Address for correspondence: Prof. José M. Delgado-García, División de Neurociencias, Laboratorio Andaluz de Biología, Universidad Pablo de Olavide, Ctra. de Utrera, Km. 1, Sevilla-41013, Spain. Voice: + 34-954-349374; fax: + 34-954-349375.
jmdelgar{at}dex.upo.es
Ann. N.Y. Acad. Sci. 978: 106-118 (2002).
The participation of the rostral-dorsal part of the posterior
interpositus nucleus in the genesis of classically-conditioned
eyelid responses in alert cats was studied. Cats were prepared
for the recording of left eyelid movements with the search-coil-in-a-magnetic-field
technique and of the electromyographic activity of the orbicularis
oculi muscle. A stimulating electrode was implanted in the contralateral
red nucleus and a guide cannula in the ipsilateral interpositus.
The cannula allowed unitary recordings, electrical microstimulation,
drug injection, and push-pull perfusion of the selected interpositus
site. Perfusate was used for amino acid analysis with an HPLC-EC
method. Animals were conditioned with a delay (CS: tone, US:
air puff) paradigm. Antidromically identified interpositus neurons
fired during eyelid conditioned responses (CRs) with a variable
delay to CR start. Some neurons (type A) increased and other
(type B) decreased their firing during CR performance. Electrical
microstimulation of posterior interpositus was able to increase
CR amplitude when applied during CS presentation. Muscimol decreased
CR amplitude in well-trained animals. The analysis of push-pull
perfusate showed a significant increase in glutamate, glycine,
and taurine, but not GABA levels, during conditioning in comparison
with habituation and extinction periods. Results indicate an
involvement of the rostral-dorsal part of the posterior interpositus
nucleus in the genesis of eyelid conditioned responses, playing
an enhancing or controlling role in CR performance, rather than
being its initiator.
