NEUROBIOLOGY LABORATORY

Maxwell R. Bennett

Research in this laboratory is concerned with understanding the determinants of quantal secretion of neurotransmitters at nerve terminals and processes involved in the plasticity of these terminals.

RESEARCH in 1993

Quantal secretory mechanisms at sympathetic nerve terminals

Quantal secretion at single visualized varicosities has been determined with extracellular electrodes placed over the varicosities. The histogram of spontaneous synaptic potential amplitudes was shown statistically to contain several modes that could be described by a Poisson mixture of Gaussians, indicating spontaneous multiquantal release. Histograms of evoked synaptic potentials were shown to consist of a Poisson mixture Gaussians so that single varicosities can secrete several multiquanta.

Quantal secretory mechanisms at preganglionic nerve terminals

Quantal secretion at the giant calyx terminal on parasympathetic avian ciliary ganglia is enhanced by nitric oxide. Nitric oxide acts to increase the quantal content of the synaptic potential. Long-term potentiation of transmission following a tetanus also involves an increase in quantal secretion. This was shown to be partly under the control of endogenous nitric oxide. The Laboratory has recently succeeded in recording quantal secretion from single preganglionic boutons. Preliminary work indicated that these may secrete multiquantal transmitter.

Quantal secretory mechanisms and their plasticity at somatic motor-nerve terminals

During development of motor-nerve terminals, histograms of spontaneous synaptic potentials do not conform to a Gaussian distribution, but contain multiple modes. Statistical tests have been introduced that show that these modes represent subquantal events. Such subquantal events were shown with rigorous statistical testing to also be present in adult histograms The results confirmed earlier studies that suggested that the quantum of transmitter may be subquantized.

Secretory mechanisms at mossy fibre boutons in the hippocampus

Probabilistic secretion of excitatory transmitters at recurrent collaterals on CA3 pyramidal cells and inhibitory transmitters on the somas of these neurones has been incorporated into a model of how the CA3 region lays down memories. It was shown that the probabilistic behaviour of the synapses increases the capacity of the system to store memories and increases the capacity for the recall of memories in this part of the brain.

Secretory mechanisms and their plasticity at retinal ganglion cell terminals

The chondroitin sulfate proteoglycan isolated from the developing rat superior colliculus has been shown to greatly improve the survival of retinal ganglion cells in vivo after a lesion to the optic nerve. This proteoglycan was also found to work in a synergistic manner with blockers of nitric oxide synthase to protect retinal ganglion cells from degeneration in vitro.

RESEARCH PLANNED for 1994

The distribution of receptors beneath single sympathetic nerve varicosities is being determined. A mode of this junction, incorporating a distributed representation of individual smooth muscle cells is near completion. The capacity of quantal secretion at one site on a motor-nerve terminal branch to inhibit secretion 50 mm away on the same branch is being investigated. The second messenger systems that mediate nitric oxide control of secretion at preganglionic nerve terminals is being elucidated. The role of calcium activated potassium channels in determining the effects of nitric oxide on secretion in the hippocampus is also being determined.

PERSONNEL in 1993 and 1994

Dr Maxwell R. Bennett	Professor (in-charge)		University	1969-
Dr Nick A. Lavidis	R.D. Wright Fellow		NHMRC		1983-
Dr Leonard Motin	Postdoctoral Fellow		ARC		1994-
Dr Roman Poznanski	Research Associate		ARC		1991-
Dr Lynne Cottee		Research Officer (part-time)	NHMRC		1993-
Lorraine Kerr		Research Officer (part-time)	NHMRC		1994-
Les Farrell		Research Officer (part-time)	ARC		1994-
Yon-Qi Lin		Research Officer		ARC		1990-
Gregory McLeod 		Research Assistant (3/5) 	NHMRC		1991-
Kerry Nichol		PhD student (R.A. p/t)		NHMRC		1988-
Shanker Karunanithi	PhD student (R.A. p/t)		NHMRC		1989-
Mathew Larkum		PhD student			APRA		1991-
Darren Warren		PhD student					1992-
Jennifer Kearns		PhD student (supervised with W. Gibson)		1994
Maria Theodorou		BSc(Hons) student				1994
Keith Brain		BScMed(Hons) student				1994
Melissa Bradley		BScMed(Hons) student				1994
Chandra Balachandrah	BScMed(Hons) student				1994
Glen Bennett		BScMed(Hons) student				1994
Yves Kerdraon		BScMed(Hons) student				1993
Svetlana Cherepanoff	GradDipSc student				1993
Frances Armson		Technical Officer Grade I (1/5)	NHMRC		1983-
Jennifer Cantrill	Administrative Assistant (1/5)	ARC		1982-
Effective full-time personnel = 18.4 
COLLABORATIONS

