A study of possible interactions between the pineal gland and the opioidergic system
- Authors: Khan, Razeeya B
- Date: 1990
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3729 , http://hdl.handle.net/10962/d1001468
- Description: Recent observations suggest a link between the pineal gland and the opioid system. Possible areas of interaction between the pineal gland and the opioidergic system in Wistar rats were investigated. The effect of opioids on the pineal gland in organ culture was monitored. Neither morphine, methadone nor the opioid antagonist naloxone was found to affect [¹⁴C]-serotonin metabolism by the pineal gland in vitro. Both the pineal gland and the opioid system are influenced by exposure to stressful stimuli. Morphine and melatonin had protective effects on stress-induced gastric lesions. The ability of melatonin to inhibit lesion formation was found not to be exerted via an opioidergic mechanism. Evidence has been obtained for a possible modulation of the stress response by the pineal gland . The opioid drugs are the most potent analgesic agents available. A possible interaction between the opioid system and the pineal gland in the modulation of the response to noxious stimuli was investigated. An intact pineal gland was found to be necessary for the manifestation of the nocturnally increased response of rats to noxious stimuli
- Full Text:
- Date Issued: 1990
- Authors: Khan, Razeeya B
- Date: 1990
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3729 , http://hdl.handle.net/10962/d1001468
- Description: Recent observations suggest a link between the pineal gland and the opioid system. Possible areas of interaction between the pineal gland and the opioidergic system in Wistar rats were investigated. The effect of opioids on the pineal gland in organ culture was monitored. Neither morphine, methadone nor the opioid antagonist naloxone was found to affect [¹⁴C]-serotonin metabolism by the pineal gland in vitro. Both the pineal gland and the opioid system are influenced by exposure to stressful stimuli. Morphine and melatonin had protective effects on stress-induced gastric lesions. The ability of melatonin to inhibit lesion formation was found not to be exerted via an opioidergic mechanism. Evidence has been obtained for a possible modulation of the stress response by the pineal gland . The opioid drugs are the most potent analgesic agents available. A possible interaction between the opioid system and the pineal gland in the modulation of the response to noxious stimuli was investigated. An intact pineal gland was found to be necessary for the manifestation of the nocturnally increased response of rats to noxious stimuli
- Full Text:
- Date Issued: 1990
A study of the effects of the pineal hormone, melatonin, on dopaminergic transmission in the central nervous system of rats
- Authors: Burton, Susan Frances
- Date: 1990
- Subjects: Dopaminergic mechanisms Melatonin Pineal gland -- Secretions Neural transmission Pineal gland Nervous system
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3726 , http://hdl.handle.net/10962/d1001463
- Description: Dopamine mechanisms in the central nervous system are important in the control of both normal and abnormal motor function. The recent observations in both animal and human studies, that melatonin, the principal hormone of the pineal gland, may have a role in the control of movement and the pathophysiology of movement disorders, have given rise to the concept that melatonin may have a modulatory influence on central dopaminergic neurotransmission. This study makes use of three animal behavioural models as well as a biochemical model of central dopaminergic function to further investigate the concept. Results from studies using the biochemical model, which investigated the effect of melatonin on dopamine and apomorphine stimulation of dopamine-sensitive adenylate cylase, suggest that melatonin is neither a competitive antagonist nor agonist at the D₁ receptor level, although the possibility of physiological stimulation or antagonism is not excluded. In behavioural studies, prior melatonin mg/kg administration (1 and 10 (8M) ip) inhibited apomorphine induced stereotypy and locomotor activity in normal rats, and apomorphine-induced rotational behaviour in 6-hydroxydopamine and quinolinic acid lesioned rats. The possibility that these results may have physiological significance is borne out by the observation that, under enviromental lighting conditions that are associated with raised endogeous melatonin levels, apomorphine- induced stereotypy and locomotor activity is attenuated. The general conclusion is that melatonin has an inhibitory influence on central nervous system dopaminergic function, suggesting therefore, that the pineal gland and melatonin may have a role in the pathophysiology and treatment of movement and behavioural disorders associated with dopaminergic dysfunction
- Full Text:
- Date Issued: 1990
- Authors: Burton, Susan Frances
- Date: 1990
- Subjects: Dopaminergic mechanisms Melatonin Pineal gland -- Secretions Neural transmission Pineal gland Nervous system
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3726 , http://hdl.handle.net/10962/d1001463
