Nictitating Membrane Extension Research Articles

Electrical activity of the lateral rectus muscle and abducens nerve during unconditioned eye retraction induced by corneal stimulation in the cat

Horizontal eye movements, the electromyogram of the lateral rectus muscle and the evoked electroneurogram of the VIth nerve were recorded in the alert cat during air puff stimulation of the cornea. A burst of activity was observed in the lateral rectus muscle following air puff stimulation of the ipsilateral or contralateral eye. This activity produced rotational eye movement. The VIth nerve produced two volleys of activity that were interpreted as the R1 and R2 parts of the reflex. It can be concluded that the lateral rectus muscle participates in the ocular retraction following trigeminal stimulation. It is further suggested that motoneurons in the main abducens nucleus participate in the corneal reflex, permitting several final pathways for conditioned and unconditioned nictitating membrane extension.

Activity of deep cerebellar nuclear cells during classical conditioning of nictitating membrane extension in rabbits

The activity of neurons in the interposed and dentate nuclei of the cerebellum was investigated during differential classical conditioning of the rabbit eye blink nictitating membrane response. Forty-seven percent of the 165 cells in the study responded to the orbital stimulation used as the unconditioned stimulus (US). The latency distribution of US-elicited responses was bimodal with peaks at 7 and 19 ms. Twenty-one percent of the cells responded with short latencies to the tones used as conditioned stimuli (CSs). These cells typically responded to both the reinforced and nonreinforced CSs. Forty-one percent of the cells responded on conditioned response (CR) trials but not on trials without CRs. The average lead of the neural response to the CR was 71.4 ms. Cells that responded on CR trials were more likely to respond to the CSs, or to the CSs and the US, than cells that did not respond on CR trials. For about half of the cells that responded on CR trials the latency of response followed trial-by-trial variations of CR latency. For the remainder, the response was time-locked to CS-onset. Cells whose responses paralleled the CR may be involved in the initiation or modulation of the CR, while those whose responses were time-locked to the CS may be involved in sensory processing underlying the initiation of the movement. The pathways that may underlie the US- and CS-elicited responses are also discussed.

Lesions of the cerebellar interpositus nucleus abolish both nictitating membrane and eyelid EMG conditioned responses

Both nictitating membrane extension and eyelid EMG activity were measured during classical conditioning of rabbits to tone-airpuff pairings. Both measures were highly correlated. Over trials, learning criterion was met earlier with eyelid EMG activity than with nictitating membrane extension. Within a trial, eyelid EMG preceded and was more robust than nictitating membrane extension. The rabbits were lesioned in the cerebellar interpositus nucleus and then trained for up to 26 days. Detailed analyses of tone alone trials demonstrate that the lesion abolished conditioned responses for both measures. These data confirm that conditioned responses are abolished by lesion of the cerebellar interpositus nucleus.

Aluminum produces age related behavioral toxicity in the rabbit

Two- to 3.4-year-old, retired breeder, rabbits received repeated aluminum (Al) lactate or sodium (Na) lactate injections. All six rabbits receiving twenty 400 μmole Al/kg SC injections died, demonstrating much higher mortality than previously seen in younger rabbits. Subsequent rabbits receiving Al were dosed with 200 μmole/kg injections. Aluminum injections inhibited body weight gain. Renal function, as measured by creatinine clearance, in these rabbits was inferior to younger rabbits, perhaps contributing to the Al induced toxicity. Renal function decreased during Al injections suggesting a nephrotoxic effect of Al. Rabbits were tested for their ability to acquire, retain and extinguish a classically conditioned reflex, nictitating membrane extension. Rabbits which received Al acquired and retained the conditioned response less well than Na lactate injected rabbits. Impaired acquisition was evidenced by lower percent conditioned responses, more trials to 1 to 10 consecutive conditioned responses and longer conditioned response latencies. Aluminum injections produced significant elevations in tissue Al concentration in frontal gray and hippocampal brain as well as most peripheral tissues studied. Aluminum induced behavioral toxicity is greater in adult and aged rabbits than in young rabbits. Aged rabbits are more susceptible to Al induced mortality than adult or young rabbits.