Quantal secretory mechanisms in the hippocampus: Prof. Steve Redman, Division of Neuroscience, John Curtin School of Medical Research, Australian National Univ. (1991-present).

Nitric oxide secretion at terminals: Prof. Peter Dunkley and Dr John Rostas, School of Medicine, Univ. of Newcastle (1993-present).

FACILITIES

The Laboratory is located in rooms 125, 131, 133, 134, 137, 139 and 145A of the Anderson Stuart Building. Prof. Bennett's office is room 138. Electrophysiology facilities include 8 separate units, each consisting of computers, patch-clamp and voltage-clamp amplifiers, microscopes and computer-driven stimulators, as well as digital imaging. Room 125 is a fully-equipped biochemistry laboratory that includes tissue culture facilities, FPLC protein purification system and Coulter Cell Sorter.

FUNDING in 1993 and 1994

ARC		Hippocampal granule cells:	Bennett MR	1991
		quantal secretion		Robinson J	1992
						Gibson W	1993	$138,000

ARC		Computational role of  		Bennett MR	1994	$110,000
		hippo-campal synapses		Robinson J	1995
						Gibson W	1996

NHMRC		Formation of neuromuscular	Everett A	1991
		synapses			Bennett MR	1992
		(*Lab's share in 1993 = $8,500)			1993	$76,000

NHMRC		Quantal secretion at neuro-	Bennett MR	1991
		muscular synapses		Lavidis NA	1992
								1993	$28,852

NHMRC		Quantal secretion at 		Lavidis NA	1991
		sympathetic neuromuscular	Bennett MR	1992
		synapses					1993	$59,000
	
NHMRC		Mechanisms of transmitter	Bennett MR	1994	$51,058
		release at neuromuscular	Lavidis N	1995
		synapses					1996
	
NHMRC		Mechanisms of transmitter	Bennett MR	1994	$67,673
		release at sympathetic 		Lavidis N	1995
		varicosities					1996

NHMRC		Syncytial integration of 	Bennett MR	1994	$35,240
		autonomic transmission		Gibson W	1995
						Phillips W	1996

NHMRC		Quantal secretory 		Bennett MR	1993 	$48,904
		mechanisms at preganglionic			1994	$49,441
		terminals					1995
	
ARC		Secretion and plasticity 	Bennett MR	1992	
(Small)		of retinal ganglion cell 			1993	$24,500
		terminals					1994	$24,500
		
Ramaciotti	Retinal ganglion terminal	Bennett MR	1993	$25,000
		plasticity

NHF		NO control of synaptic 		Bennett MR	1994	$45,000
		transmission			Dunkley P	1995
						Rostas J

Large joint grants with other members of Department*
Ramaciotti	Confocal microscopy		Bennett MR	1994	$60,000
						Allen DG
						Cook DI
						Davey DF

UEG	Confocal microscopy			Bennett MR	1994	$100,000
						Allen DG
						Cook DI
						Davey DF

*These grants are listed in the report for this academic only, even though they involve other academic staff of the Department; a section in 'Other news for 1993' later in the Annual Report provides more details of this purchase.

