Acute cardio-respiratory effects in rats of PS4alpha, an antineoplastic peptidoglycan from Mycobacterium vaccae.

PS4alpha is a high molecular weight peptidoglycan extracted from Mycobacterium vaccae, which has demonstrated considerable antineoplastic activity in-vivo without apparent toxicity. Available fortesting in only small quantities, a sensitive in-vivo method for measuring pulse and breathing rates in cannulated rats was applied to this compound at doses of 5, 50 and 500 microg kg(-1). Various parameters (mean arterial pressure, maximum transpulmonary pressure, compliance, heart rate, minute volume, respiratory rate and tidal volume) were followed for up to 1 h and demonstrated no significant deviation in the baseline values obtained before injection. This compound at doses up to 500 microg kg(-1) had no apparent acute toxicity in rats, but chronic effects at this and higher doses have to be determined by more conventional toxicological methods before proceeding to evaluate PS4alpha as an antineoplastic agent.

Analgesic and thermic effects, and cerebrospinal fluid and plasma pharmacokinetics, of intracerebroventricularly administered morphine in normal and sensitized rats.

The relationship between asthma and opioids has barely been investigated. This study examines whether active sensitization of rats changes the analgesic and thermic effects of intracerebroventricular morphine or the pharmacokinetics of the drug. Morphine (5, 10 and 20 microg) was given intracerebroventricularly to sensitized (active immunization to ovalbumin and Al(OH)3 then airway challenge with ovalbumin after 12 days) and normal (i.e. non-sensitized) male Sprague-Dawley rats. The tail-flick latencies and changes in colon temperature were determined before morphine injection and at 30 min intervals for a period of 300 min afterwards. Results were expressed as the area under the time-response curve. The analgesic and hyperthermic response to morphine for sensitized rats was less than that obtained for normal rats. Cerebrospinal fluid and blood samples were collected periodically for a period of 240 min and morphine levels were determined by a highly sensitive radioimmunoassay. The pharmacokinetic parameters half-life, terminal elimination rate constant and the mean residence time were determined in both cerebrospinal fluid and plasma by non-compartmental analysis. The area under the cerebrospinal fluid concentration-time curve from time zero to infinity was higher for sensitized rats than for normal rats for all three doses of morphine but these differences did not correspond with similar changes in pharmacological responses. In conclusion, the attenuated analgesic and thermic responses to intracerebroventricular morphine in the sensitized rats might be a result of pharmacodynamic alterations rather than to pharmacokinetic changes.

Binding of [3H][D-Ala2, MePhe4, Gly-ol5] enkephalin, [3H][D-Pen2, D-Pen5]enkephalin, and [3H]U-69,593 to airway and pulmonary tissues of normal and sensitized rats.

The role of endogenous opioid peptides in the regulation of bronchomotor tone, as well as in the pathophysiology of asthma is uncertain. We have studied the binding of highly selective [3H]labeled ligands of mu-([D-Ala2, MePhe4, Gly-ol5]enkephalin; DAMGO), delta ([D-Pen2, D-Pen5]enkephalin; DPDPE), and kappa-(U-69,593) opioid receptors to membranes of trachea, main bronchus, lung parenchyma and pulmonary artery obtained from normal (unsensitized) and actively IgE-sensitized rats acutely challenged with the specific antigen. [3H]DAMGO, [3H]DPDPE and [3H]U-69,593 bound to membranes of normal and sensitized tissues at a saturable, single high-affinity site. The rank order of receptor densities in normal tissues was delta- > or = kappa- > or = mu-, with lung parenchyma exhibiting the greatest binding capacity for delta- and mu- receptors compared to the other regions examined. The Kd values showed small differences between ligands and regions tested. The mu- and delta-opioid receptor densities were decreased in sensitized main bronchus and lung parenchyma, respectively, compared to normal tissues. By contrast, kappa-opioid receptor density was augmented in sensitized lung parenchyma but an increase in Kd values was also observed. These differential changes in the density and affinity of opioid receptor types may be related to alterations in endogenous opioid peptides during the process of sensitization.

Time course of the distribution of morphine in brain regions, spinal cord and serum following intravenous injection to rats of differing ages.

