mise à jour du
21 décembre 2009
Life Sciences
Behavioral and biochemical responses of mice
to the intraventricular administration
of acth analogs and lysine vasopressin
Howard D. Bees, Adrian J. Dunn, P. Michael Iuvone
Department of Neuroscience, University of Florida, Gainesville, U.S.A.


ACTH 1-24, ACTH 4-10, ACTH 4-10(D-phe), lysine vasopressin (LVP) or an amino acid mixture were administered to mice using bilateral intraventricular injections (5x1O9 moles per mouse). Behavioral observations were made for the subsequent 85 minutes, and the incorporation of subcutaneously injected [3H]lysine into brain proteins assayed for the last 10 minutes of this period. Mice injected with ACTH1-24, showed the previously reported stretching and yawning syndrome, an effect also observed with ACTH 1-24(D-phe) but less often. These same peptides also induced a pronounced increase in the proportion of time mice spent grooming. LVP caused a dramatic hyperactivity; mice so injected moved continuously about the cage occasionally eating or grooming, but were never still. Injection with ACT H 1-24, or ACTR 4-10(D-phe), but not ACTB 4-10 or LVP, caused significant increases in the incorporation of [3H]lysine into brain protein.
The elegant work of De Wied and his coworkers has established that administration of ACTH, vasopressin or their analogs can influence the learning and retention of behavioral tasks in rata (1). Current indications are that these effects reflect normal physiological processes and that the peptides act directly on the brain (2).
We previously observed that avoidance training and related stimulation increased the uptake and incorporation of (HJ lysine into proteins of mouse brain and liver (3). The effects seemed to be stress-related, rather than specifically training-related, and occurred in response to footshocks, loud buzzer presentations and handling, as well as to training. These effects diminished or disappeared with repeated exposure to the stimuli over a few days (3). Mediation by stress-related hormones was suspected, but adrenalectomized mice showed similar biochemical responses (4). This suggested that perhaps ACTH itself might be involved, especially since ACTH had previously been shown to stimulate the incorporation of amino acids into brain proteins of mice (5, 6). We also found that ACTH administration could mimic the observed E 3H] lyaine incorporation changes (7). Corticosterone administration to adrsnalectomired mice was not effective (Bees and Dunn, submitted for publication). Further evidence that the response to stimulation is caused by ACTH is that the effect of footshock on brain [3H]lysine incorporation was suppressed by doses of dexemethaaone that inhibited the secretion of corticoaterone and presumably therefore of ACTH (Bees and Dunn, submitted for publication). We have further observed that whereas ACTH1_21f increased [3E] lysine incorporation in both brain and liver, ACTH 4-10 was effective only in the brain (Dunn, Rees, and luvone, submitted for publication). However, the response to subcutaneously injected ACTH 1-24 or ACTH 4-10 was smaller and less consistent than that to footshock. Allen et al. (8) have provided evidence that ACTH might he secreted directly into the cerebral ventricles. Wetherefore studied the effects of intraventricular administration of the peptides on [3H]lysine incorporation. Also, since ACTH and its analogs have been reported to produce a behavioral response known as the stretching and yawning syndrome (9,10), and an enhancement of grooming behavior in rats (11), we observed the behavior of the mice for 85 minutas prior to sacrifice.
The observation of synchronized stretching and yawning behavior following intraventricular injection of ACTH replicates the observations of Ferrari et al. (9). We observed such effects most intensely with ACTH 1-24confirming earlier observations(9,l0,ll). Unlike Ferrari et al. (9), but in agreement with Baldwin et al. (10) and Cispen et al. (11) we observed very little effect with ACTH 4-10. However, ACTH 4-10(D-phe) was much more potent than ACTH 4-10, although less potent than ACTH 1-24, as also found by Cispen et al. (11). This sane order of potencies of the peptides was also observed with grooming behavior; ACTH 1-24 being most potent and ACTH 4-10(D-phe) less so. These results in mice are thus in excellent agreement with those of Cispen et al. (11) in rats. ACTH 4-10 may not be without effect since stretching behavior was often enhanced by this peptide. These behavioral effects of the peptides are not exclusive to C57B1/6J mice since we have observed very similar stretching and yawning, and grooming responses in CD-1 male mice.
