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Biomedical subjects

B L Jacobs

Publications and source records attributed to B L Jacobs.

At least 145 records · Page 8Linked to original sources
PubMed1981

Raphe unit activity during REM sleep in normal cats and in pontine lesioned cats displaying REM sleep without atonia.

Previous studies have shown that the activity of serotonin-containing raphe neurons in cats is almost completely suppressed during rapid eye movement (REM) sleep. However, since raphe unit activity is known to be grossly correlated with the level of behavioral arousal or tonic motor activity, this decrease in activity during REM sleep may be simply due to the fact that tonic EMG activity or motoric output is at a minimum. On the other hand, raphe unit activity may be related to the state (i.e. REM sleep) of the organism. To test these competing hypotheses, in the present study we compared raphe unit activity in normal cats with that in cats that display REM sleep without atonia (produced by bilateral lesions of the pontine tegmentum). These lesioned cats manifest episodes which, by all criteria, appear to be REM sleep except that they display overt behavior, presumably because the mechanism normally responsible for producing atonia has been disrupted. Although the activity of raphe neurons in lesioned cats during REM sleep without atonia was significantly below that seen in these cats during waking, the level of activity was often impressive. This is especially true when those animals that displayed the greatest degree of tonic motor activity during REM sleep (group IV animals) are considered separately. In these cats, the depression was only 40.5% below their quiet waking level, whereas in lesioned cats displaying less tonic motor activity (Group II animals), raphe discharge rate was 65.6% below their quiet waking level. The discharge rate of raphe neurons during REM sleep in lesioned cats was more than 6-fold greater than that seen in normal animals. These data, in conjunction with other recent results from our laboratory, suggest that the decrease in raphe unit activity during REM sleep is largely a concomitant of the atonia which characterizes that state. These data are discussed within the general context of the relationship between raphe unit discharge and the activity of central motor systems.

Animals↗
PubMed1981

Effects of adrenergic drugs on raphe unit activity in freely moving cats.

Previous work has suggested that central noradrenergic neurons may have an important influence on the activity of serotonergic neurons located in the dorsal raphe nucleus. Pharmacological studies have indicated that an alpha -adrenergic input is necessary to maintain the activity of these raphe cells. This issue was examined in freely moving cats by studying the effects of adrenergic drugs on raphe unit activity. Systemic administration of the selective alpha 1-antagonists WB4101 (0.5 and 1.0 mg/kg) or prazosin (10 mg/kg), or the non-competitive antagonist phenoxybenzamine (10 mg/kg), produced strong behavioral effects but had little effect on raphe unit activity. A low dose of the alpha -agonist clonidine (0.05 mg/kg), which decreases adrenergic transmission, produced similar results. These same drugs also had negligible effects on the evoked responses of raphe units to auditory or visual stimulation. Administration of d-amphetamine, a catecholamine releaser, produced behavioral stereotypy but had no significant effect on the discharge of raphe units. These data suggest that the adrenergic influence on serotonergic raphe neurons is very small in the freely moving cat. This is in contrast to the reported complete suppression of unit activity produced by alpha -adrenergic blockade in the chloral hydrate anesthetized rat.

Adrenergic alpha-Antagonists↗
PubMed1981

Dissociations between the effects of hallucinogenic drugs on behavior and raphe unit activity in freely moving cats.

The hypothesis that the action of hallucinogenic drugs is mediated by a depression of the activity of brain serotonergic (raphe) neurons was tested by examining the behavioral effects of several hallucinogenic drugs while concurrently monitoring the activity of raphe neurons in freely moving cats. LSD produced a dose-dependent decrease in raphe unit activity and a dose-dependent increase in certain behaviors (e.g. limb flick and abortive groom), and the peak of the behavioral and unit changes were temporally correlated. However, there were three important dissociations between the behavioral and electrophysiological effects of LSD. Firstly, low doses of LSD produced only small decreases in raphe unit activity but significant behavioral changes. Secondly, the duration of LSD-induced behavioral changes significantly outlasted the depression of raphe unit activity. And thirdly, raphe neurons were at least as responsive to LSD during tolerance as they were in the nontolerant condition. Psilocin produced a dose-dependent decrease in raphe unit activity, while the behavioral changes were not dose-related. However, the peak behavioral changes corresponded to the maximal depression of raphe unit activity. The phenylethylamine hallucinogens, DOM and mescaline, both produced large behavioral changes but no overall effect on raphe neurons. Following administration of DOM or mescaline, some raphe units showed a significant increase, while some showed a significant decrease, and others showed no change in activity. Therefore, the phenylethylamine hallucinogens may exert a depressant effect upon a subset of serotonin-containing neurons, and an amphetamine-like excitatory effect upon another subset of these neurons. Consistent with previous studies, all hallucinogens produced a high concentration of slow waves in the cortical EEG. Following administration of LSD or psilocin, the appearance of slow waves in the EEG was often associated with a transitory decrease in unit activity, while this was not observed for the phenylethylamine hallucinogens. The present data, in conjunction with recent data from other laboratories, suggest that the serotonin hypothesis of hallucinogenic drug action should be re-evaluated.

