Reduction of morphine-withdrawal aggression by conditional social stimuli

Sixty male hooded rats were made physically dependent on morphine by steadily increasing doses of morphine sulphate. A maintenance dose of 400 mg/kg/day was reached in 10 days and was continued for 5 additional days. At the end of the 15-day period all rats were withdrawn for 72 h and aggressive responses (attacks, rearing, and vocalization) were recorded for a 60-min period. One treatment group, in which a social experience had been paired with each morphine injection, showed significantly less morphine-withdrawal aggression than rats in two other groups which either remained socially isolated throughout the addiction period, or were grouped both at the time of morphine injection and during between-injection intervals.     

Brain acetylcholine in morphine pellet implanted rats given naloxone

Adult male rats were implanted with intraventricular (ivt.) brain cannulae for injection of 5 g of acetylseco-hemicholinium-3 (acetylseco HC-3) as a means of studying acetylcholine (ACh) utilization during morphine withdrawal. Animals were made dependent by implanting s.c. two 75 mg morphine base pellets 24 hrs apart. On the 4th day animals were given 10 mg/kg of naloxone i.p. and/or 5 g acetylseco HC-3 ivt. and sacrificed by decapitation at various times. The brains were removed and assayed for ACh using a pyrolysis gas Chromatographie procedure. Total brain ACh before or after acetylseco-HC-3 was not altered at 5, 30, 60 and 120 but was decreased at 10 min after naloxone. These results are in sharp contrast to our previous data of enhanced brain ACh utilization in withdrawn rats made dependent to morphine by several weeks of twice daily injections. It is apparent that short term morphine pellet administration does not produce the marked neurochemical and behavioral changes of long term morphine injections.Supported in part by grant DA 00830, USPHS.     

Weight loss and shock-elicited aggression as indices of morphine abstinence in rats

Weight loss and shock-elicited aggression have been compared as quantitative indices of morphine abstinence in rats. A range of doses of morphine was administered to rats by i.p. injection twice daily for 12–15 days. After injections were stopped, morphine-abstinent rats lost weight precipitously, and showed an increased frequency of fighting in response to aversive stimulation (foot-shock). Recovery of weight appeared complete after 15–20 days but a significant increase in aggression was found at 18 days post-withdrawal; this virtually disappeared after 52 days. Both the amount of weight lost and the frequency of fighting increased as a function of the previous maintenance dose of morphine; the effective dose range appeared similar for these two indices. Weight loss was much less variable than fighting, had the advantage of rapid, objective measurement, and appeared to be the more reliable index of abstinence.     

Localization of the central sympatho-inhibitory effect of a narcotic analgesic agent, fentanyl, in cats.

Fentanyl (10 and 30 mug/kg), a narcotic analgesic, induced in cats a decrease in blood pressure and heart rate and reduced spontaneous splanchnic nerve activity. Fentanyl reduced the pressor response to medullary stimulation, but did not change the pressor response to hypothalamic or cervical spinal cord stimulation. Fentanyl reduced the potential evoked in the splanchnic nerve by stimulation at low frequency of a pressor area of the medulla oblongata. The potentials evoked in the splanchnic nerve by hypothalamic or cervical spinal cord stimulation were only slightly changed. Nalorphine (0.5 mg/kg) or naloxone (30 mug/kg) induced a recovery in blood pressure, heart rate and spontaneous splanchnic discharges which had been reduced by fentanyl, but nalorphine or naloxone did not restore pressor response to medullary stimulation or potentials evoked in the splanchnic nerve by medullary stimulation, which had been decreased by fentanyl.     

Effects of cholinergic agonists and antagonists on morphine-withdrawal syndrome

The effects of pilocarpine, atropine and dexetimide were studied on the occurrence and intensity of morphine-withdrawal signs observed after cessation of chronic morphine injections. Pilocarpine was effective in reducing both wet-dog like body shakes and aggression but it increased diarrhea and weight loss. Pretreatment with atropine blocked all of the effects of pilocarpine on withdrawal signs. Methylscopolamine pretreatment blocked only diarrhea. The administration of atropine or dexetimide produced no significant effect on any of the withdrawal signs. These results indicate a role for central cholinergic mechanism in narcotic withdrawal.     

