The present study was undertaken to investigate whether the C-terminal extended Met-enkephalin heptapeptide (Met-enkephalin-Arg6-Phe7, MEAP) played a role in mediating the analgesic effect of electroacupuncture in rabbits. MEAP and its degrading enzyme inhibitor captopril as well as antiserum against MEAP were injected into the periaqueductal gray (PAG) via a previously implanted cannula. Their effects on nociception were tested by the escape response latency (ERL) elicited by radiant heat applied on the skin of the snout. (1) Microinjection of MEAP (30-240 nmol) into PAG produced a dose-dependent analgesic effect which was 2.5 times more potent than Met-enkephalin (MEK) and 3 times less potent than morphine. The complete reversal of the analgesia elicited by 240 nmol of MEAP by a small dose of naloxone (0.1 mg/kg, i.v.) indicates that the effect of MEAP is mediated by naloxone sensitive opioid receptors. (2) In rabbits, a dose-dependent analgesia was elicited by an intra-PAG injection of captopril (60-240 nmol). A single dose of 240 nmol captopril increased ERL by more than 100%. This effect could be reversed by 30 nmol of naloxone injected into the same site, or by antiserum recognizing MEAP (1 microliter, titer 1:1500) but not by antiserum recognizing MEK (1 microliter, 1:8000) suggesting that captopril was able to protect MEAP from degradation. (3) Intra-PAG injection of 60 nmol of captopril significantly potentiated the after effect of electroacupuncture (EA) induced analgesia. This effect could be blocked either by 30 nmol (but not 7.5 nmol) of naloxone, or by 1 microliter (but not 0.1 microliter) of MEAP antiserum.(ABSTRACT TRUNCATED AT 250 WORDS)

Acupuncture Therapy↗

PubMed1984

Analgesia induced by intrathecal injection of dynorphin B in the rat.

A dose-dependent analgesic effect of intrathecally injected dynorphin B was observed in rats using the tail flick as nociceptive test. Intrathecal injection of 20 nmol of dynorphin B increased the tail flick latency by 90 +/- 23%, an effect that lasted about 90 min. For the same degree of analgesia, dynorphin B was 50% more potent than morphine on a molar basis. The analgesic effect of this dose of dynorphin B was partially blocked by 10 mg/kg, but not by 1 mg/kg, of subcutaneous naloxone, showing a relative resistance to naloxone reversal as compared with morphine analgesia. The analgesia produced by dynorphin B was unchanged in morphine-tolerant rats but was significantly decreased in rats tolerant to ethylketazocine. These results suggest that dynorphin B produces its potent analgesic effect by activation of kappa rather than mu opioid receptors in the rat spinal cord.

Analgesics↗

PubMed1984

Depressor and bradycardic effect following intrathecal injection of [NMePhe3,D-Pro4]morphiceptin in rats.

The intrathecal injection of 1.25, 2.5 and 5 micrograms of [ NMePhe3 ,D-Pro4] morphiceptin (MC), a highly selective mu receptor agonist, in pentobarbital-anesthetized rats resulted in a dose-dependent decrease of mean arterial pressure, reaching a maximal effect 1 h after its administration. A marked bradycardic effect paralleled the depressor effect. These effects were totally reversed by prior intrathecal injection of 10 micrograms of naloxone. The effect of MC was fully present in bilaterally vagotomized rats and in rats under artificial respiration. These results provide evidence for the opioid control of blood pressure and heart rate via mu receptors in the spinal cord.

Animals↗

PubMed1984

Acupuncture mechanisms in rabbits studied with microinjection of antibodies against beta-endorphin, enkephalin and substance P.

