Erowid References Database
Fox PC, Dray A.
“Iontophoresis of LSD: effects on responses of single cortical neurones to visual stimulation”.
Brain Research. 1979;161:167-172.
The mechanisms by which LSD produces sensory disturbances in man and other maminals are poorly understood though LSD alters nervous activity in the visual system at several levels. In particular systemic LSD may enhance or depress the activity of neurones in the visual cortex when these cells are activated by physiological optical stimulations. However the lack of suitable control agents and the route of administration employed in these latter studies makes it uncertain whether these changes were mediated directly or were related to the hallucinogenic properties of LSD. The present report describes the effects of LSD and structurally related analogues administered by microelectrophoresis onto visual cortical neurones. Experiments were performed on adult cats anaesthetized with pentobarbitone (35 mg/kg i.p. and supplemented with thiopentone i.v. as required) during surgery. Wound edges were infiltrated with local anaesthetic (Anucaine, Calvin Chemical Corp.) and anaesthesia was maintained during recording with nitrous oxide (75%) supplemented by intravenous thiopentone. A unilateral pneumothorax was performed, the animal paralysed with gallamine and artifically ventilated. End-tidal CO2 concentration was kept within physiological limits: rectal temperature was maintained at 37¡C, blood pressure and heart rate were continuously monitored. Substances were administered systemically via a femoral cannula. Phenylephrine was used to contract the nictitating membrane and atropine to dilate the pupils. Contact lenses, corrected for refraction errors were placed over the eyes. Stimuli were usually presented at 0.1 HZ and consisted of a moving (7¡/sec) bright bar (5 x 0.6¡, 80 cd/sq.m) projected onto a screen (illuminated at 40 cd/sq.m) such that stimulus excursions started and stopped outside the receptive field. Recordings of extracellular activity were made from single cells in cortical area using one barrel (3 M sodium chloride) of a five-barelled micropipette (tip diam. 6-8 mcm). Another barrel, filled with 165 M sodium chloride, was used to eject Na+ to test for any effects of electrophoretic current. The remaining barrels contained LSD tartrate, methysergide maleate, 2-bromo-LSD (BOL), all at 1mM, pH 4.0 in 165 mM sodium chloride. Substances were made up in this way to obtain a more valid comparison of electrophoretic potency. Histograms of single cell responses were
[ Cite HTML