Previously it was demonstrated that intravenously administered morphine produced greater analgesic but lower hyperthermic responses to morphine in 24-week-old rats in comparison to 8-week-old rats. The differential pharmacological responses to morphine could not solely be attributed to the pharmacokinetic parameters, namely area under the serum morphine concentration-time curve, serum levels of morphine extrapolated to zero time, half-life, mean residence time, apparent volume of distribution at the steady state, terminal rate constant and total body clearance of morphine in serum. In order to determine whether the differences in pharmacological responses to morphine in rats from two age groups are related to differential distribution of morphine in the central nervous system, in the present study, the time course of the distribution of morphine in brain regions (hypothalamus, hippocampus, cortex, pons and medulla, amygdala, midbrain and corpus striatum), spinal cord and serum following intravenous injection of 10 mg/kg dose to 8- and 24-week-old male Sprague-Dawley rats was determined. Morphine injected intravenously produced a greater analgesic but less intense hyperthermic effect in 24-week-old rats in comparison to 8-week-old rats. In most of the brain regions and spinal cord, with few exceptions, the concentration of morphine was found to be greater in 24-week-old rats than in 8-week-old rats. Similarly, the ratio of the concentration of morphine in brain region or spinal cord to serum was significantly higher in rats from the older age group. The studies demonstrate that the altered pharmacological responses to intravenously administered morphine to rats of differing ages may be related to the higher concentration of morphine in the central nervous system of older rats, which in turn may be related to the differences in the blood-brain barrier to morphine in the two age groups.

Naltrexone-induced alterations of the distribution of morphine in brain regions and spinal cord of the rat.

The effects of naltrexone injected intravenously (i.v.) on the pharmacological actions and distribution of i.v. injected morphine in brain regions and spinal cord of male Sprague-Dawley rats were determined. Naltrexone (0.625- and 2.5-mg/kg doses) antagonized the analgesic and hyperthermic effects of morphine (10-mg/kg dose). For distribution studies, naltrexone (0.625- and 2.5-mg/kg doses) was co-administered with morphine via indwelling catheters. Rats were sacrificed at various times after drug injection and the concentration of morphine in brain regions (hypothalamus, hippocampus, cortex, pons and medulla, amygdala, midbrain and corpus striatum), spinal cord and serum was determined by radioimmunoassay. The concentration of morphine in various brain regions was found to be time dependent. Initially, at 5 min, the highest concentration of morphine was found in the hypothalamus and the lowest in the striatum. In cortex and spinal cord, the concentration of morphine was significantly higher in comparison to the other brain regions at 30- and 60-min time points. Co-administration of lower dose of naltrexone (0.625 mg/kg) did not significantly alter the distribution of morphine in brain regions and spinal cord with some exceptions. The higher dose of naltrexone (2.5 mg/kg) increased the concentration of morphine in several brain regions and spinal cord. The ratio of the concentration of morphine in brain region or spinal cord to serum was decreased by naltrexone. It is concluded that naltrexone also alters the distribution of morphine in the central nervous system.

Effects of naltrexone on pharmacodynamics and pharmacokinetics of intravenously administered morphine in the rat.

Effects of naltrexone administered intravenously on the pharmacological actions and kinetics of morphine in serum following intravenous administration of morphine were determined in male Sprague-Dawley rats. A 10 mg/kg dose of morphine produced an analgesic response as measured by the tail flick test. Morphine also produced a hyperthermic effect. Naltrexone dose (0.625-2.5 mg/kg)-dependently antagonized the analgesic and hyperthermic effects of morphine. The effect of naltrexone (0.625 and 2.5 mg/kg) on the pharmacokinetic parameters area under the serum morphine concentration time curve (AUC0-->infinity), serum levels of morphine extrapolated to zero time (Cmax), half-life (t1/2), mean residence time (MRT), total body clearance (Clt), and volume of distribution at steady state (Vss) of morphine in serum was determined. Naltrexone (0.625 mg/kg) significantly increased AUC0-->infinity, Cmax, t1/2 MRT, but decreased the Vss, elimination rate constant (k) and Clt. The higher dose of naltrexone (2.5 mg/kg) produced an increase in the Cmax value of morphine in the serum, but the other pharmacokinetic parameters were unaffected. Since increased morphine concentrations in serum produced by naltrexone cannot explain its antagonistic effects on analgesia and hyperthermia, it is concluded that naltrexone produces its effects by blocking opiate receptors at the appropriate sites. The increases in serum morphine levels by naltrexone may be related to displacement of morphine from protein binding sites and inhibition of morphine metabolism by glucuronyl transferase. This study for the first time demonstrates that in the rat, when morphine and naltrexone are given concurrently, although serum levels of morphine increase, pharmacological effects of morphine are antagonized.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on the possible role of pharmacokinetics in the development of tolerance to morphine in the rat.