R.D. Wright Fellowship
NHMRC		The effects of opiates on 	Lavidis NA	1992
		the probability of quantal 			1993	$63,072
		secretion at sympathetic			1994	$66,345
		varicosities	
		(Includes $10,000 maintenance)

Total for 1993: Grants: $332,908; Fellowship:$63,072. Grand total = $395,980 
Total for 1994: Grants: $382,912; Fellowship: $66,345 Grand total = $449,257
                                    Departmental Equipment Grants = $160,000
SCHOLARSHIPS

Australian Postgraduate Research Award 		Larkum M	1991-
TEACHING in 1993

Medical Science: Human Life Sciences 2
Lectures: 20, on the brain and its functions.
Tutorials: 4 on lecture material.
Practical classes: 4, of 3 h each, repeated, on reflexes.
Examination: 6 short essay questions
Medical Science 3/Science 3 (Neuroscience)
Lectures: 20, on the molecular basis of brain function.
Tutorials: 6, on scientific papers and 4 on neural network theory.
Practicals in laboratory: 8, of 3 h each, on electrophysiology of synaptic transmission.
Examination: 5 short essay questions.
Medicine 3
Lectures: 2 distinction lectures on the hippocampus.
Practical classes: 1, of 3 h, repeated, on electrical activity in nerves.
Tutorial: 1, as follow-up to each prac, repeated.
Total distribution (hours of formal teaching)
					HLS2	Sci3	Med3	Total
Lectures				20	20	2	42
Practical classes (no.)			16(4)	24(8)	12(4)	52
Tutorials (1 h each)			4	6	4	14
Total contact teaching time = 108 h.
Time was also spent on lecture preparation, setting and marking of exams and essays.
OTHER ACTIVITIES in 1993

Australian science administration

Australian Academy of Science:

Member, Science Policy Committee (1984-present)
Member, Science & Industry Forum (1984-1993)
Member, Boden Conference Committee (1986-present)
Member, N.S.W. Science Policy Committee (1991-present)
Australian National University:

Member, Scientific Advisory Committee, National Research School of Biological
Sciences (1991-present)
Reviewer, National University Strategic Development Fund
Australia Prize (1993)

Organization of media presentation
Australian Medical Research and Development Corporation (AMRAD)

Member of Scientific Advisory Committee (1992-present)
Conference organization

Member of Programme Committee for Australian Neural Networks 1993 Meeting
Scientific talks given

To visiting medical scientists, Park Royal, Sydney (Oct)
To Japanese Pharmaceutical Delegation, Sydney (Nov)
Service to scientific society
Australian Neuroscience Society: Member of Council as immediate Past-President Organizer of Australian Neuroscience Colloquium, Sydney (Oct). Invited Lecture at Special Symposium Honouring David Curtis, A.N.U. (Feb). Invited Lecture at Special Symposium Honouring Ian Darian-Smith, Melbourne (Feb) Lectures to Summer School students for Royal Society of N.S.W. (Jan). News media

Interviewer for ABC TV on the Australia Prize (Feb).
University administration
Member, Academic Board.
Member, Faculty of Science Board of Post-Graduate Studies.
Member, Faculty of Medicine Board of Post-Graduate Studies.
Member, Standing Committee of Faculty of Science.

Departmental administration

Co-ordinator for higher degree students
Course supervisor

Advanced Neuroscience 3 for BMedSc.
Refereeing

Manuscripts: for Brain Research (3), Neurocytology (2), Neuroscience (3), Neuroscience Letters (3).
Grant applications: for NHMRC Program Grant (1), ARC (6). 
Fellowship applications: for ARC (4).
Overseas conference attended

Stockholm International Conference on Synaptic Transmission (Organized by Nobel Committee in Physiology or Medicine): Chairperson of Opening Session and Invited Lecturer, Stockholm, Sweden (Sep).
THESES PASSED in 1993

PhD
Scott T (1993) Long-term potentiation in the ciliary ganglion.
Schulz M (1993) Growth factors for retinal ganglion cells.
5-YEAR RESEARCH PUBLICATIONS

JOURNAL ARTICLES

1989

Bennett MR, Lavidis NA (1989) The probability of quantal secretion at release
sites in different calcium concentrations in toad (Bufo marinus) muscle.
Journal of Physiology, 418, 219-233

Bennett MR, Lavidis NA, Lavidis-Armson FM (1989) The probability of quantal
secretion at release sites of different length in toad (Bufo marinus) muscle.
Journal of Physiology, 418, 235-249

Phillips WD, Bennett MR (1989) The distribution of intracellular acetylcholine
receptors and nuclei in developing avian fast-twitch muscle fibres during synapse
elimination. Journal of Neurocytology, 18, 241-255