The effects of divalent ions on morphine analgesia and abstinence syndrome in morphine-tolerant and-dependent mice

Intracerebral administration of copper sulfate potentiated morphine analgesia in morphinetolerant and-dependent mice. The stereotyped jumping response, precipitated by naloxone, was inhibited by copper in morphine-dependent mice, but copper failed to affect other abstinence signs. When abstinence was precipitated with a partial antagonist, nalorphine, stereotyped jumping was not inhibited by either calcium or copper. These modification of narcotic effects by copper were produced without alterations in the brain disposition of morphine. Total radioactivity in the brain following radioactive naloxone administration was also not altered.     

Potentiation of morphine-elicited circling by dopaminergic uptake blockade

Contraversive circling induced by unilateral infusions of morphine (7.5 nanomoles or 5 μg) into the ventral tegmental area was studied under conditions of dopamine uptake inhibition. Dopamine uptake blockade with either nomifensine (2.5 mg/kg) or GBR 13069 (2.0 mg/kg) resulted in a 3-fold increase in the rate of circling. Naloxone (1.5 mg/kg) attenuated but did not completely block the potentiated circling. These data are consistent with the hypothesis that morphine causes contraversive circling through local activation or disinhibition of dopaminergic cell firing.     

Mechanism of morphine block of electrical activity in ganglia of Auerbach''s plexus

A study was made of the effect of morphine on electrical activity within single ganglia of Auerbach's plexus of guinea pig longitudinal muscle-myenteric plexus as monitored by means of external electrodes. Morphine produces a concentration dependent block of single spike activity. This effect is competitively antagonized by naloxone. The ED₅₀ for morphine effect is about 7 × 10⁻⁷ M. Naloxone and dextrorphan have no effect on electrical activity. Acetylcholine in the concentration range of 10⁻⁷−10⁻⁵ M augments electrical activity of ganglia. Morphine has little if any effect on the enhanced stimulation produced by acetylcholine thus indicating that the drug does not act directly upon the ganglion. Our results suggest that a specific opiate receptor is present on preganglionic nerve terminals and that morphine and other opiates block ganglionic transmission by inhibiting the release of preganglionic acetylcholine.     

Potentiation of physical dependence by conjugation at the 6-position of nalorphine

The experiments concerned the effects of glucuronate or sulfate conjugation at the 6-position of nalorphine on the analgesic and antagonistic activities and also on the development of tolerance and physical dependence. Nalorphine-3-and 6-sulfate ester were synthesized for the first time. The analgesic effect of nalorphine-6-sulfate and -glucuronide was higher than that of nalorphine when assessed in the acetic acid writhing test. However, these 6-conjugates exhibited less potent agonistic activity in the test with guinea-pig ileum muscle strip and revealed no analgesic effect in the tail pinch test. The antagonistic activity of these 6-conjugates to morphine analgesia was lower on their s.c. injection, but higher on i.c.v. injection than that of nalorphine. The development of tolerance to the analgesia caused by nalorphine was not affected by the 6-modifications. Frequent withdrawal signs were seen in mice treated chronically with anlorphine-6-conjugates by challenging with naloxone while mice treated with nalorphine showed no such signs. This potent enhancing effect of 6-conjugation on the development of physical dependence was suggested to be also the case with morphine. These changes of potency due to conjugation were interpreted as due to the altered interaction with multiple opioid receptors.     

滇西嘟拉碱甲的镇痛和身体依赖性研究

用扭体法、热板法、光热-甩尾法和甲醛致痛法证实Bul有明显镇痛作用。连续给药9 d,镇痛作用无耐受现象。小鼠跳跃反应试验阴性;Bul对吗啡依赖大鼠或猴的戒断症状,均无替代作用。Bul的镇痛作用不能被纳络酮翻转;利血平可取消Bul的镇痛作用,补充5-HT或5-HTP能翻转利血平取消Bul的镇痛作用。     

Behavioral effects of naloxone and nalorphine preceding and following morphine maintenance in the rhesus monkey

The effects of morphine, naloxone, and nalorphine on responding maintained under a variable-interval schedule of food presentation were assessed in rhesus monkeys before and after successive periods of daily morphine maintenance (15.0 mg/kg/day SC). Withdrawal from morphine dependence was accomplished gradually following the first two maintenance periods and abruptly following the third period. Schedule-controlled responding was disrupted when morphine maintenance was abruptly discontinued but not when the maintenance dosage was gradually reduced to zero. Tolerance to the acute effects of IV morphine on responding developed during morphine maintenance and dissipated after daily injections were discontinued. The effects of IV naloxone and IV nalorphine following each period of morphine maintenance were generally similar to their effects in initial determinations. These data indicate that tolerance-producing regimens of repeated daily injections with morphine do not necessarily produce enduring changes in the effects of opiate antagonists on schedule-controlled behavior. Additionally, gradual withdrawal from morphine maintenance can minimize the behavioral disruptions that attend abrupt abstinence.     