- Description: Dopamine mechanisms in the central nervous system are important in the control of both normal and abnormal motor function. The recent observations in both animal and human studies, that melatonin, the principal hormone of the pineal gland, may have a role in the control of movement and the pathophysiology of movement disorders, have given rise to the concept that melatonin may have a modulatory influence on central dopaminergic neurotransmission. This study makes use of three animal behavioural models as well as a biochemical model of central dopaminergic function to further investigate the concept. Results from studies using the biochemical model, which investigated the effect of melatonin on dopamine and apomorphine stimulation of dopamine-sensitive adenylate cylase, suggest that melatonin is neither a competitive antagonist nor agonist at the D₁ receptor level, although the possibility of physiological stimulation or antagonism is not excluded. In behavioural studies, prior melatonin mg/kg administration (1 and 10 (8M) ip) inhibited apomorphine induced stereotypy and locomotor activity in normal rats, and apomorphine-induced rotational behaviour in 6-hydroxydopamine and quinolinic acid lesioned rats. The possibility that these results may have physiological significance is borne out by the observation that, under enviromental lighting conditions that are associated with raised endogeous melatonin levels, apomorphine- induced stereotypy and locomotor activity is attenuated. The general conclusion is that melatonin has an inhibitory influence on central nervous system dopaminergic function, suggesting therefore, that the pineal gland and melatonin may have a role in the pathophysiology and treatment of movement and behavioural disorders associated with dopaminergic dysfunction
- Full Text:
- Date Issued: 1990
Effect of anticonvulsant agents on pineal gland indole metabolism
- Authors: Morton, Dougal John
- Date: 1983
- Subjects: Pineal gland -- Metabolism Anticonvulsants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3844 , http://hdl.handle.net/10962/d1009518
- Description: Preface: The general indications that the pineal gland might be involved in homeostasis, and more specifically the evidence suggesting a role in amelioration of seizure states warranted further investigation . No reports had examined a possible link between anticonvulsant drug administration and pineal gland function, and few enabled any type of presumption to be made as to possible effects. This study was an attempt to evaluate in which ways anticonvulsant drugs might alter pineal gland indole metabolism, with a view to increasing understanding of the role of the pineal in modulation of epileptic discharges. In order to make the study as meaningful as possible extensive preliminary investigations were necessary. Pharmacokinetic determinations gave an indication of tissue concentrations of the drugs, which could then be related to observed effects. As far as possible, where existing information was lacking, the catalytic behaviour of the various enzymes was characterised in order to explain any observed effects at a molecular level. An attempt was also made to characterise the regulatory mechanisms controlling indole metabolism, again in order to define the pharmacological effects exerted by the drugs used. The complexity of the system made it impossible to suggest a single uniform regulatory hypothesis, although some significant observations were made. Finally, the studies involving the anticonvulsant drugs were conducted on intact animals, isolated organs and individual enzymes in an attempt to determine whether the observed effects were occuring at a molecular, local or central level.
- Full Text:
- Date Issued: 1983
- Authors: Morton, Dougal John
- Date: 1983
- Subjects: Pineal gland -- Metabolism Anticonvulsants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3844 , http://hdl.handle.net/10962/d1009518
- Description: Preface: The general indications that the pineal gland might be involved in homeostasis, and more specifically the evidence suggesting a role in amelioration of seizure states warranted further investigation . No reports had examined a possible link between anticonvulsant drug administration and pineal gland function, and few enabled any type of presumption to be made as to possible effects. This study was an attempt to evaluate in which ways anticonvulsant drugs might alter pineal gland indole metabolism, with a view to increasing understanding of the role of the pineal in modulation of epileptic discharges. In order to make the study as meaningful as possible extensive preliminary investigations were necessary. Pharmacokinetic determinations gave an indication of tissue concentrations of the drugs, which could then be related to observed effects. As far as possible, where existing information was lacking, the catalytic behaviour of the various enzymes was characterised in order to explain any observed effects at a molecular level. An attempt was also made to characterise the regulatory mechanisms controlling indole metabolism, again in order to define the pharmacological effects exerted by the drugs used. The complexity of the system made it impossible to suggest a single uniform regulatory hypothesis, although some significant observations were made. Finally, the studies involving the anticonvulsant drugs were conducted on intact animals, isolated organs and individual enzymes in an attempt to determine whether the observed effects were occuring at a molecular, local or central level.
