Book of abstracts - British Neuroscience Association

68.01
A comparison of carbachol and kainate-induced gamma and
betaII oscillations in the rodent auditory cortex
Roopun A K, Cunningham M O, Le Beau F E N, Traub R D,
Whittington M A
(1,2,3,5) School of Neurology, Neurobiology and Psychiatry, Medical
School, Newcastle University, NE2 4HH. UK. (3) Neurology, SUNY
Downstate, Med, Ctr., Brooklyn, NY, USA.
High-frequency oscillatory activity at betaII (20-30Hz) and gamma (30-
80Hz) frequencies is proposed to mediate cognitive processing in the
cortex. Oscillatory activity is mediated by a variety of neuromodulators,
including the cholinergic and glutamatergic system. Horizontal
neocortical slices (450µm) containing deafferented auditory cortex
were prepared from adult male Wistar rats and maintained at the
interface between artificial cerebrospinal fluid and carbogen gas at
34oC. Oscillatory activity was generated upon the application of the
cholinergic agonist carbachol [25µM] or the glutamatergic agonist
kainate [400nM]. Concurrent betaII and gamma oscillations were
induced by carbachol (n=25), whereas only gamma oscillations were
induced by kainate (n=25). Kainate-induced activity was resistant to
the muscarinic-receptor blocker atropinµe [10µM] (n=6), and
carbachol-induced oscillations was resistant to kainate-receptor
antagonist UBP302 [10µM] (n=5), indicating two independently-driven
networks producing a gamma oscillation. The similarities in gamma
oscillations induced by kainate and carbachol were many-fold: the
frequencies were similar, the peak power of oscillations were
generated in superficial layers of the cortex, and all oscillations were
abolished by carbenoxolone [100µM] (a gap-junction blocker),
SYM2206 [20µM] (an AMPA-receptor antagonist) and bicuculline
[2µM] (a GABAA-receptor antagonist) (n=6). Intracellular electrodes
recorded gamma frequency firing from interneurons and gamma
frequency IPSPs from pyramidal cells, suggesting an inhibitory-based
oscillatory network. BetaII oscillations were only generated by
carbachol, and may rely on intrinsically bursting (IB) cells interacting
with an interneuronal network. This study indicates that cholinergic
and glutamatergic systems operate independently in the auditory
cortex, with the cholinergic drive exclusively producing a betaII
oscillation.
68.02
Patterns of spontaneous activity in hippocampal cultures developing
on multi electrode arrays: the influence of the NMDA receptor
Charlesworth P, Eglen S J, Humphreys L, Morton A, Grant S G N
Genes to Cognition Programme, The Wellcome Trust Sanger Institute,
Hinxton, Cambridge CB10 1SA, Cambridge Computational Biology
Institute, University of Cambridge
We have used multi electrode arrays to record action potentials from
developing embryonic hippocampal cultures and a suite of software tools to
analyse the resulting network activity. Action potentials are first observed at
~ 4 days in vitro (DIV) and thereafter activity increases sigmoidally until a
plateau at maturity (~20+ DIV) with a period of very rapid increase between
~8 – 15 DIV. Concomitant with the rise in the number of spikes, a greater
number of recording sites detect activity and also an entrainment of spikes
into bursts is observed, such that by maturity most (~95+%) action
potentials occur within bursts. Furthermore, these bursts show a
progressively increasing degree of both temporal regularity and spatial
correlation. Treating cultures with APV at DIV 6-7 (just prior to the rapid
upsweep in network activity and synaptogensis) has a profound effect on
this developing spike pattern: burst patterns are less regular, both spatially
and temporally, and many more non-bursting, individual, spikes occur. The
overall number of spikes is however unaltered. We conclude that the
NMDA receptor plays an important role in the development of spike pattern
in culture, with implications for the transfer of information in neuronal
networks. It is the aim of the Genes to Cognition programme
(www.genes2cognition.org) to employ the MEA-culture platform and
analytical methods developed here to phenotype mutant mice generated
within the programme (see Kopanitsa et al, this meeting). We are also
currently developing statistical methods for the automated analysis of these
datasets as part of the CARMEN project.
68.03
Effects of DHEA administration on auditory evoked potentials
Alhaj H A, McAllister-Williams R H
Psychiatry, Leazes Wing, Royal Victoria Infirmary, Newcastle upon
Tyne NE1 4LP
Background: The adrenal steroid dehydroepiandrosterone (DHEA)
has been shown to improve memory performance and modulate
neural activity in rodents. Further, we have recently demonstrated
beneficial effects of DHEA on long-term episodic memory performance
in healthy humans. To further evaluate the effects of DHEA on
attention and short-term memory in man, a study of auditory eventrelated
potentials (ERPs) was conducted.
Methods: Double-blind placebo-controlled crossover study in 24
healthy men (aged 18 to 34). DHEA (300 mg/day) or placebo was
administered for one week. Following each treatment period, subjects
participated in an auditory oddball paradigm, during which subjects
heard high (frequent) and low (rare) tones and were instructed to
count the number of rare tones silently. Stimulus-locked ERPs were
recorded from 29 scalp electrodes. The amplitude of the N1/P2 ERP
components, and the latency and amplitude of the P3 component to
rare tones, were calculated.
Results: DHEA treatment led to a significant increase in the amplitude
of the N1 component of ERPs recorded from posterior electrodes
(p