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As is observed clinically, cessation of chronic clonidine treatment in the rat results in a syndrome characterized by sympathetic hyperactivity. After three weeks of chronic oral administration of clonidine, tyrosine hydroxylase (TOH) activity was unchanged in superior cervical ganglia and locus coeruleus, but was reduced (45%) in the celiac ganglia. Abrupt cessation of treatment resulted in increases in TOH activity in superior cervical and celiac ganglia (to 135 and 250% of controls) and in the locus coeruleus (170% of control). These data suggest a selective effect of clonidine treatment and withdrawal on vasomotor fibers. A mechanism explaining physical dependence on clonidine is proposed.

Fluctuations in the content and distribution of adenosine triphosphatase in the brain of mice during the period of morphine tolerance-dependence development as well as normal and and naloxone induced withdrawal have been studied. The histochemical investigation revealed the enzyme activity in the neurons, neuroglia and blood vessels. In the control animals the nucleus caudatus putamen, globus pallidus, hippocampus, nuclei of amygdala, nuclei hypothalami, substantia grisea centralis, griseum pontis, nucleus trapezoideus, nucleus prepositus hypoglossi, nucleus parabrachialis, nucleus vestibularis, nucleus nervi hypoglossi, nucleus dorsalis nervi vagi, nucleus olivaris and nucleus centralis superior are found to be very rich in ATPase. However, morphine treatment inhibited the enzyme in all the above nuclei and it was linear with the increase in dose and the duration of the treatment. Cytophotometric studies reveal that the differences in the enzymatic activity varies from nuclei to nuclei. Surprisingly enough, normal withdrawal as well as naloxone induced withdrawal significantly elevated the enzyme levels. All above findings have been confirmed biochemically. The study gives a firm support of the earlier finding that morphine inhibits ATPase. In addition to this, the present work also reveals a direct antagonistic effect of naloxone on the content of the enzyme in the morphine treated animals. This suggests that the observed inhibition of the enzyme is narcotic specific. The role of ATPase in the Na+, K+ transport is discussed with respect to morphine action. In the light of the present investigation, the effect of morphine on the neurotransmitter release, and the cause and effect there upon has been analyzed. It has been suggested that ATPase might be the enzyme responsible for the observed pharmacological responses of the neurons to the application of the drug by affecting the Na+, K+ flux and neurotransmitter release.

Fifty male alcoholics had serum dopamine-beta-hydroxylase (DBH) activity, and serum prolactin (PRL) levels measured on the day of withdrawal, and 22 of them also on days 7 and 28 after it. The obtained values were related to the development of withdrawal symptoms. Treatment was begun with meprobamate on the first day of withdrawal, and from day 7 it was completed with disulfiram (250 and 500 mg/day, respectively). Serum DBH activity decreased significantly by day 7, however a further fall of it occurred by day 28 only in patients receiving high doses (500 mg) of disulfiram. PRL levels rose over the period of withdrawal which reached significance level on day 28. No correlation was found between serum DBH activity and the severity of withdrawal symptoms. Serum DBH activity did not differ from that of the healthy controls at either point of time, while serum PRL level was significantly elevated throughout the period of the study.

The paper is concerned with a study of the enzyme activity which reflects the functional state of the liver in 123 patients with chronic alcoholism (without clinical signs of disturbed liver function). The blood serum was studied for sorbitdehydrogenase, frutose-I-phosphataldolase, glutamino-asparagine and glutamine-alanine transamine. It was established that there is an increase in the activity of specific and nonspecific liver enzymes. This increase was in a direct correlation with the clinical expression and severity of the disease (withdrawal syndrome, delirious condition). It is being concluded that the indices of the level of enzyme activity may be used for the evaluation of the state of the patients and its change under the effect of treatment.