Bennett MR, Davis A, Everett AW (1989) The development of topographical maps
and fibre types in toad (Bufo marinus) glutaeus muscle during synapse
elimination. Journal of Physiology, 409, 43-61

Bennett MR, Robinson J (1989) Growth and elimination of nerve terminals at
synaptic sites during polyneuronal innervation of muscle cells: a trophic
hypothesis. Proceedings of the Royal Society (London) Series B, 235, 299-320

Brown DR, Everett AW, Bennett MR (1989) Compartmental and topographical
distributions of axons in nerves to the amphibian (Bufo marinus) glutaeus
muscle. Journal of Comparative Neurology, 284, 231-241
1990

Brown DR, Everett AW (1990) Compartmental and topographical specificity of
reinnervation of the glutaeus muscle in adult toad (Bufo marinus).
Journal of Comparative Neurology, 292, 363-372

Sparrow MP, Mitchell HW, Everett AW (1990) Different ratio of myosin heavy
chain isoforms in arterial smooth muscle of spontaneously hypertensive rats.
Basic Research in Cardiology, 85, 209-214

Everett AW, Nichol KA (1990) Antiezrin immunoreactivity in neuronal subpopulations:
cellular distribution in relation to cytoskeletal proteins in sensory neurones.
Journal of Histochemistry and Cytochemistry, 38, 1137-1144

Bennett MR, Robinson J (1990) Probabilistic secretion of quanta from nerve
terminals at synaptic sites on muscle cells: non-uniformity, autoinhibition
and the binomial hypothesis. Proceedings of the Royal Society (London)
Series B, 239, 329-358

Kouts S, Bennett MR (1990) The distribution of intracellular acetylcholine
receptors and nuclei in avian slow muscle fibres during establishment of
distributed synapses. Journal of Neurocytology, 19, 421-427

Schulz M, Raju T, Ralston G, Bennett MR (1990) A retinal ganglion cell
neurotrophic factor purified from the superior colliculus. Journal of
Neurochemistry, 55, 832-841
1991

Bennett MR, Karunanithi S, Lavidis NA (1991) Probabilistic secretion of quanta
from nerve terminals in toad (Bufo marinus) muscle modulated by
adenosine. Journal of  Physiology, 433, 421-434

Bennett MR, Ho S (1991) Probabilistic secretion of quanta from nerve terminals
in avian ciliary ganglia modulated by adenosine. Journal of Physiology,
440, 513-527

Gibson WG, Robinson J, Bennett MR (1991) Probabilistic secretion of transmitter
at granule cell synapses: a role in pattern separation and activity regulation.
Philosophical Transactions of the Royal Society (London) Series B, 332, 199-220

Bennett MR, Kerr R, Nichol K (1991) Adenosine modulation of potassium currents
in postganglionic neurones of cultured avian ciliary ganglia. British
Journal of Pharmacology, 104, 459-465

Bennett MR, Lavidis NA (1991) Probabilistic secretion of quanta from nerve
terminals in toad (Bufo marinus) muscle modulated by seasonal changes.
Neuroscience Letters, 134, 79-82

Brown DR, Everett AW (1991) Position- and fibre type-dependent selectivity by
regenerating motor axons in reformation of the topographical projection to the
glutaeus muscle in the adult toad (Bufo marinus). Journal of Comparative
Neurology, 309, 495-506

Ewan K, Everett AW (1991) Evidence for the resegmentation in the formation of
the vertebral column using the novel approach of retroviral mediated gene
transfer. Experimental Cell Research, 198, 315-320
1992

Bennett MR, Ho S (1992) Adenosine modulation of potassium currents in preganglionic
nerve terminals of avian ciliary ganglia. Neuroscience Letters, 137, 41-44

Bennett MR, Kerr R, Khurana G (1992) Adenosine modulation of calcium currents
in postganglionic neurones of cultured avian ciliary ganglia. British Journal
of Pharmacology, 106, 25-32

Lavidis NA, Bennett MR (1992) Probabilistic secretion of quanta from visualized
sympathetic nerve varicosities in mouse vas deferens. Journal of Physiology,
454, 9-26

Bennett MR, Walmsley B (1992) What determines the efficacy of a synaptic connection?
International Brain Research Organization News, 20, 6-7

