Adrian Morrison - US grants

We are studying the structures and mechanisms in the caudal brainstem underlying the muscular atonia that characterizes rapid eye movement, or paradoxical sleep (PS), using electrophysiological and behavioral methods. Small bilateral dorsolateral pontine electrolytic lesions eliminate the characteristic atonia of PS, resulting in expression of such behaviors during that state as head lifting, orienting, staring, body righting, pawing, biting, forelimb support, attack and even quadrupedal walking. Other elements of PS remain intact. Behaviors expressed in PS without atonia depend upon the exact locations of lesions. We have presented evidence indicating that at least three systems are affected by the lesions: that inhibiting spinal motor neurons, a brainstem locomotor system, and in some cats one modulating aggressive behavior. We plan to dissect further the phenomenon of PS without atonia by means of thermal, knife cut and chemical lesions and electrical and chemical stimulation. Using the mircowire single unit recording technique we shall also study noradrenergic neurons in the locus coeruleus during normal PS and PS without atonia as a follow-up to our study of serotonergic dorsal raphe cells. The latter study revealed that silence of dorsal raphe neurons in PS could, in large part, be reversed by elimination of atonia in PS, indicating that dorsal raphe silence is somehow related to motor inhibiton. We shall look for similar relationships in the locus coeruleus. We shall also test for homogeneity or heterogeneity of noradrenergic cellular activity across sleep-waking states by recording from neurons in another nucleus, A5. Our long-term interest is to understand motor control during sleep and the pathophysiology of certain sleep disorders, in particular, narcolepsy.

The objective of this project is to further understanding of the nature of paradoxical sleep (PS), also known as rapid eye movement (REM) sleep. PS is a curious state in which the brain's activity resembles in many respects that observed during the orientation reaction to stimuli during wakefulness (W) without, of course, interactions with the external world. Cats prepared with chronic recording electrodes will be used to study the properties of a waveform (PGO wave) recorded in the lateral geniculate body originally thought to be solely a spontaneous event in PS, but which we have shown to be evokable by acoustic stimuli in both slow wave sleep and PS. We have also found that a wave form in W assumes characteristics similar to those of PGO waves when a cat is alerted. In W the response to stimuli habituates, but preliminary evidence indicates that PGO waves may not. Lack of habituation at the brainstem level may be a feature of PS, with arousal into W prevented by some mechanism at a higher level of the nervous system. Because we can eliminate the usual paralysis of PS by means of pontine lesions and thereby observe elaborate behavior in that state, we may also have a behavioral measure of responses to stimuli in PS as well as W. At a superficial level PGO waves bear a resemblance to the acoustic startle reflex in their response to pharmacologic manipulation with serotonergic agents. The wealth of more sophisticated pharmacologic data obtained in studies of the startle reflex will be used to compare properties of PGO waves and startle in an effort to determine how each is related to the basic process of alerting of the nervous system. Traumatic stress disorder, occasioned by emotionally powerful experiences, provide an especially promising area for clinical application of basic research in sleep and alerting. Stress disorder, such as the so-called "war-neurosis" (post-traumatic stress syndrome), commonly includes both prominent sleep disturbances like nightmares and extreme ease of startle. These illnesses are often refractory to behavioral and pharmacological interventions. Our hope is that clarifying the behavioral and pharmacological properties of alerting as a "paradoxical" phenomenon of one phase of sleep will contribute to the rational treatment of these costly and very painful conditions.

DESCRIPTION (provided by applicant): The overall objective of this project is to understand the manner in which amygdalar processing of sensory inputs modulates basic sleep-wake mechanisms. We propose to use cued fear conditioning (CFC) as an experimental paradigm for studying the more general role of the amygdala (AMY) in determining an organism's responsiveness to its environment. Specifically, we shall study changes in REM sleep (REM) after fear conditioning in rats, and related behavioral changes during wakefulness (W). In the current proposal, we focus on the lateral nucleus (LA) of AMY. As a first aim, we shall study a group of rats according to a standard CFC protocol. We shall expand our neurobehavioral assessment of these animals to include REM phasic activity during sleep and ultrasonic vocalizations (USV), novelty detection and freezing behavior during W. As a second aim, we shall study the same measures during sleep and W in a group of rats with complete bilateral electrolytic lesions of LA. We shall repeat the lesion study by making cytotoxic lesions with ibotenic acid in order to determine whether the changes observed with the former lesions originate from cellular destruction and not fiber damage. To demonstrate that LA lesions interfere with the fear conditioning of sleep-wake specifically by interrupting conditioned stimulus (CS)-unconditioned stimulus (US) associations during training, we shall, in another group of rats, make temporary bilateral lesions of LA using a local anesthetic, lidocaine, immediately before training in the CFC protocol. There is evidence that serotonin (5-HT) plays an important role in mechanisms of LA activation and inhibition, possibly by exciting GABAergic interneurons that synapse on LA principal cells. As a third aim we shall explore the modulatory role of 5-HT in the CS-US association process that occurs during training in the CFC protocol and alters sleep-wake behavior. In 1 experiment, we will inject 5-HT into LA bilaterally immediately before training a group of rats. In a second experiment, we shall inject 5-HT together with a nonspecific serotonergic antagonist. In order to begin to delineate the cellular mechanisms of 5-HT's actions, we will, in a third experiment, inject 5-HT together with a GABAA antagonist. This proposal has particular relevance to human mental disorders that arise in the aftermath of a psychologically stressful experience and involve significant abnormalities in sleep-wake behavior and the microarchitecture of sleep. In particular, we expect to gain insight into the sleep disturbance in posttraumatic stress disorder (PTSD), which is often intractable to currently available psychotherapeutic and pharmacological treatments. Primary insomnia also may be a sequel to a stressful experience, and REM interruption insomnia may occur in some individuals with PTSD. It is very important to investigate the serotonergic modulation of CFC in animals because drugs that influence 5-HT function have widespread acceptance for treating PTSD yet little is known about their actions in related animal models.