Clinical reports indicate that cessation of treatment with the antihypertensive agent clonidine is associated with a withdrawal syndrome which may include a hypertensive overshoot of critical proportions. We have attempted to produce an animal model of this syndrome in rats. Rats were treated with clonidine in the drinking water (5 microgram/ml; total dose 300-500 microgram/kg/day) which produced a significant (approx. 20%) decrease in heart rate and blood pressure. Within 24 h of cessation of treatment a significantly greater (approximately 100 beats/min) heart rate was seen in treated animals than in control animals when measurements were made in conscious animals. No hypertensive overshoot was observed. Cessation of treatment was associated with an increase in sympatho-adrenal tone as shown by a trans-synaptic induction of adrenal tyrosine hydroxylase activity. Adrenal denervation prevented the rise in adrenal tyrosine hydroxylase seen after cessation of treatment. Administration of clonidine to pregnant rats (10th day until term) did not alter the development of adrenal tyrosine hydroxylase in the offspring. The data indicate that a withdrawal syndrome is produced upon cessation of chronic clonidine treatment.

An alcohol dependent states was induced in rats via gastric intubation. Alcohol was given three times daily for seven days in increasing doses, the final dose and concentration varying from rat to rat, being adjusted according to weight loss and state of intoxication. After seven days dosing, alcohol was withdrawn and twenty hours later an audiogenic stimulus was given to induce convulsions. Na+K+ATPase activity was measured in the hippocampus of rats during alcohol administration and during withdrawal. Animals which received twenty-one doses of alcohol showed a significant increase in Na+K+ATPase activity compared with controls. On withdrawal of alcohol, the enzyme activity fell, but remained higher than control values. In the withdrawal groups, membrane Na+K+ATPase levels were increased significantly compared to control levels in the order: no convulsion less than with convulsion less than postconvulsion. It is concluded that Na+K+ATPase activity is modified during chronic alcohol administration and during seizures induced after alcohol withdrawal by audiogenic stimulation.

This study substantiates previous reports that low platelet monoamine oxidase (MAO) activity is associated with alcoholism. Catechol-o-methyltransferase (COMT) activity in erythrocytes of alcoholics did not differ from that of controls. In 20 male alcoholics low platelet MAO activity was found during the first 3 days after hospitalization. The MAO activity increased in the next 2 weeks of abstinence and then tended to decrease again.

The activity of 3-hydroxybutyrate dehydrogenase (EC 1.1.1.30) in the isolated rat liver mitochondria changes but slightly during 24 h. In animals which were fed 10% ethanol solution for 3.5 months the enzyme activity varies within the daily cycle: maximum--at 10 p. m., minimum--at 1-4 p. m. and at 4-7 a. m.; the average daily activity gets three times lower. The cessation of the alcohol consumption makes average daily activity of the enzyme only two times higher, but the character of daily changes in the activity is different: the maximum is observed at 4-7 p. m., the minimum at 4-7 a. m.

Tranylcypromine, a monoamine oxidase inhititor, was administered to rats during chronic ethanol treatment. The severity of the hyperactive withdrawal behavior observed upon removal of ethanol was, during the first 60 hours of treatment, similar in both ethanol and ethanol + tranylcypromine treated animals. However, after 84 hours of ethanol treatment, tranylcypromine slightly depressed the withdrawal severity. Rises in cerebral cortical cyclic adenosine 3',5'-monophosphate (cAMP) levels and adenylate cyclase activity associated with withdrawal behavior in ethanol-treated rats, though, were not observed. (Adenylate cyclase activity used throughout this paper refers to % conversion of 3H-adenine into 3H-cAMP). Based on this and previous data, a model invoking two neurochemical adaptations--one in adenylate cyclase and one, as yet, unknown-is proposed for the mechanism of physical dependence.

Morphohistochemical changes in the cortical structures were studied comparatively in 56 adult and young rats during two-month alcoholization and after its discontinuation. It was demonstrated that in young animals, both compensatory processes and signs of damage were more pronounced, with various cerebral components reacting differently. Thus, the neuronal bodies displayed little change while there were marked impairments in their axons. Young animals exhibited greater vascular damage whereas their glial reaction was on the contrary more adequate to experimental conditions. Nevertheless, young animals in our model experiments showed no irreversible impairments in their cerebral cortex which could be indicative of the malignancy of juvenile alcoholism. In short-term temporary alcohol intoxication, the morphofunctional resources of the cortex can recover completely following ethanol withdrawal. Evaluating the alterations detected in the cortical nerve tissue, it appears reasonable to classify them as a manifestation of the morphohistochemical constituent of the multi-level protective compensatory syndrome in alcoholism.

