Emery Zimmermann

Substance P and analgesia.

SUBSTANCE P (SP)1 has long been known to have marked effects on the central nervous system (CNS). Lembeck2 suggested that SP might be a transmitter of primary sensory impulses, an hypothesis supported by subsequent investigators3,4. Early work on SP was carried out using natural material, which unless highly purified, is known to be contaminated with bradykin or some other kinin-like material5. As bradykinin also has marked effects on the CNS, experiments carried out using impure SP may be misleading. This may account for some of the conflicting observations that exist regarding the action of SP on sensory transmission, and may also explain its interaction with opioids. Whereas impure SP has been shown to antagonise morphine6, synthetic SP was found to substitute effectively for morphine in mice chronically treated with morphine7. SP does not act like morphine in the field-stimulated guinea pig ileum8 and does not combine with morphine receptors9. Furthermore, SP has been reported to be the most potent algogenic substance known on the human blister base10. Recent reports on the characterisation and activity of enkephalin11,12 suggested that enkephalin may be acting as an analogue of SP. We have therefore examined SP for morphine-like activity.

Learned helplessness: An experimental model of the DST in rats ☆

Elevated ratings of anxiety and agitation in Dexamethasone Suppression Test (DST) nonsuppressors suggest a role for psychological stress in the generation of the hypothalamic-pituitary-adrenal cortical (HPAC) abnormalities characteristic of depression. We employed the learned helplessness model of depression to test the effectiveness of psychological stress in inducing a resistance of plasma corticosterone levels to dexamethasone suppression. Inescapably shocked rats exhibited corticosterone levels that were significantly more resistant to dexamethasone suppression than were the levels of rats receiving an equivalent amount of escapable shock or no shock. These results confirm the hypothesis that HPAC resistance to dexamethasone suppression is enhanced by the distress associated with the inefficacy of behavioral coping responses. The present findings represent the first analog of the DST in the learned helplessness model of depression. This DST model allows investigations into neurobiological mechanisms underlying the HPAC alterations in depression.

Intracerebroventricular ACTH activates the pituitary-adrenal system:dissociation from a behavioral response.

Abstract In the rat, intracerebroventricular injection of synthetic ACTH (ACTH1–24, ACTH1–16) elevated plasma corticosterone levels and induced the display of excessive grooming behavior. The grooming response could be elicited in hypophysectomized rats without concommittant elevation of plasma corticosterone. In intact rats subcutaneous injection of ACTH1–24 and not of ACTH1–16-NH2 stimulated the release of adrenal corticosteroids, whereas no excessive grooming was observed. In contrast to the reduced effectiveness of a second icv injection of ACTH in inducing the behavioral response, no single-dose tolerance was observed for the effect of icv ACTH on the pituitary-adrenal system. Therefore it was concluded that two different central mechanisms underly the observed responses to the icv applied ACTH.

Δ9-Tetrahydrocannabinol enhancement of Lordosis Behavior in estrogen treated female rats