DOM 2,5-Dimethoxy-4-Methylamphetamine↗
PubMed1981

Cats develop tolerance to d-amphetamine's effects upon locomotion and stereotyped behaviors.

Administration of d-amphetamine sulfate (7.5 mg/kg i.p.) twice daily to cats produces an initial large increase in both locomotion and behavioral stereotypy. As this regimen continues beyond three days, however, both measures show large significant decreases. We hypothesize that this tolerance to the behavioral effects of amphetamine is attributable to the concomitant decrease (approx. 70%) in presynaptic stores of dopamine and norepinephrine.

Animals↗
PubMed1981

Activity of a non-hallucinogenic ergoline derivative, lisuride, in an animal behavior model for hallucinogens.

The behavioral effects of IP administration of lisuride, a non-hallucinogenic iso-lysergic acid amide analog structurally related to d-lysergic acid diethylamide (LSD), were examined in 15 cats. Ten animals were given saline or 6.25, 12.5, 25, 50, or 100 micrograms/kg of lisuride and observed for 1 h by a rater blind to dose. There was a statistically significant effect of lisuride dose on the frequency of occurrence of the behaviors limb flicking, grooming, and abortive grooming. A time-course study with five cats at the most effective lisuride dose, 50 micrograms/kg, revealed that the frequencies of occurrence of these behaviors reached a maximum during the first 2 h post dose, and were comparable to frequencies after saline by 6 h post dose. An acute tolerance study with four cats scored for 90 min post dose revealed no significant tolerance to a 50 micrograms/kg lisuride test dose administered 6, 24, or 72 h after an initial 50 micrograms/kg dose. Acute cross tolerance studies with four cats scored for 90 min after an initial dose of 50 micrograms/kg of LSD or of lisuride, followed 24 h later by 50 micrograms/kg of lisuride or LSD, revealed no significant cross tolerance. The potency of lisuride relative to LSD was evaluated in six cats that were scored for 60 min following 25 and 50 micrograms/kg of LSD and of lisuride. On a molar basis, scores after lisuride were 51% and 67% those after LSD for limb flicking and grooming. These results indicate that lisuride, a non-hallucinogenic iso-lysergic acid derivative, is a false positive in the animal behavior model for hallucinogens.

Animals↗
PubMed1981

Behavioral and physiological correlates of brain serotoninergic unit activity.

Raphe unit activity in rats and cats displays a slow and regular discharge pattern across a variety of situations. The activity is, however, state-dependent, displaying a marked reduction during slow wave sleep and almost complete quiescence during REM sleep. Other than the level of synaptic serotonin, very little is known about the physiological variables affecting these neurons. Behaviorally, raphe neuron activity is correlated with arousal or tonic motor activity, and appears to be driven by phasic afferent input. It is hypothesized that these neurons exert a general modulatory role upon physiology and behavior.

Animals↗
PubMed1979

Long-term amphetamine treatment decreases brain serotonin metabolism: implications for theories of schizophrenia.

Long-term amphetamine administration to cats (a mean of 8.75 milligrams per kilogram twice daily for 10 days) produced large decreases (40 to 67 percent in serotonin and its major metabolite, 5-hydroxyindoleacetic acid, in all brain regions examined. This treatment also produced several behaviors that are dependent on depressed central serotonergic neurotransmission, and which normally are elicited exclusively by hallucinogenic drugs. Short-term amphetamine administration (15 mg/kg) did not produce these behaviors and resulted in small decreases in brain serotonin and no change in 5-hydroxyindoleacetic acid. These data are discussed in the context of monoamine theories of schizophrenia.

Animals↗
PubMed1979

Dissociations between the effects of LSD on behavior and raphe unit activity in freely moving cats.

The hypothesis that the action of hallucinogenic drugs is mediated by a depression of the activity of brain serotonergic (raphe) neurons was tested by examining the behavioral effects of d-lysergic acid diethylamide (LSD) while studying the activity of raphe neurons in freely moving cats. Although the results provide general support for the hypothesis, there were several important dissociations. (i) Low doses of LSD produced only small decreases in raphe unit activity but significant behavoiral changes; (ii) LSD-induced behavioral changes outlasted the depression of raphe unit activity; and (iii) raphe neurons were at least as responsive to LSD during tolerance as they were in the nontolerant condition.