1. Chronic ethanol administration to rats was previously shown to enhance brain 5-hydroxytryptamine synthesis by increasing the availability of circulating tryptophan to the brain secondarily to the NAD(P)H-mediated inhibition of liver tryptophan pyrrolase activity. 2. At 24h after ethanol withdrawal, all the above effects were observed because liver [NAD(P)H] was still increased. By contrast, all aspects of liver and brain tryptophan metabolism were normal at 12 days after withdrawal. 3. At 7--9 days after withdrawal, brain 5-hydroxytryptamine synthesis was decreased, as was tryptophan availability to the brain. Liver tryptophan pyrrolase activity at these time-intervals was maximally enhanced. 4. Administration of nicotinamide during the withdrawal phase not only abolished the withdrawal-induced enhancement of tryptophan pyrrolase activity on day 8, but also maintained the inhibition previously caused by ethanol. Under these conditions, the withdrawal-induced decreases in brain 5-hydroxytryptamine synthesis and tryptophan availability to the brain were abolished, and both functions were enhanced. Nicotinamide alone exerted similar effects in control rats. 5. It is suggested that ethanol withdrawal inhibits brain 5-hydroxytryptamine synthesis by decreasing tryptophan availability to the brain secondarily to the enhanced liver tryptophan pyrrolase activity. 6. The results are discussed in relation to the possible involvement of 5-hydroxytryptamine in dependence on ethanol and other drugs.

The authors administered at least one dexamethasone suppression test (DST) and Hamilton Rating Scale for Depression (HRSD) simultaneously to 30 psychiatric inpatients following detoxification from alcohol. Twenty-five of these were also interviewed using the NIMH Diagnostic Interview Schedule (DIS). Fifteen patients had two or three sequential DSTs at weekly intervals. Seven of the patients were clinically diagnosed as having a major depressive episode based on close observation over 2 to 4 inpatient weeks free of psychotropic medications. Fifty-eight percent of the initial cortisol determinations with the first 2 weeks showed nonsuppression, as did 60% after 2 weeks. While the level of depressive symptoms was initially high (HRSD score greater than 20) for 48% of the 27 patients interviewed within 2 weeks of abstinence, depressive symptoms cleared within 2 weeks in half of these cases. There were no associations between DST results and the presence of DSM-III major depressive disorder (lifetime or current) as assessed by the NIMH DIS, scores on the HRSD, or the presence of liver disease (elevated admission SGOT or SGPT). By the 15th-day of abstinence an examination of the clinical course of depressive symptoms differentiated those patients with a persistent major depressive episode from those with transient, alcohol-related depressive symptoms. An early positive DST had a positive predictive value of 20% for a clinical diagnosis of a major depressive episode, and a negative predictive value of 73%. After 2 weeks the positive and negative predictive values were each 50%.

In rats rendered tolerant to the dependent on morphine, striatal cyclic AMP metabolism was significantly enhanced as reflected by elevated cyclic AMP levels and adenylate cyclase activity. Following withdrawal from morphine treatment, whereas the activity of straital adenylate cyclase was significantly reduced when compared to morphine-dependent rats, the drop in cyclic AMP was not significant. Although addition of dopamine (40 muM) stimulated equally well the striatal adenylate cyclase from control or morphine-dependent animals, the activity of dopamine-stimulated enzyme was blocked in animals undergoing withdrawal. The crude synaptosomal fraction of the whole brain obtained from morphine-dependent rats exhibited an even more pronounced increase in cyclic AMP which was accompanied by elevated adenylate cyclase and protein kinase activity. Naloxone administration suppressed this rise in cyclic AMP and reversed the morphine-stimulated increases in adenylate cyclase and protein kinase. Following the withdrawal of morphine treatment, alterations in cyclic AMP metabolism were similar to those noted for the morphine-naloxone group.