1. The possible role of pharmacokinetics of morphine in the development of tolerance to the analgesic and hyperthermic effects of morphine was studied in the rat. 2. Male Sprague-Dawley rats were made tolerant to morphine by implanting 6 morphine pellets each containing 75 mg of morphine base for 7 days. The assessment of the degree of tolerance to morphine and pharmacokinetic parameters were done 72 hr after pellet removal. 3. Tolerance developed to both the analgesic and hyperthermic effects of morphine as evidenced by decreased responses to morphine in morphine pellet implanted rats compared with placebo pellet implanted rats. 4. The pharmacokinetic parameters, AUC0-->infinity, Cmax, t1/2, k, MRT, Vss and Clt were determined after injecting 5 and 10 mg/kg doses of morphine intravenously to placebo and morphine pellet implanted rats and using a highly sensitive and specific RIA method to quantitate serum levels of morphine. For a 5 mg/kg dose of morphine, the AUC0-->infinity and t1/2 in morphine pellet implanted rats were significantly higher than in placebo pellet implanted rats, but the k value was lower. The other pharmacokinetic parameters for morphine in the two treatment groups did not differ. For 10 mg/kg dose, the only change was an increase in the MRT in morphine tolerant rats when compared to nontolerant rats. 5. The results establish that the development of tolerance to the analgesic and hyperthermic effects of morphine is not related to pharmacokinetics of morphine in serum but may be related to modification of receptor systems in the central nervous system.

Distribution of morphine in brain regions, spinal cord and serum following intravenous injection to morphine tolerant rats.

In order to determine the possible contribution of altered distribution of morphine in the morphine tolerance process, the distribution of morphine was studied in brain regions and spinal cord, following its intravenous administration. Male Sprague-Dawley rats were made tolerant to morphine by implanting 6 morphine pellets, each containing 75 mg of morphine base, for 7 days. Seventy-two hours after the removal of the pellets, a time when serum morphine levels were negligible or absent and yet tolerance to the pharmacological effects of morphine was present, morphine (10 mg/kg, i.v.) was injected in placebo and morphine pellet implanted rats. At various times (5, 30, 60, 120 and 360 min) after the injection of morphine, brain regions (hypothalamus, cortex, hippocampus, midbrain, pons and medulla, striatum and amygdala), spinal cord and serum were collected. The level of morphine in the tissues was determined by using a highly sensitive and specific radioimmunoassay (RIA) method. Five minutes after morphine injection, the concentration of morphine was the highest in the hypothalamus and the lowest in amygdala. The concentration of morphine in hypothalamus, pons and medulla, hippocampus and midbrain of morphine tolerant rats was smaller than in placebo pellet implanted rats. The tissue to serum ratio of morphine in the hypothalamus, hippocampus, striatum, midbrain and cortex were also smaller in morphine tolerant than in non-tolerant rats. The concentration of morphine in brain regions with time did not exhibit linearity. At other time intervals like 30 and 60 min, the concentration of morphine in several brain regions and spinal cord was significantly higher in morphine tolerant than in non-tolerant rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Time course of the distribution of morphine in brain regions and spinal cord after intravenous injection to spontaneously hypertensive and normotensive Wistar-Kyoto rats.

