Neurotransmitters, neuroreceptors and aging.

At first glance, it is satisfying to see the progress which has been made in the study of neurotransmitters. We have learned a great deal in the last number of years. First, we have been able to identify previously unknown compounds which affect the nervous system or associated peripheral organs. We now know a great deal about the metabolism of these molecules including their synthesis and catabolism. We have learned to identify and to classify their receptors. We have learned that alterations in the effects of neurotransmitters may be responsible for certain pathologies or may be a function of normal aging. Yet, we still have far to go in our research. There are neurotransmitters still to be discovered. We need to continue our efforts because there is still a large amount of confusion in the literature, for example, far too many contradictory reports concerning the effects of age confuse rather than clarify. Possibly order may return to the literature if investigators can agree on some basic tenets. For example, we need a basic definition of old. Some research groups consider 12-month-old rats as old while other groups consider them to be young individuals. We need to have standardization of methodology so that the conclusions can have validity. Once again certain investigators use whole brain homogenates while others use only discrete portions. We need to consider whether the effect we see in our experiment is primary or secondary to aging. We can be certain that due to the aging population, the importance of basic research of age-dependent changes in neurotransmitters and neuroreceptors will increase in the future.