Effects of d-amphetamine injected into the nucleus accumbens on ethanol reinforced behavior

Rats, initiated to self-administer 10% (v/v) ethanol in an operant situation using the sucrose-fading procedure, received bilateral n. accumbens microinjections of d-amphetamine prior to operant sessions. Doses of 4 micrograms, 10 micrograms and 20 micrograms/brain were administered and some animals also received a 4 microgram/brain dose of LY171555. Three different effects were observed: increased, decreased and no change in total session responding. There was no clear relation between injection area in the n. accumbens and type of effect observed. For either an increase or decrease in total session responding, momentary response rates were decreased. Both d-amphetamine and LY171555 produced similar results. The data support the hypothesis that dopamine in the n. accumbens is involved with ethanol reinforced operant responding but in a complex manner.     

Intracranial circulation: pulse-sequence considerations in three- dimensional (volume) MR angiography

The technique and feasibility of magnetic resonance (MR) angiography of intracranial vessels were studied in 35 healthy volunteers. Variations in image orientation, repetition time (TR), and flip angle were evaluated to determine their effects on flow-related enhancement. Gradient modifications--including echo time (TE), motion compensation, bandwidth, and field of view--were also studied in an effort to reduce motion-induced phase shifts. Results indicated that a FISP (fast imaging with steady precession) sequence with a TR of 50 msec, TE of 15 msec, velocity compensation in the read and section-select directions, acceleration compensation in the read direction, anisotropic volume, and a 1.25-mm partition thickness produced three-dimensional angiographic MR images that were accurate and reproducible in the depiction of the major intracranial vessels. Difficulties with field of view, persistent signal void secondary to higher-order motion, and spatial resolution remain major problems requiring additional study.     

Paediatric dacryocystorhinostomy

Of 258 cases of dacryocystorhinostomy performed on children in the period September 1981 to September 1991, 130 were for simple, unresolved congenital nasolacrimal duct obstruction. Other indications for surgery included punctal agenesis, lacrimal fistula, post-traumatic and post-inflammatory canalicular obstruction. Of 177 children without canalicular pathology, 171 (96%) were relieved of symptoms with one operation, without canalicular intubation. Of 81 cases with canalicular disease, 55 of 70 (79%) who underwent DCR plus canalicular intubation, and 10 of 11 who underwent DCR plus Lester-Jones tube, were substantially improved with one operation. No child required peroperative or postoperative blood transfusion. Dacryocystorhinostomy in childhood, in experienced surgical hands, is a safe procedure, achieving relief of symptoms in most cases, particularly in the absence of canalicular disease.     

Regulation of G proteins by chronic antidepressant drug treatment in rat brain: tricyclics but not clorgyline increase Go alpha subunits.

The effect of long-term (3-week) administration of various antidepressant drugs on the steady-state concentrations of G protein alpha subunits, Gs alpha, Gi alpha, and Go alpha, has been investigated in rat brain using an enzyme-linked immunosorbent assay. Tricyclic antidepressants and clorgyline decreased Gs alpha and, to a lesser extent, Gi alpha in several brain regions, while Go alpha was increased by tricyclics but not clorgyline. We conclude that long-term treatment with antidepressant drugs exerts differential effects on G protein alpha subunits, and that antidepressant efficacy may potentially be based on functional modifications of signal transduction.     

Aminoglycoside-induced blockade of reflex activity in the isolated spinal cord from the neonatal rat

The subarachnoid injection of gentamicin into rats causes a transient flaccid paralysis of the hindlimbs lasting 1 to 5 hrs followed by a permanent flaccid paralysis which develops after 24 to 36 hrs. Although the early transient paralysis could be attributed to a pharmacologic blockade of central synaptic transmission, the mechanism of the blockade was not apparent. This study examines the effects of gentamicin and two other aminoglycoside antibiotics, kanamycin and neomycin, on reflex transmission in the isolated, hemisected spinal cord of the neonatal rat and the interaction with calcium. Gentamicin produced a concentration-dependent depression of reflex activity with a 50% inhibitory concentration of 1.6 mM at an external calcium concentration ([Ca2+]o) of 2.5 mM. Reducing the [Ca2+]o by half (i.e., to 1.25 mM) lowered the 50% inhibitory concentration of gentamicin to 0.22 mM. Gentamicin also increased the magnitude of homosynaptic depression of reflex activity in a manner qualitatively similar to that of decreasing [Ca2+]o. Lowering the [Ca2+]o potentiated the effect of gentamicin on homosynaptic depression. The actions of neomycin, kanamycin and magnesium on reflex transmission were nearly identical to those of gentamicin. These findings demonstrate that the early paralysis seen after subarachnoid injection of gentamicin may result from a central blockade of transmission. It is most likely that the site for blockade of reflex activity by gentamicin is presynaptic.