Biomedical subjects

E Colebrook

Publications and source records attributed to E Colebrook.

7 recordsLinked to original sources

PubMed1991

Electrophysiological studies of the gill ganglion in Aplysia californica.

1. An electrophysiological analysis was made of gill ganglion neurons in Aplysia californica. 2. Gill ganglion neurons behave similarly to neurons in the abdominal ganglion (the central nervous systems; CNS) that are involved with gill withdrawal behaviors. 3. Some gill ganglion neurons are motor neurons much like those in the CNS. 4. Neurons in the gill ganglion are electronically and dye-coupled. In addition, they receive common chemical synaptic inputs from the Int-II network in the CNS. 5. Tactile stimulation of the gill or siphon evokes synaptic activity in gill ganglion neurons whether or not the CNS is present. 6. Pedal nerve stimulation results in synaptic activity in gill ganglion neurons and facilitates synaptic input evoked by tactile stimulation of the gill or siphon. 7. Antibody staining reveals serotonin-like fibers in the branchial nerve close to the gill ganglion but no cell bodies in the ganglion. 8. The gill ganglion may play a role in the mediation of adaptive gill reflex behaviors. It may be one of the loci where the CNS and peripheral nervous system (PNS) interact and form an integrated circuit to mediate gill withdrawal reflex (GWR) behaviors.

Animals↗

PubMed1988

Classical conditioning alters the efficacy of identified gill motor neurones in producing gill withdrawal movements in Aplysia.

In a semi-intact preparation of Aplysia californica Cooper, classical conditioning training leads to changes in the synaptic strength at the sensory-motor neurone synapse. However, these changes are neither necessary nor sufficient to bring about the observed behavioural changes of the gill withdrawal reflex. We therefore tested whether the ability of a gill motor neurone to elicit a gill withdrawal response was altered following classical conditioning training of the reflex. We found that following classical conditioning training, the ability of a gill motor neurone to elicit a gill withdrawal response was significantly potentiated. In addition, in control preparations which did not receive classical conditioning training, the ability of a gill motor neurone to elicit a gill response was decreased. Thus, associative learning of this reflex appears to involve alteration in neuronal activity at loci distal to the sensory-motor neurone synapse.

Animals↗

PubMed1983

Behavioural examinations of the anti-aggressive drug fluprazine.

The behavioural influence of the anti-aggressive drug Fluprazine (DU 27716) was examined using an ethological technique. The drug inhibited aggressive behaviour but not in an entirely specific way. Fluprazine also stimulated non-social and defensive/flight behaviours; there was a greater tendency for drug-treated animals to avoid their opponents. Using an automatic recording technique the drug's anti-aggressive action was monitored for 23 h. There was a potent anti-aggressive influence that lasted for up to 4 h. However, when the drug-effect wore off there were bouts of fighting. Over 23 h Fluprazine did not significantly decrease the total aggression recorded.

Aggression↗

PubMed1979

Keratoconus, keratoplasty thickness, and endothelial morphology.

A group of successful keratonic grafts (51 eyes) up to 10 years from operation were examined to establish a relationship between graft thickness and acuity. Best acuity occurred in the grafts of normal corneal thickness. No grafts were thinner than normal; thus no tendency to keratonic thinning occurred. No relationship between age of graft and thickness was determined. Endothelial cell studies in vivo of a small number of grafts showed that cell counts a third of normal coexisted with normal acuity and corneal thickness.

Cornea↗

PubMed1979

Keratoplasty sensitivity.

Analysis of graft sensitivity showed a return to normal after 3 years in only one-third of the eyes. It is not known whether this is due to regeneration of abnormal or superficial nerve fibres. Contact lens wearers showed less sensitivity than spectacle wearers.

Contact Lenses↗

PubMed1979

Keratoconus keratoplasty curvatures and contact lens wear.

Fifty-three grafted keratoconus corneas chosen at random from several hundred operated upon over a 10-year period showed an increase in myopia after removal of sutures but a decrease in astigmatism. With the photoelectrokeratograph machine the spherical zone was shown to be limited to 3 mm with gross eccentricities. Half the patients chose to wear contact lenses after surgery and 10% had no correction. Contact lens wearers showed a much greater decrease in astigmatism than spectacle wearers.

Astigmatism↗

PubMedDate not supplied

Neuronal mechanisms of learning in an in vitro Aplysia preparation: sites other than the sensory-motor neuron synapse are involved.

Classical conditioning of the gill withdrawal reflex can be demonstrated in two different in vitro Aplysia preparations. The data obtained show that as conditioning of the gill withdrawal reflex proceeds there are changes in synaptic efficacy at the central sensory-motor neurone synapse. These changes in synaptic efficacy, however, are not necessary nor are they sufficient for the observed changes in gill reflex behaviour. Changes must be occurring at other loci within the nervous system to mediate the associative learning. We hypothesized, based on data obtained from one type of in vitro preparation, that changes occur in the ability of the motor neurone to elicit a gill withdrawal response as a result of classical conditioning training. In order to test this hypothesis we depolarized an identified gill motor neurone before and after classical conditioning and found that the motor neurone's ability to elicit a gill movement was facilitated following classical conditioning training. In control preparations that received an explicitly unpaired stimulus paradigm (which does not lead to classical conditioning of the reflex) there was a decrease in the efficacy of a gill motor neurone to elicit a gill withdrawal response. There are a number of possible sites within the integrated central (CNS) and peripheral (PNS) nervous systems where changes could occur to bring about the alterations in motor neurone efficacy. Our results suggest that changes in neuronal activity which underlie learning occur at multiple sites within the nervous system and that a complete understanding of the mechanisms of associative learning can only be obtained when all of these sites are taken into account.

Animals↗