1. Intracellular recordings were obtained from neurones in layers 2 and 3 of the rat frontal neocortex in an in vitro slice preparation. Three distinct types of stimulation‐evoked post‐synaptic potentials were recorded in these neurones: excitatory post‐synaptic potentials (e.p.s.p.s); bicuculline‐sensitive, chloride‐dependent inhibitory post‐synaptic potentials (i.p.s.p.s) with times to peak of 20‐25 ms (fast(f)‐i.p.s.p.s); bicuculline‐insensitive, potassium‐dependent i.p.s.p.s with bicuculline‐insensitive, potassium‐dependent i.p.s.p.s with times to peak of 150‐250 ms (long(l)‐i.p.s.p.s). 2. The effects of baclofen were investigated on seventy‐one neurones. Baclofen was applied by ionophoresis or pressure ejection from micropipettes or was added to the superfusion medium. 3. Baclofen depressed stimulation‐evoked e.p.s.p.s in fifty‐seven of the sixty neurones tested. This effect was associated with an increase in the stimulation intensity required to produce a synaptically evoked action potential for thirty‐nine of forty‐four neurones. 4. Baclofen depressed f‐i.p.s.p.s in thirty‐seven of the thirty‐nine neurones tested and l‐i.p.s.p.s in each one of the seventeen neurones tested. Reversal potential values for each type of i.p.s.p. were not changed by baclofen and its depressions of each were independent of membrane potential (Em). Baclofen reduced the magnitude and the duration of the conductance increases that were associated with f‐ and l‐i.p.s.p.s. 5. Baclofen hyperpolarized forty of seventy‐one neurones and produced outward currents in three of four neurones recorded in voltage clamp at holding potentials between ‐55 and ‐65 mV. These actions were associated with 10‐58% reductions of neuronal input resistance (RN) and 10‐20% increases in neuronal input conductance (gN), respectively. Baclofen decreased the direct excitability of twenty‐three of twenty‐seven neurones tested. Determinations of the reversal potential for baclofen‐induced changes of Em indicate that baclofen increases the conductance of rat neocortical neurones to potassium ions. 6. The EC50 for each action of DL‐baclofen was approximately 1 microM. L‐Baclofen was greater than 100 times more potent than D‐baclofen. 7. Concentrations of bicuculline that blocked f‐i.p.s.p.s and responses to ionophoretically applied gamma‐aminobutyric acid (GABA) had no effect on the depressions of e.p.s.p.s or the hyperpolarizations and decreases in RN that baclofen produced. 8. Baclofen did not reduce the duration of action potentials that were prolonged with intracellular injections of caesium ions or by superfusions with medium that contained 10 mM‐tetraethylammonium (TEA).(ABSTRACT TRUNCATED AT 400 WORDS)
The Journal of Physiology – Wiley
Published: Mar 1, 1987
It’s your single place to instantly
discover and read the research
that matters to you.
Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.
All for just $49/month
Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly
Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.
Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.
Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.
All the latest content is available, no embargo periods.
“Hi guys, I cannot tell you how much I love this resource. Incredible. I really believe you've hit the nail on the head with this site in regards to solving the research-purchase issue.”Daniel C.
“Whoa! It’s like Spotify but for academic articles.”@Phil_Robichaud
“I must say, @deepdyve is a fabulous solution to the independent researcher's problem of #access to #information.”@deepthiw
“My last article couldn't be possible without the platform @deepdyve that makes journal papers cheaper.”@JoseServera