The catecholamine-stimulated adenosine triphosphatase (ATP-ase) activities in mouse brain synaptosomes were inhibited by morphine both in vitro and in vivo. Morphine up to 10(-3) M had no effect on basal ATPase activities but at 10(-4) M significantly inhibited dopamine-sensitive ATPase activities in vitro. The morphine effect was antagonized by an opiate antagonist, naloxone. The catecholamine-sensitive ATPase activities were also inhibited by acute administration of morphine. The inhibition was dose-dependent. However, naloxone partially antagonized the morphine inhibition of depamine-sensitive ATPase activity but not norepinephrine-sensitive ATPase activity. A significant decrease in the sensitivity of synaptosomal ATPase to catecholamines was observed in mice rendered tolerant by morphine pellet implantation. The Na+,K+-ATPase was more affected by morphine as compared to Mg++-ATPase activity. The dopamine-sensitive Na+,K+-ATPase activity was restored by 50% in precipitated withdrawal mouse brain synaptosomes. Norepinephrine-sensitive ATPase activity was also restored partially in precipitated withdrawal animals. These results suggest that in mouse brain synaptosomes morphine may be interacting with ATPase at or near the catecholamine-active sites.

The possible role of succinic dehydrogenase (SD) in producing physical dependence to morphine by affecting tissue respiration was investigated in Swiss albino mice during the development of morphine tolerance through a period of addiction and naloxone withdrawal therapy. Tolerance and physical dependence were induced by injecting the mice with morphine sulfate subcutaneously at 8-hour intervals, increasing the dose from 10 mg/kg BW every 24 h for 15 days. The animals were considered to be addicted when they were able to tolerate an otherwise lethal dose of 150 mg/kg 3 times a day. Results indicated that succinic dehydrogenase was inhibited throughout the 15-day period of morphine administration and that this effect was greatest in tolerant animals. Increasing the dose and duration of treatment did not cause further decreases in enzyme activity; instead, after 15 days levels of enzyme activity increased in addicted animals compared with tolerant mice. Furthermore, morphine abstinence for 2 days, markedly increased the levels of SD activity, while 6 days of abstinence had little effect. Naloxone withdrawal at each stage was associated with increased SD activity, but the increase was significant only in tolerant mice.

The effect of an 8 day liquid diet containing 7% v/v ethanol and the effect of ethanol withdrawal on several drug metabolizing enzyme activities, cytochrome P-450 content and glutathione S-transferase activity (GST) has been studied in male C57/BL mice. After treatment, hepatic microsomal activities toward benzphetamine (BNZ), biphenyl (BPH) and dimethylnitrosamine (DMN) and cytosolic GST activity towards 1-chloro-2,4-dinitrobenzene (CDNB) were determined. Ethanol treatment caused a differential time dependent increase in the metabolism of the 4 xenobiotics. Increased BPH-4-hydroxylase activity correlated most closely with that of the increased concentration of hepatic P-450. That is, both values were increased (5.8-fold) over controls after 8 days of ethanol treatment. Ethanol withdrawal (24 h) resulted in a 46% reduction in the P-450 content and a 26% reduction in BPH-4-hydroxylase activity compared to the elevated values at day 8. By 48 h, the values were no different from controls. DNA-N-demethylase, BNZ-N-demethylase and GST activities all increased after 4 days of ethanol treatment and remained the same at 8 days. However, ethanol withdrawal resulted in differential time dependent changes in the activities towards BNZ, DMN, and CDNB. While DMN-N-demethylase activity returned to control activity within 24 h, BNZ-N-demethylase activity did not change for the first 24 h of withdrawal, but returned to control activity by 48 h. GST activity had not decreased by 48 h of withdrawal. These data suggest that ethanol induces several cytochrome P-450 isozymes that have a time difference in induction by ethanol and reduction following ethanol withdrawal. Furthermore, ethanol induction of GSTs occurs quickly (4 days) and remains elevated at least 48 h after ethanol withdrawal.

