Short-term effects of intrahypothalamic colchicine

A Hypothesis Regarding Neurosecretory Inhibition of Stress Mediators by Colchicine in Preventing Stress-Induced Familial Mediterranean Fever Attacks

Familial Mediterranean fever (FMF) is a monogenic autoinflammatory disease characterized by recurrent episodes of fever and serositis. Colchicine (Col) has a crucial role in the prevention of amyloidosis and FMF attacks. The effect of Col on innate immune cells is based on the inhibition of the microtubule system. The microtubule system is also very important for neurosecretory functions. The inhibitory effect of Col on neurosecretory functions is an overlooked issue. Considering that the neuroimmune cross-talk process plays a role in the development of inflammatory diseases, the effect of Col on the neuronal system becomes important. FMF attacks are related to emotional stress. Therefore, the effect of Col on stress mediators is taken into consideration. In this hypothetical review, we discuss the possible effects of Col on the central nervous systems (CNS) and peripheral nervous systems (PNS) in light of mostly experimental study findings using animal models. Studies to be carried out on this subject will shed light on the pathogenesis of FMF attacks and the other possible mechanisms of action of Col apart from the anti-inflammatory features.

Cardiovascular effects of catecholamines injected into the DBB of rats, influence of urethane anaesthesia and local colchicine

In a previous publication it was shown that 1 microgram colchicine injected into the diagonal band of Broca (DBB) produced a significant decrease in femoral artery blood pressure (and/or volume) measured in urethane-anaesthetised rats. In order to test if the central catecholamines were involved in this effect, guide cannulae were implanted in the DBB and a catheter in the femoral artery. On-line pressure recordings were taken before during and after alpha1, alpha2 and beta adrenoreceptor agonists and antagonists were injected into the region of the DBB of non-anaesthetised and urethane anaesthetised male Wistar rats with and without injection of colchicine. Arterial pressure was significantly increased in the non-anaesthetised rats (114.6+/-2.6 n=11 vs. 149.3+/-3.3 mmHg n=12, p<0.01) yet significantly reduced (82.0+/-3.9 n=11 vs. 63.8+/-4.5 mmHg n=12, p<0.01) in the urethane treated rats by the alpha2 agonist clonidine. The alpha2 antagonist yohimbine blocked these effects in both preparations. In contrast, the beta adrenoreceptor agonist isoprenaline produced a significant decrease in arterial pressure in both preparations (107.7+/-3.9 n=11 vs. 85.9+/-4.0 mmHg n=12, p<0.01) (102.6+/-6.7 n=11 vs. 81.7+/-3.4 mmHg n=12, p<0.01) and this effect was blocked by the beta antagonist propranolol. Colchicine injected into the DBB abolished the effects of the alpha2 agonist and antagonist in the non-anaesthetised but not the anaesthetised rats. The responses to the beta agonist and antagonist were not greatly affected by the colchicine in the non-anaesthetised rats whereas in the anaesthetised rat beta agonist injection tended to totally depress arterial pressure. These results suggest that the sympathetic nervous system in the DBB plays a significant role in the central control of arterial pressure and that the alpha2 component is significantly affected by the state of anaesthesia.

Orphan neurones and amine excess: the functional neuropathology of Parkinsonism and neuropsychiatric disease

The aetiology and treatment of Parkinsonism is currently conceptualised within a dopamine (DA) deficiency-repletion framework. Loss of striatal DA is thought to cause motor impairment of which tremor, bradykinaesia and rigidity are prominent features. Repletion of deficient DA should at least minimise parkinsonian signs and symptoms. In Section 2, based on extensive pre-clinical and clinical findings, the instability of this approach to Parkinsonism is scrutinised as the existing negative findings challenging the DA deficiency hypothesis are reviewed and reinterpreted. In Section 3 it is suggested that Parkinsonism is due to a DA excess far from the striatum in the area of the posterior lateral hypothalamus (PLH) and the substantia nigra (SN). This unique area, around the diencephalon/mesencephalon border (DCMCB), is packed with many ascending and descending fibres which undergo functional transformation during degeneration, collectively labelled 'orphan neurones'. These malformed cells remain functional resulting in pathological release of transmitter and perpetual neurotoxicity. Orphan neurone formation is commonly observed in the PLH of animals and in man exhibiting Parkinsonism. The mechanism by which orphan neurones impair motor function is analogous to that seen in the diseased human heart. From this perspective, to conceptualise orphan neurones at the DCMCB as 'Time bombs in the brain' is neither fanciful nor unrealistic [E.M. Stricker, M.J. Zigmond, Comments on effects of nigro-striatal dopamine lesions, Appetite 5 (1984) 266-267] as the DA excess phenomenon demands a different therapeutic approach for the management of Parkinsonism. In Section 4 the focus is on this novel concept of treatment strategies by concentrating on non-invasive, pharmacological and surgical modification of functional orphan neurones as they affect adjacent systems. The Orphan neurone/DA excess hypothesis permits a more comprehensive and defendable interpretation of the interrelationship between Parkinsonism and schizophrenia and other related disorders.

