Low-dose alcohol self-administration in freely-moving rats and its effect on the firing rate of
ventral tegmental area GABA neurons.
Faculty Mentor: Scott Steffensen, Neuroscience Center
Each year, more and more people become the slaves of addiction to narcotics, alcohol, and
nicotine. These addictions destroy families and ruin lives. The brain’s chemistry is influenced
by these drugs. This study aimed to evaluate how alcohol and other drugs affect the brain’s
chemistry and identify potential avenues for therapy.
In this project we focused on the role of ventral Tegmental area (VTA) GABA neurons in
alcohol self administration. Dr. Steffensen’s previous research found VTA GABA neurons
accelerate their firing rates when associated with rewarding or reinforcing behavior such as
intracranial self-stimulation (ICSS) (Steffensen, Lee et al. 2001). ICSS involves stimulating
areas of the brain associated with pleasure such as the nucleus accumbens invoking a sensation
of pleasure. In Steffensen, Svingos, et al (1998), they recently characterized a homogeneous
population of VTA non-DA neurons that are distinguishable from DA neurons
electrophysiologically, anatomically, and pharmacologically from DA neurons. These non-DA
neurons were determined to be GABA-containing projection neurons with widespread
distribution to limbic structures. VTA GABA neurons modulate the mesocorticolimbic
dopamine (DA) system which is implicated in both natural and drug rewards. The firing rate of
VTA GABA neurons is markedly sensitive to acute intoxicating doses of ethanol (i.e. passive
administration) and undergoes adaptation to chronic ethanol (Gallegos, Criado et al. 1999). Most
importantly, VTA GABA neurons accelerate in anticipation of rewarding stimuli, such as ICSS
(Steffensen, Lee et al. 2001). We have recently found that VTA GABA neurons accelerate in
association with heroin and sucrose self-administration. Taken together, these findings indicate
that VTA GABA neurons play a role, whether contributory or reflective, in rewarding behaviors.
Our proposed model would evaluate the effect of low-dose ethanol on the VTA GABA neuron’s
discharge rates in freely-moving rats.
We implanted rats with electrodes in the VTA for chronic recording of VTA GABA
neurons and a jugular catheter for administration of intravenous ethanol at low doses (0.10
mg/kg). We hoped to set up an operant-type chamber in which the rat would nose-poke to
receive a desired stimuli, such as a low-dose of ethanol. Complications from the implant
procedure made this impossible. After several attempts, we decided we didn’t have the means to
safely implant the catheter into the rats for the purpose of this study.
I redirected my efforts into a new study titled, “Pilot Study: Ameliorization of seizures by
The current treatment of epilepsy, whether congenital or acquired, has been treated with
phenobarbital, carbamazapines and lamotrigine. While these drugs are therapeutically useful, the
line between the suggested dose and the lethal dose is very thin. Alternative treatments for
epilepsy are eagerly being sought.
Botulinum B, a member of the family of Botulinum toxins, has recently come to be
considered as a candidate for treating epilepsy. Botulinum toxins (clinically known as Botox)
are known to interfere with vesicular fusion with the presynaptic membranes in neuromuscular
junctions. It is use clinically to treat for muscle spasms (Chapman et al., 2007), hyperactive
sweat glands (Glaser et al., 2007), and wrinkles (Kim et al., 2007).
Research has found that Botulinum B increases the threshold for seizures in rats when
administered directly into the hippocampus (Costatin et al., 2005). Botulinum toxins cleave the
SNAP protein involved in fusing vesicles containing neurotransmitters to the cell membrane.
Botulinum toxin is commonly supposed to be unable to breech the blood-brain-barrier (Simpson,
2004). However, anecdotal observations by Dr. Gary Borodic have noted that patients who
recently underwent Botox procedures in the periorbital region have altered moods. This suggests
that the toxin may be transported into the cranium.
To test if the clinical form of Botulinum can indeed cross the blood brain barrier, we
replicated the kindling model of epilepsy (Costatin et al., 2005) and administered known
therapeutics (Pentobarbital) for epilepsy to evaluate our
model for validity. Then, we administered the Botulinum
toxin periorbitally (on the forehead).
The kindling model involves implanting a
stimulating electrode into the dentate gyrus of the
hippocampus, a known locus for epilepsy. We then
stimulated the rat at regular intervals and at slightly
increased voltage until the rat exhibited seizure like
behaviors and electroencephalography (EEG) recordings.
The figure to the right shows the EEG recordings of an
animal before the kindling has taken affect, a characteristic
seizure after kindling and the effect of Pentobarbital on
The animal subject responded well to the implants
and to the kindling procedure. Several study groups and
control groups were then kindled and had the toxin
administered periorbitally. Unfortunately, no significant decrease was found to result from the
administration of the Botulinum toxin. After these groups finished their protocol we ended the
I presented a poster at the 2008 Mary Lou Fulton Student Research Conference here at
BYU. These studies may not have discovered a significant finding and shared it with the
community but I learned a great deal about the scientific process. Perhaps most importantly, I
learned that a failure doesn’t mean we haven’t learned anything. It just means we have to change
the course of our study.
I am immensely grateful for the opportunity that the ORCA grant afforded me. I’m now
in medical school, largely in part to these research experiences. Thank you for your support and