levo-alpha-Acetylmethadol was orally administered via a sucrose solution to rats in their drinking water for 24 days. A control group received only sucrose. Bodyweight and fluid consumption were monitored daily. The behavioral effects during chronic drug administration and during eight days of withdrawal were studied using behavior controlled by a fixed-interval schedule of food reinforcement. Body weights of treated animals remained stable during drug administration but decreased by approximately 25% during withdrawal. There were no significant differences in volume of fluid consumed by the two groups. Response rate and number of reinforcements were decreased during drug administration. During withdrawal, response rates were greater than pre-drug control rates.Abstract Estrogen and progesterone (PROG) are both considered essential hormones for the display of sexual receptivity in the female rat. Δ 9 -tetrahydrocannabinol (THC), one of the active components of marijuana, was tested in ovariectomized rats for possible estrogenic and anti-estrogenic activity using the display of lordosis behavior, one of the components of sexual receptivity, as an endpoint. Test animals were treated with THC (1.25, 2.50 or 10.00 mg/kg/day) or estradiol benzoate (EB) + THC (2.0 μg/kg/day and 10.0 mg/kg/day, respectively) followed by 500 μg PROG and tested for lordosis behavior on Day 5. The animals treated with THC alone failed to show any lordosis behavior, similar to oil and vehicle controls, while the behavioral effects of EB were not antagonized by the 10.0 mg/kg dose of THC. Thus, the estrogenic effects of THC, using the lordosis system as an end point, are at best minimal, if present at all. The effects of acute THC in EB primed rats (2.0 μg/kg/day × 3) were also tested in this study. At relatively low doses (0.5 and 1.5 mg/kg) of THC, a significant increase in the lordosis quotient (LQ; number of lordosis responses/number of mounts × 100) was noted. At a higher dose (3.0 mg/kg) of THC, a significant reduction in the LQ was noted, indicating a dose-dependent effect of THC. Following adrenalectomy, the dose-response curve for THC was shifted to the left, as a lower dose (0.15 mg/kg) of THC was now capable of enhancing the LQ, while the 0.5 and 1.5 mg doses were no longer effective (similar to the 3.0 mg/kg dose in non-adrenalectomized animals). The biphasic action of PROG on LQ was also utilized to rule out adrenal involvement in the enhanced behavior seen in the EB primed and THC treated animals. When a behaviorally effective dose of PROG was administered, 18 hr prior to PROG followed by a behavioral test, it antagonized the behavioral effects of the second dose of PROG, while a behaviorally effective dose of THC, given 18 hr prior to PROG followed by a behavior test, was ineffective in antagonizing the behavioral effects of PROG, indicating that minimal, if any, PROG is released from the adrenal following a behaviorally effective dose of THC. Thus, it appears that THC is capable of enhancing sexual receptivity of female rats by a direct action on the central nervous system.

Modulation of cat monosynaptic reflexes by substance P.

Substance P (SP) applied by iontophoresis at different current strengths to single motoneurons of cat spinal cord did not cause these units to discharge. SP produced a gradual and prolonged change in synaptic excitability as measured by response to dorsal root stimulation. The effect outlasted application of SP. The lowest effective dose of SP diminished motoneuron response to dorsal root stimulation (inhibitory modulation). Doses 2-4 times as great enhanced the response to dorsal root stimulation (facilitatory modulation) without causing the motoneuron to discharge spontaneously. These observations suggest that one physiological role of SP is modulation of synaptic transmission, i.e. alteration of efficacy of transmission without acting as a primary transmitter at the postsynaptic membrane.

Direct redioimmune assay of 16-glucosiduronate metabolites of estriol in human plasma and urine

It has been established that the 16-glucosiduronate metabolites of estriol comprise the major estriol component in pregnancy plasma [ 1 ] , urine [ 1,2] and amniotic fluid [3]. However, little is known about their physiological or pathological correlations. One reason is the fact that assays for individual metabolites of estriol either do not exist or are unsuitable for practical processing of large numbers of clinical samples. The possibility that immune assays might provide a useful means of measuring individual estriol metabolites prompted us to develop and investigate various antigens. A non-specific 16a-glucosiduronate antiserum has been reported [4]. This report describes radioimmune experiments in which picogram quantities of the 16-glucosiduronate metabolites of estriol were measured in the presence of vast excesses of estriol, other estrogens and/or their metabolites. Antibody specificity together with the natural preponderance of the 16-glucosiduronate metabolites made possible their direct measurement in plasma and urine.

Adult behavior and adrenocortical function following neonatal morphine treatment in rats

