Differential cannabinoid-induced electrophysiological effects
in rat ventral tegmentum

Cheer JF, Kendall DA, Mason R, Marsden CA.
School of Biomedical Sciences,
University of Nottingham Medical School,
Queen's Medical Centre, UK.
Neuropharmacology. 2003 Apr;44(5):633-41


Cannabinoids are known to exert mainly excitatory effects on dopaminergic cells of the ventral tegmental area (VTA). We have utilized an in vivo multiple-single unit electrophysiological approach to assess different neuronal contributions that may ultimately lead to excitation in this area. Baseline neuron recordings, using low impedance microwires, showed a variety of waveforms with a wide range of durations (0.8-3.2 ms). In the first experiment systemic injection of the potent cannabinoid agonist HU210 (100 microg/kg, i.p.) led predominantly to an increase in firing rate (approximately 214%, compared to pre-drug) in slowly firing cells with broad action potentials, possibly driven by a majority of presumed dopaminergic neurons (n = 31). However, the firing rate of some units was either unaffected (<25%, n = 9) or even decreased (approximately 67%, n = 9) following cannabinoid injection concomitantly with excitation. Apomorphine (75 microg/kg, i.p.) injected following HU210 produced a marked inhibition of both responses (approximately 76%) in 39 out of 49 cells. The second group of animals was treated with the CB(1) receptor antagonist SR141716A (1 mg/kg, i.p.), which had no effect when injected alone but prevented all HU210-evoked changes in firing rate suggesting that cannabinoid receptors mediated the observed responses (n = 39). Taken together, the present results suggest that the observed actions of cannabinoids may involve complex neurotransmitter interactions leading to differential effects on dopamine release. These heterogeneous neuronal responses are likely to underly the behavioural discrepancies reported in animal models of cannabinoid reinforcement.

Just say know
Tolerant mice
Forgetful rodents
Stoned as a newt?
The nectar of delight
Stoned chocaholics?
Rodent cannabis abuse
Cannabis-tainted money
Cannabis and schizophrenia
Cannabinoids/Parkinson's disease

01 02 03 04 05 06 07 08 09 10 11 12 13 14 15


Future Opioids
BLTC Research
Utopian Surgery?
The Hedonistic Imperative
MDMA: Utopian Pharmacology
When Is It Best To Take Crack Cocaine?

swan image
The Good Drug Guide
The Responsible Parent's Guide
To Healthy Mood Boosters For All The Family