Autonomic Nervous System Laboratory

Dr Phil Jobling

Our research centres on the structure and function of nerves which control our internal organs.  This includes,  the sensory neurons which give us information on the state of our internal organs,  and the autonomic neurons which modify organ function.  We are interested in how autonomic  neurons receive information from other  parts of the nervous system and how they process this information before  sending signals to the final target organ.  At present we are focussing on control of the female reproductive tract using a number of animal  models.  To study these complex nervous pathways we use a combination of  electrical recording techniques,  to monitor the activity of individual  neurons,  and anatomical techniques to visualise the shape and chemical content of neurons.

Research Projects: 

At present there are several ongoing or proposed projects within the laboratory. Each of these has a component suitable for research student participation.  Should you wish to undertake an undergraduate research elective, honours year or postgraduate study please  contact Dr Jobling to arrange a meeting.  All experiments undertaken in the laboratory conform to the NHMRC policy on animal research and all projects are approved by the University of Newcastle  Animal Ethics Committee.

How does the nervous system process sensory information from the female reproductive tract?

Pelvic pain is a common and debilitating condition in women. Indeed, pain arising from reproductive organs is one of the most frequent reasons women seek medical attention. Data from Australian studies place the reported prevalence of transient pelvic pain (usually dysmenorrhea) at ~80% in some cohorts, while the reported prevalence of chronic pelvic pain is ~ 12%. Pelvic pain is also a predictor for hysterectomy. Supporting data from the USA suggest that 10% of outpatient gynaecological visits are for intractable pelvic pain and it is the primary reason for 12% - 18% of hysterectomies. Thus, as well as causing suffering and distress pelvic pain results in significant health costs. One of the major obstacles to effective treatment is the lack of knowledge about the way the nervous system processes signals (both innocuous and noxious) originating in pelvic organs, especially those of the female reproductive tract (FRT).

In this project we use in vivo intracellular patch-clamp recording which permits direct measurement of synaptic responses in mouse spinal cord. We record from dorsal horn (DH) neurons after stimulation of different regions (uterus, cervix and vagina) of the FRT. Our technique also permits extensive characterization of a neuron’s response to current injection, its morphology, precise lamina location in the spinal cord, and its neurotransmitter phenotype. Characterisation of these nerve circuits will significantly add to our understanding of the synaptic mechanisms that underlie processing of sensory signals transmitted from the FRT. Data from this project will help identify specific DH targets that are most amenable to development of new therapies. Information gained in this project will also contribute to our knowledge of pain arising from other pelvic organs such as the bladder and colon.

Subthreshold synaptic responses and discharge properties of DH neurons in thoracolumbar and lumbosacral spinal cord. A. Synaptic responses during stimulation of the skin (brush) and cervix (via custom-made probe) in thoracolumbar spinal cord. Note, the neuron responded to both somatic (skin) and visceral (cervix) stimulation. Insets show, on an expanded time base, the low background noise and detail that can be resolved from the synaptic response. B. Similar high-resolution synaptic responses recorded in a lumbosacral DH neuron during mechanical stimulation of the cervix. C. Response of the neuron in B. to hyperpolarizing and depolarising current injection. The neuron fired one spike and is classified as a single spiking neuron [RC10]. Such information on discharge properties is recorded for each DH neuron and has not been previously available for in vivo studies. This information is an invaluable step forward and unique to the proposed study. Furthermore, our novel data can be compared to the very large in vitro (slice) literature on the discharge and intrinsic properties of DH neurons.

This project is supported by a grant from the  HMRI.

Calcium channel expression in autonomic neurons

Neurons communicate with each other through chemical synapses dependent on calcium. The link between calcium entry into the nerve terminal and neurotransmitter release has been the subject of considerable study over recent decades. Whilst many of the underlying principles common to all synapses have been elucidated, it is becoming apparent that the relationship between calcium entry and synapse function varies considerably between synapses. Of note is differential expression of calcium channel subtypes which provide the source of calcium necessary for neurotransmitter release. The reasons for such diversity are unclear. Perhaps they allow the vastly different patterns of communication which we see in different neural circuits? As in the central nervous system, peripheral synapses which control autonomic targets show heterogeneity in the calcium channel subtypes they express. In this study we will use the unique anatomical properties of autonomic ganglia to probe the link between calcium channel subtype and synaptic function.

Synaptic transmission and electrical properties of neurons in pelvic ganglia of female mice

Few studies have investigated synaptic properties of female pelvic neurons. A previous study in guinea-pigs indicated that pelvic neurons receive one or two strong nicotinic preganglionic synaptic inputs as well as slow EPSPs which can evoke sustained action potential (AP) discharge [1]. The aim of this project is to investigate synaptic transmission in pelvic ganglia of female mice and determine if the innervation pattern observed in guinea-pigs is representative of all rodents. Data so far.  15 Mice (C57/B16) were killed by overdose of ketamine (90 mgkg-1) or sodium pentobarbitone (150 mgkg-1) prior to removal of the pelvic plexus. Neurons in small anterior ganglia close to the entry of the hypogastric nerve or within the larger posterior ganglion were impaled with microelectrodes. Neurons could be classified as rapidly adapting (10 neurons) or slowly adapting (7 neurons) in response to current injection. AP discharge was independent of location within the plexus. Considerable variation was observed in duration of the AHP following an AP. Voltage clamp revealed a slow IAHP in some neurons. Neurons received few convergent synaptic inputs following pelvic or hypogastric nerve stimulation. These synaptic inputs were suprathreshold at RMP (-49 mv) with a high safety factor for initiation of an action potential (9/11 pelvic, 5/7 hypogastric inputs). Trains of stimuli (300 @10Hz) delivered to the hypogastric nerve in three neurons or pelvic nerve in one neuron failed to evoke slow EPSPs or spontaneous firing. These results indicate that neurons in pelvic ganglia of female mice integrate few synaptic inputs consistent with data from guinea-pigs. Evidence of slow EPSPs remain to be determined for these neurons [1]. Jobling P, Gibbins IL, Morris, JL (2005). Proc. ANS 16: POS-Tues-226.