Microinjections of dopamine (DA) were made into specific forebrain loci in goldfish (Carassius auratus: 40-85 g) to study the involvement of DA in behavioral thermoregulation. Injections of 25, 50, 100 and 250 ng DA into the anterior aspect of the nucleus preopticus periventricularis (NPP) led to consistent, dose-dependent decreases in selected temperature. Minor decreases or no effect on selected temperature was observed following injections of 5 or 10 ng DA. Injections of the control solution were without effect. Injections of DA into other forebrain loci, including the posterior half of the NPP, either had no thermoregulatory effect or had minor thermoregulatory effects which, in comparison, to injections into the most effective sites, were inconsistent and required larger doses to obtain. The decrease in selected temperature following injections of 100 ng DA into the anterior NPP was blocked by haloperidol, a dopaminergic antagonist, but not by phentolamine, a noradrenergic antagonist. Injections of haloperidol alone resulted in a minor, but statistically significant, increase in selected temperature. The most sensitive DA sites lie caudal to the sites most sensitive to norepinephrine within the anterior NPP. DA acts on the dopaminergic receptors of central thermoregulatory neurons in the anterior NPP of goldfish. These receptors appear to mediate behavioral responses to excessively warm environments.

Cannulas were implanted into forebrain loci of goldfish (Carassius auratus; 45-90 g) to determine the effects and site of action of intracranial norepinephrine (NE) injections on behavioral thermoregulation. Following 30 min in a thermal gradient, implanted fish were injected with norepinephrine-bitartrate salt (2.5-500 ng NE) in 0.2 microliter 0.7% NaCl. Injections of 5, 10, 25, and 50 ng NE into the anterior aspect of the nucleus preopticus periventricularis (NPP, Ref. 25) led to consistent dose-dependent decreases in selected temperature (Tsel). No effect on Tsel was observed following injections of 2.5 ng NE or control injections of 100 ng tartaric acid. The effects of injections into other loci, including intraventricular injections, were dependent on the dose and proximity to the anterior NPP; at sites adjacent to the anterior NPP, larger doses were required, and the effects became inconsistent. At sites further removed, no effect on Tsel was observed. Included in this category were more caudal sites within the NPP and the nucleus preopticus. We postulate that in fish the anterior NPP is an important locus for thermoregulatory integration and that increased release of NE in this area leads to the selection of cooler water.

Goldfish (Carassius auratus) (40-80g) were injected with dopamine into the forebrain to study the possible involvement of this amine in central temperature regulation in these fish.Dopamine caused a decrease in selected temperature after injection into the rostral nucleus preopticus periventricularis (NPP). This effect was dependent on the dose of dopamine administered. Doses of 25, 50, 100 and 250 ng were used, injected in a volume of 2 0.2µ1. Injections in regions adjacent to the NPP elicited hypothermic effects only at the higher dosages. These effects were not consistent. Injections in caudal regions of the NPP elicited no effect. The effects of dopamine were blocked by haloperidol, a selective antagonist of dopamine.It is suggested that dopamine acts on central Since the organism receives inputs on the temperature of its body and that of the environment and then reacts in an appropriate way to these inputs, it is likely that a neuronal circuit is present which integrates inputs and activates effectors appropriately. This circuit, in vertebrates, most likely involves the hypothalamus. In support of this assertion is the finding that the preoptic area of the hypothalamus of many mammals is the only part of the nervous system whose temperature, if shifted only 1-2 C above or below the normal, can lead to activation of heat loss or heat gain mechanisms respectively (Hammel, 1968).Animals for which this is true are the dog, cat, rabbit, rat, ox, goat and baboon (Hammel, 1968). Also, if the afferent n~ural connections to this part of the brain are destroyed by ablating the region dorsal to the hypothalamus the animal can maintain its normal body temperature under cold stress and will only slightly increase its temperature under heat stress (Hammel, 1968). This further suggests that the hypothalamic temperature, when transduced into neural activity, can be used to aid in the regulation of body temperature. Neural input into the preoptic area is, however, needed for normal, precise thermoregulation (Hammel, 1968).Nelson and Prosser (1979) (Hammel, 1968). Further support is leant by the finding mentioned above that neural input into the preoptic area is required for normal thermoregulation. 5The neural wiring of the controlling centers and the connections of the afferents with the centers are only partially understood (Crawshaw~ ,al., 1985). However, The results of these studies have not always been consistent and generalizations as to the effects of each particular drug ~njected even in the same species cannot easily be made. However, norepinephrine in most animals has been found to have a hypothermic effect (Bruinvels, 1979). This has has also been shown to be the case in goldfish where Wollmuth~ .aJ.. (in press) showed that norepinephrine has a hypothermic effect when injected into the hypothalamus.Serotonin predominantly elicits a hyperthermic effect in cats, dogs and monkeys and a hypothermic effect in goats, oxen, mice, pigeons and chickens. Rabbits, rats and sheep show either response (Jacob and Girault, 19...