- Full Text:
- Date Issued: 1983
The evaluation of melatonin as a possible antidepressive
- Authors: Skene, Debra Jean
- Date: 1980
- Subjects: Melatonin , Antidepressants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3728 , http://hdl.handle.net/10962/d1001465
- Description: Melatonin, a hormone of the pineal gland, was evaluated in a variety of animal models of depression. Measurements of the frog righting reflex and rat locomotor activity showed that low doses of melatonin have a serotonin-like potentiating effect following monoamine oxidase inhibition. High doses of melatonin caused a reduction in the duration of rat immobility in the Porsolt model of depression and exerted a chlorpromazine-like effect on conditioned avoidance behaviour. In view of the indoleamine hypothesis of depressive disorders, the possibility of melatonin being a potential antidepressive is discussed and it is concluded that melatonin might be useful in the treatment of "agitated" depressions
- Full Text:
- Date Issued: 1980
- Authors: Skene, Debra Jean
- Date: 1980
- Subjects: Melatonin , Antidepressants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3728 , http://hdl.handle.net/10962/d1001465
- Description: Melatonin, a hormone of the pineal gland, was evaluated in a variety of animal models of depression. Measurements of the frog righting reflex and rat locomotor activity showed that low doses of melatonin have a serotonin-like potentiating effect following monoamine oxidase inhibition. High doses of melatonin caused a reduction in the duration of rat immobility in the Porsolt model of depression and exerted a chlorpromazine-like effect on conditioned avoidance behaviour. In view of the indoleamine hypothesis of depressive disorders, the possibility of melatonin being a potential antidepressive is discussed and it is concluded that melatonin might be useful in the treatment of "agitated" depressions
- Full Text:
- Date Issued: 1980
Adreno-active substances and the pineal gland
- Authors: Midlane, Graham Wallace
- Date: 1979
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3738 , http://hdl.handle.net/10962/d1001530
- Description: The pineal gland, a biochemically very active neuroendocrine transducer which is innervated by the sympathetic nervous system, was used in vivo to evaluate the effect of different þ-adrenoceptor agonists and antagonists on pineal enzyme levels. Hydroxyindole-O-methyltransferase (HIOMT), an enzyme with a circadian activity and unknown control was not significantly affected by these drugs. The activity of serotonin N-acetyltransferase, another pineal enzyme with a greater amplitude of circadian rhythmicity and which is under noradrenergic neural control, the degree of blockade depending on the selectivity and affinity of the agent used. An attempt was also made to alter the oestrous cycle of the rat by dosing with þ-active substances. Only propranolol had any effect on the oestrous cycle. It was not possible to establish an absolute link between the alteration in pineal enzyme activity and an influence on the oestrous cycle. It was concluded that the pineal enzyme studies are useful pharmacological means for evaluating þ-active substances
- Full Text:
- Date Issued: 1979
- Authors: Midlane, Graham Wallace
- Date: 1979
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3738 , http://hdl.handle.net/10962/d1001530
- Description: The pineal gland, a biochemically very active neuroendocrine transducer which is innervated by the sympathetic nervous system, was used in vivo to evaluate the effect of different þ-adrenoceptor agonists and antagonists on pineal enzyme levels. Hydroxyindole-O-methyltransferase (HIOMT), an enzyme with a circadian activity and unknown control was not significantly affected by these drugs. The activity of serotonin N-acetyltransferase, another pineal enzyme with a greater amplitude of circadian rhythmicity and which is under noradrenergic neural control, the degree of blockade depending on the selectivity and affinity of the agent used. An attempt was also made to alter the oestrous cycle of the rat by dosing with þ-active substances. Only propranolol had any effect on the oestrous cycle. It was not possible to establish an absolute link between the alteration in pineal enzyme activity and an influence on the oestrous cycle. It was concluded that the pineal enzyme studies are useful pharmacological means for evaluating þ-active substances
- Full Text:
- Date Issued: 1979
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