Colchicine injected into the anterior forebrain in rats decreases blood pressure without changing the responses to haemorrhage

In a previous publication rats were shown to develop a marked positive sodium balance 6 days after injection of 1 microgram colchicine into their anterior forebrains. This was thought to be the normal hydromineral balance response to correct an hypothesised colchicine-induced decrease in blood volume (and/or pressure). To test this hypothesis, fluid and sodium intakes and excretion were measured before and then for 6 days following injection of colchicine (1 microgram in 250 nl) into the anterior forebrain, around the diagonal band of Broca, in male Wistar rats. At the end of the 6 days the animals were anaesthetised with urethane and blood pressure measured continuously before during and after a 3.5 ml haemorrhage. Blood pressure was significantly reduced (86.4 +/- 3.9 n = 11 vs. 67.7 +/- 3.4 mm Hg n = 12, p < 0.01) in the colchicine-treated rats compared to the controls and failed to recover following the haemorrhage. Measured blood parameters were similar in both colchicine-treated and nontreated groups, including plasma levels of vasopressin both before and following the haemorrhage. These results suggest that the colchicine injections may have compromised a central component of the sympathetic nervous system, thereby leading to the significant decrease in blood pressure without compensatory vasopressin release, and the lack of recovery of the decrease in blood pressure following a haemorrhage.

Effect of reserpine and colchicine on neuropeptide mRNA levels in the rat hypothalamic paraventricular nucleus

Using in situ hybridization and immunohistochemistry, we have studied mRNA and peptide levels in the hypothalamic paraventricular nucleus (PVN) 24 h after a single large dose of reserpine (10 mg/kg, i.p.) and 24 h after an intraventricular (i.c.v.) injection of colchicine (120 microliters/20 microliters saline). Sections of the PVN were hybridized using synthetic oligonucleotide probes complementary to mRNA for corticotropin-releasing hormone (CRH), neurotensin (NT), enkephalin (ENK), vasoactive intestinal polypeptide (VIP) and thyrotropin-releasing hormone (TRH). For immunohistochemistry rabbit antisera to CRH, NT, ENK, VIP and TRH were used. In situ hybridization showed a clear increase in CRH mRNA as compared to control rats after both treatments. Also NT and VIP mRNA could be seen in parvocellular neurons in reserpine and in colchicine-treated rats, whereas we so far have not been able to demonstrate these mRNAs in untreated rats. No changes in TRH mRNA could be detected after reserpine of colchicine. These results provide final evidence that subpopulations of parvocellular PVN neurons can synthesize not only CRH and ENK, but also NT and VIP, in agreement with earlier immunohistochemical results. With immunochemistry, after reserpine, many CRH-, but no NT- or VIP- positive neurons could be observed in the parvoecellular part of the PVN. The present results demonstrate that treatment with two drugs, the monoamine depleting drug reserpine and the mitosis inhibitor colchicine, causes increased levels of mRNA for several peptides in neurons of the PVN, located almost exclusively in its parvocellular part and being part of the hypothalamo-pituitary adrenal axis.

Peptidergic neurohormonal systems in the basal hypothalamus of the ferret and the mink: immunocytochemical study of variations during the annual reproductive cycle

The hypothalamic systems secreting corticotropin-releasing hormone (CRF), somatostatin, oxytocin, vasopressin and luteinizing hormone-releasing hormone (LHRH) were characterized using immunochemistry, and variations were studied in relation to the recrudescence of testicular activity in the ferret and the mink, two species with opposite photoregulation of their annual reproductive cycles. Under the present conditions of study, the immunoreactivity of the CRF, somatostatin, and oxytocin systems showed no significant variation in either species. In contrast, in these two species, the immunoreactivity of the LHRH system varied considerably depending on the date of observation. The increase in the number and immunoreactivity of the LHRH-secreting neurons that occurred in November in the mink and in January in the ferret, is in agreement with previous results showing that the photoperiod plays an essential role in regulating the annual activity of the testis and that the photoperiodic environmental conditions required for the activation of the LHRH system differ between the species. Similarly, correlations could be found between an increase in immunoreactivity of the vasopressinergic axons projecting to the external median eminence and the recrudescence of testicular activity.