Synaptic connections between primary trigeminal afferents and accessory abducens motoneurons in the monitor lizard, Varanus exanthematicus.

We studied the anatomical pathway underlying the nictitating reflex in the monitor lizard Varanus exanthematicus by the anterograde degeneration technique combined with retrograde transport of horseradish peroxidase (HRP) and electron microscopy. After application of HRP to the abducens nerve, retrogradely labeled neurons were observed in the ipsilateral principal and accessory abducens motor nuclei. The transection, in the same experiments, of the root of the trigeminal nerve resulted in massive degeneration of myelinated fibers in the descending trigeminal tract. In the ipsilateral accessory abducens nucleus, we observed electron-dense degenerating axon terminals that formed asymmetric synaptic contacts with the primary and secondary dendrites of large neurons retrogradely labeled with HRP. A few of the degenerating terminals could be traced in serial sections to myelinated axons. No terminal degeneration was found in the contralateral accessory abducens nucleus or in the ipsilateral and contralateral principal abducens nuclei. The present results are complementary with the findings of previous light microscopic experimental tracing studies (Barbas-Henry, H.A., and A.H.M. Lohman, J. Comp. Neurol. 1986, 254:314-329; see also J. Comp. Neurol. 1988, 267:370-386), and strongly suggest the existence in Varanus of a monosynaptic, unilateral reflex pathway in which trigeminal fibers, presumably originating from the cornea, synapse with motoneurons of the bursalis and retractor bulbi muscles, which are located in the accessory abducens nucleus. This monosynaptic pathway may mediate a rapid unilateral eyeball retraction and nictitating membrane extension.

The role of the extraocular muscles in the rabbit nictitating membrane response: a re-examination

Berthier and Moore 1 showed that the rabbit nictitating membrane (NM) response principally results from contracting the retractor bulbi muscle which pulls the globe into the socket thereby passively effecting NM extension. They concluded that the remaining extraocular muscles can effect NM extension if the retractor bulbi is denervated. A re-examination of the role of the recti and oblique extraocular muscles in nictitating membrane extension was undertaken in the light of recent results of Marek et al. 10, suggesting that the facial nerve, and not the extraocular muscles, participates in extension of the NM. In contrast to Marek et al. 10, the present results indicated that section of the extraocular muscles was necessary to abolish eyeshock or tactilly elicited NM extension when the abducens and facial nerves were severed. It is therefore likely that extraocular (recti and oblique) muscles participate in globe retraction and NM extension, as originally noted by Lorente de No 9.

Selective, naloxone-reversible morphine depression of learned behavioral and hippocampal responses.

Morphine administered intravenously causes immediate and complete abolition of a simple learned response (classically conditioned nictitating membrane extension in rabbit) and of the associated learning-induced increase in hippocampal neuron activity. Both effects are completely reversed by low doses of naloxone. Morphine has no effect at all on behavioral performance of the unconditioned reflex response.

A minicomputer program for stimulus control and analog data for discrete trial paradigms in biological preparations: Classical conditioning

The application of computer technology to classical conditioning requires: control software that will repeatedly generate stimulus events, and analog-to-digital (A/D) recording capabilities for the resolution of analog data from phasic response systems (e.g., nictitating membrane extension, leg flexion). An earlier software package implemented on a 4K PDP-8/E (Millenson, Kehoe, Tait, & Gormezano, 1973) successfully met these requirements. However, the program’s capabilities were restricted to the presentation of only two unique stimuli with a maximum of 4 sec duration, and data reduction in only uniphasic response systems. The present program, employing the same hardware, relaxed these previous constraints and extended the range of data analysis through the revamping of the interactive assembler, operating system, and on-line data processing routines.