These results differ from the effects of ACTH peptides on avoidance behavior, in which ACTH 4-10 and ACTH 1-24 were equipotent in delaying extinction, whereas ACTH14...10(D-phe) accelerated extinction (1). Apparently this effect of ACTH-10 (D-phe) was not caused simply by competition with endogenous ACTH since ACTH 4-10(Dphe) was effective in hypophysectomized rats. However, ACTH 4-10(Dphe) was as potent as ACTR 4-10 in facilitating passive avoidance behavior (15). These data suggest then that there may be separate receptors for ACTH 1-24 and ACTH 4-10(D-phe).
That ACTH peptides should affect the incorporation of amino acids irto protein is consistent with earlier data. Semiginovsky and Jakoubek (5) showed that ACTH increased the incorporation of [U-14C]Ieucine into mouse brain protein. kudman et al. (6) also showed that ACTH or B-MSH increased the incorporation of [U-14C]valine, [UC]tyrosine, [U-14C]Ieucine and [U-1C]lysine into mouse brain protein. Using ACTH 4-10, Reading (16) observed an increased incorporation of [11C]leucine into rat brain protein and we have observed a similar effect with [311]lysine in mice (Dunn, Rees and luvone, submitted for publication). In hypophysectomized rats there is a decreased rate of cerebral protein synthesis indicated by a diminished aggregation of ribosomes and polyribosomes (17) and a decreased in vitro protein synthesis (18). In these animals ACTH stimulated the incorporation of [3H]leucine into protein (19). Furthermore, ACTH 11D in vitro stimulated [3H]leucine incorporation into brain stem slices from hypophysectomized rats (20,21).
The effects of ACTH 4-10 D (D-phe) obtained here are inconsistent with the observations of Schotman et al. (19) who found that this peptide decreased the [3H]leucine incorporation of hypophysectomized rats and with those of Reith et al. (21) who found no effect on the incorporation by brain stem slices from hypophysectonized rats.
The dramatic behavioral effects of intraventricular LVP have not been previously reported and are worthy of further study. It is interesting to speculate to what extent they might be related to the effects of adrenergic compounds (22). The lack of effect of LVP on [3R]lysine incorporation into brain protein is also consistent with the lack of effect of subcutaneously injected LVP (Dunn, Rees and luvone, submitted for publication).
The results of the present study suggest that the effect of ACTH on brain protein synthesis might be mediated centrally as also indicated by the results of Reith et al. (20,21) mentioned above. The observations further indicate that the intraventricular route of administration is effective. This is consistent with the behavioral data of de Wiedts group (see for example Ref. 23) and may also explain why in our studies the effects of stimulation (electric footshock) are larger end more consistent then those of peripheral administration of ACTH (Dunn, Race and luvone, submitted for publication). That ACTH is secreted into the ventricles is indicated by its presence in human CSF and the lack of correlation between plasma and CSF concentrations of peripherally administered ACTH (8).
The dosage of ACTH 1-24 used in these studies (about 15 pg or 1500 nU per mouse) is above the physiological rangs, but is similar to the dosages used by several other investigators (9,10,11). Increased grooming behavior has been reported following intraventricular injection of as little as 0.01 pg of ACTH 1-24 in rats (11).
Our results indicate a correlation between the activity of ACTH peptides in eliciting grooming, stretching and yawning behavior, and their effects on [3H]lysine incorporation. The correlation between grooming behavior and [3H]lysine incorporation into cerebrum protein was significant (coefficient of linear regression r-0.38, df-22, p<O.O5) when the results of all treatments were combined. Whether or not these behavioral activities bear any relation to the effects on leaning remains to be seen. However, the observations are consistent with a central action of the peptides and a possible role in leaning mediated by changes in cerebral protein synthesis.