Bennett MR (1992) Essentials of neural development. Quarterly Reviews of Biology, 67, 233

Karunanithi S, Lavidis NA, Bennett MR (1992) Effects of adenosine on spontaneous
and evoked quantal secretion from different release sites of amphibian motor-nerve
terminals. Neuroscience Letters, 147, 49-52

Lavidis NA, Bennett MR (1992) Sympathetic axon varicosity distributions on the
surface of the mouse vas deferens. Journal of Autonomic Nervous System, 45, 87-100
1993

Khurana G, Bennett MR (1993) Nitric oxide and arachidonic acid modulation of
calcium currents in postganglionic neurones of cultured avian ciliary ganglia.
British Journal of Pharmacology, 109, 480-485

Bennett MR, Gibson W, Poznanski R (1993) Electrical current flow and potential
during synaptic transmission in the smooth muscle syncytium. Philosophical
Transactions of the Royal Society, B 342, 89-99

Bennett MR (1993) The probability of quantal secretion at visualized varicosities
of sympathetic nerve terminals. News in Physiological Sciences, 8, 199-201

Huxlin KR, Sefton AJ, Schulz M, Bennett MR (1993) Effect of proteoglycan purified
from rat superior colliculus on the survival of murine retinal ganglion cells.
Developmental Brain Research, 74, 207-217

Bennett MR, Gibson WG, Robinson J (1993) Dynamics of the CA3 pyramidal neurone
autoassociative memory network in hippocampus. Philosophical Transactions of
the Royal Society, B, 343, 167-187

Lavidis NA, Bennett MR (1993) Probabilistic secretion of quanta from visualized
varicosities along single sympathetic nerve terminals. Journal of Autonomic
Nervous System, 43, 41-50

Cetiner M, Bennett MR (1993) Nitric oxide modulation of calcium-activated potassium
channels in postganglionic neurones and cultured avian ciliary ganglia. British
Journal of Pharmacology, 110, 995-1002

Scott TRD, Bennett MR (1993) The effect of ions and second messengers on long-term
potentiation of chemical transmission in avian ciliary ganglion. British Journal
of Pharmacology, 110, 461-469

Scott TRD, Bennett MR (1993) The effect of nitric oxide on the efficacy of synaptic
transmission through the chick ciliary ganglion. British Journal of Pharmacology,
110, 627-632

Karunanithi S, Lavidis NA, Bennett MR (1993) Evidence that each nerve varicosity
on the surface of the mouse vas deferens secretes ATP. Neuroscience Letters,
161, 157-160

Bennett MR (1993) Understanding the brain in the twenty-first century.
Proceedings of the Royal Society of New South Wales, 126, 167-190

Bennett MR (1993) A consideration of Humphrey's "cerebral sentinent loop"
explanation of consciousness. Proceedings of the Royal Society of New South
Wales, 126, 111-124
Early 1994

Larkum ME, Warren DA, Bennett MR (1994) Calcium concentration changes in the
calciform nerve terminal of the avian ciliary ganglion after tetanic stimulation.
Journal of Autonomic Nervous System, 46, 175-188

Nickolaris P, Lin YQ, Bennett MR (1994) Effect of nitric oxide synthase inhibition
on long-term potentiation at associational-commissural and mossy fibre synapses
on CA3 pyramidal neurones. British Journal of Pharmacology, 111, 521-524

Nichol KA, Everett AW, Schulz M, Bennett MR (1994) Retinal ganglion cell survival
in vitro maintained by a chondroitin sulfate proteoglycan from the superior
colliculus carrying the HNK-1 epitope. Journal of Neuroscience Research,
37, 623-632

Poznanski RR (1994) Electrotonic length estimations of CA3 hippocampal pyramidal
neurons. Neuroscience Research Communications, 14, 93-100

Poznanski RR (1994) Nonlinear summation of junction potentials in a three-dimensional
syncytium. Annals of Biomedical Engineering, 21, 401-405

MacLeod G, Lavidis N, Bennett MR (1994) Calcium dependence of quantal secretion
from visualized sympathetic nerve varicosities on the mouse vas deferens.
Journal of Physiology (in press)