The effects of a reversible colchicine-induced lesion of the anterior ventral region of the third cerebral ventricle in rats

Colchicine was injected into the region of the organum vasculosum lamina terminalis/anterior region of the third cerebral ventricle (OVLT/AV3V) to produce a temporary disruption of the nervous connections of this area and the rest of the anterior hypothalamus, but to maintain the vascular connections intact. Rats were kept in metabolism cages throughout the experiment and food and water intake plus urine and electrolyte excretion and body weight were measured each day. Food intake, body weight gain and urine and sodium excretion were reduced for several days after the injection of colchicine and the rats went into a marked positive sodium balance from the third day postinjection. Following 24 h water deprivation, 7 days after the colchicine injection, water intake was increased for 2 days. Urine and electrolyte excretion and food intake were also increased on the second day after the deprivation. Following a second deprivation, 10 days later, the colchicine-injected animals behaved as the control rats had done during both the deprivation periods. Injections of colchicine into the OVLT region of the AV3V, that would have blocked neural activity while maintaining a constant blood supply, produced some of the characteristics of a 'normal' lesion in this area; the rats decreased sodium excretion and increased their water intake in response to water deprivation. Therefore, colchicine may provide a useful means of investigating what role the constituent areas of the AV3V play in body fluid regulation.

Atrophy of the striatum and motor disturbance induced by colchicine

To determine the functional role of the striatonigral system in the circling behavior of rats and the mode of action of colchicine, we investigated the circling behavior induced by dopamine agonists after microinjection of colchicine into the unilateral striatum. Both apomorphine and methamphetamine produced ipsilateral circling behaviors in rats injected with colchicine, indicating that ipsilateral striatonigral pathways were damaged by the drug. Histological and biochemical examinations showed that intracaudate injection of colchicine damaged not only the dopaminergic neurons but also caused atrophy of the striatum with loss of neuronal perikarya. These results suggest that treatment with colchicine may be used as a model of senile atrophy or degenerative atrophy in these animals.

Time-dependent neurobiological effects of colchicine administered directly into the hippocampus of rats

Rats were given bilateral injections of colchicine into the dorsal and ventral hippocampus. Behavioral, neurochemical and histopathological measurements were taken, up to 12 weeks after surgery. Colchicine produced a consistent increase in spontaneous motor activity, enhanced acoustic startle reactivity, and accelerated acquisition of two-way shuttle box avoidance, but did not affect reactivity to a noxious thermal stimulus. Measurement of dynorphin in the hippocampus indicated that colchicine rapidly depleted this neuropeptide, which is thought to be contained preferentially in the mossy fibers of granule cells of the hippocampus. Colchicine also decreased Met-enkephalin in the hippocampus, but the magnitude of the change (22%) was less than that (89% depletion) observed for hippocampal dynorphin. Examination of hippocampal morphology using light microscopic techniques indicated that colchicine caused approximately 60% degeneration of granule cells in the hippocampus. Although the length of the pyramidal cells was decreased (12-16%), the width of the CA1 and CA3 region of the hippocampus was not affected. These data underscore the importance of the granule cells in the mediation of behavioral processes such as motor activity, startle reactivity and performance of shuttle box avoidance.

Amine accumulation in Parkinson's disease and other disorders

Amine accumulation in the axons of degenerating, amine-containing neurones is a natural component of neurone death in many species, including man. While it is becoming increasingly clear that this phenomenon may have functional significance in animal models of Parkinson's Disease, its potential importance in the clinical syndrome has been pretermitted. There are several reasons for this. Failure to sample tissue which contains accumulated amines, the masking of accumulation by adjacent depleted tissues and the degradation of accumulated amines in post-mortem tissues from Parkinsonian brains could account for the low incidence of detection of accumulation in this disorder. Increased levels of amines have been detected in the brains of patients with other conditions including cerebral infarction, Alzheimer's Disease and Huntington's Chorea. These increases have been attributed previously to enhanced aminergic activity, rather than a stage in the degenerative process, as our hypothesis suggests. In addition to the potential importance of amine accumulation in the pathophysiology of various clinical syndromes, a more thorough investigation of this phenomenon in animal models would seem essential since they are used routinely to both describe the basic principles of dopamine function and to evaluate therapeutic possibilities in Parkinson's Disease.