Injection of protein-A purified antibodies against Met-enkephalin and beta-endorphin into the periaqueductal gray matter (PAG) was shown to decrease the analgesic effect of electroacupuncture (EA) in rabbits. Met-enkephalin antibodies were more potent than the beta-endorphin antibodies in causing a statistically-significant effect on electroacupuncture analgesia. Antibodies to Met-enkephalin were also active at the spinal level, whereas antibodies against beta-endorphin were without effect: this is in agreement with a rich enkephalinergic innervation and absence of beta-endorphin-containing fibres in the spinal cord. Substance P, the other neuropeptide of this study, also seems to be important in mediating effects of electroacupuncture. Injection of antibodies into the periaqueductal gray caused decrease of the effect of electroacupuncture whereas intrathecal administration of Fab-fragment substance P antibodies caused a marked potentiation. The demonstration of site specificity of the neuropeptides in mediating analgesia induced by electroacupuncture supports the validity of this experimental approach.

Acupuncture Therapy↗

PubMed1984

MR imaging of the skull base.

Fifty-four patients with abnormalities primarily involving the base of the skull were evaluated by magnetic resonance (MR) imaging. The results were compared with information obtained by other radiologic studies, primarily X-ray CT. On MR imaging, better anatomic definition of soft tissues in the deep compartments of the nasopharynx was achieved through the high level of tissue contrast discrimination and lack of bone artifacts. The parapharyngeal fat plane, separating pterygoid from pharyngeal musculatures, was consistently demonstrated. However, the inability of MR to image compact bone proved to be a major drawback where bony detail was required. In general, MR imaging demonstrated 100% sensitivity to abnormalities involving the posterior compartment (clivus and craniovertebral junction) and was least valuable in the evaluation of the anterior compartment (orbits, cribiform plate, and sinuses.

Adolescent↗

PubMed1984

Head trauma evaluated by magnetic resonance and computed tomography: a comparison.

Magnetic resonance (MR) images and computed tomograms of 25 patients with head trauma were compared. MR proved to be superior in many ways for demonstrating extracerebral as well as intracerebral traumatic lesions. Isodense subdural hematomas, which present a diagnostic dilemma on CT images were clearly seen on MR, regardless of their varying CT densities. In a case of epidural hematoma, the dura mater was shown directly as nearly devoid of signal on MR. Direct coronal images provided excellent visualization of extracerebral collections along the peritentorial space and subtemporal area. In a patient with intracerebral hematoma, CT failed to demonstrate residual parenchymal changes in a 3-month follow-up study, but MR clearly depicted the abnormalities. The superiority of MR over CT was also well illustrated in a patient with post-traumatic osteomyelitis of the calvarium.

Adolescent↗

PubMed1984

Magnetic resonance imaging in the evaluation of the brainstem.

Magnetic resonance (MR) images of the brainstem region from 100 normal or asymptomatic individuals were reviewed in addition to those of 17 patients with intra-axial brainstem lesions and 15 patients with extra-axial masses around the brainstem. MR was able to demonstrate consistently the normal anatomy of the brainstem and adjacent cisterns, though the distinction between gray and white matter was seldom possible with the present technology. Masses in and around the brainstem were all accurately identified on MR and its sensitivity was superior to that of x-ray computed tomography (CT). These study results show that despite its technical limitations, MR is presently the examination of choice for the evaluation of brainstem abnormalities and eventually it will undoubtedly replace metrizamide CT cisternography.

Adolescent↗

PubMed1984

Magnetic resonance imaging of the orbit: a preliminary experience.

Eleven patients with various space-occupying lesions in the orbit were examined, using a 0.3-tesla superconducting magnet to assess the capabilities and limitations of magnetic resonance (MR) imaging in the investigation of orbital lesions. Although the images provided valuable anatomic data, the bright signal intensity of fat and the partial volume effects of large section thickness resulted in loss of resolution for small, low-signal-intensity structures. The limitations of MR imaging were also reaffirmed by the lack of visualization of calcifications and of the bony orbit. These preliminary results show that MR offers no advantage over x-ray computed tomography except for its lack of ionizing radiation. Further technical improvements are needed before MR imaging will be made useful in this area.

Adult↗