Characterization of opioid dependence of isolated ileum of morphine dependent and of chronically stressed Wistar-Kyoto (WKY)-rats.

The opioid antagonist naloxone induced tonic contraction ("gut dependence") of isolated ilia of both morphine dependent WKY-rats and WKY-rats chronically stressed by immobilization. Morphine and met-enkephalin but neither dynorphine nor leu-enkephalin antagonized the naloxone induced "gut dependence" of isolated ilia obtained from morphine dependent WKY-rats. Met-enkephalin as well as dynorphine inhibited the "gut dependence" of chronically stressed rats; morphine and leu-enkephalin had no inhibitory effect.

Modulation of spinal synaptic transmission by beta-melanocyte stimulating hormone (beta-MSH).

Synaptic modulation refers to altered excitability of a synapse by a substance that does not produce a spike potential at the synapse. Available evidence points to the conclusion that beta-melanocyte stimulating hormone (beta-MSH) modulates synaptic transmission through monosynaptic pathways in the cat spinal cord. Earlier evidence is reviewed, and new data are presented.

A fragment of substance P with specific central activity: SP(1-7).

Amino-terminal fragments of substance P (SP), SP(1-7) and SP(1-8), were found to produce naloxone-reversible antinociception in the mouse similar to that produced by SP. Similar to SP, these peptides produce antinociception only within a narrow dose range. They have no activity on smooth muscle or blood pressure.

Endorphin levels in opioid-dependent human subjects: a longitudinal study.

Endorphin levels were measured in 51 cerebrospinal fluid samples from 27 opioid-dependent or postdependent subjects. Radioreceptor assay showed the endorphin levels to be higher than those found in normal subjects. These high levels were found even while subjects were on methadone maintenance.

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.

Synaptic modulation by substance P.

The phrase "synaptic modulation," to describe a role of neurotropic peptides, has been used in a number of different ways by a number of different investigators. Using the phrase in its original context, i.e.

Inhibition by Z-Pro-D-Leu of development of tolerance to and physical dependence on morphine in mice.

The peptide-Z-Pro-D-Leu, injected daily in mice receiving morphine chronically, was found to prevent development of physical dependence as measured by changes in body temperature and body weight due either to abrupt or to naloxone-induced withdrawal. On the other hand, administration of Z-Pro-D-Leu only on the last day of morphine treatment did not alter the overt signs of withdrawal. Daily administration of Z-Pro-D-Leu was also effective in blocking the development of tolerance to the analgesic and the hypothermic effects of subsequent challenge doses of morphine.

An effect of beta-melanocyte stimulating hormone (beta-MSH) on alpha-motoneurones of cat spinal cord.

Actions of beta-MSH and of melatonin on the recovery cycle of single spinal neurones were studied in the decerebrate-spinal cat. beta-MSH facilitated the rate of post-excitation recovery of alpha-motoneurones and some internuncial neurones, and melatonin inhibited the rate of post-excitation recovery. These observations provide additional evidence that beta-MSH functions in the nervous system as a modulator, and may help explain actions of beta-MSH in modifying acquisition of conditioned avoidance responses as well as its interaction with drugs such as morphine.

Changes in muscle action potentials of patients with diseases of motor units following the infusion of a peptide fragment of ACTH.

The polypeptides ACTH and ATCH4-10 (OI 63) witha sequence of amino acids H-Met-Glu-His-Phe-Arg-Trp-Gly-OH, have similar stimulating effects on motor units in lower mammals. Their actions differ primarily in that ACTH4-10 is not corticotropic. Since the corticotropic action of ACTH frequently presents a problem during its clinical use in treatment of motor unit diseases, the action of ACTH4-10 was studied in two patients with muscular atrophy.

Influence of peptides on reduced response of rats to electric footshock after acute administration of morphine.

Acute treatment of rats with morphine (10 mg/kg) resulted in a marked reduction of motor response to inescapable electric footshock (EFS). Nalorphine (2mg/kg) antagonized this action of morphine. Pretreatment with synthetic ACTH 1-24 (10 IU) 60 min prior to testing also inhibited this morphine-induced reduction, whereas other ACTH-like peptides, lacking corticotrophic activity, were ineffective.

Facilitation of development of resistance to morphine analgesia by desglycinamide9-lysine vasopressin.

Desglycinamide(9)-lysine vasopressin facilitates development of resistance to the analgesic action of morphine in mice if morphine is administered before the peptide. Desglycinamide(9)-lysine vasopressin is not a morphine antagonist, and does not appear to cause either hyperalgesia or alteration of the response to the technique used for evaluating analgesia.

Actions of morphine on the segmental reflex of the decerebrate-spinal cat.

1. The actions of morphine were studied on the segmental reflex of the decerebrate-spinal cat. Morphine decreased arterial blood pressure.