Denervation-like postsynaptic supersensitivity to dopamine agonists induced by microinjection of colchicine into the substantia nigra pars compacta

Circling behavior induced by dopamine (DA) agonists following microinjection of colchicine or 6-hydroxydopamine (6-OHDA) into the substantia nigra pars compacta (SNC) or electrolytic lesions of the SNC was investigated. Methamphetamine produced a contralateral circling behavior 3, 7 and 14 days following injection of colchicine into the SNC. Apomorphine produced an ipsilateral circling behavior followed by a contralateral rotation 3 and 7 days after the infusion of colchicine, whereas only an ipsilateral circling behavior was produced by apomorphine on day 14. 6-OHDA lesions of the SNC produced a contralateral circling behavior to apomorphine and an ipsilateral circling to methamphetamine, whereas both apomorphine and methamphetamine induced ipsilateral circling behaviors in rats with electrolytic lesions of the SNC. The possible mechanisms of action of colchicine are discussed in relation to the known effects of colchicine on axoplasmic transport.

The effects of colchicine in mammalian brain from rodents to rhesus monkeys

The injection of colchicine into rats and monkeys produced two different types of brain damage. At selected doses, intradentate colchicine preferentially destroyed DGC in rats, whereas damage was less selective and more severe in monkeys. Experiments were performed with different tubulin-binding drugs to investigate the structure-function relationship of tubulin binding and DGC death. The tubulin-binding characteristics of these and other drugs reported in the literature did not correlate with their ability to damage DGC. The role of seizure-induced cell death was investigated by recording the EEG in monkeys and in rats treated with phenobarbital. The data suggest that seizures are an infrequent epiphenomenon of colchicine's action. We proposed that colchicine is not a selective neurotoxin and that it causes brain damage by inducing a non-specific inflammatory response. This response is both dose- and species-dependent. We concluded by discussing the medical implications of the present and proposed uses of colchicine.

Amine accumulation in behavioural pathology

When nigro-striatal and meso-cortical neurons degenerate there is a loss of dopamine in the terminal fields and an accumulation of amines in the axons of these systems as they traverse the hypothalamus through the medial forebrain bundle. Traditional lines of thought have attributed the occurrence of motor and consummatory deficits which occur after dopamine neuron degeneration to the loss of functional dopamine neurotransmitter in the terminal fields. However, we have hypothesized that hypothalamic amine accumulation represents an area of brain tissue where processes such as neurotransmitter release, ephaptic transmission or local axon swelling may be affecting adjacent neurons and may thereby participate in the production of behavioural deficits. There is a considerable amount of evidence from studies on both peripheral and central catecholamine-containing neurons indicating that when their axons degenerate a release of functional neurotransmitter can occur. Information from neuropharmacological studies indicates that several drugs which facilitate behavioural recovery from dopamine-depleting lesions may do so by affecting amine release or receptor sensitivity near areas of accumulation rather than depleted terminal fields. We conclude that amine accumulation is a component of dopamine neuron degeneration which should be considered when assessing the role of the central catecholamine systems in the control of various behavioural and physiological processes.

Catecholamine-blocking drugs injected at sites of amine accumulation reverse catecholamine degeneration associated deficits

It has been hypothesized that catecholamine (CA) accumulation in the axons of degenerating neurons may represent areas of functional neurotransmitter, and may be producing some of the consummatory and locomotory deficits which occur after central CA-depleting lesions. To test this hypothesis further, haloperidol (0.5 microliter of a 7 nM sol.), propranolol (0.5 microliter of a 175 nM sol.) or isotonic saline (0.5 microliter) were injected 1.5 h, 24 h and 48 h after the injection of 6-hydroxydopamine (6-OHDA; 2 microliter of 8 micrograms/microliters) into the lateral hypothalamus (LH) of Sprague-Dawley rats to determine if the hypothermia, motor impairment and consummatory deficits could be reversed. Although haloperidol injection significantly enhanced the hypothermia seen 1.5 h after 6-OHDA injection, open field performance and consummatory responses were significantly improved after haloperidol was injected into the LH where accumulation is known to occur. Three consecutive days of intracerebral haloperidol treatment produced a recovery of body weight regulation lasting for 6 days. Treatment with propranolol enhanced open field performance 1 day after 6-OHDA injection but failed to enhance recovery of consummatory behaviour and body weight control. These results suggest that CA released from areas of accumulation act on adjacent CA receptors to participate in the production of behavioural deficits previously attributed only to the loss of functional neurotransmitter in terminal fields in the forebrain.