Behavioural and biochemical studies were carried out in rats given a single daily dose (1 mg/kg, i.p.) of haloperidol for 30 days and subsequently withdrawn for 7 days. Long-term administration of haloperidol resulted in supersensitivity of dopamine receptors. This was manifested by enhanced stereotypic biting, rearing, locomotor and floor activity of haloperidol withdrawn rats when challenged to a low dose of apomorphine (0.5 mg/kg, s.c.) on the 8th day. Chronic haloperidol treatment significantly decreased dopamine synthesis and release as evidenced by low activity of tyrosine hydroxylase and low level of homovanillic acid in striatum. Dopamine levels did not change in the frontal cortex, striatum and midbrain. Haloperidol treatment significantly increased striatal gamma-aminobutyric acid content and glutamic acid decarboxylase activity by 17% and 16% respectively. The decreased tyrosine hydroxylase activity and homovanillic acid level in corpus striatum might, in part, be due to an inhibitory effect of GABAergic neurons on dopaminergic system. Rats withdrawn from chronic haloperidol treatment showed significant increases in GABA level and glutamic acid decarboxylase activity. This probably resulted in further inhibition of dopamine release as evidenced by marked accumulation of dopamine in the corpus striatum and midbrain. No significant alterations in the endogenous levels of norepinephrine, 5-hydroxytryptamine and 5-hydroxyindoleacetic acid were observed in haloperidol-treated and subsequently withdrawn rats. These data suggest that chronic haloperidol treatment and subsequent withdrawal results in the development of behavioural dopamine supersensitivity as well as biochemical alterations in dopaminergic and GABAergic system. The changes in these two neuronal systems seem to be interrelated.

In synaptosomal fractions of rat brain the activities of phospholipase A2 and the phospholipid base-exchange enzymes are highly dependent on external Ca2+ concentrations. Their activity is inhibited by the presence of 50 mM ethanol in vitro. Administration of ethanol to rats by inhalation causes a progressive increase in the activity of these enzymes in synaptosomal preparations at all Ca2+ concentrations studied. The increased activity of these enzymes persists in preparations from rats undergoing a physical syndrome of withdrawal from ethanol. The addition of ethanol in vitro to preparations from animals that had received ethanol in vivo had no significant effect on enzyme activity. The results are discussed in relation to the possible roles of membrane lipid metabolism and synaptic Ca2+ sensitivity in ethanol tolerance and physical dependence.

Normal human urine contains an endogenous monoamine oxidase inhibitor. We have now investigated its activity in urine samples from psychiatric patients in various diagnostic categories. Significantly higher values were observed in alcoholics recently withdrawn from ethanol, compared with controls. Inhibitory activity was not specifically related to primary affective disorders. Inhibitor output may be positively related to certain symptom clusters rather than to disease entities (i.e. alcohol withdrawal, agitation, and hyperkinesis). Significantly lower inhibitor output was also found in a small group of patients with chronic schizophrenia.

Programmed-feeding polydipsia results in a reliable model of chronic alcoholism in the rat. High oral ethanol comsumption and a predictable withdrawal reaction associated with audiogenic seizures are produced. The maintenance of high blood ethanol levels for three weeks in 18 male Charles River rats was associated with audiogenic seizures after 6 or 8 hours of withdrawal. These chronic alcoholic rats had enhanced blood clearance of ethanol. The cerebral cortical crude mitochondrial fraction showed a decrease in total and magnesium-dependent adenosine triphosphatase activity in alcoholic and control (water-fed) rats compared with normal rats.