Previous studies from this laboratory have demonstrated that the analgesic and hyperthermic effects of morphine were found to be greater in spontaneously hypertensive (SHR) rats than in normotensive Wistar-Kyoto (WKY) rats. The enhanced response to morphine could not be explained on the basis of any of the pharmacokinetic parameters of morphine in the serum. In order to determine the possible contribution of altered distribution of morphine in the central nervous system in the differences in the pharmacological response to morphine in the two strains, the time course of the distribution of morphine was determined in brain regions and spinal cord after its i.v. administration. SHR and WKY rats were injected with morphine (10 mg/kg). At various times (5, 30, 60, 120 and 360 min) after the injection of morphine, brain regions (hypothalamus, cortex, hippocampus, midbrain, pons and medulla, striatum and amygdala) and spinal cord were collected. The level of morphine in the tissues was determined by using a highly sensitive and specific radioimmunoassay method. Five minutes after morphine injection, the concentration of morphine was the highest in the spinal cord. Among the brain regions, the highest concentration of morphine was in the hypothalamus and the lowest in the amygdala. In all the brain regions and spinal cord, the concentration of morphine was significantly higher in the SHR than in the WKY rats. Similar effects were observed at 30, 60 and 120 min after morphine injection. At 360 min, the hypothalamus, cortex and spinal cord of the SHR rats had higher concentrations of morphine than the WKY rats, but the other regions did not show differences in the morphine levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacodynamics and pharmacokinetics of intravenously administered morphine in spontaneously hypertensive and normotensive Wistar-Kyoto rats.

The analgesic and hyperthermic effects of i.v. administered morphine were determined in age-matched male spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. Two doses of morphine (5 and 10 mg/kg) were used. In the doses used, morphine produced analgesia in WKY rats as measured by the tail-flick test and expressed as area under the time-response curve. The intensity and duration of the analgesic area under the time-response curve was significantly greater in SHR rats in comparison to WKY rats. For example, whereas the effect of a 10-mg/kg dose lasted for 4 hr in WKY rats; in SHR rats the effect lasted for 10 hr. Similarly, the intensity and duration of morphine-induced hyperthermic response was greater in SHR rats in comparison to WKY rats. In order to determine if the differences in responses to morphine in SHR and WKY were related to its kinetics, the pharmacokinetic parameters of morphine in serum were determined. The area under the serum morphine concentration-time curve, serum levels of morphine extrapolated to zero time, T1/2, apparent volume of distribution at steady state, terminal elimination rate constant and total body clearance values for morphine in SHR and WKY rats did not differ. Previous studies from this laboratory indicate that the density of mu opiate receptors labeled with [3H]D-Ala2.MePhe4,Gly-ol5-enkephalin and [3H]naltrexone and of kappa-opiate receptors labeled with [3H]ethylketocyclazocine in the brain of SHR rats is higher than in WKY rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacodynamics and kinetics of loss of tolerance and physical dependence on morphine induced by pellet implantation in the rat.

The decay characteristics of tolerance and physical dependence on morphine induced by a pellet implantation procedure were determined in male Sprague-Dawley rats. Rats were implanted subcutaneously with 6 morphine pellets during a 7-day period. The pellets were removed, and at various times thereafter tolerance to the analgesic and hyperthermic effects of morphine was measured by determining the response in rats implanted with morphine and placebo pellets. Similarly, the physical dependence was assessed by monitoring withdrawal signs following an injection of naloxone. A high degree of tolerance developed to the analgesic and hyperthermic effects of morphine. Similarly, a high degree of physical dependence also developed as evidenced by a high incidence of jumping response, teeth chattering and production of fecal boli induced by injections of naloxone. In addition, loss of body weight and body temperature also occurred. The analgesic and hyperthermic response to morphine recovered very gradually. There was no significant difference in the analgesic and hyperthermic responses to morphine on day 4 after the pellet removal in rats implanted with morphine and placebo pellets. The decay of tolerance was linear with time for the analgesic effect (r = 0.98) and for the hyperthermic effect (r = 0.93). The change in symptoms of physical dependence on morphine with time depended on the specific symptom monitored. The average number of jumps and teeth chattering decreased with time in a linear fashion with r values of 0.98 and 0.99, respectively. However, the number of fecal boli and wet dog shakes increased linearly with time (r = 0.97). The recovery of loss of body weight was also linear with time. Thus, it is clear that fecal boli and wet dog shakes, which increase in number as the dependence decays, are signs of a low degree of dependence. The results suggest that different central or peripheral mechanisms may be operating in different withdrawal symptoms. These studies may prove to be useful when studying the mechanisms involved in the induction and reversibility of tolerance and dependence processes, and in long-term effects of opiates at a time when the tolerance and physical dependence is no longer evident.