Adrenal, plasma and urinary corticosteroids during single or repeated administration of morphine in cats.

Corticosteroids and ascorbic acid in the adrenal glands of adult cats have been investigated after single or repeated administration of morphine. Also plasma levels and urinary excretion of corticosteroids were determined. A significant increase in the content of corticosteroids in the glands and plasma was found after initial injection of morphine. After 7 days of consecutive morphine treatment a fall of corticosteroids in the glands was observed; after 2 weeks of daily injections the content of adrenal corticosteroids was significantly lower than in the control animals but no change was found in the plasma. Administration of the drug during 1 month led to a highly significant decrease of corticosteroids in the glands as well as in plasma. No significant change in adrenal ascorbic acids was found whether the adrenal corticosteroids were higher or lower than in the control cats. Urinary corticosteroids were high during the first week of morphine treatment but thereafter the excretion declined progressively and was lower than the control level after 13 days of treatment. The significant decrease of corticosteroids observed after repeated administration of morphine and the rise in adrenal corticosteroids found after the injection of nalorphine to the morphinized animals suggest that some kind of morphine dependence had been developed in the cats after repeated administration of the drug.     

Effects of morphine and nalorphine on kainic acid-induced hypothermia in rats

Intraventricular administration of kainic acid at the dose of 0.1 g induces a significant depression of rectal temperature followed rapidly by its slight elevation. Morphine (40.0 mg·kg^-1 IP), which by itself elicited biphasic effect on the body temperature of rats—initially hypothermia followed by hyperthermia—slightly increased the kainic acid-induced hypothermia. Kainic acid did not cause any changes in the hyperthermic effect of low doses of morphine (10.0 mg·kg^-1). Pretreatment of rats with nalorphine enhanced the kainic acid-induced hypothermia. On the contrary, nalorphine reversed the hypothermic effect produced by morphine at the dose of 40.0 mg·kg^-1. The results suggest that morphine and kainic acid-induced hypothermia are not mediated by the influence on the same type of receptors.     

Morphine dependence in rats produced after five days of ingestion

In the first experiment dose-dependent withdrawal signs following a nalorphine injection (either 2, 4, 8, 16, or 32 mg/kg, i.p.) were seen in rats that had been drinking sucrose morphine for 21 days. A non-dependent control group was generally unaffected by an injection of the antagonist (16 mg/kg, i.p.). In Experiment II, morphine withdrawal signs, both nalorphine induced and without nalorphine injection, were observed in rats which had been placed on only five days of morphine-adulterated food and sucrose morphine. Although both groups showed clear withdrawal signs after the drug was removed from their diet, the nalorphine-injected group showed more severe symptoms. By the eleventh day of withdrawal all rats had resumed normal eating and drinking and had nearly recovered their pre-drug body weights. It is concluded that reliable morphine dependence can be induced in five days, using a morphine-adulterated diet.This work was supported by NSF research grants B023365 and P2B0349 to K. A. Khavari.     

Interactions of morphine and nalorphine with physostigmine on operant behavior in the rat

Morphine and nalorphine were tested alone and in combination with physostigmine (0.0625 mg/kg) in rats trained under a continuous avoidance schedule with an escape contingency. When tested alone, nalorphine increased avoidance rate in doses up to 32 mg/kg but exerted no other effects. Morphine, 1 mg/kg, increased avoidance response rate while higher doses produced a graded depression of all behavior. In the presence of physostigmine, nalorphine produced a well-defined graded depression of avoidance responding and increased the number of shocks received by the animals over a 16-fold dose range. Physostigmine failed to potentiate the prominent depressant effects of morphine in the same test situation. The finding that in the presence of cholinesterase inhibition nalorphine acts as a depressant of operant behavior in the rat supports existing evidence that cholinergic mediation should be considered as a factor in some of the actions of strong analgesics.Publication No. 1028 of the Division of Basic Health Sciences of Emory University. This investigation was supported by USPHS Grants SO-1-FR05364 and MH12870-04.A preliminary report of this investigation appeared in Fed. Proc, 30, 390 (1971).Postdoctoral trainee of NIH Graduate Pharmacology Training Grant GM-179 during part of this work.     