Serum dopamine beta-hydroxylase (DBH) activity varies greatly between individuals but is usually relatively constant within individuals. DBH activity was determined in 20 normal subjects and 6 chronic alcoholics during alcohol ingestion and withdrawal, under controlled and standardized conditions. For all subjects mean random DBH was 423 +/- 249 (mean +/- SD) nmol phenylethanolamine/h per millilitre serum. Between-day serum DBH values vary more than within-day values (21.1% vs 15.1%). Cold-pressor testing or sudden standing does not increase mean DBH; however, some individuals show a significant increase which cannot be elicited on repeat testing. Mean DBH activity did not vary significantly over 24 h. Clinically useful correlations between single random DBH and blood pressure or 24-h urine catechols should not be expected.

Chronically alcoholized intoxication (1.5--2 months) induces adaptation of cerebral neurones to changing equilibrium states of biochemical processes by altering the activity of enzymes of GABA metabolism, reduction of alanine and aspartate transaminase activity and increase of LDH and succinate dehydrogenase activity. In the cerebellum and cerebral hemispheres during alcohol abstinacy the activity of GABA-T, succinate dehydrogenase and aspartate transaminase was reduced while that of LDH and alanine transaminase was increased. The administration of fusarinic acid (100 mg/kg i. p.) to control animals induced a sharp increase of GAD activity in both structures of the brain. The stimulatory effects of fusarinic acid were not observed when it was administered to animals receiving alcohol chronically. Motor activity or rats was markedly reduced during chronical alcoholism and the first days of alcohol abstinacy (24--48 h), as well as following injection fusarinic acid and homopantothenic acid. The increase of locomotion and the vertical component of motor activity was observed only following one week or one month after alcohol abstinacy.

In mice chronically treated with ethanol (in a liquid diet containing 6% ethanol ad libitum for 2 weeks), brain tryptophan hydroxylase (TPH) activity was increased (by 30-45% in whole brain), while brain tyrosine hydroxylase activity remained unchanged. Such chronic ethanol treatment also induced susceptibility to audiogenic seizures during withdrawal (60% incidence). When ethanol treatment was given to adrenalectomized (Adx) mice, the increase of brain TPH activity and the development of withdrawal audiogenic seizures were both prevented. In Adx mice receiving daily injections of corticosterone (0.5 mg/mouse), the ethanol-induced increase of brain TPH activity and the occurrence of withdrawal audiogenic seizures were both restored. Similarly, the ethanol-induced increase of liver alcohol dehydrogenase activity (by 60%) was prevented in Adx mice and restored by corticosterone replacement. It was noted that in all three cases replacement with such large doses of the corticoid did not enhance the ethanol effects, but merely restored the effects to the levels observed in intact mice. Apparently, glucocorticoids are required in a permissive role in order for the ethanol effects to occur.

Liver microsomal mixed-function oxidase activities were determined in female Sprague-Dawley rats after 3 weeks of ethanol feeding and for up to 10 days after withdrawal. Ethanol (36% of total calories) was administered in a high fat liquid diet and was replaced isocalorically by carbohydrates in controls. Chronic ethanol feeding similarly enhanced both microsomal cytochrome P-450 content and benzphetamine N-demethylase activity, per mg of protein, and resulted in a disproportionate increase in both aniline hydroxylase and 7-ethoxycoumarin O-deethylase activities. A 6- to 7-day withdrawal period was apparently necessary for the overall disappearance of these effects of ethanol. Marked differences, however, were seen in the time courses of return of these variables to control levels, as also indicated by changes, during this period and specially during the first 24 hr after withdrawal, in the apparent molar activity of the microsomal fraction with the three substrates tested. The results were interpreted as indicating that the distinct ethanol-inducible cytochrome P-450 isozyme, with a high specific activity toward aniline, undergoes a very rapid turnover in liver microsomes. Induction of another form of cytochrome P-450, differing from the former by its slower turnover rate, would explain the induction by ethanol of 7-ethoxycoumarin O-deethylase activity. The withdrawal of ethanol was followed by a rapid but transient increase in benzphetamine N-demethylase activity above the ethanol-induced level, at a time when other activities were rapidly declining. This could suggest that the microsomal content of other cytochrome P-450 isozyme(s), with high specific activity toward this substrate, would also be temporarily altered during ethanol withdrawal. Important alterations in microsomal cytochrome P-450-dependent mixed-function oxidase activities occurred during the initial 24-hr period of withdrawal, even in the absence of a change in microsomal cytochrome P-450 content, indicating that the effects of chronic ethanol ingestion on hepatic drug-metabolizing enzyme activities may also be highly dependent on the proximity of ethanol intake.

