°C, remained without any movement, and subsequently through a small incision of 3 mm in diameter in the medial antero region and dorsal cephalothorax region, a surgical section of the cerebral ganglion was performed. Immediately after surgery, metal microelectrodes were implanted to collect the activity of the photoreceptors and visual fibers.Results: Once the defense reflex begins to recover in previously decerebrated crayfish, it means that it shows signs of reconnection. The isolated protocerebrum with the deutocerebrum olfactory lobe remain alive for several days and the neuronal connections were reestablished, as measured throughout the bilateral defense activity. The defense reflex was observed in all animals and then recovered after surgery.Conclusions: The crayfish is an excellent model to work the visual activity, all coding of visual information was suppressed in de-cerebrated crayfish. The recovery of the neural disconnection is observed from 40 days, where the defence reflex appears again before visual stimuli.
ABSTRACT
Volatile anesthetics alter the arterial baroreflex (BRX) but its mechanisms are poorly understood. This study was designed to determine the effect of 1 and 2 minimal alveolar concentrations (MAC) of enflurane on the BRX parameters in unanesthetized brain stem-intact and decerebrate rats. Under enflurane anesthesia, the femoral artery and both femoral vein were catheterized for pressor (phenylephrine) and depressor (nitroprusside) drug delivery and continuous blood pressure measurements. Decerebration was performed at midcollicular level. BRX tests were performed in 3 time periods; before enflurane (conscious brain-intact), during 1 or 2 MAC enflurane exposure 1 hour after a sham operation or a decerebration operation, and 2 hours after the termination of enflurane (zero enflurane). Mean arterial pressure (MAP) and heart rate (HR) were fitted to a sigmoid logistic equation, the Boltzman equation. The curve of best fit was obtained with a computer program. 1 MAC and 2 MAC of enflurane shifted MAP-HR baroreflex curves to the left in the all groups and significantly attenuated the baroreflex range. The slope of conscious intact period and zero enflurane period of each group did not change significantly, but during the enflurane period the slope was significantly lowered. Enflurane depressed the baroreflex sensitivity (slope) and the HR range in a similar dose-dependant manner in both brain stem-intact and decerebrate rats. Such results draw into question whether the suprapontine sites contribute to enflurane's actions on cardiovascular autonomic regulation.