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Recording Chamber (recording + chamber)
Selected AbstractsCooling Abolishes Neuronal Network Synchronization in Rat Hippocampal SlicesEPILEPSIA, Issue 6 2002Sam P. Javedan Summary: ,Purpose: We sought to determine whether cooling brain tissue from 34 to 21°C could abolish tetany-induced neuronal network synchronization (gamma oscillations) without blocking normal synaptic transmission. Methods: Intracellular and extracellular electrodes recorded activity in transverse hippocampal slices (450,500 ,m) from Sprague,Dawley male rats, maintained in an air,fluid interface chamber. Gamma oscillations were evoked by afferent stimulation at 100 Hz for 200 ms. Baseline temperature in the recording chamber was 34°C, reduced to 21°C within 20 min. Results: Suprathreshold tetanic stimuli evoked membrane potential oscillations in the 40-Hz frequency range (n = 21). Gamma oscillations induced by tetanic stimulation were blocked by bicuculline, a ,-aminobutyric acid (GABA)A -receptor antagonist. Cooling from 34 to 21°C reversibly abolished gamma oscillations in all slices tested. Short, low-frequency discharges persisted after cooling in six of 14 slices. Single-pulse,evoked potentials, however, were preserved after cooling in all cases. Latency between stimulus and onset of gamma oscillation was increased with cooling. Frequency of oscillation was correlated with chamber cooling temperature (r = 0.77). Tetanic stimulation at high intensity elicited not only gamma oscillation, but also epileptiform bursts. Cooling dramatically attenuated gamma oscillation and abolished epileptiform bursts in a reversible manner. Conclusions: Tetany-induced neuronal network synchronization by GABAA -sensitive gamma oscillations is abolished reversibly by cooling to temperatures that do not block excitatory synaptic transmission. Cooling also suppresses transition from gamma oscillation to ictal bursting at higher stimulus intensities. These findings suggest that cooling may disrupt network synchrony necessary for epileptiform activity. [source] Context-dependent behavioural and neuronal sensitization in striatum to MDMA (ecstasy) administration in ratsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2006Kevin T. Ball Abstract To investigate the neuronal mechanisms underlying the behavioural alterations that accompany repeated exposure to MDMA (ecstasy), we recorded the activity of >,200 striatal units in response to multiple, intermittent, locomotor-activating doses (5.0 mg/kg) of MDMA. Rats were treated with once-daily injections of either saline or MDMA for 5 days when housed in their home cage, followed by a challenge injection 3,5 days later when housed in a recording chamber. Because contextual drug associations might be particularly important to the expression of behavioural sensitization to chronic MDMA, a separate group of rats received repeated injections of MDMA alternately in the recording chamber or home cage, according to the above timeline. A sensitized locomotor response was observed only in rats that had previously experienced MDMA in the context of the recording chamber, and only on the challenge day. These sensitized animals also showed a decreased basal firing rate in neurons that were subsequently excited by MDMA when compared with the same category of neurons earlier in the treatment regimen. This resulted in a greater percentage increase from the baseline firing rate on the challenge day compared with the first and fifth days of treatment, even though this trend was not evident with an analysis of absolute firing rate. These results strongly support a role for context in the expression of MDMA-induced locomotor sensitization, and implicate striatal involvement in the neurobehavioural changes associated with the repeated use of MDMA. [source] REM sleep: a sensitive index of fear conditioning in ratsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2005Sushil K. Jha Abstract To examine the influence of conditioned fear stimuli on sleep-wake states, we recorded sleep in Sprague,Dawley rats after exposure to tones previously paired with footshock. After habituation to a recording chamber and the recording procedure, a baseline sleep recording was obtained the next day. One day later, experimental animals were exposed to shock training designed to induce conditioned fear (FC), consisting of five tone-footshock pairings. The 5-s tones (conditioned stimuli; CS) co-terminated with 1-s footshocks (unconditioned stimuli; US). The next day sleep was recorded for 4 h in the recording chamber after presentation of five CSs alone. Sleep efficiency (total sleep time/recording period) and REM sleep (REM) and non-REM (NREM) measures were determined. While sleep efficiency was not significantly changed after CS presentation, the percentage of total sleep time spent in REM (REM percentage) was reduced in the FC animals. The reduction in REM percentage in the FC animals was due to a decrease in the number of REM bouts. In a separate experiment, we repeated the procedures, except the tones and shocks were presented in an explicitly unpaired (UP) fashion. The next day, presentation of the tones increased REM percentage in the UP group. Results are discussed in terms of the decreases in REM as a response to conditioned fear, and the relevance of these findings to the sleep changes seen in post-traumatic stress disorder (PTSD). [source] Activity of corneal nociceptive nerve fibers during allergic challenge of the ocular surfaceACTA OPHTHALMOLOGICA, Issue 2009J GALLAR Purpose The aim of this work was to study in vitro the spontaneous and stimulus-evoked electrical activity of corneal nociceptive nerve fibers during acute allergic inflammation of the ocular surface induced in the guinea-pig. Methods Animals received i.p. 10% ovalbumin (OVA). 14 days later, a 10µl drop of OVA was applied topically to each eye. Blinking and scratching movements directed to the eye were measured during 10 min, and ocular symptoms (edema and hyperemia) and tear rate were measured. Animals were killed afterwards and both eyes were immediately excised and mounted in a superfused (32°C) recording chamber. Electrical activity of corneal sensory receptors was recorded from nerve filaments dissected from the ciliary nerves. Mechanical (calibrated von Frey hairs), thermal (bath solution temperature down to 20°C or up to 52°C), and chemical stimulation (30s-pulses of 98%CO2) were performed. Spontaneous (SA) and stimulus-evoked activity were analyzed. Results After the allergic challenge, eye-scratching behavior was present in 4 out of 15 animals and blinking movements increased from 1±0.05 to 26±5. Tearing also increased compared to control (33±3 vs. 5±1 mm). Compared to naive eyes, proportion of nociceptors with SA (17% vs. 5%) and spontaneous discharge rate (0.13±0.07 vs. 0.01±0.01 imp/s) were increased. Mechanical threshold of mechano-nociceptive units decreased significantly (0.37±0.05 vs. 0.89±0.13 mN). Chemosensitivity of polymodal nociceptors was slightly increased (1.87±0.42 vs. 1.34±0.23 imp/s). Conclusion Changes in corneal sensory nerve activity observed acutely after allergic challenge of the eye surface may constitute the basis of itching and discomfort sensations, and hypersensitivity observed in allergic patients. [source] | ||||||||||