Adult behavioral and endocrine effects of neonatal administration of morphine (M) were studied in female rats injected s.c. with M on either days 3–12 (M1) or days 12–21 (M2). The dose given twice daily was increased to 8 mg/kg in group M1 and to 16 mg/kg in group M2. Compared to saline-treated controls, growth rates were temporarily suppressed (P<0.05) and body weights were reduced (P<0.05) util day 20 in M1 and until day 64 in M2 rats. The open-field test performed on days 29–31 failed to differentiate between neonatal treatment groups. On days 90–95 M1 but not M2 animals showed impaired learning of a conditioned emotional responses (CER). On day 40 all groups showed similar increased levels of plasma corticosterone 30 min following injection of naloxone (5 mg/kg). Compared to controls on day 156, both M1 and M2 rats showed diminished (P<0.05) analgesic responses (hot-plate test) to M (10 mg/kg). In response to M challenge (40 mg/kg) on day 170, all groups showed comparable acute increases in plasma corticosterone levels. These findings provide further evidence that early exposure to M results in growth retardation and protracted tolerance and that, depending on dose and time of exposure, neonatal M may result in impaired learning of CER in adulthood. These effects suggest that early morphine can produce long-lasting alterations of learned behavior without lasting impairment of pituitary-adrenal function.

The effect of home or novel environment on the facilitation of passive avoidance by post-training ethanol

Passive avoidance behavior of mice is improved when mice are injected with ethanol immediately after footshock training. Further study has shown that avoidance can be affected by ethanol injections given within 1 h, but not at 90 or 180 min, after training. The present study was conducted to investigate the possibility that events which occur in the homecage during this sensitive period may influence the effect of ethanol on subsequent avoidance. Male Swiss-Webster mice were housed either singly in a novel environment for 90 min or returned to their (group) homecage following one-trial, step-through, passive avoidance training (0.1 mA footshock) and intraperitoneal injection of 3.0 g/kg ethanol (15% v/v) or saline. As in previous studies, when ethanol-treated mice were returned to their homecage, avoidance was significantly increased at 24 h compared to the behavior of saline-treated mice. However, when mice were isolated in the novel environment for 90 min immediately following treatment, the memory facilitating effects of ethanol were not observed. The avoidance behavior of mice injected with saline was the same regardless of their post-training environment. Also, the number of mice (6 or 10) housed per homecage did not significantly influence the effects of ethanol or post-training environment on avoidance. These findings indicate that environmental factors may interact with the effects of ethanol to modify avoidance behavior. The possible influence of variables such as aggression, thermoregulation, and behavioral arousal on the effects of ethanol in this paradigm are discussed.

Continuous measurement of cerebrospinal fluid pressure in unrestrained rats

Abstract A sensitive method for measuring intracranial pressure in unrestrained, unanesthetized rats has been developed. Two identically calibrated pressure transducers connected to fluid-filled polyethylene catheters were used to simultaneously monitor ventricular cerebrospinal fluid (CSF) pressure and head position. Artifacts due to changing head position were electronically subtracted from ventricular pressure, yielding a continuous dynamic record of “true” CSF pressure. A simple technique for precisely calibrating pressure transducers is also described. The mean CSF pressure obtained in 27 non-stressed freely-behaving adult rats was 64 ± 2 mm H 2 O. Handling caused a prompt increase in intracranial pressure of approximately 80–120 mm H 2 O. Moment-to-moment fluctuations in intracranial pressure closely reflect changes in central venous pressure. The techniques described are applicable to continuous measurement of CSF pressure in laboratory or clinical settings.

MEASUREMENT OF DELTA 9-TETRAHYDROCANNABINOL (THC) IN WHOLE BLOOD SAMPLES FROM IMPAIRED MOTORISTS

The major psychoactive cannabinoid in marihuana, delta 9-tetrahydrocannabinol (THC) was measured in 1792 randomly selected blood specimens from erratic motorists arrested for impairment who submitted to blood alcohol sampling. Of these specimens, 14.4% were positive for THC (greater than or equal to 5.5 ng/mL). In those erratic driver specimens negative for alcohol THC positives rose to 23%. Drivers who used marihuana covered a broad age range. Aliquots of hemolyzed blood (10 microL) were analyzed by a sensitive radioimmunoassay (RIA) not requiring extraction. RIA accuracy and specificity were validated by gas liquid chromatography/mass spectroscopy (GLC/MS) split pair analysis (correlation coefficient = 0.93). This initial experience should facilitate and amplify a program designed to set forth the epidemiology of marihuana use in motorists and possible behavioral correlates.