Animals↗
PubMed1979

Raphe unit activity in freely moving cats: correlation with level of behavioral arousal.

Dorsal raphe unit activity in freely moving cats showed a slow, rhythmic discharge rate during quiet waking (X=2.82 +/- 0.17 spikes/sec), and displayed a strong positive correlation with level of behavioral arousal. Presentation of an auditory stimulus during quiet waking resulted in significant increases in unit activity of 112% and 39% during the first sec and first 10 sec after the stimulus, respectively. This effect rapidly habituated with repeated stimulus presentations. During active waking, unit activity was significantly increased by 22% as compared to quiet waking, but there was no correlation between unit activity and gross body movements. Raphe unit activity showed a significant decrease of 17% during drowsiness (first appearance of EEG synchronization) as compared to quiet waking, and then progressive decreases during the early (--34%), middle (--52%) and late (--68%) phases of slow wave sleep. During all phases of slow wave sleep, the occurrence of sleep spindles was frequently associated with a transitory decrease in unit activity. The discharge rate would typically decrease during the few seconds immediately preceding the spindle, remains at this low level during the occurrence of the spindle, and then increase immediately after the spindle. Raphe unit activity showed decreases of 81% during pre-REM (the 60 sec immediately before REM onset) and 98% during REM, as compared to quiet waking. Unit activity reappeared 3.2 sec before the end of REM, with significant increases in unit activity of 83% and 17% during the first sec and first 10 sec of unit activity, respectively, as compared to quiet waking. The results of these studies are discussed in relation to the hypothesis that serotonin may play a modulatory, rather than mediative, role in behavioral and physiological processes.

Animals↗
PubMed1979

Effects of 5-methoxy-N,N-dimethyltryptamine on behavior and raphe unit activity in freely moving cats.

5-methoxy-N,N-dimethyltryptamine (5-MeODMT) produced a dose-dependent decrease in the discharge rate of serotonin-containing neurons in the dorsal raphe nucleus of freely moving cats. This ranged from a 15% decrease at 10 microgran/kg, i.m., to a virtual complete depression of activity at 250 microgram/kg. 5-MeODMT's effects on raphe units occurred with a very short latency (3-5 min) and its duration of action was dose-dependent and limited to an hour or less. The degree of depression of raphe unit activity was directly related to the frequency of occurrence of a number of hallucinogen-specific cat behaviors such as limb flick and abortive groom. There was also a close temporal correlation between the depression of raphe unit activity and the occurrence of these behaviors. These data indicate that the effects of 5-MeODMT may be primarily dependent on its actions upon brain serotonin neurons.

Animals↗
PubMed1979

Chronic amphetamine administration to cats: behavioral and neurochemical evidence for decreased central serotonergic function.

Chronic administration of amphetamine to cats (twice daily, in doses increasing from 5 to 15 mg/kg over a 10-day period) elicited a number of behaviors, e.g., limb flick and abortive groom, characteristic of the action of hallucinogenic drugs and dependent on a depression of central serotonergic neurotransmission. This drug treatment produced large decreases (-40 to -60%) in central nervous system serotonin (5-HT) and its major metabolite, 5-hydroxyindoleacetic acid (5-HIAA), when measured either 6 or 24 hr after the last amphetamine injection. The rate of limb flicking returned to a predrug level approximately 5 days after drug withdrawal, at which time 5-HT and 5-HIAA levels had returned to within 30 to 40% of base line. Both 5-HT and 5-HIAA returned to base-line levels within 14 days after drug withdrawal. Norepinephrine (NE), dopamine (DA) and DA metabolites were decreased 60 to 95% by chronic amphetamine treatment and showed little recovery within the 14 days after drug withdrawal. A second experiment examined the latency to onset of the behavioral and neurochemical changes with a constant dose of amphetamine (7.5 mg/kg, twice daily). Limb flicking was significantly increased above base-line levels following 3 days of amphetamine administration, at which time 5-HT and 5-HIAA levels were decreased 30 to 40%. NE, DA and DA metabolites were decreased approximately 50 to 90% by this treatment regimen. A third experiment examined the effects of a low dose of amphetamine (3.75 mg/kg), injected more frequently (every 6 hr for 6 days), to approximate the administration pattern in human amphetamine abuse. This treatment produced significant increases in limb flicking and abortive grooming on days 5 and 6 and resulted in 30 to 40% depletions of 5-HT and 5-HIAA. NE, DA and DA metabolites were decreased by approximately 50 to 90%. These data are discussed in relation to a role for serotonin in amphetamine psychosis and schizophrenia.

Animals↗