Independent Epileptiform Discharge Patterns in the Olfactory and Limbic Areas of the In Vitro Isolated Guinea Pig Brain During 4-Aminopyridine Treatment

In vitro studies performed on brain slices demonstrate that the potassium channel blocker 4-aminopyridine (4AP, 50 μM) discloses electrographic seizure activity and interictal discharges. These epileptiform patterns have been further analyzed here in a isolated whole guinea pig brain in vitro by using field potential recordings in olfactory and limbic structures. In 8 of 13 experiments runs of fast oscillatory activity ( fast runs, FRs) in the piriform cortex (PC) propagated to the lateral entorhinal cortex (EC), hippocampus and occasionally to the medial EC. Early and late FRs were asynchronous in the hemispheres showed different duration [1.78 ± 0.51 and 27.95 ± 4.55 (SD) s, respectively], frequency of occurrence (1.82 ± 0.49 and 34.16 ± 6.03 s) and frequency content (20–40 vs. 40–60 Hz). Preictal spikes independent from the FRs appeared in the hippocampus/EC and developed into ictal-like discharges that did not propagate to the PC. Ictal-like activity consisted of fast activity with onset either in the hippocampus ( n = 6) or in the mEC ( n = 2), followed by irregular spiking and sequences of diffusely synchronous bursts. Perfusion of the N-methyl-d-aspartate receptor antagonist 2-amino-5-phosphonopentanoic acid (100 μM) did not prevent FRs, increased the duration of limbic ictal-like discharges and favored their propagation to olfactory structures. The AMPA receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (50 μM) blocked ictal-like events and reduced FRs. In conclusion, 4AP-induced epileptiform activities are asynchronous and independent in olfactory and hippocampal-entorhinal regions. Epileptiform discharges in the isolated guinea pig brain show different pharmacological properties compared with rodent in vitro slices.

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Distribution of the Olfactory Fiber Input Into the Olfactory Tubercle of the In Vitro Isolated Guinea Pig Brain

Journal of Neurophysiology ◽

10.1152/jn.90792.2008 ◽

2009 ◽

Vol 101 (3) ◽

pp. 1613-1619 ◽

Cited By ~ 19

Author(s):

Giovanni Carriero ◽

Laura Uva ◽

Vadym Gnatkovsky ◽

Marco de Curtis

Keyword(s):

Guinea Pig ◽

Piriform Cortex ◽

Field Potential ◽

Lateral Part ◽

Olfactory Tubercle ◽

Olfactory Tract ◽

Pig Brain ◽

Guinea Pig Brain ◽

Stimulation Of

The olfactory tubercle (OT) is a cortical component of the olfactory system involved in reward mechanisms of drug abuse. This region covers an extensive part of the rostral ventral cerebrum and is relatively poorly studied. The intrinsic network interactions evoked by olfactory input are analyzed in the OT of the in vitro isolated guinea pig brain by means of field potential analysis and optical imaging of voltage-sensitive signals. Stimulation of the lateral olfactory tract induces a monosynaptic response that progressively decreases in amplitude from lateral to medial. The monosynaptic input induces a disynaptic response that is proportionally larger in the medial portion of the OT. Direct stimulation of the piriform cortex and subsequent lesion of this pathway showed the existence of an associative disynaptic projection from the anterior part of the piriform cortex to the lateral part of the OT that integrates with the component mediated by the local intra-OT collaterals. Optical and electrophysiological recordings of the signals evoked by stimulation of the olfactory tract during arterial perfusion with the voltage-sensitive dye di-2-ANEPEQ confirmed the pattern of distribution of the mono and disynaptic responses in the OT. Finally, current source density analysis of laminar profiles recorded with 16-channel silicon probes confirmed that the monosynaptic and disynaptic potentials localize in the most superficial and the deep portions of the plexiform layer I, as suggested by previous reports. This study sets the standard for further analysis of the modulation of network properties in this largely unexplored brain region.

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Associative Synaptic Potentials in the Piriform Cortex of the Isolated Guinea-pig Brain In Vitro

European Journal of Neuroscience ◽

10.1111/j.1460-9568.1995.tb01020.x ◽

1995 ◽

Vol 7 (1) ◽

pp. 54-64 ◽

Cited By ~ 29

Author(s):

Gerardo Biella ◽

Marco Curtis

Keyword(s):

Guinea Pig ◽

Piriform Cortex ◽

Synaptic Potentials ◽

Pig Brain ◽

Guinea Pig Brain

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Slow Periodic Events and Their Transition to Gamma Oscillations in the Entorhinal Cortex of the Isolated Guinea Pig Brain

Journal of Neurophysiology ◽

10.1152/jn.01063.2002 ◽

2003 ◽

Vol 90 (1) ◽

pp. 39-46 ◽

Cited By ~ 31

Author(s):

Clayton T. Dickson ◽

Gerardo Biella ◽

Marco de Curtis

Keyword(s):

Membrane Potential ◽

Guinea Pig ◽

Entorhinal Cortex ◽

Gamma Oscillations ◽

Oscillatory Activity ◽

Periodic Field ◽

Slow Potential ◽

Pig Brain ◽

Guinea Pig Brain

Slow (<1 Hz) periodic activity is a distinctive discharge pattern observed in different cortical and sub-cortical structures during sleep and anesthesia. By performing field and cellular recordings, we demonstrated that slow periodic events (0.02–0.4 Hz) are spontaneously generated in the entorhinal cortex of the in vitro isolated whole brain of the guinea pig. These events were characterized by gradually developing runs of low-amplitude (50–300 μV), high-frequency (25–70 Hz) oscillations superimposed on a slow potential that lasted 1–3 s. Both slow and fast components showed a phase reversal in the superficial layers. In layer II-III entorhinal neurons, the slow periodic events correlated to a slowly developing depolarizing envelope capped by subthreshold membrane potential oscillations and action potential discharge. Slow periodic field events propagated tangentially across the entorhinal cortex and could be triggered by stimulation of superficial associative fibers, suggesting that they were generated by and propagated via network interactions in the superficial layers. Slow periodic events were reversibly abolished by muscarinic excitation elicited by carbachol (50 μM) that promoted intracellular membrane potential depolarization associated with continuous fast oscillatory activity in the gamma frequency range. These results suggest that, as proposed in vivo, activity changes in the entorhinal cortex of the in vitro isolated guinea-pig brain reflect different activation states that are under cholinergic control.

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Incorporation of isotopic carbon into cerebral glycogen from non-glucose substrates

Biochemical Journal ◽

10.1042/bj1460185 ◽

1975 ◽

Vol 146 (1) ◽

pp. 185-189 ◽

Cited By ~ 21

Author(s):

M E Phillips ◽

R V Coxon

Keyword(s):

Guinea Pig ◽

Incubation Medium ◽

Specific Radioactivity ◽

Brain Slices ◽

Fresh Tissue ◽

Radioactive Carbon ◽

Glucose Carbon ◽

Pig Brain ◽

Guinea Pig Brain

1. Measurable incorporation of radioactive carbon from [U-14C]pyruvate, [U-14C]-glutamate and [14C]bicarbonate into the glycogen synthesized by brain slices in vitro was demonstrated. 2. The fructose diphosphatase activity of guinea-pig brain was determined and found to be about 0.03 μmol of substrate degraded/min per g of fresh tissue. 3. The specific radioactivity of the glucose carbon from glycogen relative to that of the precursor added to the incubation medium gave approximate values of 0.195 for glucose, 0.006 for pyruvate, 0.039 for glutamate and 0.001 for bicarbonate.

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