Neuronal unit activity was recorded from the abducens (6th nerve) nucleus, the "final common path," during classical conditioning of the nictitating membrane (NM) response in the rabbit, with the use of a tone conditioned stimulus, an air puff unconditioned stimulus (UCS), 250-msec interstimulus interval, and 60-sec intertrial interval. Animals were given 2 days of conditioning training (104 trials in eight blocks per day) and 1 day of extinction. Control animals were given comparable periods of stimulus presentations, explicitly unpaired. Activity of small clusters of units--"multiple unit" recording--was compared with the amplitude-time course of the NM response. Between-blocks comparisons of neural and behavioral responses indicated an essentially perfect correlation during acquisition of the conditioned response (Day 1, r = .99; Day 2, r = .98) and a slightly lower correlation during extinction (r = .93) for the conditioning animals. Within-blocks comparisons indicated a close correspondence between the histograms of unit activity and the amplitude-time course of the NM response for the conditioning animals in all phase of training and for the control animals in the UCS trial blocks.

Abducens Nerve↗

PubMed1976

Mechanisms of efferent neuronal control of the reflex nicitating membrane response in rabbit (Oryctolagus cuniculus)

Efferent mechanisms controlling the nicitating membrane (NM) reflex response to air puff in the albino rabbit were analyzed using stimulation, lesions, and recording techniques. In brief, stimulation of the sixth nerve (abducens) yields short-latency NM extension. Stimulation of the fourth and seventh nerves and the superior cervical ganglion has essentially no effect on the NM. Stimulation of the third nerve causes short-latency retraction of the NM. Lesions and recording data are consistent with this result - the sole efferent neuronal control of NM extension is the sixth cranial nerve and of NM retraction is the third cranial nerve. The NM extension response appears to be mediated by mechanical actions via retraction of the eyeball by the retractor bulbi muscle, and NM retraction appears to result from direct activation of muscle fibers in the NM by the third nerve. The superior cervical ganglion appears to play no role in reflex NM retraction in the rabbit, in contrast to its action in the cat.

Abducens Nerve↗

PubMed1976

Tone-induced changes in excitability of abducens motoneurons and of the reflex path of nictitating membrane response in rabbit (Oryctolagus cuniculus).

Excitability of the reflex nicitating membrane (NM) response to air puff and of the abducens motoneurons (final common path) to direct electrical stimulation (measured as amplitude of the evoked NM response) in rabbit was tested at various times after onset and offset of a 350-msec tone. Excitability to air puff showed a substantial increase during tone on a gradual decrease following tone off, in agreement with Ison and Leonard. Excitability of motoneurons showed a similar marked increase during tone on a transient decrease immediately following tone off, and then a gradual decrease. It is suggested that these excitability changes, which parallel closely the interstimulus-interval conditionability function reported by Gormezano for the same preparation, may provide an independent measure of the "molar stimulus trace". Excitability of abducens motoneurons tested in the intertrial intervals during subsequent tone-air puff conditioning showed no consistent changes. Surprisingly, animals given tone-abducens nucleus shock testing developed conditioned responses. In subsequent conditioning, using standard tone-air puff training, they showed 85% savings in acquisition relative to nonstimulated controls.

Abducens Nerve↗

PubMed1973

Effects of a classical conditioning paradigm on hind-limb flexor nerve response in immobilized spinal cats.

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Animals↗

PubMedDate not supplied

Effects of MSH/ACTH 4-10 on the classically-conditioned rabbit nictitating membrane.

Subjects were conditioned/extinguished under four experimental conditions using either MSH/ACTH 4-10(A) or diluent (D): D/D, D/A, A/D, and A/A. The major question investigated was whether or not the peptide has an effect on this classically-conditioned behavior similar to that reported for instrumental conditioning paradigms. The results indicated that it does not. An effect was seen on performance, not on learning or attentional processes. Animals treated with the peptide performed more poorly (i.e., displayed fewer conditioned responses) during both acquisition and extinction. In addition, there was an apparent residual effect of the peptide that lasted 24 but not 48 hours.

Adrenocorticotropic Hormone↗

PubMedDate not supplied

A rabbit headholder for stereotaxic use with gaseous anesthetics.

A headholder is described which allows a rabbit to be maintained on a gaseous anesthetic (e.g., halothane) while the head is securely held without the use of earbars. The animal's head can be aligned, without being loosened, in three stereotaxic planes by three thumb screws.

Animals↗