Nichol KA, Chan N, Davey DF, Bennett MR (1994) Location of nitric oxide synthase
in the developing avian ciliary ganglion. Journal of the Autonomic Nervous
System (in press)

Bennett MR (1994) Long-term potentiation and nitric oxide in autonomic ganglia.
General Pharmacology (in press)

Karunanithi S, Lavidis NA, Bennett MR (1994) Effect of yohimbine on the contractile
response of the mouse vas deferens to short, low frequency trains of impulses.
European Journal of Pharmacology (in press)

Lin YQ, Bennett MR (1994) Nitric oxide modulation of quantal secretion in chick
ciliary ganglia. Journal of Physiology (in press)
CHAPTERS IN BOOKS

Bennett, MR (1993) Probability of neurotransmitter secretion at individual release
sites. Neurotransmitter Release and Modulation, Powis D, ed, Cambridge University Press

Bennett MR (1994) The concept of neurotransmitter release. Introduction to
Symposium on Cellular and Molecular Mechanisms of Neurotransmitter Release,
Stärne L, ed, Raven Press, Stockholm (in press)

Bennett MR (1994) Quantal secretion from single visualized varicosities of
sympathetic nerve terminals. Symposium on Cellular and Molecular Mechanisms
of Neurotransmitter Release, Stärne L, ed, Raven Press, Stockholm (in press)
CONFERENCE ABSTRACTS AND PRESENTATIONS in 1993

Huxlin KR, Sefton AJ, Carr R, Schulz M, Bennett MR (1993) Collicular chondroitin
sulfate proteoglycan prevents the natural death of retinal ganglion cells in
situ. Proceedings of the Australian Neuroscience Society,
4, ORA-13-3. Melbourne (Feb)

Brown CS, Davey DF, Nichol KA, Schulz M, Bennett MR (1993) Molecules bearing the
HNK-1 epitope have an in vitro survival action on purified chick motoneurones.
Proceedings of the Australian Neuroscience Society,
4, ORA-13-5. Melbourne (Feb)

Lavidis NA, Thompson PC, Robinson J, Bennett MR (1993) Probabilistic secretion
of acetylcholine quanta during a nerve impulse does not involve autoinhibition
of nerve terminals. Proceedings of the Australian Neuroscience Society,
4, ORA-14-3. Melbourne (Feb)

Poznanski RR, Gibson WG, Bennett MR (1993) Quantal secretion from varicosities
in a smooth muscle syncytium: analytical solution to the problem of current flow
and potential. Proceedings of the Australian Neuroscience Society,
4, ORA-14-4. Melbourne (Feb)

Karunanithi S, Lavidis NA, Bennett MR (1993) Evidence that each visualized
varicosity on the mouse vas deferens may secrete a quantum of ATP.
Proceedings of the Australian Neuroscience Society,
4, ORA-14-5. Melbourne (Feb)

Macleod GT, Bennett MR (1993) The calcium dependence of quantal secretion from
visualized varicosities in the mouse vas deferens. Proceedings of the
Australian Neuroscience Society, 4, ORA-14-6 Melbourne (Feb)

Nicolarakis PJ, Lin YQ, Bennett MR (1993) Nitric oxide modulation of long-term
potentiation from recurrent collaterals to CA3 pyramidal neurones in the rat
hippocampus. Proceedings of the Australian Neuroscience Society,
4, ORA-17-4. Melbourne (Feb)

Scott TRD, Bennett MR (1993) The role of cGMP in the persistent enhancement of
the efficacy of synaptic transmission in the chick ciliary ganglia. Proceedings
of the Australian Neuroscience Society, 4, ORA-17-5. Melbourne (Feb)

Nichol KA, Bennett MR (1993) Nitric oxide and chondroitin sulfate proteoglycan
act to determine retinal ganglion cell development in vitro. Proceedings of
the Australian Neuroscience Society, 4, P83. Melbourne (Feb)

Armson PF, Huxlin KR, Nichol KA, Schulz MW, Sefton AJ, Bennett MR (1993) Retinal
ganglion cell survival can be maintained in vitro by a thalamically derived
factor distinct from that isolated from the superior colliculus. Proceedings
of the Australian Neuroscience Society, 4, P84. Melbourne (Feb)