The focus of this review of intracranial chemical injection (ICI) is on the methods used and how variations in the use of these methods affect the results obtained. A brief historical review indicates that investigators at the turn of the century were concerned with the local nature of ICI. Since this problem remains at this time, the logic of the protocols then used is considered applicable to present problems. After a review of the available methods, a checklist containing a standard set of recommended procedures is provided. These recommendations do not depart from current practices, but serve to identify sources of variability among experiments that could readily be reduced. A consideration of the sphere of influence of ICI focuses on the evaluation of the author's ventricular hypothesis. This hypothesis, as originally formulated, called attention to the potential of spread from sites of ICI to the ventricular system. This would blur the anatomical localization which is one of the major virtues of the ICI method. It is considered necessary to expand the view of spread from the application site to include an important contribution of the vasculature. The failure to find species generality is taken as one indicant that the critical sites of action of cholinergic agents which provoke drinking have not been discovered. Recent evidence indicates that the subfornical organ may be one important site of carbachol-induced drinking. Such evidence does not deny the possibility of a "thirst circuit" but it is clear that such a circuit has not been adequately defined. Discrepancies concerning the alpha- and beta-adrenergic systems involved in feeding and the influence of dopamine applied to the striatum on motor behavior is briefly reviewed in terms of the different methods used.
ASJC Scopus subject areas
- Environmental Science(all)
- Earth and Planetary Sciences(all)