Analgesic and hyperthermic effects of intravenously administered morphine in the rat are related to its serum levels.

The analgesic response, colonic temperature changes and the pharmacokinetic parameters of i.v. administered morphine sulfate (2.5, 5.0 and 10.0 mg/kg) through indwelling cannulas in the jugular vein were determined in male Sprague-Dawley rats. The analgesic and hyperthermic responses were determined before and at 30-min intervals for a period of 360 min after the morphine injection and were expressed as area under the time-response curve. Blood samples were collected periodically for a period of 24 h. Serum was separated and was used for the estimation of morphine by the highly sensitive radioimmunoassay. The pharmacokinetic parameters, half life, the terminal elimination rate constant, the mean residence time, the apparent volume of distribution at steady state and the total clearance were determined by using noncompartmental analysis. The area under the serum concentration-time curve from time zero to infinity was related to the dose of morphine. The other parameters were the same for all the doses of morphine, except the serum levels of morphine extrapolated to zero time which increase gradually with the dose. Dose-dependent analgesic and hyperthermic responses were related to the area under the serum concentration-time curve. It is concluded that the dose-dependent pharmacological effects of morphine were related to the area under the serum concentration-time curve from time zero to infinity for serum levels of morphine but not to the other pharmacokinetic parameters.

Analgesic and thermic responses to intravenously administered morphine in 8- and 24-week-old rats.

The analgesic and thermic responses to morphine (5 and 10 mg/kg) injected intravenously to 8- and 24-week-old male Sprague-Dawley rats were determined. Greater analgesic and lower hyperthermic responses to morphine in 24-week-old rats in comparison to 8-week-old rats were observed. The pharmacokinetic parameters of morphine administered intravenously were also determined. Cmax for 5 and 10 mg/kg doses of morphine were smaller in 24-week-old rats in comparison to 8-week-old rats; however, AUC0----infinity was smaller only for 5 mg/kg dose. For 10 mg/kg dose, mean residence time (MRT) and the apparent steady state volume of distribution (Vss) for the older rats were higher than for the younger ones, but for 5 mg/kg dose the values did not differ. The enhanced responses to morphine in older age group of rats for 5 mg/kg dose cannot be explained solely on the basis of pharmacokinetics. However, for 10 mg/kg dose of morphine, the greater responses in 24-week-old rats could probably be related to increases in MRT and Vss. Factors other than serum kinetics, like kinetics of morphine in the brain as well as the brain opiate receptors, may also be involved in the differential effects of morphine in rats of different ages.

Tolerance-dependence and serum elimination of morphine in rats implanted with morphine pellets.

1. In order to determine whether the degree of tolerance to and physical dependence on morphine induced by pellet implantation procedure in the rat depends on the dose used and the kinetic parameters, the effect of implantation of different number of pellets on tolerance-dependence and elimination kinetics of morphine from serum was determined. 2. Male Sprague-Dawley rats were implanted subcutaneously with pellets. Each pellet contained 75 mg of morphine free base. Three schedules of implantation were used. They included 2 pellets during a 3-day period (2/3), 4 pellets during a 3-day period (4/3) and 6 pellets during a 7-day period (6/7). Placebo pellets which did not contain morphine were implanted in rats which served as controls. 3. The degree of tolerance to and physical dependence on morphine increased as the number of morphine pellets implanted increased. 4. In separate groups of rats implanted with pellets, elimination kinetics of morphine was studied using radioimmunoassay. The kinetic parameters were: area under serum morphine concentration time curve (AUC0----infinity), serum concentration of morphine extrapolated to time zero (Cmax), half-life (t1/2), elimination rate constant (k), mean residence time (MRT) and total body clearance (Clt). 5. The AUC0----infinity and Cmax increased in proportion to the number of pellets implanted. The t1/2, k, MRT and Clt values for 2/3 and 4/3 schedules did not differ, but for 6/7 schedule were significantly different from the other two schedules. The degree of tolerance to and physical dependence on morphine was directly related to the AUC0----infinity and Cmax. The longer t1/2 and MRT and lower Clt and k values in 6/7 schedule may reflect a saturation of glucuronic acid transferase, the main enzyme metabolizing morphine in the liver, and may account for the greater degree of tolerance and physical dependence.