The masking of amine accumulation by catecholamine depletion

6-Hydroxydopamine (2 microliter of 8 micrograms/microliter) was injected bilaterally into the lateral hypothalamus of male Sprague-Dawley rats to produce depletion of forebrain terminal fields and an accumulation of amines proximal to the site of injection. Two additional groups of animals were injected with either vehicle or were food and water intake-matched to those receiving 6-hydroxydopamine. Motor performance, food and water intake and body weight were measured in all animals for 2 days before and 6 days after injection. Animals were then sacrificed and brain tissue was prepared for biochemical assay or fluorescence histochemistry. The area of hypothalamic tissue proximal to 6-hydroxydopamine injection, that which contains the amine accumulation, was sectioned from the surrounding tissue with a biopsy punch and assayed for noradrenaline and dopamine content. The nucleus caudatus-putamen, basomedial hypothalamus, and tissue containing the olfactory tubercle and accumbens nucleus were also assayed. Fluorescent histochemical examination of tissue showed that in addition to the depletion of catecholamines in various terminal fields there was also an increase in the fluorescent amine accumulation proximal to the injection site in the impaired animals. This accumulation was not detected with the biochemical assay and is probably due to the occurrence of a masking effect by adjacent depletions. A significant rise in noradrenaline levels was seen in the basomedial hypothalamus of intake-matched controls. However, this too was not detected in 6-OHDA-treated animals and was probably due to masking by adjacent depletions in these areas.(ABSTRACT TRUNCATED AT 250 WORDS)

A role for amine accumulation in the syndrome of ingestive deficits following lateral hypothalamic lesions

Lesions of the lateral hypothalamus produce ascending catecholamine neuron degeneration which results in terminal depletion and proximal accumulation above the lesions. The occurrence of deficits in ingestive behaviour has been attributed traditionally to the loss of functional dopamine neurotransmitter in the terminal fields. However, release of functional amines may occur in the lateral hypothalamus at areas of accumulation, to produce at least some of the behavioural symptoms characterizing the lateral hypothalamic syndrome. Recovery from behavioural deficits as a result of various pharmacological treatments, after dopamine-depleting lesions, may be mediated by changes in amine release or modified sensitivity of receptors affected by released amines. We conclude that amine accumulation should be considered when interpreting experiments implicating central catecholamine systems in the control of consumatory behaviour and the regulation of body weight.

Deficits in locomotor behaviour and thermoregulation produced by intrahypothalamic dopamine injections

When nigrostriatal dopamine neurones degenerate, a loss of functional dopamine in the striatum occurs and is accompanied by increased dopamine in the degenerating axons which traverse the hypothalamus. While the behavioural deficits which occur after nigrostriatal degeneration have been attributed to the loss of functional dopamine neurotransmission, evidence produced by us suggests that the increased levels of amines in the degenerating axons may be neuroactive and participate in the production of these behavioural deficits. To test this hypothesis further, albino rats were injected bilaterally with 200 nmol of dopamine in a location just rostral to the diencephalon/mesencephalon border, where amine accumulation is commonly observed following lateral hypothalamic damage. The effect of these injections upon open field performance, thermoregulation and motor reflex control was determined 40 min after dopamine injection. In a second study, pargyline (15 mg/kg. i.p.) was administered 30 min before intracerebral dopamine to determine whether this treatment would increase the severity of motor and thermoregulatory deficits which occurred after dopamine injections alone. Deficits in locomotion, rearing and the ability to regulate body temperature were seen after the dopamine injections while motor reflex control in these animals was similar to that seen in vehicle-injected controls. The behavioural deficits displayed by pargyline pretreated, dopamine injected animals were slightly but not significantly more severe than those displayed by animals receiving dopamine injections alone. Fluorescent histochemical assessment of injection sites revealed that dopamine injection produced an increase in fluorescence or "amine accumulation" at the site of injection but this was considerably less than that seen after catecholamine degeneration.(ABSTRACT TRUNCATED AT 250 WORDS)