Posts Tagged ‘Neuroscience research’

Such observations suggest that pre-existing psychopathology is not a requisite for initial or even continued drug taking’and that drugs themselves are powerful reinforcers, even in the absence of physical dependence (Gilman et al. 1985:534).

Please note: the above quote was in my previous post. It is repeated here because it should have been followed by the following paragraph:

The ‘reinforcing capacity of a drug’ became the term referring to a particular drug’s inherent capacity to induce animals to repeat actions which result in drug administration. The reinforcing factor appeared to differ for each drug. For example, under a that particular laboratory set-up, rats would press a bar 250 times to obtain caffeine, 4,000 times for heroin, but 10,000 consecutive times to obtain cocaine (Spotts and Shontz 1980:15).

Although wild animals do not have comparable access to drugs, there are numerous examples of them ingesting psychoactive substances. There is a close association between reindeer and the psychoactive fly agric mushroom in Siberia (Furst 1976:101). It is commonly accepted that grazing animals prefer fermented fallen fruit and that birds sometimes select nectars which intoxicate. Altogether, by the 1980s, increasing evidence demonstrated that animals seek out psychoactive experiences. Researchers from the University of California claim knowledge of more than 2,000 cases of animals consuming psychoactive substances, of which 310 were investigated and their use found to be ‘intentional and addictive’ (Greenberg 1983:300). And see next post.

About the same time as queries began about excessive drug seeking, a rush of interest grew in the unfolding science of neurobiology. Instead of electricity firing the brain as formerly thought, scientists discovered that central nervous system activity depended upon at least fifty chemical compounds academics named ‘neurotransmitters’. The latter controlled and coordinated flows of information between the neurons within the brain, including data about emotions, memories and pleasures.

The main chemical transmitters include dopamine, acetylcholine, nor epinephrine, serotonin, gamma amino butyric acid, and the recently discovered opioid peptides. Each possesses a specific molecular and spatial arrangement which enables it to ‘plug’ into a receptor in a target neuron, rather like a key into a lock. The neuron is thus activated: information passes from one neuron to the next, and the neurotransmitter, its function accomplished, decays.

This may seem far distant from packing a cone or sipping gin and tonic. Here is the connection. Human and non- human mammals are not the only natural phenomena containing neurotransmitters. Some plants contain (almost) identical chemicals. A unique situation results. The nicotine in tobacco, for example, fits receptors designed for the acetylcholine receptor and, once plugged into the receptor, nicotine activates the same processes that acetylcholine can activate. Similarly, morphine from opium poppies fits receptors for the body’s endogenous opiates… and so on for each of those plants which contain chemical compounds which are analogous to brain neurotransmitters.

Olds, acknowledged now as one of the fathers of neuroscience, raised the suggestion that mammal brains (that is, those of human plus non-human mammals) might possess a ‘reward’ strata; Olds had in mind some sort of pay-off which would automatically follow mating, eating, and drinking, and thus encourage repetition of these acts. The concept of a reward structure gradually found acceptance, and in 1976 Olds suggested that drug use may also involve the neural substrate concerned with the brain reward system. Olds based this on the structural resemblances between psychoactive drugs and neurotransmitters, and the fact that drug use clearly reinforced further drug use.

Subsequent studies justify Old’s hypothesis and revealed that people consuming drugs are strengthening or inhibiting neurotransmitters in their brains, or changing their synthesis, storage or release. Through this, drug consumers alter emotions, mood, memory, reasoning powers and perceptions of self and others (Levine 1978:344; Nahas 1981).

However, some differences exist between the two situations: ie in the behaviour of brain transmitters versus drugs analogous to natural brain transmitters. Appetite, satiation, sexual depletion and other biological restraints govern mammal capacity to eat drink, and mate. Consequently the latter activities are not constantly reinforced to the extent that drug use is. See below. Additionally, the plant chemicals drug users select are much more resistant to decay than are the mammal neurotransmitters of which the plant chemical are analogues. Consequently plant chemicals remain longer at the site than the genuine neurotransmitters, and often become potent neurotoxic agents (Kosterlitz and Hughes 1978:412).


