Functional plasticity of the flexor withdrawal reflex in the rat following peripheral tissue injury

S128 FUNCTIONAL

PLASTICITY

RAT FOLLOWING R.

O’Neil), Aim of

OF THE

PERIPHERAL

Dept. of Investigation:

FLEXOR WITHDRAWAL

TISSUE

Anatomy,

INJURY.

C.J.

University

REFLEX Woolf*

College

IN THE

186 Slide 2:30 I_~_Sun UK.1 Vashon

(SPON.

London,

Peripheral tissue injury is accompanied by sensory disturbances that include ongoing pain, allodynia and hyperalgesia. This study has investigated whether in addition to producing changes in thresholds and responses of nociceptors (sensitization) tissue injury also alters the function of the CNS. Methods: The hindlimb flexor withdrawal reflex has been studied as a means of monitoring changes in sensory input and processing in the spinal cord. Behavioural and electrophysiological techniques have been used to detect changes in the flexor reflex of acutely or chronically decerebrated rats following peripheral tissue injury, Results: Peripheral tissue injury produces a reduction in the threshold andxrease in the responsiveness of the flexor withdrawal reflex which has been found to be the result, at least in part, to an increase in the excitability of the spinal cord. Conclusions: The afferent input generated by a peripheral tissue injury can trigger an alteration in the function of the spinal cord changing, for examp 1 e , the cutaneous receptive field properties of flexor motor neurones and the gain of the input/output relations of the spinal cord. This functional plasticity of the spinal cord may contribute to the apparent uncoupling of the relationship between sensory input and the pain perceived in patients suffering from chronic pain syndromes.

BRAIN AND SPINAL

CORD NEUROPEPTIDES

TION WITH AND WITHOUT

A,

P.Sacerdotel

A.Martinir

Depts.Pharmacology

and Psychology,

and

less understood

attempted

to

identify

them by pharmacological Methods: or 10

mm

the

sciatic

Rats

were

01‘ chlorimipramine,

baclofen,

tryptophan

either

starting

were killed

of

is

one

biochemical

the

of

and drug treatment modifications

nerve

treated

more

is symptom-

modifications.

and

sectioned

W3S

twice

nortriptyline,

to

daily

normalize

its

origin

either

saline

at

with

diphenylhydantoin,

the day after surgery

60 days after surgery

levels,while

these

2:45

l’ashon

Italy.

pain

of the underlying

Slide

treatments.

right

distally.

20129,

pathologies

some

A.E.Pane-

U. of Milano,

deafferentation

atic and not on the knowledge We

Milano,

187 Sun

NERVE SEC-

TREATMENTS.

M.A.Villamirar

Aim of investigation: intriguing

AFTER SCIATIC

PHARMACOLOGICAL

and spinal

5-hydroxy-

or 30 days thereafter.

cord dissected

at

Rats

different

right and left brain were separated and discrete areas dissecP were measured by Somatostatin, Met-enkephalin,Substance

ted. B-endorphin, radioimmunoassay Results: trations

P was slightly

increase

in re-establish Conclusions: centrations lesion

dramatically

in most brain areas involved

Substance induced

in all regions.

deafferentation

affected

in the spinal

in the serotoninergic normal

modified

concentrations

only B-endorphin

in pain modulation,

while

concen-

only

cord. The pharmacologically

tone proved

to be the most effective

of the peptides.

deafferentation induces dramatic modifications of the conapparently regardless of the side of the

of neuropeptides,

and some pharmacological

treatments

overcome

these changes.