Effect of morphine and naloxone on intestinal transit in mice

Morphine caused a dose-dependent slowing of the rate of intestinal transit in mice. This inhibitory effect of morphine was antagonised by naloxone administration. Pretreatment with a single dose of morphine did not induce any detectable tolerance to the inhibitory effect of a second dose of morphine given 5 h later. However, naloxone was more effective in antagonising this inhibitory effect of morphine-pretreated mice than in saline-pretreated animals. Molecular sieve morphine pellet implantation for 24 h induced detectable tolerance to the inhibitory effect of morphine administered 3 h after removal of the pellet. In addition, the antagonistic effect of naloxone was also augmented when compared with blank pellet-implanted control animals. The present study has shown that the enhanced naloxone potency against the inhibitory effect of morphine on intestinal transit was observable before the development of overt tolerance, and that tolerance to the effect of morphine on the small intestine could be induced by implantation of a molecular sieve morphine pellet for 24 h.     

Effect of intracerebroventricular administration of morphine upon intestinal motility in rat and its antagonism with naloxone

Morphine, intracerebroventricularly (i.c.v.) or intraperitoneally (i.p.) administered to rats, inhibited intestinal propulsion as tested by a charcoal meal. Such an inhibition was shown to be linearly related to the log of administered doses for both routes of administration and the two linear regressions are parallel, so that morphine was calculated to be 206 times more potent when administered i.c.v. than i.p. A dose of morphine fully active by the i.c.v. route was completely inactive when injected by the i.v., i.p., i.m. and s.c. routes. Naloxone, administered i.c.v., blocked the antipropulsive effect of morphine i.c.v. or i.p. The pA2 of naloxone versus morphine, both administered i.c.v. was determined and calculated to be 7.14 (6.76-7.62).     

Control of morphine-withdrawal hypothermia by conditional stimuli

Male rats were given increasing doses of morphine sulfate to cause addiction. Each injection was paired with a bell. After a number of pairings, the bell acquired conditional-stimulus property in that, like morphine, it prevented withdrawal hypothermia during 72 h of withholding morphine. In another group the withdrawal hypothermia was precipitated by withholding of morphine injections. The bell reversed that hypothermia.     

Peripheral stimulation in mice induces short-duration analgesia preventable by naloxone.

Peripheral stimulation was applied to mice by mild caudal electrostimulation, by mechanical pressure or by footshock for 30 sec, before testing on a 52 degrees C hot plate. Reaction times to paw lick and to escape from the hot plate were recorded. Analgesia could be elicited and measured by these procedures. It was of short duration, declining in a minute, and was antagonized by low doses of naloxone. The analgesia measured by the escape reaction time could be elicited after multiple caudal electrostimulation as well as in morphine-tolerant mice, and it could still be reversed by naloxone. An opioid link is thus involved in this phenomenon, which also supports the notion of more than one opioid pathway existing in the brain. The short period of analgesic cover afforded in the face of noxious stimuli would permit aversive action to be taken in nature and thus might represent the prime functional role of enkephalins in the brain.     

The effect of substantia nigra stimulation and morphine on α-motoneurones and the tail-flick response

Rats were used to study the effect of unilateral stimulation of the substantia nigra on the reflex discharge of α-motoneurones and on the reaction time of the tail-flick response. In preparations with prenigral decerebration, nigral stimulation facilitated monosynaptic α-reflex activity ehilst γ-reflex activity remained unchanged. The facilitation of monosynaptic α-reflex activity was reduced by naloxone (1 mg/kg); morphine (2 mg/kg) did not change the number of α-reflex discharges, but it reduced the α-reflex latency, enhanced the effect of nigral stimulation on the latency and abolished the effect of naloxone on nigral facilatation. Nigral stimulation prolonged the reaction time of the tail-flick response in rats with an intact brain and after prenigral decerebration. Naloxone did not influence the anti-nociceptive effect of nigral stimulation, whilst morphine enhanced it in rats with an intact brain. The anti-nociceptive effect exerted by morphine in animals with an intact brain was abolished by prenigral decerebration, and an additional spinalization restored it. Inactivating the nigral neurones by unilateral microinjections of procaine or GABA into the substantia nigra depressed the nociceptive reflex. It is concluded that (1) activation of nigral neurones influenced mono- and polysynaptic reflexes in a reciprocal fashion by a pathway descending via brain stem relays to the spinal cord, (2) inactivation of nigral neurones produced similar changes in reflex activity by altering the function of the nigro-striatal feedback system, the outlet from the system to the spinal cord not being the substantia nigra, (3) morphine influenced the nociceptive reflex by an action at different levels of the central nervous system.