The results of animal research has received extensive critical scrutiny. It has to do with money. New synthetic drugs are more likely to receive approval from the United States Food and Drug Administration if they have little or no reinforcing capacity. To evaluate this, three research methods are utilized: drug substitution procedures; continuous self administration with naive animals; and use of escape/avoidance behavioral baselines (Thompson and Young 1978:119 129). Tests use a variety of species (e.g. rat, dog, cat, and non human primates); and investigators use different devices (e.g. lever press, panel press), and different routes of drug administration (e.g. intravenous, oral, intragastric, and inhalation) (Kalant et al.1978:466). Research indicates a number of factors exist which can modify individual animal response. However test results for particular drugs are consistent from laboratory to laboratory even with different experimental parameters and test situations.

Neither is the applicability of the findings to human beings in doubt. The Committee on Problems of Drug Dependence of the National Research Council National Academy of Sciences has addressed this matter as have Thompson and Young (1978), and Johanson and Balster (1978). These sources conclude that the model is valid in respect to humans since the results with a particular drug are consistent from laboratory to laboratory. And these results accord with empirical observation: laboratory animals largely self administer the same drugs which are abused by humans, but do not self administer drugs which are not abused by humans. Hallucinogens seem to be an exception; laboratory animals do not self administer these, even though humans do. However, as noted earlier, there are records of wild animals seeking out hallucinogenic plants so the problem here may be one of failure to deliver the drug to the appropriate tissue.

The conclusion therefore, is that drug users everywhere experience changes in the functioning of reward processes in the limbic system of the brain. As a result, in a situation free of effective controls, users in any society with open access to drugs will consume them in an open ended, unscheduled fashion, and without reference to controls which operate with foods, that is, appetite and satiation.

This does not imply that the effects of drugs on reward centres always ‘induce a compulsive drug oriented behaviour’ (Nahas 1981:1). It is the chemical interaction between drugs and neurotransmitters which is similar in both human and non human animals, not the subsequent behaviour.

Human behaviour depends upon values: social, economic, legal and religious. In fact, the late Schuster, one of the seminal figures in research into drug seeking behaviour among animals, clearly appreciated the sociological implications of his work, particularly the increased importance it gives to social controls.

We are depending on a variety of countervailing influences to prevent the organism [Homo sapiens] from engaging in behavior which evolutionary mechanisms have made extremely seductive…. Why is it that members of this symposia audience, most of whom have access to the major drugs of abuse do not use them in an unregulated manner? We know far too little about the social and psychological factors which produce this resistance to the abuse of drugs. It is our position that this is a major area which must be researched if we are to develop effective prevention to unregulated drug use. In conclusion, our major message is that drug taking is biologically normal and society must learn to live with that fact and to develop the necessary constraints to prevent unregulated drug use (Schuster, Renault and Blaine 1979:17) (italics added).


The Committee on Problems of Drug Dependence of the National Research Council National Academy of Sciences
Furst, P. (1972). Flesh of the gods:the ritual use of hallucinogens. London:George Allen & Unwin.

(1979). Hallucinogens and culture.San Francisco: Chandler & Sharp.

Gilman, A.G., L.S. Goodman, T.W. Rall, and F. Murad (eds.) (1985). Goodman and Gilman’s pharmacological basis of therapuetics. 7th ed. New York: Macmillan.

Greenberg, J. (1983). Natural habits in natural habitats. Science News 124: 300-301.
Johanson, C., and R. Balster. (1978). A summary of the results of a drug self-administered study using substitution procedures in rhesus monkeys. Bulletin on Narcotics 30: 627-628.

Kalant, H. et al. (1978). Behavioral aspects of addition: group report. In J. Fleishman (ed.) The bases of addiction: Report of the Dahlem Workshop on the Bases of Addiction. Abakon: Verlagsgesellscgaft.
Kosterlitz, H.W. & J. Hughes. (1978). Endogenous opoid peptides. In J. Fleishman (ed.) The bases of addiction: Report of the Dahlem Workshop on the Bases of Addiction. Abakon: Verlagsgesellscgaft.

Levine, R.R. (1978). Pharmacology: Drug actions and reactions. Boston: Little Brown and Company.

Nahas, G.G. (1981). A pharmacological classification of drugs  of abuse. Bulletin on Narcotics 33: 1-19.

Schuster, C.R., P.F. Renault, and J. Blaine. (1979). An analysis of the relationship of psychopathology to non-medical drug use. In R. Pickens and L. Heston (eds.) Psychiatric factors in drug abuse. New York: Grune & Stratton.

Spotts, J. & F. Shontz. (1980). Cocaine users : a representative approach. New York: Macmillan Publishing Company.

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