INVESTIGADORES
MARIN BURGIN Antonia
congresos y reuniones científicas
Título:
Inhibition helps shape the spatial and temporal profiles of the local bend response of the medicinal leech.
Autor/es:
D.A. WAGENAAR; S.M. BACA; ANTONIA MARIN BURGIN; W. B. KRISTAN JR
Lugar:
San Diego
Reunión:
Congreso; Meeting of the society for neuroscience; 2007
Institución organizadora:
Society for Neuroscience
Resumen:
In response to local pressure applied anywhere on its body,
the European medicinal leech contracts muscles ipsilateral to the
pressure and relaxes contralateral muscles, thus bending its body away
from the touch location. Previous work from our lab has shown that the
relative strength of contraction and relaxation around the body
circumference directs bending precisely away from the stimulus, despite
the fact that only 4 sensory neurons per ganglion respond to pressure
stimuli. Here we study the role of inhibition in shaping a
well-controlled response.
We used a mechanical stimulator to deliver forces of 0.75--400 mN
(corresponding to pressures of about 0.75--400 kPa) to a section of
leech body wall innervated by a single ganglion, and recorded the
consequent motion of the skin using a computer-attached CCD camera.
These measurements were repeated after inhibition was blocked using bath
application of bicuculline methiodide (BMI), a blocker of GABA-A
receptors. This resulted in a roughly twofold increase in contraction
ipsilateral to the stimulus, at all force levels. Contralateral to the
stimulus, the (normally weak and brief) initial contractile phase was
augmented in amplitude and duration, and the subsequent relaxation was
delayed and reduced, or even abolished. This shows that the role of
inhibition goes well beyond mediating contralateral relaxation; it
strongly tempers the ipsilateral contraction as well. Conversely,
contralateral relaxation is tempered by a contractile force which is
revealed when inhibition is blocked. While four of the motor neurons
involved in the response are inhibitory, applying BMI locally to the
muscles had no effect. Thus, the observed effects must be central.
In conclusion, inhibition regulates the dynamic balance between
contraction and relaxation in response to contralateral touch, and it
controls the amplitude of the contraction in response to ipsilateral
touch as well as its spatial extent.