In order to define the roles of cAMP and inositol phosphates (IPx) in the mechanisms governing dopamine (DA)-regulated PRL release, we have carried out studies with enriched lactotrophs from dispersed anterior pituitaries of estrogen-treated rats. Changes in the intracellular levels of cAMP as well as IPx were determined in response to the acute addition or removal of DA. The withdrawal of DA from the incubation medium in cells cultured with DA (500 nM) for 24 h resulted in a rapid and significant increase in cAMP concentration from 1.29 +/- 0.098 to 3.89 +/- 0.199 pmol/dish. On the other hand, the administration of DA for 10 min to cells cultured without it resulted in a significant decrease in intracellular cAMP (from 3.04 +/- 0.208 to 1.62 +/- 0.057 pmol/dish). Similarly, PRL released into the medium was stimulated (95.1 +/- 9%) or inhibited (46.9 +/- 6%) after DA withdrawal or addition, respectively. Cells incubated 24 h with [3H]inositol and DA (500 nM) responded to DA withdrawal with a significant increase in the concentration of [3H]IPx (5148 +/- 199 vs. 8,376 +/- 164 cpm/dish), whereas acute DA administration had no effect on the level of [3H]IPx. The administration of 8-Br-cAMP (0.5 and 2.5 mM) and forskolin (10 microM) for 10 min to cells tonically cultured in the presence of DA had no effect on the intracellular concentration of [3H]IPx, although they decreased the relative proportion of [3H]IP3 fraction from 22.1% to 11.6%, 13.6%, and 9.6%, respectively. The administration of TRH (100 nM), either under tonic DA inhibition or 10 min after the transient removal of DA inhibition, resulted in a similar stimulation of IPx formation (from 5,625 +/- 155 to 21,830 +/- 100 and 24,870 +/- 80 cpm/dish, respectively). However, the release of PRL induced by TRH was potentiated 6-fold (38.2 +/- 2.17 vs. 227 +/- 41 ng/dish) by the transient removal of DA. These findings support the conclusions that: 1) DA receptors in lactotrophs are negatively coupled to adenylate cyclase as seen during the addition or removal of DA. 2) DA receptors are negatively coupled to phospholipase C; however activation is only seen upon the removal of DA. 3) The effect of DA withdrawal on the formation of IPx is not secondary to the activation of adenylate cyclase. 4) The potentiation of the PRL response to TRH after DA withdrawal does not involve increased production of IPx.

Changes in succinic dehydrogenase (SDH), during morphine dependence development, normal and antagonists (naloxone and naltrexone) precipitated withdrawals, have been analysed in the spinal cord and medulla oblongata of mice. The study reveals the following highlights. 1. There is a progressive inhibition of SDH upto six days of morphine treatment. However, the physically dependent animals demonstrate a significant recovery of the enzyme suggesting that steady-state level of the enzyme is achieved. 2. Antagonists application to morphine treated animals significantly reverted the enzyme, but the control level is achieved only with naloxone in single dose treated animals. 3. The abstinence of drug for two days not only recovered but also significantly raised the enzyme level both in spinal cord and in medulla oblongata. The antagonists treatment to these animals are insignificant. 4. A further withdrawal of the drug recovered the enzyme towards the control level, and on 15th day SDH is completely recovered. The antagonist treatments in withdrawal groups demonstrated insignificant changes. Overall data clearly show that enzymatic changes are morphine mediated, and at least 15 days of drug abstinence is needed for a complete recovery of the enzyme (Acta neurol. belg., 1988, 88, 281-289).